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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2016	Mar. 01, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Trading Symbol	OCUL
Entity Registrant Name	Ocular Therapeutix, Inc.
Entity Central Index Key	0001393434
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		28,756,870
Entity Public Float			$ 88

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 32,936	$ 30,784
Marketable securities	35,209	74,280
Accounts receivable	250	193
Inventory	113	134
Prepaid expenses and other current assets	1,390	1,592
Total current assets	69,898	106,983
Property and equipment, net	3,313	3,095
Restricted cash	1,728	228
Total assets	74,939	110,306
Current liabilities:
Accounts payable	2,116	1,957
Accrued expenses and deferred rent	4,635	3,379
Deferred revenue		42
Notes payable, net of discount, current	1,549
Total current liabilities	8,300	5,378
Deferred rent, long-term	537	68
Notes payable, net of discount, long-term	14,094	15,272
Total liabilities	22,931	20,718
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at December 31, 2016 and 2015; no shares issued or outstanding at December 31, 2016 and 2015
Common stock, $0.0001 par value; 100,000,000 shares authorized at December 31, 2016 and 2015; 25,024,100 and 24,750,281 shares issued and outstanding at December 31, 2016 and 2015, respectively	3	2
Additional paid-in capital	225,889	218,830
Accumulated deficit	(173,879)	(129,176)
Accumulated other comprehensive income (loss)	(5)	(68)
Total stockholders' equity	52,008	89,588
Total liabilities and stockholders' equity	$ 74,939	$ 110,306

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	25,024,100	24,750,281
Common stock, shares outstanding	25,024,100	24,750,281

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Product revenue	$ 1,845	$ 1,354	$ 460
Collaboration revenue	42	396	312
Total revenue	1,887	1,750	772
Costs and operating expenses:
Cost of product revenue	443	319	91
Research and development	27,065	26,611	18,880
Selling and marketing	6,701	3,852	1,982
General and administrative	11,004	9,165	6,913
Total costs and operating expenses	45,213	39,947	27,866
Loss from operations	(43,326)	(38,197)	(27,094)
Other income (expense):
Interest income	304	166	7
Interest expense	(1,680)	(1,724)	(1,119)
Other income (expense), net	(1)	7	(442)
Total other expense, net	(1,377)	(1,551)	(1,554)
Net loss	(44,703)	(39,748)	(28,648)
Accretion of redeemable convertible preferred stock to redemption value			(11)
Net loss attributable to common stockholders	$ (44,703)	$ (39,748)	$ (28,659)
Net loss per share attributable to common stockholders, basic and diluted	$ (1.80)	$ (1.71)	$ (2.69)
Weighted average common shares outstanding, basic and diluted	24,816,348	23,244,162	10,652,865
Comprehensive loss:
Net loss	$ (44,703)	$ (39,748)	$ (28,648)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	63	(68)
Total other comprehensive income (loss)	63	(68)
Total comprehensive loss	$ (44,640)	$ (39,816)	$ (28,648)

Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Series A, B, C, D and D-1 Redeemable Convertible Preferred Stock	Total
Temporary equity, balance at Dec. 31, 2013					$ 74,344
Temporary equity, balance, shares at Dec. 31, 2013					32,842,187
Redeemable Convertible Preferred Stock
Accretion of redeemable convertible preferred stock to redemption value					$ 11
Conversion of preferred stock to common stock					$ (74,355)
Conversion of preferred stock to common stock, shares					(32,842,187)
Balance at Dec. 31, 2013		$ 1,308	$ (60,780)			$ (59,472)
Balance, shares at Dec. 31, 2013	2,676,648
Stockholders' Equity (Deficit)
Issuance of common stock and restricted common stock, shares	148,227
Issuance of common stock upon exercise of stock options		35				35
Issuance of common stock upon exercise of stock options, shares	44,094
Issuance of common stock in connection with employee stock purchase plan		64				64
Issuance of common stock in connection with employee stock purchase plan, shares	5,395
Issuance of common stock in payment of consultant fees		699				699
Issuance of common stock in payment of consultant fees, shares	79,545
Issuance of common stock in payment of licensing fees		1,665				1,665
Issuance of common stock in payment of licensing fees, shares	189,393
Accretion of redeemable convertible preferred stock to redemption value		(11)				(11)
Issuance of common stock	$ 1	69,517				69,518
Number of shares issued	5,750,000
Issuance costs		(3,113)				(3,113)
Conversion of preferred stock to common stock	$ 1	74,354				74,355
Conversion of preferred stock to common stock, shares	12,440,205
Conversion of preferred stock warrants to common stock warrants		960				960
Stock-based compensation expense		2,644				2,644
Net loss			(28,648)			(28,648)
Balance at Dec. 31, 2014	$ 2	148,122	(89,428)			58,696
Balance, shares at Dec. 31, 2014	21,333,507
Stockholders' Equity (Deficit)
Issuance of common stock upon exercise of stock options		207				207
Issuance of common stock upon exercise of stock options, shares	141,848
Issuance of common stock in connection with employee stock purchase plan		249				249
Issuance of common stock in connection with employee stock purchase plan, shares	20,916
Issuance of common stock upon cashless exercise of warrants, shares	54,010
Issuance of common stock		66,176				66,176
Number of shares issued	3,200,000
Issuance costs		(564)				(564)
Unrealized gain (loss) on marketable securities				$ (68)		(68)
Stock-based compensation expense		4,640				4,640
Net loss			(39,748)			(39,748)
Balance at Dec. 31, 2015	$ 2	218,830	(129,176)	(68)		89,588
Balance, shares at Dec. 31, 2015	24,750,281
Stockholders' Equity (Deficit)
Issuance of common stock upon exercise of stock options		199				$ 199
Issuance of common stock upon exercise of stock options, shares	105,114					105,114
Issuance of common stock in connection with employee stock purchase plan		278				$ 278
Issuance of common stock in connection with employee stock purchase plan, shares	66,628
Issuance of common stock	$ 1	871				872
Number of shares issued	102,077
Issuance costs		(245)				(245)
Unrealized gain (loss) on marketable securities				63		63
Stock-based compensation expense		5,956				5,956
Net loss			(44,703)			(44,703)
Balance at Dec. 31, 2016	$ 3	$ 225,889	$ (173,879)	$ (5)		$ 52,008
Balance, shares at Dec. 31, 2016	25,024,100

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (44,703)	$ (39,748)	$ (28,648)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	5,956	4,640	2,644
Licensing and consultant fees paid in common stock			2,364
Non-cash interest expense	371	166	103
Depreciation and amortization expense	881	754	547
Revaluation of preferred stock warrants			380
Loss on extinguishment of debt			57
(Gain)/loss on disposal of property and equipment	1,269	(3)	4
Purchase of premium on marketable securities	(37)	(338)	(133)
Amortization of premium on marketable securities	186	283	24
Changes in operating assets and liabilities:
Accounts receivable from related party			19
Accounts receivable	(57)	136	(79)
Prepaid expenses and other current assets	924	(53)	(36)
Inventory	21	(1)	(133)
Accounts payable	(159)	348	507
Accrued expenses and deferred rent	1,389	219	1,946
Deferred revenue	(42)	(146)	(62)
Net cash used in operating activities	(34,001)	(33,743)	(20,496)
Cash flows from investing activities:
Purchases of property and equipment	(1,919)	(1,778)	(1,260)
Proceeds from sale of property and equipment	2	7
Change in restricted cash	(1,500)	60
Purchases of marketable securities	(41,699)	(91,684)	(37,326)
Proceeds from maturities of marketable securities	80,684	54,826
Net cash provided by (used in) investing activities	35,568	(38,569)	(38,586)
Cash flows from financing activities:
Proceeds from issuance of notes payable and preferred stock warrants		1,897	14,877
Proceeds from exercise of stock options	199	207	35
Proceeds from issuance of common stock pursuant to employee stock purchase plan	278	249	64
Proceeds from issuance of public offering, net	872	66,176	69,518
Payments of offering costs	(245)	(564)	(3,018)
Payments of insurance costs financed by a third-party	(519)	(762)	(233)
Repayment of notes payable		(1,500)	(2,273)
Net cash provided by financing activities	585	65,703	78,970
Net increase (decrease) in cash and cash equivalents	2,152	(6,609)	19,888
Cash and cash equivalents at beginning of period	30,784	37,393	17,505
Cash and cash equivalents at end of period	32,936	30,784	37,393
Supplemental disclosure of cash flow information:
Cash paid for interest	1,301	1,251	844
Supplemental disclosure of non-cash investing and financing activities:
Accretion of redeemable convertible preferred stock to redemption value			11
Conversion of redeemable convertible preferred stock to common stock			74,354
Conversion of warrants for redeemable convertible preferred stock to warrants for common stock			960
Additions to property and equipment included in accounts payable and accrued expenses	451	293	169
Insurance premium financed by a third party	$ 722	$ 706	623
Initial public offering costs included in accounts payable			$ 95

Nature of the Business and Basis of Presentation	12 Months Ended
Nature of the Business and Basis of Presentation	Dec. 31, 2016
Nature of the Business and Basis of Presentation
Nature of the Business and Basis of Presentation	OCULAR THERAPEUTIX, INC. NOTES TO FINANCIAL STATEMENTS (Amounts in thousands, except share and per share data) 1. Nature of the Business and Basis of Presentation Ocular Therapeutix, Inc. (the “Company”) was incorporated on September 12, 2006 under the laws of the State of Delaware. The Company is a biopharmaceutical company focused on the development and commercialization of innovative therapies for diseases and conditions of the eye using its proprietary hydrogel platform technology. The Company’s bioresorbable hydrogel-based product candidates are designed to provide sustained delivery of therapeutic agents to the eye. Since inception, the Company’s operations have been primarily focused on organizing and staffing the Company, acquiring rights to intellectual property, business planning, raising capital, developing its technology, identifying potential product candidates, undertaking preclinical studies and clinical trials, manufacturing initial quantities of its products and product candidates and building the initial sales and marketing infrastructure for the commercialization of the Company’s approved product and product candidates. The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations, regulatory approval, uncertainty of market acceptance of products and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization. As of December 31, 2016, the Company’s lead product candidates were in clinical stage development. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval and adequate reimbursement or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants. The Company may not be able to generate significant revenue from sales of any product for several years, if at all. Accordingly, the Company will need to obtain additional capital to finance its operations, including to support the planned commercial launch of DEXTENZA, subject to receiving FDA approval. The Company has incurred losses and negative cash flows from operations since its inception. As of December 31, 2016, the Company had an accumulated deficit of approximately $174,000. The Company expects to continue to generate operating losses in the foreseeable future. The Company believes that its existing cash and cash equivalents and marketable securities, including net amounts raised under in January 2017 stock offering of approximately $23,500 in net proceeds (Note 18) and additional borrowings totaling approximately $2,400 from its March 2017 debt refinancing (Note 18) will enable it to fund its operating expenses, debt service obligations and capital expenditure requirements for at least 12 months from the issuance date of the financial statements. The Company will seek additional funding through public or private financings, debt financing and collaboration agreements. The Company has two additional $10,000 tranches of borrowing capacity under its credit facility, which are contingent upon achieving FDA approval and certain sales levels of DEXTENZA, respectively. The inability to access these funds or obtain other funding, as and when needed, would have a negative impact on the Company’s financial condition and ability to pursue its business strategies. The Company would be forced to delay, reduce or eliminate its research and development programs or any future commercialization efforts or to relinquish valuable rights to its technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to the Company if it were unable to access the additional borrowing capacity under the credit facility or obtain other financing. The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). On July 30, 2014, the Company completed an initial public offering (“IPO”) of its common stock through the issuance and sale of 5,000,000 shares of its common stock at a public offering price of $13.00 per share, resulting in net proceeds of $57,337 after deducting underwriting discounts and other offering costs. Upon the closing of the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock were automatically converted into 12,440,205 shares of the Company’s common stock and all outstanding warrants for the Company’s redeemable convertible preferred stock were automatically converted into warrants for the Company’s common stock. In August 2014, the underwriters of the Company’s IPO exercised their over-allotment option to purchase an additional 750,000 shares of common stock at the initial public offering price of $13.00 per share, less underwriting discounts, resulting in additional net proceeds of $9,068 after deducting underwriting discounts (Note 10). In June 2015, the Company completed a follow-on offering of its common stock at a public offering price of $22.00 per share. The offering consisted of 4,600,000 shares of common stock, of which 3,200,000 shares were issued and sold by the Company and 1,400,000 shares were sold by certain stockholders of the Company, including those shares sold in connection with the exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds from the follow-on offering of $65,612 after deducting underwriting discounts and other offering expenses (Note 10). In November 2016, the Company entered into an At-the-Market sales agreement, (the “2016 ATM Agreement”) with Cantor Fitzgerald & Co., (“Cantor”), under which shares of common stock having aggregate proceeds of up to $40,000 may be sold from time to time. During the fourth quarter of 2016, the Company sold 102,077 shares of common stock under the 2016 ATM Agreement at a weighted average exercise price of $8.80 per share resulting in net proceeds of approximately $600 after underwriting discounts, commission and other offering expenses (Note 10). In January 2017, the Company sold 161,341 shares of common stock under the 2016 ATM Agreement at a weighted average exercise price of $8.91 per share resulting in net proceeds of approximately $1,400 after deducting underwriting discounts and commissions (Note 18). In January 2017, the Company completed a follow-on offering of its common stock at a public offering price of $7.00 per share. The offering consisted of 3,571,429 shares of common stock sold by the Company. The Company received net proceeds from the follow-on offering of $23,464 after deducting underwriting discounts, commissions and expenses (Note 18).

