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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	May 05, 2020
Document and Entity Information
Entity Registrant Name	KALA PHARMACEUTICALS, INC.
Entity Central Index Key	0001479419
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		55,715,876
Entity Shell Company	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash	$ 196,456	$ 85,449
Accounts receivable, net	4,794	11,563
Inventory	5,272	4,648
Prepaid expenses and other current assets	3,725	3,824
Total current assets	210,247	105,484
Non-current assets:
Property and equipment, net	2,566	2,698
Long-term inventory	3,821	3,778
Right-of-use assets	29,308	29,781
Restricted cash	12,584	12,582
Total assets	258,526	154,323
Current liabilities:
Accounts payable	1,187	2,518
Accrued expenses and other current liabilities	14,711	20,929
Current portion of lease liabilities	1,375	1,327
Total current liabilities	17,273	24,774
Long-term liabilities:
Long-term lease liability - less current portion	28,305	28,673
Long-term debt	71,438	71,184
Total long-term liabilities	99,743	99,857
Total liabilities	117,016	124,631
Commitments and Contingencies (Note 12)
Stockholders' equity:
Common stock, $0.001 par value; 120,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 54,585,636 and 36,086,254 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	55	36
Additional paid-in capital	458,866	325,112
Accumulated deficit	(317,411)	(295,456)
Total stockholders' equity	141,510	29,692
Total liabilities and stockholders' equity	$ 258,526	$ 154,323

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
CONSOLIDATED BALANCE SHEETS
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	120,000,000	120,000,000
Common stock, shares issued	54,585,636	36,086,254
Common stock, shares outstanding	54,585,636	36,086,254

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CONSOLIDATED STATEMENTS OF OPERATIONS
Product revenues, net	$ 1,071	$ 1,386
Costs and expenses:
Cost of product revenues	354	241
Selling, general and administrative	15,408	18,236
Research and development	5,434	6,959
Total costs and expenses	21,196	25,436
Loss from operations	(20,125)	(24,050)
Other income (expense):
Interest income	298	756
Interest expense	(2,128)	(2,094)
Total other expense	(1,830)	(1,338)
Net loss	$ (21,955)	$ (25,388)
Net loss per share—basic and diluted	$ (0.54)	$ (0.75)
Weighted average shares outstanding—basic and diluted	40,761,984	33,878,021

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance as of beginning of period at Dec. 31, 2018	$ 34	$ 306,053	$ (201,109)	$ 104,978
Balance as of beginning of period (in shares) at Dec. 31, 2018	33,863,077
Stockholders' Equity
Exercise of stock options		39		39
Exercise of stock options (in shares)	19,780
Stock-based compensation expense		2,738		2,738
Net loss			(25,388)	(25,388)
Balance as of end of period at Mar. 31, 2019	$ 34	308,830	(226,497)	82,367
Balance as of end of period (in shares) at Mar. 31, 2019	33,882,857
Balance as of beginning of period at Dec. 31, 2018	$ 34	306,053	(201,109)	104,978
Balance as of beginning of period (in shares) at Dec. 31, 2018	33,863,077
Balance as of end of period at Dec. 31, 2019	$ 36	325,112	(295,456)	29,692
Balance as of end of period (in shares) at Dec. 31, 2019	36,086,254
Stockholders' Equity
Common stock offering, net of issuance cost and underwriting fees of $8.1 millio	$ 16	118,191		118,207
Common stock offering, net of issuance cost and underwriting fees (in shares)	16,000,000
At-the-market offering, net of sales agent commission and fees	$ 3	12,543		12,546
At-the-market offering, net of sales agent commission and fees (in shares)	2,352,671
Exercise of stock options		167		167
Exercise of stock options (in shares)	61,158
Issuance under employee stock purchase plan		269		269
Issuance under employee stock purchase plan (in shares)	85,553
Stock-based compensation expense		2,584		2,584
Net loss			(21,955)	(21,955)
Balance as of end of period at Mar. 31, 2020	$ 55	$ 458,866	$ (317,411)	$ 141,510
Balance as of end of period (in shares) at Mar. 31, 2020	54,585,636

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY
Issuance cost and underwriting fees	$ 8.1
Sales agent commission	$ 0.4