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2016

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses, including clinical trials, and the valuation of common stock and stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Cash Equivalents

The Company considers all short-term, highly liquid investments with original maturities of ninety days or less at date of purchase to be cash equivalents. Cash equivalents, which primarily consist of money market accounts, are stated at fair value.

Revenue Recognition

The Company recognizes revenue when the following four criteria are met in accordance with Accounting Standards Codification (“ASC”) 605, Revenue Recognition: persuasive evidence of a sales arrangement exists; delivery of goods has occurred through transfer of title and risk and rewards of ownership; the selling price is fixed or determinable; and collectability is reasonably assured.

The Company records revenue from product sales net of applicable provisions for returns, chargebacks, discounts, wholesaler management fees, government and commercial rebates, and other applicable allowances in the same period in which the related sales are recorded, based on the underlying contract terms.

The Company analyzes multiple-element arrangements based on the guidance in ASC Topic 605-25, Revenue Recognition—Multiple-Element Arrangements (“ASC 605-25”). Pursuant to this guidance, the Company evaluates multiple-element arrangements to determine (1) the deliverables included in the arrangement and (2) whether the individual deliverables represent separate units of accounting or whether they must be accounted for as a combined unit of accounting. This evaluation involves subjective determinations and requires management to make judgments about the individual deliverables and whether such deliverables are separable from the other aspects of the contractual relationship. Deliverables are considered separate units of accounting provided that: the delivered item has value to the customer on a standalone basis and, if the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item is considered probable and substantially in the control of the Company. In assessing whether an item has standalone value, the Company considers factors such as the research, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can use the other deliverables for their intended purpose without the receipt of the remaining elements, whether the value of the deliverable is dependent on the undelivered items and whether there are other vendors that can provide the undelivered elements.

Arrangement consideration that is fixed or determinable is allocated among the separate units of accounting using the relative selling price method. Then, the applicable revenue recognition criteria in ASC 605 are applied to each of the separate units of accounting in determining the appropriate period and pattern of recognition. The Company determines the selling price of a unit of accounting following the hierarchy of evidence prescribed by ASC 605-25. Accordingly, the Company determines the estimated selling price for units of accounting within each arrangement using vendor-specific objective evidence (“VSOE”) of selling price, if available; third-party evidence (“TPE”) of selling price, if VSOE is not available; or best estimate of selling price (“BESP”), if neither VSOE nor TPE is available. The Company typically uses BESP to estimate the selling price as it generally does not have VSOE or TPE of selling price for its units of accounting. Determining the BESP for a unit of accounting requires significant judgment. In developing the BESP for a unit of accounting, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the BESP for units of accounting by evaluating whether changes in the key assumptions used to determine the BESP will have a significant effect on the allocation of arrangement consideration between multiple units of accounting.

The Company recognizes arrangement consideration allocated to each unit of accounting when all of the revenue recognition criteria in ASC 605 are satisfied for that particular unit of accounting. The Company will recognize as revenue arrangement consideration attributed to licenses that have standalone value relative to the other deliverables to be provided in an arrangement upon delivery. The Company will recognize as revenue arrangement consideration attributed to licenses that do not have standalone value relative to the other deliverables to be provided in an arrangement over the Company’s estimated performance period, as the arrangement would be accounted for as a single unit of accounting.

At the inception of an arrangement that includes milestone payments, the Company evaluates whether each milestone is substantive and at risk to both parties on the basis of the contingent nature of the milestone. This evaluation includes an assessment of whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance, and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone and the level of effort and investment required to achieve the respective milestone in making this assessment. There is considerable judgment involved in determining whether a milestone satisfies all of the criteria required to conclude that a milestone is substantive. Accordingly, pursuant to the guidance of ASC Topic 605-28, Revenue Recognition—Milestone Method (“ASC 605-28”), revenue from milestone payments will be recognized in its entirety upon successful accomplishment of the milestone, assuming all other revenue recognition criteria are met.

Other contingent, event-based payments received for which payment is either contingent solely upon the passage of time or the results of a collaborative partner’s performance would not be considered milestones under ASC 605-28. In accordance with ASC 605-25, such payments will be recognized as revenue when all of the four basic revenue recognition criteria are met.

Whenever the Company determines that an element is delivered over a period of time, revenue is recognized using either a proportional performance model or a straight-line model over the period of performance. At each reporting period, the Company reassesses its cumulative measure of performance and makes appropriate adjustments, if necessary. The Company recognizes revenue using the proportional performance model whenever the Company can make reasonably reliable estimates of the level of effort required to complete its performance obligations under an arrangement. Revenue recognized under the proportional performance model at each reporting period is determined by multiplying the total expected payments under the contract (excluding payments contingent upon achievement of milestones) by the ratio of the level of effort incurred to date to the estimated total level of effort required to complete the performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the proportional performance model as of each reporting period. Alternatively, if the Company cannot make reasonably reliable estimates the level of effort required to complete its performance obligations under an arrangement, then revenue under the arrangement is recognized on a straight-line basis over the period expected to complete the Company’s performance obligations. If and when a contingent milestone payment is earned, the additional consideration to be received is added to the total expected payments under the contract. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined on a straight-line basis as of the period end date. If the Company cannot reasonably estimate when its performance obligation period ends, then revenue is deferred until the Company can reasonably estimate when the performance obligation period ends.

Inventory Valuation

Inventory is valued at the lower of cost or market, determined by the first-in, first-out (“FIFO”) method.

Prior to approval by the Food and Drug Administration (“FDA”) or other regulatory agencies of the Company’s products, the Company expenses inventory costs in the period incurred as research and development expenses. After such time as the product receives approval, the Company begins to capitalize the inventory costs related to the product. The Company also reviews its inventories for potential obsolescence.

Inventory consisted of the following:


	December 31,
	2016		2015
Raw materials	$	58	$	75
Work-in-process		40		41
Finished goods		15		18
	$	113	$	134

Restricted Cash

As of December 31, 2016 and 2015, the Company held a certificate of deposit of $1,728 and $228, respectively, as security deposits for the lease of the Company’s current and future corporate headquarters (Note 13). The Company has classified this as long-term restricted cash on its balance sheet.

Concentration of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents and marketable securities. The Company has all cash and cash equivalents and marketable securities balances at one accredited financial institution, in amounts that exceed federally insured limits. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company is dependent on a small number of third-party manufacturers to supply products for research and development activities in its preclinical and clinical programs and for sales of its ReSure Sealant product. The Company’s development programs as well as revenue from future sales of ReSure Sealant could be adversely affected by a significant interruption in the supply of any of the components of these products.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level 1—Quoted prices in active markets for identical assets or liabilities.

Level 2—Observable inputs (other than Level 1 quoted prices) such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents and marketable securities are carried at fair value determined according to the fair value hierarchy described above (Note 3). The carrying value of accounts receivable, accounts payable and accrued expenses approximate their fair value due to the short-term nature of these assets and liabilities. At December 31, 2016 and 2015, the carrying value of the Company’s outstanding notes payable (Note 7) approximates fair value of a level 2 reflecting interest rates currently available to the Company.

Marketable Securities

The Company’s marketable securities are classified as available-for-sale and are carried at fair value with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Realized gains and losses and declines in value judged to be other than temporary are included as a component of other income (expense), net based on the specific identification method. Fair value is determined based on quoted market prices.

At December 31, 2016, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	35,216	$	1	$	(8)	$	35,209
Total	$	35,216	$	1	$	(8)	$	35,209

At December 31, 2015, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	44,587	$	—	$	(53)	$	44,534
Agency bonds		29,761		—		(15)		29,746
Total	$	74,348	$	—	$	(68)	$	74,280

At December 31, 2016, marketable securities consisted of investments that mature within one year.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over a three- to five-year estimated useful life. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Expenditures for repairs and maintenance of assets are charged to expense as incurred. Upon retirement or sale, the cost and related accumulated depreciation of assets disposed of are removed from the accounts and any resulting gain or loss is included in loss from operations.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows.

Research and Development Costs

Research and development costs are expensed as incurred. Included in research and development expenses are salaries, stock-based compensation and benefits of employees and other operational costs related to the Company’s research and development activities, including external costs of outside vendors engaged to conduct preclinical studies and clinical trials, manufacturing costs of the Company’s products prior to regulatory approval, costs related to collaboration agreements and facility-related expenses.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the United States. Certain of these agreements have cancellation clauses, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are recorded as general and administrative expenses as incurred, as recoverability of such expenditures is uncertain.

Accounting for Stock-Based Compensation

The Company measures all stock options and other stock-based awards granted to employees and directors at the fair value on the date of the grant using the Black-Scholes option-pricing model. The fair value of the awards is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions.

For stock-based awards granted to consultants and non-employees, compensation expense is recognized over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is re-measured using the then-current fair value of the Company’s common stock and updated assumption inputs in the Black-Scholes option-pricing model.

The Company classifies stock-based compensation expense in its statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre-vesting forfeitures for service-based awards. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual forfeiture rate is materially different from the Company’s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Segment Data

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on advancing its bioresorbable hydrogel-based product candidates for the sustained delivery of therapeutic agents, specifically for ophthalmology. All tangible assets are held in the United States.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the year ended December 31, 2016 comprehensive loss included a $63 unrealized gain on marketable securities. For the year ended December 31, 2015, comprehensive loss included a $68 unrealized loss on marketable securities. For the year ended December 31, 2014, there was no difference between net loss and comprehensive loss.

Net Income (Loss) Per Share

Prior to the closing of its IPO of common stock, the Company followed the two-class method when computing net income (loss) per share, as the Company had outstanding shares that met the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) attributable to common stockholders is computed by adjusting income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities, including outstanding stock options, unvested restricted common stock, common stock warrants and warrants for the purchase of Redeemable Preferred Stock. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock options, common stock warrants and unvested restricted common stock.

The Company’s Redeemable Preferred Stock outstanding prior to the IPO, contractually entitled the holders of such shares to participate in dividends but did not contractually require the holders of such shares to participate in losses of the Company. Similarly, restricted stock awards granted by the Company entitle the holder of such awards to dividends declared or paid by the board of directors, regardless of whether such awards are unvested, as if such shares were outstanding common shares at the time of the dividend. However, the unvested restricted stock awards are not entitled to share in the residual net assets (deficit) of the Company. Accordingly, in periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2016, 2015 and 2014.

Recently Issued and Adopted Accounting Pronouncements

In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40). ASU 2014-15 requires management to perform interim and annual assessments of an entity’s ability to continue as a going concern for a one year period subsequent to the date of issuance of its financial statements. An entity must provide certain disclosures if conditions or events raise substantial doubt about the entity’s ability to continue as a going concern. The Company adopted ASU 2014-15 during the fourth quarter of 2016. Adoption did not require additional disclosures in the Company’s financial statements.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), (“ASU 2014-09”). ASU 2014-09 outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a five-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of Effective Date which amends ASU 2014-09. As a result, the standard effective date will be in the first quarter of 2018 with early adoption permitted in the first quarter of 2017.

Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU 2016-08, “Revenue from Contracts with Customers (Topic 606), Principal versus Agent Considerations (Reporting Revenue Gross versus Net),” (“ASU 2016-08”); ASU 2016-10, “Revenue from Contracts with Customers (Topic 606), Identifying Performance Obligations and Licensing,” (“ASU 2016-10”); ASU 2016-12, “Revenue from Contracts with Customers (Topic 606) Narrow-Scope Improvements and Practical Expedients,” (“ASU 2016-12”); and ASU 2016-20, “Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers,” (“ASU 2016-20”), which are intended to provide additional guidance and clarity to ASU 2014-09. The Company must adopt ASU 2016-08, ASU 2016-10, ASU 2016-12 and ASU 2016-20 along with ASU 2014-09 (collectively, the “New Revenue Standards”).

The New Revenue Standards may be applied using one of two retrospective application methods: (1) a full retrospective approach for all periods presented, or (2) a modified retrospective approach that presents a cumulative effect as of the adoption date and additional required disclosures. The Company expects to adopt the New Revenue Standards in the first quarter of 2018 using the modified retrospective approach and is in the process of completing its initial analysis identifying the revenue that will be impacted by the adoption of this new standard and the impact to its financial statements and footnote disclosures.

In February 2016, the FASB issued ASU No. 2016-02, Leases (ASC 842) (“ASU 2016-02”). ASU 2016-02 requires lessees to recognize most leases on the balance sheet. This is expected to increase both reported assets and liabilities. The new lease standard does not substantially change lessor accounting. For public companies, the standard will be effective for the first interim reporting period within annual periods beginning after December 15, 2018, although early adoption is permitted. Lessees and lessors will be required to apply the new standard at the beginning of the earliest period presented in the financial statements in which they first apply the new guidance, using a modified retrospective transition method. The requirements of this standard include a significant increase in required disclosures. The Company is currently assessing the impact that adopting this new accounting guidance will have on its financial statements and footnote disclosures.

In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (“ASU 2016-09”). ASU 2016-09 identifies areas for simplification involving several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the statement of cash flows. The amendments in this update will be effective for the first interim period within annual reporting periods beginning after December 15, 2016. Early adoption is permitted. The Company is currently assessing the impact that adopting this new accounting guidance will have on its financial statements and footnote disclosures.

In August 2016, the FASB issued Accounting Standards Update No. 2016-15, Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 is intended to clarify guidance on the classification of certain cash receipts and payments in the statement of cash flows and to eliminate the diversity in practice related to such classifications. The guidance in ASU 2016-15 is required for annual reporting periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the potential impact of the adoption of ASU 2016-15 on its statement of cash flows.

In November 2016, the FASB issued ASU 2016-18, “Statement of Cash Flows (Topic 230) - Restricted Cash,” (ASU 2016-18). ASU 2016-18 requires a statement of cash flows to explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of- period total amounts shown on the statement of cash flows. The effective date will be the first quarter of fiscal year 2018. The Company is currently assessing the impact that adopting this new accounting guidance will have on its financial statements and footnote disclosures.

Fair Value of Financial Assets and Liabilities

12 Months Ended

Dec. 31, 2016

Fair Value of Financial Assets and Liabilities

Fair Value of Financial Assets and Liabilities

3. Fair Value of Financial Assets and Liabilities

The following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2016 and 2015 and indicate the level of the fair value hierarchy utilized to determine such fair value:


	Fair Value Measurements as of
	December 31, 2016 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	20,734	$	—	$	20,734
Agency bonds		—		8,994		—		8,994
Marketable securities:
United States treasury notes		—		35,209		—		35,209
Total	$	—	$	64,937	$	—	$	64,937


	Fair Value Measurements as of
	December 31, 2015 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	29,879	$	—	$	29,879
Marketable securities:
United States treasury notes		—		44,534		—		44,534
Agency bonds		—		29,746		—		29,746
Total	$	—	$	104,159	$	—	$	104,159

During the years ended December 31, 2016, 2015 and 2014, there were no transfers between Level 1, Level 2 and Level 3.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, net

12 Months Ended

Dec. 31, 2016

Property and Equipment, net

Property and Equipment, net

4. Property and Equipment, net

Property and equipment, net consisted of the following:


	December 31,
	2016		2015
Equipment	$	4,361	$	3,359
Leasehold improvements		906		894
Furniture and fixtures		418		403
Software		89		54
Construction in progress		1,357		1,324
		7,131		6,034
Less: Accumulated depreciation		(3,818)		(2,939)
	$	3,313	$	3,095

Depreciation expense was $881, $754 and $547 for the years ended December 31, 2016, 2015 and 2014, respectively.

For the year ended December 31, 2016, the construction in progress is related to the build-out of the Company’s new facility and equipment that will be used in that facility. For the years ended December 31, 2015 and 2014 the construction in progress is related to the build-out of an aseptic manufacturing suite clean room.

For the year ended December 31, 2016, the Company wrote off $1,263 of manufacturing equipment that was included in construction in progress at December 31, 2015.

Accrued Expenses and Deferred Rent

12 Months Ended

Dec. 31, 2016

Accrued Expenses and Deferred Rent

Accrued Expenses and Deferred Rent

5. Accrued Expenses and Deferred Rent

Accrued expenses consisted of the following:


	December 31,
	2016		2015
Accrued payroll and related expenses	$	2,146	$	1,582
Accrued professional fees		1,018		471
Accrued research and development expenses		360		430
Accrued insurance		591		389
Accrued other		520		507
	$	4,635	$	3,379

Collaboration and Feasibility Agreements	12 Months Ended
Collaboration and Feasibility Agreements	Dec. 31, 2016
Collaboration and Feasibility Agreements
Collaboration and Feasibility Agreements	6. Collaboration and Feasibility Agreements The Company had a feasibility agreement with a biopharmaceutical company entered into in 2013. Under this agreement, the biopharmaceutical company agreed to pay up to $500 for completing certain tasks and achieving certain milestones. In the event that the agreement was terminated in advance of the completion of the tasks or achievement of the milestones, the Company would have been required to refund portions of the amounts received, based on the actual work completed or milestones achieved as of the date of termination. In 2014, the Company completed the tasks related to the first milestone at which time $250 became non-refundable, therefore the Company recorded revenue of $250. The biopharmaceutical company has indicated that they will not proceed with the second phase of the agreement. The Company does not have any further obligations in connection with this agreement and no further payments will be received. The Company had entered into a feasibility agreement with a biotechnology company in October 2014. Under this agreement, the biotechnology company would pay up to $700, of which $250 was a non-refundable payment due upon contract execution and $450 will be due upon the achievement of certain milestones. The Company recognized the total expected payments under the contract which included only the non-refundable payments on a straight-line basis over the estimated performance period. When a contingent milestone payment was earned, the additional consideration to be received was added to the total expected payments under the contract then recognized over the estimated performance period. In January 2015, the first milestone under the feasibility agreement was achieved triggering a non-refundable payment due of $250 such that the total non-refundable payments that were recognized over the estimated performance period totaled $500. This agreement was terminated in the second quarter of 2016 and the Company does not have any further obligations. The Company recognized revenue of $42, $396 and $63 for the years ended December 31, 2016, 2015 and 2014, respectively. As of December 31, 2016, the Company had no deferred revenue and no accounts receivable related to this agreement. As of December 31, 2015, the Company had deferred revenue of $42 and no accounts receivable related to this agreement. On October 10, 2016, the Company entered into a Collaboration, Option and License Agreement (the “Collaboration Agreement”) with Regeneron Pharmaceuticals, Inc. (“Regeneron”) for the development and potential commercialization of products containing the Company’s sustained-release hydrogel depot in combination with Regeneron’s large molecule VEGF-targeting compounds for the treatment of retinal diseases. The Collaboration Agreement does not cover the development of any products that deliver small molecule drugs, including TKIs, or deliver large molecule drugs other than those that target VEGF proteins. Under the terms of the Collaboration Agreement, the Company and Regeneron have agreed to conduct a joint research program with the aim of developing a sustained-release formulation of aflibercept, currently marketed under the tradename Eylea, that is suitable for advancement into clinical development. The Company has granted Regeneron an option (the “Option”) to enter into an exclusive, worldwide license to develop and commercialize products containing the Company’s sustained-release hydrogel depot in combination with Regeneron’s large molecule VEGF-targeting compounds (“Licensed Products”). If the Option is exercised, Regeneron will conduct further preclinical development and an initial clinical trial under a collaboration plan. The Company is obligated to reimburse Regeneron for certain development costs incurred by Regeneron under the collaboration plan during the period through the completion of the initial clinical trial, subject to a cap of $25,000, which cap may be increased by up to $5,000 under certain circumstances. If Regeneron elects to proceed with further development following the completion of the collaboration plan, it will be solely responsible for conducting and funding further development and commercialization of product candidates. If the Option is exercised, Regeneron is required to use commercially reasonable efforts to research, develop and commercialize at least one Licensed Product. Such efforts shall include initiating the dosing phase of a subsequent clinical trial within specified time periods following the completion of the first-in-human clinical trial or the initiation of preclinical toxicology studies, subject to certain extensions. Under the terms of the Collaboration Agreement, Regeneron has agreed to pay the Company $10,000 upon the exercise of the Option. The Company is also eligible to receive up to $145,000 per Licensed Product upon the achievement of specified development and regulatory milestones, $100,000 per Licensed Product upon first commercial sale of such Licensed Product and up to $50,000 based on the achievement of specified sales milestones for all Licensed Products. In addition, the Company is entitled to tiered, escalating royalties, in a range from a high-single digit to a low-to-mid teen percentage of net sales of Licensed Products.

Notes Payable

12 Months Ended

Dec. 31, 2016

Notes Payable

Notes Payable

7. Notes Payable

The Company entered into a credit and security agreement in 2014 (the “2014 Credit Facility”) which had a total borrowing capacity of $15,000 which was fully drawn down. As part of the 2014 Credit Facility a previously outstanding credit agreement issued in 2011 (the “2011 Credit Facility”) was terminated. Additional capacity of $5,000 available to be drawn down under the 2014 Credit Facility was not drawn down and this additional capacity is no longer available to the Company. Promissory notes issued under the 2014 Credit Facility were to mature on April 1, 2018 and were collateralized by substantially all of the Company’s personal property, other than its intellectual property. There were no financial covenants associated with the 2014 Credit Facility; however, there were negative covenants restricting the Company’s activities, including limitations on dispositions, mergers or acquisitions; encumbering its intellectual property; incurring indebtedness or liens; paying dividends; making certain investments; and engaging in certain other business transactions. The obligations under the 2014 Credit Facility were subject to acceleration upon the occurrence of specified events of default, including a material adverse change in the Company’s business, operations or financial or other condition.

The Company was obligated to make monthly, interest-only payments until September 30, 2015 and, thereafter, to pay 30 consecutive, equal monthly installments of principal from October 1, 2015 through March 1, 2018 plus interest. The loan under the 2014 Credit Facility bears interest at an annual rate of 8.25%. In addition, a final payment equal to 3.75% of amounts drawn under the 2014 Credit Facility was due upon its maturity date. This amount was being accreted to the carrying value of the debt, using the effective interest method. In connection with the draw-down in 2014, the lenders received warrants to purchase 100,000 shares of the Company’s Series D-1 redeemable convertible preferred stock with an exercise price of $3.00 per share, which are exercisable until April 2021. The fair value of the warrants as of the issuance date totaling $326 was recorded as a preferred stock warrant liability. Of this amount, $290 was allocated to the 2014 Credit Facility and recorded as debt discount and $36 was allocated to the 2011 Credit Facility and recorded as loss on extinguishment of debt (see below). The effective annual interest rate of the outstanding debt under the 2014 Credit Facility was 11%.

The terms of the 2014 Credit Facility required that the existing outstanding borrowings be repaid. Accordingly, on April 17, 2014, the Company repaid $1,898 then due under the 2011 Credit Facility, consisting of $1,667 of principal, $6 of interest and $225 of a final payment. The Company accounted for the termination of the 2011 Credit Facility as an extinguishment in accordance with the guidance in ASC 470-50, Debt. The total amount of unamortized debt discount of $10 was reflected as a loss on extinguishment of debt and included in other expense within the statements of operations and comprehensive loss in 2014. Additionally, fees paid to the lenders that were allocated to the existing debt and treated as an extinguishment, inclusive of the value of warrants issued and debt issuance costs paid, totaling $47, were also reflected as a loss on extinguishment of debt included in other expense within the statements of operations and comprehensive loss in 2014.

In December 2015, the 2014 Credit Facility was amended (the “Amended 2014 Credit Facility”) to increase the aggregate principal amount to $15,600 and extend both the interest-only payment period and the maturity date. At the time of the amendment, the Company had $13,500 in outstanding principal. Net proceeds from the amended 2014 Credit Facility were $1,897. The Company is obligated to make monthly interest-only payments under the Amended 2014 Credit Facility until December 31, 2016 and, thereafter, are required to make monthly payments of principal and interest from January 1, 2017 through December 1, 2019. The interest rate under the Amended 2014 Credit Facility is unchanged at an annual rate of 8.25%. In addition, a final payment equal to 3.75% of amounts drawn under the Amended 2014 Credit Facility is due upon the new maturity date. There are no financial covenants associated with the Amended 2014 Credit Facility and the negative covenants remain unchanged. The Company accounted for the amendment of the Amended 2014 Credit Facility as a modification in accordance with the guidance in ASC 470-50, Debt. Amounts paid to the lenders were recorded as debt discount and a new effective interest rate was established. The effective annual interest rate of the outstanding debt under the Amended 2014 Credit Facility is 10.6%.

As of December 31, 2016, the annual repayment requirements for the Amended 2014 Credit Facility, inclusive of the final payment of $585 due at expiration and after consideration of the 2017 refinancing discussed below, were as follows:


			Interest and
			Final
Year Ending December 31,	Principal		Payment		Total
2017		1,300		1,423		2,723
2018		5,294		1,339		6,633
2019		6,353		819		7,172
2020		2,653		919		3,572
	$	15,600	$	4,500	$	20,100

In March 2017, the Company amended the terms of its debt with existing lenders and increased the total commitment to $38.0 million including borrowings of $18,000 drawn at closing, which was used primarily to pay-off outstanding balances as of the closing date, and options on two additional tranches of $10,000 each contingent upon the achievement by the Company of regulatory and commercial milestones related to DEXTENZA. (Note 18) The interest only period was extended through February 1, 2018. Given the debt was refinanced prior to the issuance of the 2016 financial statements, the Company has classified the debt balance at December 31, 2016, with the exception of payments made prior to the refinancing, as long-term in accordance with the terms of the 2017 amended agreement.