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (21,955)	$ (25,388)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation	230	170
Non-cash operating lease cost	473	437
Amortization of debt discount and other non-cash interest	253	231
Stock-based compensation	2,497	2,473
Change in operating assets and liabilities:
Accounts receivable	6,769	(4,674)
Prepaid expenses and other current assets	99	619
Inventory	(579)	(1,056)
Accounts payable	(1,332)	(3,206)
Accrued expenses and other current liabilities	(6,023)	(766)
Lease liabilities and other long-term liabilities	(312)	(10)
Net cash used in operating activities	(19,880)	(31,170)
Cash flows from investing activities:
Purchases of property and equipment	(292)	(444)
Net cash used in investing activities	(292)	(444)
Cash flows from financing activities:
Proceeds from common stock offerings, net of underwriters' discounts and offering cost	130,754
Payment of principal on finance lease	(8)	(10)
Proceeds from exercise of stock options and issuance of common stock under employee stock purchase plan	435	39
Net cash provided by financing activities	131,181	29
Net increase/(decrease) in cash and restricted cash:	111,009	(31,585)
Cash and restricted cash at beginning of period	98,031	183,104	$ 183,104
Cash and restricted cash at end of period	209,040	151,519	98,031
Reconciliation of cash and restricted cash:
Cash and restricted cash at end of period	209,040	151,519	$ 98,031	$ 209,040	$ 98,031	$ 151,519
Less restricted cash				(12,584)	(12,582)	(12,575)
Cash at end of period				$ 196,456	$ 85,449	$ 138,944
Non-cash investing and financing activities:
Right-of-use asset obtained in exchange for finance lease obligation		136
Purchases of property and equipment in accounts payable		409
Supplemental disclosure:
Cash paid for interest	$ 1,875	1,862
Right-of-use assets obtained in exchange of operating lease obligations		$ 1,878