Warrants	12 Months Ended
Warrants	Dec. 31, 2016
Warrants
Warrants	8. Warrants Upon the closing of the Company’s IPO in July 2014, the Company’s outstanding preferred stock warrants for the purchase of 236,836 shares of preferred stock were converted to warrants for the purchase of 89,708 shares of common stock at a weighted average exercise price of $6.32 per share. During the year ended December 31, 2016, no warrants were exercised. During the year ended December 31, 2015, warrants for 70,769 shares of common stock were exercised via net share settlement resulting in the issuance of 54,010 shares of common stock as a result of the exercise. Warrants for the purchase of 18,939 shares of common stock remain outstanding at December 31, 2016 at a weighted average exercise price of $7.92 per share and an expiration date of April 17, 2021.

Redeemable Convertible Preferred Stock	12 Months Ended
Redeemable Convertible Preferred Stock	Dec. 31, 2016
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	9. Redeemable Convertible Preferred Stock Prior to the Company’s IPO, the Company had issued Series A, Series B, Series C, Series D and Series D-1 redeemable convertible preferred stock (collectively, the “Redeemable Preferred Stock”). The Redeemable Preferred Stock was classified outside of stockholders’ equity (deficit) because the shares contained redemption features that were not solely within the control of the Company. On July 10, 2014, the Company effected a 1-for-2.64 reverse stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of Redeemable Preferred Stock. Accordingly, all share and per share amounts for all periods presented in these financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this reverse stock split and adjustment of the preferred stock conversion ratios. Upon the closing of the Company’s IPO in July 2014, all outstanding shares of the Company’s Redeemable Preferred Stock were converted into 12,440,205 shares of common stock.

Common Stock and Preferred Stock	12 Months Ended
Common Stock and Preferred Stock	Dec. 31, 2016
Common Stock and Preferred Stock
Common Stock and Preferred Stock	10. Common Stock and Preferred Stock On July 30, 2014, the Company adopted an amended and restated certificate of incorporation increasing the number of its authorized shares of its common stock to 100,000,000 shares. In conjunction with the IPO and the amended and restated certificate of incorporation, the Company is authorized to issue 5,000,000 shares of preferred stock, $0.0001 par value, all of which is undesignated. On August 19, 2014, the Company completed the sale of an additional 750,000 shares of common stock at the initial public offering price of $13.00 per share to the underwriters of the Company’s IPO pursuant to the exercise of their over-allotment option. The Company received additional net proceeds of $9,068 after deducting underwriting discounts and offering costs. In June 2015, the Company completed a follow-on offering of its common stock at a public offering price of $22.00 per share. The offering consisted of 4,600,000 shares of common stock, of which 3,200,000 shares were issued and sold by the Company and 1,400,000 shares were sold by certain stockholders of the Company, including those shares sold in connection with the exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds from the follow-on offering of $65,612 after deducting underwriting discounts and offering expenses. In November 2016, the Company entered into the 2016 ATM Agreement with Cantor, under which the Company may offer and sell its common stock having aggregate proceeds of up to $40,000 from time to time. During the fourth quarter of 2016, the Company sold 102,077 shares of common stock under the 2016 ATM Agreement at a weighted average exercise price of $8.80 per share resulting in net proceeds of approximately $600 after underwriting discounts, commission and other offering expenses. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. As of December 31, 2016, the Company had reserved 4,719,717 shares of common stock for the exercise of outstanding stock options and the number of shares remaining available for grant under the Company’s 2014 Stock Option Plan, the number of shares available for issuance under the 2014 Employee Stock Purchase Plan (Note 11), and the outstanding warrants to purchase common stock (Note 8).

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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+ Details

Stock-Based Awards

12 Months Ended

Dec. 31, 2016

Stock-Based Awards

Stock-Based Awards

11. Stock-Based Awards

2014 Stock Incentive Plan

The 2014 Stock Incentive Plan (the “2014 Plan”) provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The number of shares initially reserved for issuance under the 2014 Plan was 1,336,907 shares of common stock, which was increased to 2,126,907 on January 1, 2015. The number of shares reserved for issuance may be increased by the number of shares under the 2006 Stock Option Plan (the “2006 Plan”) that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company. The number of shares of common stock that may be issued under the 2014 Plan is subject to increase on the first day of each fiscal year, beginning on January 1, 2015 and ending on December 31, 2024, equal to the least of 1,659,218 shares of the Company’s common stock, 4% of the number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year, and an amount determined by the Company’s board of directors. On January 1, 2016, the number of shares available for issuance under the 2014 Plan increased by 990,012. As of December 31, 2016, 1,346,083 shares remained available for issuance under the 2014 Plan.

As required by the 2006 Plan and 2014 Plan, the exercise price for stock options granted is not to be less than the fair value of common shares as of the date of grant. Prior to the IPO, the value of common stock was determined by the board of directors by taking into consideration its most recently available valuation of common shares performed by management and the board of directors as well as additional factors which might have changed since the date of the most recent contemporaneous valuation through the date of grant.

During the years ended December 31, 2016, 2015 and 2014, the Company granted options to purchase 1,147,025, 680,231 and 753,886 shares of common stock, respectively, to certain employees, consultants and directors. The vesting of most of these awards is time-based and the restrictions typically lapse over three to four years.

2014 Employee Stock Purchase Plan

The Company’s has a 2014 Employee Stock Purchase Plan (the “ESPP”) with a total of 207,402 shares of common stock reserved for issuance under this plan which increased to 232,402 shares of common stock on January 1, 2015. The number of shares of common stock that may be issued under the ESPP will automatically increase on the first day of each fiscal year, commencing on January 1, 2015 and ending on December 31, 2024, in an amount equal to the least of 207,402 shares of the Company’s common stock, 0.5% of the number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year, and an amount determined by the Company’s board of directors. On January 1, 2016, the number of shares available for issuance under the 2014 Plan increased by 123,752. During the years ended December 31, 2016, 2015 and 2014, 66,628, 20,916 and 5,395 shares, respectively were issued under the plan. As of December 31, 2016, 263,215 shares of common stock remain available for issuance.

Stock Option Valuation

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Prior to the Company’s IPO in July 2014, the Company had been a private company and lacked company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. Beginning in 2016, the Company estimates its expected volatility using a weighted average of the historical volatility of its publicly traded peer companies and the volatility of its common stock, and expect to continue to do so until such time as the Company has adequate historical data regarding the volatility of its traded stock price. The expected term of the Company’s stock options to employees has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to nonemployees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

As of December 31, 2016, there were outstanding unvested service-based stock options held by nonemployees for the purchase of 5,985 shares of common stock.

The assumptions that the Company used to determine the fair value of the stock options granted to employees and directors are as follows, presented on a weighted average basis:


	Year Ended
	December 31,
	2016		2015		2014
Risk-free interest rate	1.42	%	1.67	%	2.24	%
Expected term (in years)	6		6		6
Expected volatility	85	%	71	%	77	%
Expected dividend yield	—	%	—	%	—	%

The following table summarizes the Company’s stock option activity:


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Shares Issuable	Exercise		Contractual	Intrinsic
	Under Options	Price		Term	Value
				(In years)
Outstanding as of December 31, 2015	2,115,519	$	12.78	6.9	$	5,897
Granted	1,147,025		6.42
Exercised	(105,114)		1.90
Forfeited	(65,950)		13.72
Outstanding as of December 31, 2016	3,091,480	$	10.77	7.3	$	6,659
Options vested and expected to vest as of December 31, 2016	3,009,110	$	10.74	7.2	$	6,510
Options exercisable as of December 31, 2016	1,569,255	$	9.80	6.0	$	4,365

There was no restricted stock activity in 2016. The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised was $575, $3,192 and $323 during the years ended December 31, 2016, 2015 and 2014, respectively.

The weighted average grant date fair value of stock options granted to employees and directors during the years ended December 31, 2016, 2015, 2014 was $4.52, $18.12 and $6.55 per share, respectively.

Restricted Common Stock

The 2006 and 2014 Plans provide for the award of restricted common stock. The Company has granted restricted common stock with time-based vesting conditions. Unvested shares of restricted common stock may not be sold or transferred by the holder. These restrictions lapse according to the time-based vesting conditions of each award.

The aggregate intrinsic value of restricted stock awards is calculated as the positive difference between the prices paid, if any, of the restricted stock awards and the fair value of the Company’s common stock. The aggregate intrinsic value of restricted stock awards that vested during the years ended December 31, 2016, 2015 and 2014 was $0, $265, and $1,142, respectively.

Stock-based Compensation

The Company recorded stock-based compensation expense related to stock options, vesting of restricted common stock and grants of common stock in the following expense categories of its statements of operations:


	Year Ended December 31,
	2016		2015		2014
Research and development	$	1,900	$	1,589	$	397
Selling and marketing		490		340		68
General and administrative		3,566		2,711		2,179
	$	5,956	$	4,640	$	2,644

As of December 31, 2016, the Company had an aggregate of $10,315 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 2.2 years.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2016

Net Loss Per Share

Net Loss Per Share

12. Net Loss Per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the years ended December 31, 2016, 2015 and 2014:


	Year Ended December 31,
	2016		2015		2014
Numerator:
Net loss	$	(44,703)	$	(39,748)	$	(28,648)
Accretion of redeemable convertible preferred stock to redemption value		—		—		(11)
Net loss attributable to common stockholders	$	(44,703)	$	(39,748)	$	(28,659)
Denominator:
Weighted average common shares outstanding, basic and diluted		24,816,348		23,244,162		10,652,865
Net loss per share attributable to common stockholders, basic and diluted	$	(1.80)	$	(1.71)	$	(2.69)

The Company excluded the following common stock equivalents, outstanding as of December 31, 2016, 2015, and 2014, from the computation of diluted net loss per share attributable to common stockholders for the years ended December 31, 2016, 2015 and 2014 because they had an anti-dilutive impact due to the net loss attributable to common stockholders incurred for the periods.


	December 31,
	2016	2015	2014
Options to purchase common stock	3,091,480	2,115,519	1,611,991
Non-vested restricted common stock	—	—	28,437
Warrants for the purchase of common stock	18,939	18,939	89,708
	3,110,419	2,134,458	1,730,136

Commitments and Contingencies

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies.

Commitments and Contingencies

13. Commitments and Contingencies

Leases

The Company leases office, laboratory and manufacturing space in Bedford, Massachusetts and certain office equipment under non-cancelable operating leases that expire in June 2017, June 2018 and July 2027.

Future minimum lease payments for its operating leases as of December 31, 2016 are as follows:


Year Ending December 31,
2017	$	1,162
2018		1,461
2019		1,235
2020		1,270
2021		1,305
Thereafter		7,940
Total	$	14,373

During the years ended December 31, 2016, 2015 and 2014, the Company recognized $1,084, $778 and $649, respectively, of rental expense, related to its office, laboratory and manufacturing space and office equipment.

On June 17, 2016, the Company entered into a lease agreement for approximately 70,712 square feet of general office, research and development and manufacturing space in Bedford, Massachusetts. The lease term will commence on February 1, 2017 and expire on July 31, 2027. No base rent will be due under the lease until August 1, 2017. The initial annual base rent is approximately $1,200 and will increase annually beginning on February 1 of each year. The Company is obligated to pay all real estate taxes and costs related to the premises, including costs of operations, maintenance, repair, and replacement and management of the new leased premises. The Company posted a customary letter of credit in the amount of approximately $1,500 as a security deposit. The Company intends to relocate its corporate headquarters to the new leased premises beginning in 2017 and intends to relocate all of its operations to the new leased premises by 2018. The lease agreement allows for a landlord provided construction allowance not to exceed approximately $2,800 to be applied to the total construction costs of the new leased premises. The construction allowance must be used on or before December 31, 2017, or it will be deemed forfeited with no further obligation by the landlord of the new leased premises.

Intellectual Property Licenses

The Company has a license agreement with Incept, LLC (“Incept”) (Note 16) to use and develop certain patent rights (the “Incept License”). Under the Incept License, as amended and restated, the Company was granted a worldwide, perpetual, exclusive license to develop and commercialize products that are delivered to or around the human eye for diagnostic, therapeutic or prophylactic purposes relating to ophthalmic diseases or conditions. The Company is obligated to pay low single-digit royalties on net sales of commercial products developed using the licensed technology, commencing with the date of the first commercial sale of such products and until the expiration of the last to expire of the patents covered by the license. Any of the Company’s sublicensees also will be obligated to pay Incept a royalty equal to a low single-digit percentage of net sales made by it and will be bound by the terms of the agreement to the same extent as the Company. The Company is obligated to reimburse Incept for its share of the reasonable fees and costs incurred by Incept in connection with the prosecution of the patent applications licensed to the Company under the Incept License. Through December 31, 2016, royalties paid under this agreement related to product sales were $95.

On February 12, 2014, the Company issued to Incept 189,393 shares of its common stock in connection with the expansion of the scope of the license to include back-of-the-eye technology held by Incept (Note 16).

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management team that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its financial statements as of December 31, 2016.

Purchase Commitments

Purchase commitments represent non-cancelable contractual commitments associated with certain clinical trial activities within the Company’s clinical research organization.

Manufacturing Commitments

Manufacturing contracts generally provide for termination on notice, and therefore are cancelable contracts but are contracts that the Company is likely to continue, regardless of the fact that they are cancelable.

Collaboration Agreement

On October 10, 2016, the Company entered into a Collaboration Agreement with Regeneron (Note 6). If the Option to enter into an exclusive worldwide license is exercised, Regeneron will conduct further preclinical development and an initial clinical trial under a collaboration plan. The Company is obligated to reimburse Regeneron for certain development costs incurred by Regeneron under the collaboration plan during the period through the completion of the initial clinical trial, subject to a cap of $25,000, which cap may be increased by up to $5,000 under certain circumstances, the timing of such payments are not known. If Regeneron elects to proceed with further development following the completion of the collaboration plan, it will be solely responsible for conducting and funding further development and commercialization of product candidates. If the Option is exercised, Regeneron is required to use commercially reasonable efforts to research, develop and commercialize at least one Licensed Product. Such efforts shall include initiating the dosing phase of a subsequent clinical trial within specified time periods following the completion of the first-in-human clinical trial or the initiation of preclinical toxicology studies, subject to certain extensions. Through December 31, 2016, the Option has not been exercised and no payments have been made to Regeneron.

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Taxes

Income Taxes

14. Income Taxes

During the years ended December 31, 2016, 2015 and 2014, the Company recorded no income tax benefits for the net operating losses incurred in each year or interim period, due to its uncertainty of realizing a benefit from those items.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2016		2015		2014
Federal statutory income tax rate	(34.0)	%	(34.0)	%	(34.0)	%
Federal and state research and development tax credit	(2.9)		(3.1)		(2.5)
State taxes, net of federal benefit	(4.8)		(2.0)		(4.6)
Stock-based compensation	1.4		1.2		1.6
Other	(0.6)		(0.2)		0.8
Change in deferred tax asset valuation allowance	40.9		38.1		38.7
Effective income tax rate	—	%	—	%	—	%

Net deferred tax assets consisted of the following:


	December 31,
	2016		2015
Net operating loss carryforwards	$	31,960	$	22,554
Research and development tax credit carryforwards		5,482		4,052
Capitalized start-up costs		1,723		1,915
Capitalized research and development expenses, net		26,943		21,357
Accrued expenses and other temporary differences		4,128		2,091
Total gross deferred tax assets		70,236		51,969
Valuation allowance		(70,236)		(51,969)
Net deferred tax assets	$	—	$	—

Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2016, 2015 and 2014 related primarily to the increase in net operating loss carryforwards, capitalized research and development expenses and research and development tax credit carryforwards and were as follows:


	Year Ended December 31,
	2016		2015		2014
Valuation allowance as of beginning of year	$	51,969	$	36,825	$	25,776
Decreases recorded as benefit to income tax provision		—		—		—
Increases recorded to income tax provision		18,267		15,144		11,049
Valuation allowance as of end of year	$	70,236	$	51,969	$	36,825

As of December 31, 2016, the Company had net operating loss carryforwards for federal and state income tax purposes of $85,246 and $73,876, respectively, which begin to expire in 2026 and 2029, respectively. Included in the federal and state net operating loss carryforwards are approximately $2,029 of deductions related to the exercise of stock options for which the tax benefit will be realized when it results in the reduction of cash income tax in accordance with ASC 718. As of December 31, 2016, the Company also had available research and development tax credit carryforwards for federal and state income tax purposes of $4,085 and $2,116, respectively, which begin to expire in 2026 and 2025, respectively. Utilization of the net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company has not conducted a study to assess whether a change of control has occurred or whether there have been multiple changes of control since inception due to the significant complexity and cost associated with such a study. If the Company has experienced a change of control, as defined by Section 382, at any time since inception, utilization of the net operating loss carryforwards or research and development tax credit carryforwards would be subject to an annual limitation under Section 382, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and development tax credit carryforwards before utilization. Further, until a study is completed and any limitation is known, no amounts are being presented as an uncertain tax position.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets, including the Company’s history of cumulative net losses incurred since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2016 and 2015. Management reevaluates the positive and negative evidence at each reporting period.

The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2016 or 2015.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years are still open under statute from December 31, 2013 to the present. Earlier years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision.

401(k) Savings Plan	12 Months Ended
401(k) Savings Plan	Dec. 31, 2016
401(k) Savings Plan
401(k) Savings Plan	15. 401(k) Savings Plan The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. Company contributions to the plan may be made at the discretion of the board of directors. Through December 31, 2016, no contributions have been made to the plan by the Company.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2016
Related Party Transactions
Related Party Transactions	16. Related Party Transactions The Company has a license agreement with Incept to use and develop certain patent rights that it entered into in 2007. Royalties incurred and payable to Incept have not been material to date. On February 12, 2014, the Company issued 189,393 shares of its common stock to Incept in connection with the expansion of the scope of the Incept License to include back-of-the eye technology held by Incept. The fair value of the shares of $1,665 as of the issuance date was recorded as research and development expense. Incept and certain owners of Incept participated in the Company’s Series A, Series B and Series C preferred stock financing and have also been granted shares of common stock and redeemable convertible preferred stock of the Company. In addition, certain employees of the Company are shareholders of Incept. The Company’s President and Chief Executive Officer is a general partner of Incept. On February 12, 2014, the Company issued 79,545 shares of common stock to a former member of the Company’s board of directors and current stockholder of Incept for consulting services rendered. The fair value of the shares of $699 as of the issuance date was recorded as general and administrative expense. During the years ended December 31, 2016, 2015 and 2014, the Company invoiced Augmenix, Inc. (“Augmenix”) $0, $4 and $82, respectively, for consulting and other services. During the years ended December 31, 2016, 2015 and 2014, Augmenix invoiced the Company $0, $0 and $27 for legal fees paid by Augmenix on behalf of the Company. Certain shareholders of Augmenix were holders of the Company’s redeemable convertible preferred stock and common stock which is now entirely common stock. In addition, certain employees of the Company are shareholders of Augmenix. The Company’s President and Chief Executive Officer was also the Chief Executive Officer of Augmenix up until April 2014 and is currently the Chairman of the board of directors of Augmenix. In April 2014, the Company granted 28,437 shares of restricted common stock to its Chief Executive Officer, which grant was in lieu of $250 of the Chief Executive Officer’s 2015 base salary. During 2015, due to an administrative error, the Company did not appropriately adjust the base salary to reflect this reduction. As a result, the Company paid the full base salary for 2015. Upon discovery of the error, the Chief Executive Officer promptly repaid the full $250 to the Company on April 1, 2016. The Company recorded a reduction to payroll expense in the first quarter of 2016. The effect of this error on the statement of operations was considered immaterial for all related periods. In March 2016, the Company entered into a Master Service Agreement with Axtria, Inc. (“Axtria”) in which Axtria will provide certain sales and marketing analytics to the Company. Jaswinder Chadha, co-founder and Chief Executive Officer of Axtria, is also a member of the Company’s Board of Directors and is related to the Company’s President and Chief Executive Officer. Through December 31, 2016, payments paid to Axtria under this agreement were $150 (Note 18). The Company has engaged Wilmer Cutler Pickering Hale and Dorr LLP (“WilmerHale”) to provide certain legal services to the Company. The Company's Chief Medical Officer is married to a partner at WilmerHale, who has not participated in providing legal services to the Company. The Company incurred fees for legal services rendered by WilmerHale of approximately $874 for the year ended December 31, 2016.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2016

Selected Quarterly Financial Data (Unaudited)

Selected Quarterly Financial Data (Unaudited)

17. Selected Quarterly Financial Data (Unaudited)


	Three Months Ended
	Dec. 31,		Sept. 30,		June 30,		Mar 31,		Dec. 31,		Sept. 30,		June 30,		Mar 31,
	2016		2016		2016		2016		2015		2015		2015		2015
Statements of Operations Data:
Product revenue	$	511	$	477	$	441	$	416	$	394	$	388	$	334	$	238
Collaboration revenue		—		—		—		42		42		41		125		188
Revenue		511		477		441		458		436		429		459		426
Loss from operations		(12,472)		(9,238)		(11,107)		(10,509)		(10,275)		(11,174)		(9,635)		(7,113)
Net loss		(12,822)		(9,596)		(11,445)		(10,840)		(10,637)		(11,524)		(10,009)		(7,578)
Net loss attributable to common stockholders		(12,822)		(9,596)		(11,445)		(10,840)		(10,637)		(11,524)		(10,009)		(7,578)
Basic and diluted net loss attributable to common stockholders per share	$	(0.52)	$	(0.39)	$	(0.46)	$	(0.44)	$	(0.43)	$	(0.47)	$	(0.45)	$	(0.35)

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2016
Subsequent Events
Subsequent Events	18. Subsequent Events The number of shares of common stock that may be issued under the 2014 Plan is subject to increase on the first day of each fiscal year, beginning on January 1, 2015 and ending on December 31, 2024, equal to the least of 1,659,218 shares of the Company’s common stock, 4% of the number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year, and an amount determined by the Company’s board of directors. On January 1, 2017, the number of shares available for issuance under the 2014 Plan increased by 1,000,964. The number of shares of common stock that may be issued under the ESPP will automatically increase on the first day of each fiscal year, commencing on January 1, 2015 and ending on December 31, 2024, in an amount equal to the least of 207,402 shares of the Company’s common stock, 0.5% of the number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year, and an amount determined by the Company’s board of directors. On January 1, 2017, the number of shares available for issuance under the ESPP increased by 125,121. In January 2017, the Company sold 161,341 shares of common stock under the 2016 ATM Agreement at a weighted average exercise price of $8.91 per share resulting in net proceeds of approximately $1,400 after underwriting discounts and commissions. In January 2017, the Company completed a follow-on offering of its common stock at a public offering price of $7.00 per share. The offering consisted of 3,571,429 shares of common stock sold by the Company. The Company received net proceeds from the follow-on offering of $23,464 after deducting underwriting discounts, commissions and expenses. In February 2017, the Company entered into statement of work totaling approximately $1,400 in which Axtria will provide data warehouse implementation, operations and maintenance support services to the Company. Jaswinder Chadha, co-founder and Chief Executive Officer of Axtria, is also a member of the Company’s Board of Directors and is related to the Company’s President and Chief Executive Officer (Note 16). In March 2017, the Amended 2014 Credit Facility was amended (the “Amended 2017 Credit Facility”) to increase the total commitment to $38,000, including $18,000 of borrowings drawn at closing, which was used primarily to pay-off outstanding balances as of the closing date, and options on two additional tranches of $10,000, each contingent upon the achievement by the Company of regulatory and commercial milestones related to DEXTENZA. The interest-only payment period was also extended through February 1, 2018 and there are provisions to further extend the interest-only period based on the achievement of certain milestones. Amounts borrowed under the 2017 Amended Credit Facility is at LIBOR base rate, subject to 1.00% floor, plus 7.25% with an indicative interest rate of 8.25% as of the closing date. In addition, a final payment equal to 3.5% of amounts drawn under the Amended 2017 Credit Facility is due upon the new maturity date of December 1, 2020. There are no financial covenants associated with the Amended 2017 Credit Facility and the negative covenants remain unchanged.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2016

Summary of Significant Accounting Policies

Inventory is valued at the lower of cost or market, determined by the first-in, first-out (“FIFO”) method.

Inventory consisted of the following:


	December 31,
	2016		2015
Raw materials	$	58	$	75
Work-in-process		40		41
Finished goods		15		18
	$	113	$	134

Restricted Cash

Concentration of Credit Risk and of Significant Suppliers

Fair Value Measurements

Level 1—Quoted prices in active markets for identical assets or liabilities.

Marketable Securities

At December 31, 2016, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	35,216	$	1	$	(8)	$	35,209
Total	$	35,216	$	1	$	(8)	$	35,209

At December 31, 2015, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	44,587	$	—	$	(53)	$	44,534
Agency bonds		29,761		—		(15)		29,746
Total	$	74,348	$	—	$	(68)	$	74,280

At December 31, 2016, marketable securities consisted of investments that mature within one year.