Nature of business and basis of presentation	3 Months Ended
Nature of business and basis of presentation	Mar. 31, 2020
Nature of business and basis of presentation
Nature of business and Basis of Presentation	1. NATURE OF BUSINESS AND BASIS OF PRESENTATION Nature of Business— Kala Pharmaceuticals, Inc. (the “Company”) was incorporated on July 7, 2009, and is a biopharmaceutical company focused on the discovery, development and commercialization of innovative therapies for diseases of the eye. The Company has applied its AMPPLIFY® mucus-penetrating particle (“MPP”) Drug Delivery Technology to loteprednol etabonate (“LE”), a corticosteroid designed for ocular applications, resulting in the U.S. Food and Drug Administration’s (the “FDA”) approval of INVELTYS® (loteprednol etabonate ophthalmic suspension) 1% as the first and only topical twice-daily ocular corticosteroid for treatment of post-operative inflammation and pain following ocular surgery, and the development of its lead product candidate, KPI-121 0.25%, which if approved it plans to commercialize under the brand name EYSUVISTM (loteprednol etabonate ophthalmic suspension) 0.25%, for the short-term treatment of the signs and symptoms of dry eye disease. In October 2018, the Company submitted a New Drug Application (“NDA”) to the FDA for EYSUVIS. In August 2019, the Company announced that it received a complete response letter (“CRL”) from the FDA indicating that positive efficacy data from an additional clinical trial would be needed to support a resubmission of the NDA. Based upon the previous recommendation of the FDA, the Company initiated an additional Phase 3 clinical trial (“STRIDE 3”) (STRIDE- Short Term Relief In Dry Eye), in July 2018. On March 9, 2020, the Company announced that STRIDE 3 met both of its primary symptom endpoints and its key secondary sign endpoint. The Company believes that the data from STRIDE 3 replicates the positive efficacy data from previous clinical trials for both signs and symptoms of dry eye disease and will satisfy the recommendation in the CRL for an additional positive trial. On April 30, 2020, the Company resubmitted the NDA for EYSUVIS. The Company believes this application will be considered a Class 2 resubmission, with a targeted six-month review timeline under the Prescription Drug User Fee Act (“PDUFA”). In January 2019, the Company launched its first commercial product, INVELTYS, in the United States. The Company is engaged in the commercialization of INVELTYS, pursuing FDA approval of, and preparing to launch, EYSUVIS, research and development activities, raising capital and recruiting skilled personnel. The Company is subject to a number of risks similar to those of other companies conducting high‑risk, research and development of pharmaceutical product candidates and launching products for the first time. Principal among these risks are dependence on key individuals and intellectual property, competition from other products and companies and the technical risks associated with the successful research, development and marketing of its product candidates. The Company’s success is dependent upon its ability to obtain regulatory approval of EYSUVIS, the success of commercializing its products, the success of its research and development efforts, its ability to obtain regulatory approval of its other product candidates, its ability to raise additional capital when needed and, ultimately, attain profitable operations. The Company is evaluating opportunities for MPP nanosuspensions of LE with less frequent daily dosing regimens for the treatment of the signs and symptoms of dry eye disease and for potential chronic treatment of dry eye disease. The Company is also evaluating compounds in its receptor Tyrosine Kinase Inhibitor program (the “rTKI program”), that inhibit the vascular endothelial growth factor (“VEGF”), pathway, for the potential treatment of a number of retinal diseases, and novel next-generation anti-inflammatories designed to exhibit steroid-like anti-inflammatory action for eye disease with the goal of eliminating the risk of interocular pressure (“IOP”) increase and cataract formation. Liquidity— Since inception, the Company has incurred significant losses from operations and negative cash flows from operations. As of March 31, 2020, the Company had an accumulated deficit of $317.4 million. The Company has generated only limited revenues to date from product sales and has financed operations primarily through proceeds from its initial public offering of common stock (“IPO”), public common stock offerings and sales of its common stock under its at-the-market offering facility, private placements of preferred stock, convertible debt financings, borrowings under credit facilities, and warrants. The Company has devoted substantially all of its financial resources and efforts to research and development, including preclinical studies and clinical trials and engaging in activities to launch and commercialize INVELTYS. The Company expects to continue to incur significant expenses and operating losses. Net losses may fluctuate significantly from quarter-to-quarter and year-to-year. The Company believes that its existing cash on hand as of March 31, 2020, will enable it to fund its planned operating expenses, debt service obligations and capital expenditure requirements for at least twelve months from the date these condensed consolidated financial statements were issued. This evaluation is based on relevant conditions and events that are known and reasonably knowable at the date that the condensed consolidated financial statements are issued. As a result, the Company could deplete its available capital resources sooner than it currently expects. COVID-19 – The ongoing novel coronavirus pandemic, commonly referred to as COVID-19, which was declared a global pandemic by the World Health Organization on March 11, 2020, has caused federal, state, and local governments to implement measures to slow the spread of the outbreak through quarantines, strict travel restriction and bans, heightened border scrutiny and other measures. The Company is following, and will continue to follow, recommendations from the U.S. Centers for Disease Control and Prevention (“CDC”) as well as federal, state, and local governments regarding working-from-home practices for non-essential employees. As a result, the Company has suspended substantially all in-person interactions with customers, including visits to physician offices, clinics, and hospitals, all office-based personnel have been instructed to work from home and the Company’s laboratory facilities, that support our early-stage research activities, are partially closed. The moratorium on routine medical appointments and elective surgeries in many jurisdictions, including ocular surgeries, has adversely affected the market for INVELTYS, which is indicated for the treatment of inflammation and pain following ocular surgery, resulting in a significant reduction in the demand for INVELTYS. The extent of the impact of COVID-19 on the Company’s operational and financial performance will depend on certain developments, including the length and severity of this pandemic, impact on its customers, employees, vendors, and government agencies, all of which are uncertain and cannot be predicted. The Company cannot reasonably estimate the extent to which the disruption may materially impact its consolidated results of operations or financial position. Use of Estimates—The preparation of condensed consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, expense, and related disclosures. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. Estimates and assumptions relied upon in preparing these condensed consolidated financial statements relate to, but are not limited to, revenue recognition, inventory, the present value of lease liabilities and the corresponding right-of-use assets, the fair value of warrants, stock compensation, accrued expenses and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Actual results may differ from these estimates under different assumptions or conditions. Net Loss per Share—Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the sum of the weighted average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential shares of common stock, including the assumed exercise of stock options and warrants. The weighted average number of common shares included in the computation of diluted net loss gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, and warrants. Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. 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 three months ended March 31, 2020 and 2019. Unaudited Interim Financial Information—The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. The accompanying condensed consolidated financial statements reflect all adjustments consisting of normal, recurring adjustments, that are necessary for a fair presentation of the financial position, results of operations, statement of stockholders’ equity and cash flows for the interim periods presented. Interim results are not necessarily indicative of results for a full year. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2019 (the “Annual Report”). The unaudited condensed consolidated financial statements include the accounts of Kala Pharmaceuticals, Inc. and its wholly owned subsidiary, Kala Pharmaceuticals Security Corporation. All intercompany transactions and balances have been eliminated in consolidation.

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2020
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies,” to the consolidated financial statements included in the Annual Report. There have been no material changes to the significant accounting policies during the period ended March 31, 2020. Recent Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”). ASU 2018-13 is intended to improve the effectiveness of disclosures in the notes to financial statements related to fair value measurements in Topic 820. This ASU will become effective for annual periods beginning after December 15, 2019, including interim periods within that period, and early adoption is permitted. The ASU was effective on January 1, 2020 and the adoption of ASU 2018-13 did not have a material effect on the Company’s condensed consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software -Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the accounting for implementation costs incurred in a hosting arrangement that is a service contract with the guidance on capitalizing costs associated with developing or obtaining internal-use software. This ASU became effective for annual periods beginning after December 15, 2019, including interim periods within that period, and early adoption is permitted. The ASU was effective on January 1, 2020 and the adoption of ASU 2018-15 did not have a material effect on the Company’s condensed consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. ASU 2016-13 will require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, which will generally result in earlier recognition of allowances for credit losses on loans and other financial instruments. In November 2019, the FASB issued ASU 2019-10, Financial Instruments - Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) (“ASU 2019-10”), which is effective for public business entities that meet the definition of an SEC filer, excluding entities eligible to be Smaller Reporting Companies (SRCs) as defined by the SEC, for fiscal years beginning after December 15, 2019, including interim period within those fiscal years and for all other entities, including SRCs, for fiscal years beginning December 15, 2022, including interim periods within those fiscal years. Upon adoption, beginning January 1, 2023, the Company does not expect ASU 2019-10 to have a material effect on its condensed consolidated financial statements.

Revenue and Trade Receivables

3 Months Ended

Mar. 31, 2020

Revenue and Trade Receivables

Revenue and Trade Receivables

3. REVENUE & ACCOUNTS RECEIVEABLE, NET

The Company accounts for revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers. Under ASC Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to be entitled in exchange for those goods or services. The Company performs the following five steps to recognize revenue under ASC Topic 606: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only recognizes revenue when it is probable that it will collect the consideration to which it is entitled in exchange for the goods or services that will be transferred to the customer.

Product revenues, net

The Company sells INVELTYS to wholesalers and/or specialty distributors in the United States (collectively, “Customers”). These Customers subsequently resell the Company’s products to specialty and other retail pharmacies. In addition to agreements with Customers, the Company enters into arrangements with payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts for the purchase of the Company’s products.

The goods promised in the Company’s product sales contracts represent a single performance obligation; as the promise to transfer the individual products to the Customer is not separately identifiable from other promises in the contracts and, therefore, not distinct. The Company recognizes revenue from product sales at the point the Customer obtains control of the product, which occurs upon delivery. The transaction price (“net sales price”) that is recognized as revenue for product sales includes the selling price to the Customer and an estimate of variable consideration. Components of variable consideration include prompt pay and other discounts, product returns, government rebates, third-party payor rebates, coverage gap rebates, incentives such as patient co-pay assistance, and other fees paid to Customers where a distinct good or service is not received. Variable consideration is recorded on the consolidated balance sheet as either a reduction of accounts receivable, if payable to a Customer, or as a current liability, if payable to a third-party other than a Customer. The Company considers all relevant information when estimating variable consideration such as assessment of its current and anticipated sales and demand forecasts, information from third parties regarding the payor mix for products, information from third parties regarding the units remaining in the distribution channel, specific known market events and trends, industry data and current contractual and statutory requirements that are reasonably available. The Company includes estimated amounts in the net sales price to the extent it is determined probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved.

Payment terms with Customers do not exceed one year and, therefore, the Company does not account for a significant financing component in its arrangements. The Company expenses incremental cost of obtaining a contract with a Customer when incurred as the period of benefit is less than one year.

Reserves for Variable Consideration:

Trade Discounts and Allowances

The Company provides its Customers with certain trade discounts and allowances including discounts for prompt payments and fees paid for distribution, data and administrative services. These discounts and fees are based on contractually-determined percentages and are recorded as a reduction of revenue and accounts receivable in the period in which the related product revenue is recognized.

Chargebacks

Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These components of variable consideration are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Reserves for chargebacks consist of credits the Company expects to issue for units that remain in the distribution channel at the end of each reporting period and that the Company expects will be sold to qualified healthcare providers, as well as chargebacks that Customers have claimed, but for which the Company has not yet issued a credit.

Product Returns

Consistent with industry practice, the Company has a product returns policy that provides Customers a right of return for product purchased within a specified period prior to and subsequent to the product’s expiration date. The Company estimates the amount of its products that may be returned and presents this amount as a reduction of revenue in the period the related product revenue is recognized, in addition to establishing a liability. The Company’s estimates for product returns are based upon available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel.

Commercial Payor and Medicare Part D Rebates

The Company contracts with certain third-party payors, primarily pharmacy benefit managers (“PBMs”) and health plans (“Plans”), for the payment of rebates with respect to utilization of its product. These rebates are based on contractual percentages applied to the amount of product prescribed to patients who are covered by the PBMs or the Plans with which it contracts. The Company estimates the rebates for commercial and Medicare Part D payors based on the contractual discount percentage, the various payor mix for INVELTYS as well as future rebates that will be made for product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. The Company also estimates the number of patients in the prescription drug coverage gap for whom it will owe an additional liability under the Medicare Part D program. Such estimates are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability.