Property and Equipment

Impairment of Long-Lived Assets

Research and Development Costs

Research Contract Costs and Accruals

Patent Costs

Accounting for Stock-Based Compensation

Income Taxes

Segment Data

Comprehensive Loss

Net Income (Loss) Per Share

Recently Issued and Adopted Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Significant Accounting Policies

Components of Inventories


	December 31,
	2016		2015
Raw materials	$	58	$	75
Work-in-process		40		41
Finished goods		15		18
	$	113	$	134

Summary of Marketable Securities by Security Type

At December 31, 2016, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	35,216	$	1	$	(8)	$	35,209
Total	$	35,216	$	1	$	(8)	$	35,209

At December 31, 2015, marketable securities by security type consisted of:


			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
United States treasury notes	$	44,587	$	—	$	(53)	$	44,534
Agency bonds		29,761		—		(15)		29,746
Total	$	74,348	$	—	$	(68)	$	74,280

Fair Value of Financial Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value of Financial Assets and Liabilities

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis


	Fair Value Measurements as of
	December 31, 2016 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	20,734	$	—	$	20,734
Agency bonds		—		8,994		—		8,994
Marketable securities:
United States treasury notes		—		35,209		—		35,209
Total	$	—	$	64,937	$	—	$	64,937


	Fair Value Measurements as of
	December 31, 2015 Using:
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	—	$	29,879	$	—	$	29,879
Marketable securities:
United States treasury notes		—		44,534		—		44,534
Agency bonds		—		29,746		—		29,746
Total	$	—	$	104,159	$	—	$	104,159

Property and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2016

Property and Equipment, net

Schedule of Property and Equipment net


	December 31,
	2016		2015
Equipment	$	4,361	$	3,359
Leasehold improvements		906		894
Furniture and fixtures		418		403
Software		89		54
Construction in progress		1,357		1,324
		7,131		6,034
Less: Accumulated depreciation		(3,818)		(2,939)
	$	3,313	$	3,095

Accrued Expenses and Deferred Rent (Tables)

12 Months Ended

Dec. 31, 2016

Accrued Expenses and Deferred Rent

Schedule of Accrued Expenses


	December 31,
	2016		2015
Accrued payroll and related expenses	$	2,146	$	1,582
Accrued professional fees		1,018		471
Accrued research and development expenses		360		430
Accrued insurance		591		389
Accrued other		520		507
	$	4,635	$	3,379

Notes Payable (Tables)

12 Months Ended

Dec. 31, 2016

Notes Payable

Schedule of Annual Repayment Requirements for Credit Facility


			Interest and
			Final
Year Ending December 31,	Principal		Payment		Total
2017		1,300		1,423		2,723
2018		5,294		1,339		6,633
2019		6,353		819		7,172
2020		2,653		919		3,572
	$	15,600	$	4,500	$	20,100

Stock-Based Awards (Tables)

12 Months Ended

Dec. 31, 2016

Stock-Based Awards

Schedule of Assumptions Used to Determine Fair Value of Stock Options Granted to Employees and Directors Presented on Weighted Average Basis


	Year Ended
	December 31,
	2016		2015		2014
Risk-free interest rate	1.42	%	1.67	%	2.24	%
Expected term (in years)	6		6		6
Expected volatility	85	%	71	%	77	%
Expected dividend yield	—	%	—	%	—	%

Schedule of Stock Option Activity


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Shares Issuable	Exercise		Contractual	Intrinsic
	Under Options	Price		Term	Value
				(In years)
Outstanding as of December 31, 2015	2,115,519	$	12.78	6.9	$	5,897
Granted	1,147,025		6.42
Exercised	(105,114)		1.90
Forfeited	(65,950)		13.72
Outstanding as of December 31, 2016	3,091,480	$	10.77	7.3	$	6,659
Options vested and expected to vest as of December 31, 2016	3,009,110	$	10.74	7.2	$	6,510
Options exercisable as of December 31, 2016	1,569,255	$	9.80	6.0	$	4,365

Schedule of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock


	Year Ended December 31,
	2016		2015		2014
Research and development	$	1,900	$	1,589	$	397
Selling and marketing		490		340		68
General and administrative		3,566		2,711		2,179
	$	5,956	$	4,640	$	2,644

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2016

Net Loss Per Share

Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders


	Year Ended December 31,
	2016		2015		2014
Numerator:
Net loss	$	(44,703)	$	(39,748)	$	(28,648)
Accretion of redeemable convertible preferred stock to redemption value		—		—		(11)
Net loss attributable to common stockholders	$	(44,703)	$	(39,748)	$	(28,659)
Denominator:
Weighted average common shares outstanding, basic and diluted		24,816,348		23,244,162		10,652,865
Net loss per share attributable to common stockholders, basic and diluted	$	(1.80)	$	(1.71)	$	(2.69)

Schedule of Antidilutive Securities, Excluded from Computation of Diluted Net Loss per Share


	December 31,
	2016	2015	2014
Options to purchase common stock	3,091,480	2,115,519	1,611,991
Non-vested restricted common stock	—	—	28,437
Warrants for the purchase of common stock	18,939	18,939	89,708
	3,110,419	2,134,458	1,730,136

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies.

Summary of Future Minimum Lease Payments for Operating Leases

Future minimum lease payments for its operating leases as of December 31, 2016 are as follows:


Year Ending December 31,
2017	$	1,162
2018		1,461
2019		1,235
2020		1,270
2021		1,305
Thereafter		7,940
Total	$	14,373

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes

Reconciliation of Federal Income Tax Rate


	Year Ended December 31,
	2016		2015		2014
Federal statutory income tax rate	(34.0)	%	(34.0)	%	(34.0)	%
Federal and state research and development tax credit	(2.9)		(3.1)		(2.5)
State taxes, net of federal benefit	(4.8)		(2.0)		(4.6)
Stock-based compensation	1.4		1.2		1.6
Other	(0.6)		(0.2)		0.8
Change in deferred tax asset valuation allowance	40.9		38.1		38.7
Effective income tax rate	—	%	—	%	—	%

Net Deferred Tax Assets


	December 31,
	2016		2015
Net operating loss carryforwards	$	31,960	$	22,554
Research and development tax credit carryforwards		5,482		4,052
Capitalized start-up costs		1,723		1,915
Capitalized research and development expenses, net		26,943		21,357
Accrued expenses and other temporary differences		4,128		2,091
Total gross deferred tax assets		70,236		51,969
Valuation allowance		(70,236)		(51,969)
Net deferred tax assets	$	—	$	—

Changes in Valuation Allowance for Deferred Tax Assets


	Year Ended December 31,
	2016		2015		2014
Valuation allowance as of beginning of year	$	51,969	$	36,825	$	25,776
Decreases recorded as benefit to income tax provision		—		—		—
Increases recorded to income tax provision		18,267		15,144		11,049
Valuation allowance as of end of year	$	70,236	$	51,969	$	36,825

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Selected Quarterly Financial Data (Unaudited)

Schedule of Quarterly Financial Data


	Three Months Ended
	Dec. 31,		Sept. 30,		June 30,		Mar 31,		Dec. 31,		Sept. 30,		June 30,		Mar 31,
	2016		2016		2016		2016		2015		2015		2015		2015
Statements of Operations Data:
Product revenue	$	511	$	477	$	441	$	416	$	394	$	388	$	334	$	238
Collaboration revenue		—		—		—		42		42		41		125		188
Revenue		511		477		441		458		436		429		459		426
Loss from operations		(12,472)		(9,238)		(11,107)		(10,509)		(10,275)		(11,174)		(9,635)		(7,113)
Net loss		(12,822)		(9,596)		(11,445)		(10,840)		(10,637)		(11,524)		(10,009)		(7,578)
Net loss attributable to common stockholders		(12,822)		(9,596)		(11,445)		(10,840)		(10,637)		(11,524)		(10,009)		(7,578)
Basic and diluted net loss attributable to common stockholders per share	$	(0.52)	$	(0.39)	$	(0.46)	$	(0.44)	$	(0.43)	$	(0.47)	$	(0.45)	$	(0.35)

Nature of the Business and Basis of Presentation - Nature of Business (Details) $ in Thousands			1 Months Ended		12 Months Ended
	Mar. 10, 2017 USD ($) tranche	Mar. 10, 2017 USD ($) tranche	Jan. 31, 2017 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Nature of Business
Accumulated deficit					$ 173,879	$ 129,176
Net proceeds from issuance of common stock					$ 872	$ 66,176	$ 69,518
Subsequent Event
Nature of Business
Minimum time period from the issuance date of the financial statements, Company believes it will be able to fund operations, debt service and capital requirements		12 months
Amended 2017 Credit Facility \| Subsequent Event
Nature of Business
Additional borrowings from debt refinance	$ 2,400
Number of tranches \| tranche	2	2
Tranche one, capacity available under debt facility contingent on FDA approval and achievement of certain sales levels of DEXTENZA	$ 10,000	$ 10,000
Tranche two, capacity available under debt facility contingent on FDA approval and achievement of certain sales levels of DEXTENZA	$ 10,000	$ 10,000
Follow-on Offering \| Common Stock
Nature of Business
Net proceeds from issuance of common stock				$ 65,612
Follow-on Offering \| Common Stock \| Subsequent Event
Nature of Business
Net proceeds from issuance of common stock			$ 23,464

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended				3 Months Ended	12 Months Ended
	Aug. 19, 2014	Jul. 30, 2014	Jan. 31, 2017	Nov. 30, 2016	Jun. 30, 2015	Aug. 31, 2014	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Disclosures
Net proceeds from issuance of common stock								$ 872	$ 66,176	$ 69,518
Common Stock
Stock Disclosures
Number of shares issued								102,077	3,200,000	5,750,000
Number of common shares issued on conversion of redeemable convertible preferred stock										12,440,205
IPO \| Common Stock
Stock Disclosures
Number of shares issued		5,000,000
Common stock, price per share		$ 13.00
Net proceeds from issuance of common stock		$ 57,337
Number of common shares issued on conversion of redeemable convertible preferred stock		12,440,205
Over-allotment Option \| Common Stock
Stock Disclosures
Number of shares issued	750,000					750,000
Common stock, price per share	$ 13.00					$ 13.00
Net proceeds from issuance of common stock	$ 9,068					$ 9,068
Follow-on Offering \| Common Stock
Stock Disclosures
Number of shares issued					4,600,000
Common stock, price per share					$ 22.00
Net proceeds from issuance of common stock					$ 65,612
Number of shares offered by company					3,200,000
Number of shares offered by stockholders					1,400,000
Follow-on Offering \| Subsequent Event \| Common Stock
Stock Disclosures
Number of shares issued			3,571,429
Common stock, price per share			$ 7.00
Net proceeds from issuance of common stock			$ 23,464
2016 ATM Agreement \| Common Stock
Stock Disclosures
Number of shares issued							102,077
Net proceeds from issuance of common stock							$ 600
Maximum aggregate proceeds from offering				$ 40,000
2016 ATM Agreement \| Common Stock \| Weighted Average
Stock Disclosures
Common stock, price per share							$ 8.80	$ 8.80
2016 ATM Agreement \| Subsequent Event \| Common Stock
Stock Disclosures
Number of shares issued			161,341
Net proceeds from issuance of common stock			$ 1,400
2016 ATM Agreement \| Subsequent Event \| Common Stock \| Weighted Average
Stock Disclosures
Common stock, price per share			$ 8.91

Summary of Significant Accounting Policies - Inventory Valuation (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Summary of Significant Accounting Policies
Raw materials	$ 58	$ 75
Work-in-process	40	41
Finished goods	15	18
Total inventory	$ 113	$ 134

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash
Certificate of deposit	$ 1,728	$ 228
Certificates of Deposit
Restricted Cash
Certificate of deposit	$ 1,728	$ 228

Summary of Significant Accounting Policies - Summary of Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Marketable Securities
Amortized Cost	$ 35,216	$ 74,348
Gross Unrealized Gains	1
Gross Unrealized Losses	(8)	(68)
Estimated Fair Value	$ 35,209	74,280
Maturity period for marketable securities classified as available-for-sale	1 year
United States Treasury Notes
Marketable Securities
Amortized Cost	$ 35,216	44,587
Gross Unrealized Gains	1
Gross Unrealized Losses	(8)	(53)
Estimated Fair Value	$ 35,209	44,534
Agency Bonds
Marketable Securities
Amortized Cost		29,761
Gross Unrealized Losses		(15)
Estimated Fair Value		$ 29,746

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies
Income tax examination, likelihood of settlement, description	The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement.
Income tax examination, likelihood of settlement, percentage	50.00%
Unrealized gain (loss) on marketable securities	$ 63	$ (68)
Minimum
Summary Of Significant Accounting Policies
Property and equipment, estimated useful life	3 years
Maximum
Summary Of Significant Accounting Policies
Property and equipment, estimated useful life	5 years

Fair Value of Financial Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Marketable securities	$ 35,209	$ 74,280
Recurring Basis
Assets:
Total assets at fair value	64,937	104,159
Recurring Basis \| United States Treasury Notes
Assets:
Marketable securities	35,209	44,534
Recurring Basis \| Agency Bonds
Assets:
Marketable securities		29,746
Money Market Funds \| Recurring Basis
Assets:
Cash equivalents	20,734	29,879
Agency bonds \| Recurring Basis
Assets:
Cash equivalents	8,994
Level 2 \| Recurring Basis
Assets:
Total assets at fair value	64,937	104,159
Level 2 \| Recurring Basis \| United States Treasury Notes
Assets:
Marketable securities	35,209	44,534
Level 2 \| Recurring Basis \| Agency Bonds
Assets:
Marketable securities		29,746
Level 2 \| Money Market Funds \| Recurring Basis
Assets:
Cash equivalents	20,734	$ 29,879
Level 2 \| Agency bonds \| Recurring Basis
Assets:
Cash equivalents	$ 8,994