Government Rebates

The Company is subject to discount obligations under Medicaid and other government programs. For Medicaid, reserves are based on estimates of future Medicaid beneficiary utilization applied to the Medicaid unit rebate formula established by the Centers for Medicaid and Medicare Services. The Company’s liability for these rebates consists of estimates of claims for the current period and estimated future claims that will be made for product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability.

Co-pay Assistance Program

The Company offers a co-pay assistance program (the “co-pay program”), which is intended to provide financial assistance to patients who may or may not be covered by commercial insurance or who opt out of Medicare Part D programs. The calculation of accruals for the co-pay program is based on actual claims processed during the period as well as an estimate of the number and cost per claim that the Company expects to receive associated with product that has been recognized as revenue but remains in the distribution channel at the end of each reporting period. Allowances for estimated co-pay claims are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability.

The following table summarizes activity in each of the Company’s product revenue provision and allowance categories for the three months ended March 31, 2020:


	Trade Discounts,
	Allowances and				Rebates and
	Chargebacks (1)		Product Returns (2)		Incentives (3)

Balance at December 31, 2019	$	1,783	$	180		10,044
Provision related to current period sales		725		—		4,576
Changes in estimate related to prior period sales		2		(66)		93
Credit/payments made		(1,114)		—		(8,090)
Balance at March 31, 2020	$	1,396	$	114	$	6,623

(1)

Trade allowances and chargebacks include fees for distribution service fees, prompt pay discounts, and chargebacks. Trade allowances and chargebacks are deducted from gross revenue at the time revenues are recognized and are recorded as a reduction to accounts receivable in the Company’s Consolidated Balance Sheets.

(2)

Provisions for product returns are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities in the Company’s Consolidated Balance Sheets.

(3)

Rebates and incentives includes managed care rebates, government rebates, co-pay program incentives, and sales incentives and allowances. Provisions for rebates and discounts are deducted from gross revenues at the time revenues are recognized and are included in accrued expenses and other current liabilities in the Company’s Consolidated Balance Sheets.

Accounts Receivable, net

Accounts receivable are reported on the consolidated balance sheets at outstanding amounts due from Customers for product sales. The Company deducts sales discounts for prompt payments and contractual fees for service arrangements from accounts receivable. The Company evaluates the collectability of accounts receivable on a regular basis, by reviewing the financial condition and payment history of Customers, an overall review of collections experience on other accounts, and economic factors or events expected to affect future collections experience. An allowance for doubtful accounts is recorded when a receivable is deemed to be uncollectible.

The Company recorded no allowance for doubtful accounts as of March 31, 2020 or March 31, 2019. The Company recorded an allowance of $1.4 million and $0.8 million for expected sales discounts, related to prompt pay discounts and contractual fee for service arrangements, to wholesalers and distributors as of March 31, 2020 and March 31, 2019, respectively.

Inventory

3 Months Ended

Mar. 31, 2020

Inventory

Inventory

4. INVENTORY

Current inventory and long-term inventory consist of the following (in thousands):


	March 31,		December 31,
	2020		2019

Raw materials	$	1,387	$	1,387
Work in progress		3,541		4,166
Finished goods		4,165		2,873
Total inventory	$	9,093	$	8,426

As of March 31, 2020, the Company had $5.3 million of current inventory and $3.8 million of long-term inventory. As of December 31, 2019, the Company had $4.6 million of current inventory and $3.8 million of long-term inventory.

Accrued Expenses

3 Months Ended

Mar. 31, 2020

Accrued Expenses

Accrued Expenses

5. ACCRUED EXPENSES


	March 31,		December 31,
	2020		2019

Compensation and benefits	$	4,080	$	6,502
Accrued revenue reserves (1)		6,737		9,482
Development costs		984		1,600
Professional services		1,417		760
Commercial cost		408		930
Contract manufacturing		620		630
Other		465		1,025
Accrued expenses	$	14,711	$	20,929

(1) There were additional revenue reserves included in accounts payable of $0 and $0.7 million, as of March 31, 2020 and December 31, 2019, respectively.

Lease

3 Months Ended

Mar. 31, 2020

Lease

Leases

6. LEASES

Operating leases

On February 28, 2018, the Company entered into a lease agreement for the lease of a portion of the building located at 490 Arsenal Way, Watertown, Massachusetts (the “Watertown Lease”) to be used as the Company’s corporate headquarters. The Company recognized the right-of-use asset and corresponding lease liability on November 15, 2018, by calculating the present value of lease payments, discounted at 9.9%, the Company’s estimated incremental borrowing rate, over the 13-year expected term.

In connection with the Watertown Lease, the Company issued a letter of credit to the landlord for $2.0 million. The Company secured the letter of credit for the full amount of the letter with cash on deposit, which is reported as restricted cash as of March 31, 2020 and December 31, 2019.

For the three months ended March 31, 2020 and 2019, the variable lease expense for the Watertown Lease, which includes common area maintenance and real estate taxes, was $0.4 million and $0.1 million, respectively. The remaining lease term was 11.6 years as of March 31, 2020.

Vehicle Fleet lease

During the year ended December 31, 2019, the Company entered into a master fleet lease agreement (the “Vehicle Fleet Lease”), pursuant to which it currently leases approximately 65 vehicles. In connection with the Vehicle Fleet Lease, the Company issued a letter of credit for $0.5 million, which was reported as restricted cash on the balance sheet. The lease has an expected term of three years, which commenced upon the delivery of the vehicles in March 2019. As of March 31, 2020, the remaining lease term was 1.9 years.

The components of lease expense and related cash flows were as follows (in thousands):


	Three Months Ended March 31,
	2020		2019
Lease cost
Operating lease cost	$	1,185	$	1,102
Variable lease cost		410		124
Total lease cost	$	1,595	$	1,226

Operating cash outflows from operating leases	$	1,444	$	743

Debt

3 Months Ended

Mar. 31, 2020

Debt

Debt

7. DEBT

Athyrium Credit Facility

On October 1, 2018, the Company entered into a credit agreement (the “Athyrium Credit Facility”), with Athyrium Opportunities III Acquisition LP (“Athyrium”) for up to $110.0 million. The Athyrium Credit Facility provides for a Term Loan A in the aggregate principal amount of $75.0 million (the “Term Loan A”), and a Term Loan B in the aggregate principal amount of $35.0 million (the “Term Loan B”). On October 1, 2018, the Company borrowed the entire principal amount of the Term Loan A. The Company may draw down the Term Loan B upon either (i) FDA approval of EYSUVIS for a dry eye disease indication or (ii) reaching certain net product revenues for INVELTYS, in each case, on or prior to June 30, 2020; however, the Company does not expect to satisfy either such condition on or prior to June 30, 2020 and, as a result, does not currently expect that it will be eligible to draw down any of the Athyrium Term Loan B funds. The maturity date of the Athyrium Credit Facility is October 1, 2024, the six-year anniversary of the close.

The Term Loan A bears interest at a rate of 9.875% per annum, with quarterly, interest-only payments until the fourth anniversary of the Term Loan A. The unpaid principal amount of the Term Loan A is due and payable in quarterly installments starting on the fourth anniversary of the loan. The Company may make voluntary prepayments, in whole or in part, and subject to certain exceptions, is required to make mandatory prepayments upon the occurrence of certain events of default as defined in the agreement, including but not limited to, the occurrence of a change of control. In addition, upon payment or repayment of any outstanding balance under the Athyrium Credit Facility, the Company will have to pay a 1% exit fee of the total principal payments (whether mandatory, voluntary, or at maturity) made throughout the term. The exit fee of $0.7 million based on the $75.0 million principal amount outstanding, will be accreted to the carrying amount of the debt using the effective interest method over the term of the loan.

All mandatory and voluntary prepayments of the Athyrium Credit Facility are subject to the payment of prepayment premiums as follows: (i) if prepayment occurs prior to the second anniversary of the applicable date of issuance, an amount equal to the amount by which (a) the present value of 105% of the principal prepaid plus all interest that would have accrued on such principal through such second anniversary exceeds (b) the amount of principal prepaid, (ii) if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary of such issuance, an amount equal to 3% of the principal prepaid, and (iii) if prepayment occurs on or after the third anniversary of the applicable date of issuance but prior to the fourth anniversary of such issuance, an amount equal to 2% of the principal prepaid. No prepayment premium is due on any principal prepaid after the fourth anniversary of the applicable date of issuance.

The Athyrium Credit Facility includes features requiring (1) additional interest rate upon an event of default accrued at an additional 3%, or a total interest rate of 12.875%, and (2) the lender’s right to declare all outstanding principal and interest immediately payable upon an event of default. These two features were analyzed and determined to be embedded derivatives to be valued as separate financial instruments. These embedded derivatives were bundled and valued as one compound derivative in accordance with the applicable accounting guidance for derivatives and hedging transactions. The Company determined that, due to the unlikely event of default, the embedded derivatives have a de minimis value as of March 31, 2020. The derivative liability will be remeasured at fair value at each reporting date, with changes in fair value being recorded as other income (expense) in the consolidated statements of operations.