Fair Value of Financial Assets and Liabilities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value of Financial Assets and Liabilities
Transfers between fair value measurement levels	$ 0	$ 0	$ 0

Property and Equipment, net - Schedule of Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment, net
Property and equipment, gross	$ 7,131	$ 6,034
Less: Accumulated depreciation	(3,818)	(2,939)
Property and equipment, net	3,313	3,095
Depreciation expense	881	754	$ 547
Equipment
Property and Equipment, net
Property and equipment, gross	4,361	3,359
Leasehold Improvements
Property and Equipment, net
Property and equipment, gross	906	894
Furniture and Fixtures
Property and Equipment, net
Property and equipment, gross	418	403
Software
Property and Equipment, net
Property and equipment, gross	89	54
Construction in Progress
Property and Equipment, net
Property and equipment, gross	1,357	$ 1,324
Write off of manufacturing equipment	$ 1,263

Accrued Expenses and Deferred Rent - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Expenses and Deferred Rent
Accrued payroll and related expenses	$ 2,146	$ 1,582
Accrued professional fees	1,018	471
Accrued research and development expenses	360	430
Accrued insurance	591	389
Accrued other	520	507
Total	$ 4,635	$ 3,379

Collaboration and Feasibility Agreements - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended					12 Months Ended
	Oct. 10, 2016	Oct. 31, 2014	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collarboration and Feasibility Agreements
Revenue recognized			$ 42,000	$ 42,000	$ 41,000	$ 125,000	$ 188,000	$ 42,000	$ 396,000	$ 312,000
Deferred revenue				42,000					42,000
Accounts receivable				193,000				250,000	193,000
Feasibility Agreement \| Biopharmaceutical
Collarboration and Feasibility Agreements
Maximum revenue that could be recognized											$ 500
Non-Refundable revenue				250,000					250,000
Revenue recognized									250,000
Feasibility Agreement \| Biotechnology
Collarboration and Feasibility Agreements
Maximum revenue that could be recognized		$ 450,000
Revenue recognized									63,000
Potential agreement revenue		700
Non-Refundable revenue entitled to receive on milestone achievement		$ 250,000
Deferred revenue				$ 42,000					$ 42,000
Accounts receivable								$ 0
Collaboration Agreement \| Regeneron
Collarboration and Feasibility Agreements
Payment receivable upon exercise of option	$ 10,000,000
Collaboration Agreement \| Regeneron \| Maximum
Collarboration and Feasibility Agreements
Reimbursable clinical development costs	25,000,000
Potential increase in reimbursable clinical development costs	5,000,000
Potential payment receivable per Licensed Product upon the achievement of specified development and regulatory milestones	145,000,000
Potential payment receivable per Licensed Product upon first commercial sale of such Licensed Product	100,000,000
Potential payment receivable due for achievement of specified sales milestones for all Licensed Products	$ 50,000,000

Notes Payable - Additional Information (Details)		1 Months Ended	12 Months Ended
Notes Payable - Additional Information (Details)	Apr. 17, 2014 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2014 USD ($) $ / shares shares	Mar. 10, 2017 USD ($) tranche
Subsequent Event
Notes Payable
Outstanding borrowings under credit facility					$ 18,000,000
2014 Credit Facility
Notes Payable
Borrowing capacity under the agreement				$ 15,000
Credit facility, Monthly repayment period				30 consecutive, equal monthly installments
Last installment payment				Mar. 01, 2018
First date of principal repayment				Oct. 01, 2015
Outstanding borrowings, Interest rate				8.25%
Credit facility, Final payment percent of amounts drawn under the facility				3.75%
Warrants to purchase shares of redeemable convertible preferred stock \| shares				100,000
Weighted average exercise price to purchase common stock \| $ / shares				$ 3.00
Warrants, Date from which warrants or rights exercisable				Apr. 30, 2021
Grant date fair value of warrants granted as preferred stock warrant liability				$ 326,000
Debt discount				$ 290,000
Outstanding borrowings, Effective annual interest rate				11.00%
Outstanding borrowings under credit facility		$ 13,500,000
2014 Credit Facility \| Promissory Notes
Notes Payable
Debt instrument, Maturity date				Apr. 01, 2018
2014 Credit Facility \| Tranche 2 Loan
Notes Payable
Borrowing capacity under the agreement				$ 5,000
2011 Credit Facility
Notes Payable
Fair value of warrants relating to loss on extinguishment			$ 36,000
Repayments of debt	$ 1,898,000
Repayments of debt, Principal	1,667,000
Repayments of debt, Interest	6,000
Additional final payment	$ 225,000
2011 Credit Facility \| Extinguishment of Debt
Notes Payable
Debt discount				10,000
Fees paid to lenders				$ 47,000
Amended 2014 Credit Facility
Notes Payable
Borrowing capacity under the agreement		$ 15,600,000
Last installment payment		Dec. 01, 2019
First date of principal repayment		Jan. 01, 2017
Outstanding borrowings, Interest rate		8.25%
Credit facility, Final payment percent of amounts drawn under the facility		3.75%
Outstanding borrowings, Effective annual interest rate		10.60%
Repayments of debt, Principal			15,600,000
Repayments of debt, Interest			4,500,000
Additional final payment			$ 585,000
Net proceeds from credit facility		$ 1,897,000
Amended 2017 Credit Facility \| Subsequent Event
Notes Payable
Borrowing capacity under the agreement					$ 38,000,000
Number of tranches \| tranche					2
Tranche one, amount contingent upon the achievement of regulatory and commercial milestones related to DEXTENZA					$ 10,000,000
Tranche two, amount contingent upon the achievement of regulatory and commercial milestones related to DEXTENZA					$ 10,000,000

Notes Payable - Schedule of Annual Repayment Requirements for Credit Facility (Details) - Amended 2014 Credit Facility $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
Annual repayment requirements
Credit Facility, Principal	$ 15,600
Credit Facility, Interest and Final Payment	4,500
Credit Facility, Total	20,100
2017
Annual repayment requirements
Credit Facility, Principal	1,300
Credit Facility, Interest and Final Payment	1,423
Credit Facility, Total	2,723
2018
Annual repayment requirements
Credit Facility, Principal	5,294
Credit Facility, Interest and Final Payment	1,339
Credit Facility, Total	6,633
2019
Annual repayment requirements
Credit Facility, Principal	6,353
Credit Facility, Interest and Final Payment	819
Credit Facility, Total	7,172
2020
Annual repayment requirements
Credit Facility, Principal	2,653
Credit Facility, Interest and Final Payment	919
Credit Facility, Total	$ 3,572

Warrants - Additional Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jul. 31, 2014
Warrants for Preferred Stock
Warrants
Number of shares callable by warrants				236,836
Warrants for Common Stock Converted from Warrants for Preferred Stock
Warrants
Number of shares callable by warrants				89,708
Warrants for Common Stock Converted from Warrants for Preferred Stock \| Weighted Average
Warrants
Weighted average exercise price to purchase common stock				$ 6.32
Warrants for Common Stock
Warrants
Number of shares callable by warrants	18,939
Shares covered under warrants exercised	70,769
Warrants for Common Stock \| Weighted Average
Warrants
Weighted average exercise price to purchase common stock	$ 7.92
Common Stock
Warrants
Number of shares issued	102,077	3,200,000	5,750,000
Warrant \| Common Stock
Warrants
Number of shares issued	54,010

Redeemable Convertible Preferred Stock - Additional Information (Details)			12 Months Ended
	Jul. 30, 2014 shares	Jul. 10, 2014	Dec. 31, 2014 shares
Stock Disclosures
Reverse stock split ratio		3.78
Common Stock
Stock Disclosures
Number of common shares issued on conversion of redeemable convertible preferred stock			12,440,205
IPO \| Common Stock
Stock Disclosures
Number of common shares issued on conversion of redeemable convertible preferred stock	12,440,205

Common Stock and Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			3 Months Ended	12 Months Ended
	Aug. 19, 2014	Jul. 30, 2014	Nov. 30, 2016	Jun. 30, 2015	Aug. 31, 2014	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock and Preferred Stock
Common stock, shares authorized						100,000,000	100,000,000	100,000,000
Preferred stock, shares authorized						5,000,000	5,000,000	5,000,000
Preferred stock, par value						$ 0.0001	$ 0.0001	$ 0.0001
Net proceeds from issuance of common stock							$ 872	$ 66,176	$ 69,518
Voting right description							Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company's stockholders.
2014 Stock Option Plan
Common Stock and Preferred Stock
Common stock shares, reserved						4,719,717	4,719,717
Common Stock
Common Stock and Preferred Stock
Number of shares issued							102,077	3,200,000	5,750,000
Number of common shares issued on conversion of redeemable convertible preferred stock									12,440,205
Common stock, shares authorized		100,000,000
Preferred Stock
Common Stock and Preferred Stock
Preferred stock, shares authorized		5,000,000
Preferred stock, par value		$ 0.0001
IPO \| Common Stock
Common Stock and Preferred Stock
Number of shares issued		5,000,000
Common stock, price per share		$ 13.00
Number of common shares issued on conversion of redeemable convertible preferred stock		12,440,205
Net proceeds from issuance of common stock		$ 57,337
Over-allotment Option \| Common Stock
Common Stock and Preferred Stock
Number of shares issued	750,000				750,000
Common stock, price per share	$ 13.00				$ 13.00
Net proceeds from issuance of common stock	$ 9,068				$ 9,068
Follow-on Offering \| Common Stock
Common Stock and Preferred Stock
Number of shares issued				4,600,000
Common stock, price per share				$ 22.00
Net proceeds from issuance of common stock				$ 65,612
Number of shares offered by company				3,200,000
Number of shares offered by stockholders				1,400,000
2016 ATM Agreement \| Common Stock
Common Stock and Preferred Stock
Maximum aggregate proceeds from offering			$ 40,000
Number of shares issued						102,077
Net proceeds from issuance of common stock						$ 600
2016 ATM Agreement \| Common Stock \| Weighted Average
Common Stock and Preferred Stock
Common stock, price per share						$ 8.80	$ 8.80

Stock-Based Awards - Additional Information (Details) - shares			12 Months Ended
	Jan. 01, 2016	Jan. 01, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-Based Awards
Options granted to purchase shares of common stock			1,147,025
Unvested service-based stock options held by nonemployees			5,985
Common Stock
Stock-Based Awards
Issuance of common stock in connection with employee stock purchase plan, shares			66,628	20,916	5,395
2014 Stock Incentive Plan
Stock-Based Awards
Options granted to purchase shares of common stock			1,147,025	680,231	753,886
2014 Stock Incentive Plan \| Minimum
Stock-Based Awards
Stock options vesting period			3 years
2014 Stock Incentive Plan \| Maximum
Stock-Based Awards
Stock options vesting period			4 years
2014 Stock Incentive Plan \| Common Stock
Stock-Based Awards
Number of shares of common stock authorized for issuance		2,126,907		1,336,907
Number of shares of common stock available for issuance			1,346,083
Increased number of shares of common stock reserved for issuance		1,659,218
Additional number of shares of common stock , percentage		4.00%
Additional number of shares authorized for issuance	990,012
2014 Employee Stock Purchase Plan \| Common Stock
Stock-Based Awards
Number of shares of common stock authorized for issuance		232,402		207,402
Number of shares of common stock available for issuance			263,215
Increased number of shares of common stock reserved for issuance		207,402
Additional number of shares of common stock , percentage		0.50%
Issuance of common stock in connection with employee stock purchase plan, shares			66,628	20,916	5,395

Stock-Based Awards - Fair Value Assumptions (Details)	12 Months Ended
Stock-Based Awards - Fair Value Assumptions (Details)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assumptions Used to Determine Fair Value of Stock Options Granted to Employees and Directors Presented on a Weighted Average Basis
Risk-free interest rate	1.42%	1.67%	2.24%
Expected term (in years)	6 years	6 years	6 years
Expected volatility	85.00%	71.00%	77.00%