The Athyrium Credit Facility is secured by a pledge of substantially all of the Company’s assets and contains affirmative and negative covenants customary for financings of this type, including limitations on the Company’s and its subsidiaries’ ability to, among other things, incur and prepay additional debt, grant or permit additional liens, make investments and acquisitions, merge or consolidate with others, dispose of assets, change in the nature of business, enter into sale and leaseback transactions, make distributions, and enter into affiliate transactions, in each case, subject to certain exceptions. In addition, the Athyrium Credit Facility also contains a financial covenant requiring the Company to maintain at least $10.0 million of cash and cash equivalents. As a result of this financial covenant, the Company has recorded $10.0 million as restricted cash as of March 31, 2020 and December 31, 2019.

In connection with the Athyrium Credit Facility, the Company issued a warrant (“Warrant”), to purchase up to 270,835 shares of the Company’s common stock, at an exercise price per share of $12.18456. The Warrant is immediately exercisable as to 184,660 shares and will become exercisable as to the remaining 86,175 shares only upon the Company’s draw of the Term Loan B; however, as noted above, it is unlikely the Company will satisfy either condition to draw down on the Term Loan B. The Warrant is exercisable through October 1, 2025 and is classified as an equity instrument. The Company allocated the proceeds from the Term Loan A to the Warrant using the relative fair value method. The fair value of the Warrant of $1.9 million was recognized as equity and a corresponding debt discount.

In addition, the Company paid certain fees to Athyrium and other third-party service providers. These fees paid to Athyrium were recorded as a debt discount while the fees paid to other third-party service providers were recorded as debt issuance cost. These costs, along with the fair value of the Warrant of $1.9 million are being amortized using the effective interest method over the term of the Athyrium Credit Facility. The amortization of debt discount and debt issuance cost is included in interest expense within the Condensed Consolidated Statements of Operations. As of March 31, 2020, and 2019, the effective interest rate was 11.63% and 11.42%, respectively, which takes into consideration the non-cash accretion of the exit fee and the amortization of the debt discount and issuance costs. During each of the three months ended March 31, 2020 and March 31, 2019, the Company recognized interest expense of $2.1 million, which consisted of amortization of the debt discount of $0.2 million, and the contractual coupon interest expense of $1.9 million.

The components of the carrying value of the debt as of March 31, 2020, and December 31, 2019 are detailed below (in thousands):


	March 31,		December 31,
	2020		2019
Principal loan balance	$	75,000	$	75,000
Unamortized debt discount and issuance cost		(3,782)		(3,999)
Cumulative accretion of exit fee		220		183
Long-term debt, net	$	71,438	$	71,184

The annual principal payments due under the Athyrium Credit Facility as of March 31, 2020 were as follows (in thousands):


Years Ending December 31,
2020 (remaining nine months)	$	—
2021		—
2022		16,665
2023		33,330
2024		25,005
Total	$	75,000

Warrants

3 Months Ended

Mar. 31, 2020

Warrants

Warrants

8. WARRANTS

The Company issued warrants in connection with debt transactions that were completed prior to 2017. Upon the completion of the IPO, the Company’s then outstanding warrants to purchase preferred stock converted into warrants to purchase common stock. The Company also issued the Warrant to purchase common stock in connection with the Athyrium Credit Facility, described further in Note 6.

The following table summarizes the common stock warrants outstanding as of March 31, 2020 and December 31, 2019, each exercisable into the number of shares of common stock set forth below as of the specified dates:


					Shares Exercisable at
	Exercise		Expiration	Exercisable	March 31,	December 31,
Issued	Price		Date	From	2020	2019
2013	$	7.50	April 2021	July 2017	82,816	82,816
2014	$	7.50	November 2024	July 2017	16,000	16,000
2016	$	8.27	October 2026	September 2017	14,512	14,512
2018	$	12.18	October 2025	October 2018	184,660	184,660
2018	$	12.18	October 2025	(1)	—	—
					297,988	297,988

(1)

As of March 31, 2020, and December 31, 2019, warrants outstanding to acquire 86,175 shares of common stock are not exercisable and are only exercisable upon draw down of the Term Loan B.