Stock-Based Awards - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares Issuable Under Options
Shares Issuable Under Options, Beginning balance	2,115,519
Shares Issuable Under Options, Granted	1,147,025
Shares Issuable Under Options, Exercised	(105,114)
Shares Issuable Under Options, Forfeited	(65,950)
Shares Issuable Under Options, Ending balance	3,091,480	2,115,519
Shares Issuable Under Options, Vested and expected to vest	3,009,110
Shares Issuable Under Options, Exercisable	1,569,255
Weighted Average Exercise Price
Weighted Average Exercise Price, Beginning balance	$ 12.78
Weighted Average Exercise Price, Granted	6.42
Weighted Average Exercise Price, Exercised	1.90
Weighted Average Exercise Price, Forfeited	13.72
Weighted Average Exercise Price, Ending balance	10.77	$ 12.78
Weighted Average Exercise Price, Vested and expected to vest	10.74
Weighted Average Exercise Price, Exercisable	$ 9.80
Weighted Average Remaining Contractual Term	7 years 3 months 18 days	6 years 10 months 24 days
Weighted Average Remaining Contractual Term, Vested and Expected to vest	7 years 2 months 12 days
Weighted Average Remaining Contractual Term, Exercisable	6 years
Other disclosures
Aggregate Intrinsic Value	$ 6,659	$ 5,897
Aggregate Intrinsic Value, Vested and Expected to vest	6,510
Aggregate Intrinsic Value, Exercisable	4,365
Aggregate intrinsic value of stock options exercised	$ 575	$ 3,192	$ 323
Weighted average fair value of stock option granted	$ 4.52	$ 18.12	$ 6.55

Stock-Based Awards - Restricted Common Stock (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Common Stock
Restricted Common Stock
Aggregate intrinsic value of restricted stock award vested	$ 0	$ 265	$ 1,142

Stock-Based Awards - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based Compensation
Stock-based compensation expense	$ 5,956	$ 4,640	$ 2,644
Unrecognized stock-based compensation cost	$ 10,315
Weighted average period of unrecognized stock-based compensation cost expected to be recognized	2 years 2 months 12 days
Research and Development Expense
Stock-based Compensation
Stock-based compensation expense	$ 1,900	1,589	397
Selling and Marketing Expense
Stock-based Compensation
Stock-based compensation expense	490	340	68
General and Administrative Expense
Stock-based Compensation
Stock-based compensation expense	$ 3,566	$ 2,711	$ 2,179

Net Loss Per Share - Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic and diluted net loss per share attributable to common stockholders:
Net loss	$ (12,822)	$ (9,596)	$ (11,445)	$ (10,840)	$ (10,637)	$ (11,524)	$ (10,009)	$ (7,578)	$ (44,703)	$ (39,748)	$ (28,648)
Accretion of redeemable convertible preferred stock to redemption value											(11)
Net loss attributable to common stockholders	$ (12,822)	$ (9,596)	$ (11,445)	$ (10,840)	$ (10,637)	$ (11,524)	$ (10,009)	$ (7,578)	$ (44,703)	$ (39,748)	$ (28,659)
Weighted average common shares outstanding, basic and diluted									24,816,348	23,244,162	10,652,865
Net loss per share attributable to common stockholders, basic and diluted	$ (0.52)	$ (0.39)	$ (0.46)	$ (0.44)	$ (0.43)	$ (0.47)	$ (0.45)	$ (0.35)	$ (1.80)	$ (1.71)	$ (2.69)

Net Loss Per Share - Schedule of Antidilutive Securities, Excluded from Computation of Diluted Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total options, warrants and restricted stock	3,110,419	2,134,458	1,730,136
Options to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total options, warrants and restricted stock	3,091,480	2,115,519	1,611,991
Non-vested Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total options, warrants and restricted stock			28,437
Common Stock \| Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total options, warrants and restricted stock	18,939	18,939	89,708

Net Loss Per Share - Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic and diluted net loss per share attributable to common stockholders:
Net loss	$ (12,822)	$ (9,596)	$ (11,445)	$ (10,840)	$ (10,637)	$ (11,524)	$ (10,009)	$ (7,578)	$ (44,703)	$ (39,748)	$ (28,648)
Accretion of redeemable convertible preferred stock to redemption value											(11)
Net loss attributable to common stockholders	$ (12,822)	$ (9,596)	$ (11,445)	$ (10,840)	$ (10,637)	$ (11,524)	$ (10,009)	$ (7,578)	$ (44,703)	$ (39,748)	$ (28,659)
Weighted average common shares outstanding, basic and diluted									24,816,348	23,244,162	10,652,865
Net loss per share attributable to common stockholders, basic and diluted	$ (0.52)	$ (0.39)	$ (0.46)	$ (0.44)	$ (0.43)	$ (0.47)	$ (0.45)	$ (0.35)	$ (1.80)	$ (1.71)	$ (2.69)

Commitments and Contingencies - Summary of Future Minimum Lease Payments for Operating Leases (Details) $ in Thousands		12 Months Ended
	Jun. 17, 2016 USD ($) ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Leases
Rental expense		$ 1,084	$ 778	$ 649
Future minimum lease payments
2017		1,162
2018		1,461
2019		1,235
2020		1,270
2021		1,305
Thereafter		7,940
Total		$ 14,373
Lease Agreement, June 2016, Bedford, Massachusetts
Leases
Area of lease \| ft²	70,712
Initial annual base rent of leased space	$ 1,200
Letter of credit	1,500
Construction allowance under lease agreement	$ 2,800

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Oct. 10, 2016	Feb. 12, 2014	Dec. 31, 2016	Dec. 31, 2016
Incept
Commitments and Contingencies
Payments for Royalties				$ 95
Incept \| Common Stock
Commitments and Contingencies
Common stock, shares issued		189,393
Regeneron \| Collaboration Agreement
Commitments and Contingencies
Payments made under the collaboration agreement			$ 0
Regeneron \| Collaboration Agreement \| Maximum
Commitments and Contingencies
Reimbursable clinical development costs	$ 25,000
Potential increase in reimbursable clinical development costs	$ 5,000

Income Taxes - Reconciliation of Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes
Income tax benefit	$ 0	$ 0	$ 0
Reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate
Federal statutory income tax rate	(34.00%)	(34.00%)	(34.00%)
Federal and state research and development tax credit	(2.90%)	(3.10%)	(2.50%)
State taxes, net of federal benefit	(4.80%)	(2.00%)	(4.60%)
Stock-based compensation	1.40%	1.20%	1.60%
Other	(0.60%)	(0.20%)	0.80%
Change in deferred tax asset valuation allowance	40.90%	38.10%	38.70%

Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes
Net operating loss carryforwards	$ 31,960	$ 22,554
Research and development tax credit carryforwards	5,482	4,052
Capitalized start-up costs	1,723	1,915
Capitalized research and development expenses, net	26,943	21,357
Accrued expenses and other temporary differences	4,128	2,091
Total gross deferred tax assets	70,236	51,969
Valuation allowance	$ (70,236)	$ (51,969)	$ (36,825)	$ (25,776)

Income Taxes - Changes in Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes
Valuation allowance as of beginning of year	$ 51,969	$ 36,825	$ 25,776
Increases recorded to income tax provision	18,267	15,144	11,049
Valuation allowance as of end of year	$ 70,236	$ 51,969	$ 36,825

Income Taxes - Net Operating Loss Carryforwards (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Net operating loss carryforwards
Unrealized net operating loss carryforwards related to stock options	$ 2,029
Federal
Net operating loss carryforwards
Net operating loss carryforwards	85,246
State
Net operating loss carryforwards
Net operating loss carryforwards	$ 73,876

Income Taxes - Tax Credit Carryforwards (Details) - Research and Development $ in Thousands	Dec. 31, 2016 USD ($)
Federal
Tax credit carryforwards
Tax credit carryforwards	$ 4,085
State
Tax credit carryforwards
Tax credit carryforwards	$ 2,116

Income Taxes - Other (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Other (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement [Table]
Increased ownership percentage	50.00%
Unrecognized tax benefits	$ 0	$ 0

401(k) Savings Plan - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
401(k) Savings Plan
Contributions to savings plan	$ 0

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 12, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Incept \| Common Stock
Related Party Transactions
Common stock, shares issued	189,393
Incept \| Research and Development Expense \| Common Stock
Related Party Transactions
Common stock, shares issued	189,393
Fair value of shares issued	$ 1,665
Incept \| General and Administrative Expense \| Common Stock \| Former Board of Director
Related Party Transactions
Common stock, shares issued	79,545
Fair value of shares issued	$ 699
Legal Fees \| WilmerHale
Related Party Transactions
Invoiced for consulting and other services		$ 874
Receivables \| Augmenix, Inc. \| Consulting and Other Services
Related Party Transactions
Invoiced for consulting and other services		0	$ 4	$ 82
Payables \| Legal Fees
Related Party Transactions
Invoiced for consulting and other services		$ 0	$ 0	$ 27

Selected Quarterly Financial Data (Unaudited) - Schedule of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statements of Operations Data:
Product revenue	$ 511	$ 477	$ 441	$ 416	$ 394	$ 388	$ 334	$ 238	$ 1,845	$ 1,354	$ 460
Collaboration revenue				42	42	41	125	188	42	396	312
Revenue	511	477	441	458	436	429	459	426	1,887	1,750	772
Loss from operations	(12,472)	(9,238)	(11,107)	(10,509)	(10,275)	(11,174)	(9,635)	(7,113)	(43,326)	(38,197)	(27,094)
Net loss	(12,822)	(9,596)	(11,445)	(10,840)	(10,637)	(11,524)	(10,009)	(7,578)	(44,703)	(39,748)	(28,648)
Net loss attributable to common stockholders	$ (12,822)	$ (9,596)	$ (11,445)	$ (10,840)	$ (10,637)	$ (11,524)	$ (10,009)	$ (7,578)	$ (44,703)	$ (39,748)	$ (28,659)
Basic and diluted net loss attributable to common stockholders per share	$ (0.52)	$ (0.39)	$ (0.46)	$ (0.44)	$ (0.43)	$ (0.47)	$ (0.45)	$ (0.35)	$ (1.80)	$ (1.71)	$ (2.69)

Subsequent Events (Details) $ / shares in Units, $ in Thousands					1 Months Ended			3 Months Ended	12 Months Ended
	Mar. 10, 2017 USD ($) tranche	Jan. 01, 2017 shares	Jan. 01, 2016 shares	Jan. 01, 2015 shares	Feb. 28, 2017 USD ($)	Jan. 31, 2017 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Subsequent Events
Net proceeds from issuance of common stock \| $									$ 872	$ 66,176	$ 69,518
Common Stock
Subsequent Events
Number of shares issued \| shares									102,077	3,200,000	5,750,000
Common Stock \| 2016 ATM Agreement
Subsequent Events
Number of shares issued \| shares								102,077
Net proceeds from issuance of common stock \| $								$ 600
Common Stock \| 2016 ATM Agreement \| Weighted Average
Subsequent Events
Common stock, price per share \| $ / shares								$ 8.80	$ 8.80
Common Stock \| Follow-on Offering
Subsequent Events
Number of shares issued \| shares							4,600,000
Common stock, price per share \| $ / shares							$ 22.00
Net proceeds from issuance of common stock \| $							$ 65,612
Common Stock \| 2014 Stock Incentive Plan
Subsequent Events
Increased number of shares of common stock reserved for issuance \| shares				1,659,218
Additional number of shares of common stock , percentage				4.00%
Additional number of shares authorized for issuance \| shares			990,012
Common Stock \| 2014 Employee Stock Purchase Plan
Subsequent Events
Increased number of shares of common stock reserved for issuance \| shares				207,402
Additional number of shares of common stock , percentage				0.50%
Subsequent Event
Subsequent Events
Outstanding borrowings under credit facility \| $	$ 18,000
Subsequent Event \| Amended 2017 Credit Facility
Subsequent Events
Borrowing capacity under the agreement \| $	$ 38,000
Number of tranches \| tranche	2
Tranche one, amount contingent upon the achievement of regulatory and commercial milestones related to DEXTENZA \| $	$ 10,000
Tranche two, amount contingent upon the achievement of regulatory and commercial milestones related to DEXTENZA \| $	$ 10,000
Final payment due (as a percent)	3.50%
Subsequent Event \| LIBOR \| Amended 2017 Credit Facility
Subsequent Events
Interest rate floor (as a percent)	1.00%
Basis spread (as a percent)	7.25%
Indicative interest rate (as a percent)	8.25%
Subsequent Event \| Axtria \| Board of Director \| Implementation, Operations and Maintenance Support Services
Subsequent Events
Statement of work amount \| $					$ 1,400
Subsequent Event \| Common Stock \| 2016 ATM Agreement
Subsequent Events
Number of shares issued \| shares						161,341
Net proceeds from issuance of common stock \| $						$ 1,400
Subsequent Event \| Common Stock \| 2016 ATM Agreement \| Weighted Average
Subsequent Events
Common stock, price per share \| $ / shares						$ 8.91
Subsequent Event \| Common Stock \| Follow-on Offering
Subsequent Events
Number of shares issued \| shares						3,571,429
Common stock, price per share \| $ / shares						$ 7.00
Net proceeds from issuance of common stock \| $						$ 23,464
Subsequent Event \| Common Stock \| 2014 Stock Incentive Plan
Subsequent Events
Additional number of shares authorized for issuance \| shares		1,000,964
Subsequent Event \| Common Stock \| 2014 Employee Stock Purchase Plan
Subsequent Events
Additional number of shares authorized for issuance \| shares		125,121