Equity Financings	3 Months Ended
Equity Financings	Mar. 31, 2020
Equity Financings
Equity Financings	9. EQUITY FINANCINGS On August 9, 2018, the Company filed a shelf registration statement on Form S-3 with the SEC, which was declared effective on August 27, 2018 (the “Shelf Registration”). Under the Shelf Registration, the Company may offer and sell up to $250.0 million of a variety of securities including common stock, preferred stock, warrants, depositary shares, debt securities, purchase contracts, purchase units or any combination of such securities during the three-year period that commenced upon the Shelf Registration becoming effective. In connection with the filing of the Shelf Registration, the Company entered into a sales agreement with Jefferies, LLC (the “Sales Agreement”) pursuant to which the Company may issue and sell, from time to time, up to an aggregate of $50.0 million of its common stock in an at-the-market equity offering (“ATM Offering”) through Jefferies, LLC, as sales agent. As of December 31, 2019, the Company issued 2,592,934 shares of its common stock under the ATM Offering, resulting in net proceeds to the Company of approximately $13.1 million. During the first quarter of 2020, the Company issued an aggregate of 2,352,671 shares of its common stock under the ATM Offering, resulting in net proceeds to the Company of $12.5 million. On March 10, 2020, the Company notified Jefferies LLC (“Jefferies”) that it was suspending and terminating the prospectus related to the Sales Agreement. The Company will not make any sales of its common stock pursuant to the Sales Agreement unless and until a new prospectus is filed. On March 11, 2020, the Company sold 16,000,000 shares of the Company’s common stock (the “2020 Offering Shares”) in an underwritten offering (the “2020 Offering”), pursuant to the Shelf Registration filed with the SEC in August 2018, at a public offering price of $7.89 per share, before underwriting discounts, commissions, and offering expenses, resulting in net proceeds of $118.2 million. In addition, the underwriters of the offering were granted the option for a period of 30 days to purchase up to an additional 2,400,000 shares of common stock offered in the public offering at the public offering price, less underwriting discounts, commissions and offering expenses. On April 3, 2020, the underwriters exercised their option and purchased an additional 979,371 shares of common stock at $7.89 per share, before underwriting discounts, commissions, and offering expenses, resulting in net proceeds to the Company of $7.2 million. The total number of shares sold by the Company in the 2020 Offering was 16,979,371, resulting in total net proceeds to the Company, after underwriting discounts, commissions, and offering expenses, of approximately $125.4 million. As of March 31, 2020, there was approximately $26.1 million of securities available to be issued under the Shelf Registration. As a result of the underwriters’ option exercised as noted above, there was approximately $18.3 million of securities available to be issued under the Shelf Registration as of April 3, 2020.

Stock-based Compensation

3 Months Ended

Mar. 31, 2020

Stock-based Compensation

Stock-based Compensation

10. STOCK‑BASED COMPENSATION

Stock Incentive Plans—In December 2009, the Board of Directors (the “Board”) adopted the 2009 Employee, Director and Consultant Equity Incentive Plan (the “2009 Plan”) for the issuance of common stock and stock options to employees, officers, directors, consultants, and advisors.

In July 2017, the Company’s 2017 Equity Incentive Plan (the “2017 Plan”) became effective. The 2017 Plan was established to provide equity-based ownership opportunities for employees, officers, directors, consultants, and advisors. As of March 31, 2020, there were 138,513 shares of common stock available for grant under the 2017 Plan. In addition, any shares of common stock subject to awards under the 2009 Plan that expire, are forfeited, or are otherwise surrendered, without having been fully exercised or resulting in any common stock being issued will become available for issuance under the prior plan, up to an additional 2,439,678 shares, which is the number of shares issuable pursuant to outstanding awards granted under the prior plan.

Also approved under the 2017 Plan is an annual increase for each of the years through December 31, 2027, equal to the least of (i) 3,573,766 shares of common stock, (ii) 4% of the shares of common stock outstanding on December 31 of the prior year and (iii) an amount determined by the Board.

Under the plans, the Board determines the number of shares of common stock to be granted pursuant to the awards, as well as the exercise price and terms of such awards. The exercise price of incentive stock options cannot be less than the fair value of the common stock on the date of grant. Stock options awarded under the plans expire 10 years after the grant date, unless the Board sets a shorter term. Options granted under the plans generally vest over a four‑year period. A portion of the unvested stock options will vest upon the sale of all or substantially all of the stock or assets of the Company.

In the past, the Company had granted stock options which contain performance‑based vesting criteria. These criteria were milestone events that were specific to the Company’s corporate goals. Stock‑based compensation expense associated with performance‑based stock options is recognized if the achievement of the performance condition is considered probable using management’s best estimates. As of March 31, 2020, there were no performance-based awards outstanding.

Inducement Stock Option Awards—During the three months ended March 31, 2020 and 2019, the Company granted non-statutory stock options to purchase an aggregate of 4,000 shares and 85,500 shares of the Company’s common stock, respectively. These stock options will vest over a four-year period, with 25% of the shares underlying each option award vesting on the one-year anniversary of the applicable employees’ new hire date and the remaining 75% of the shares underlying each award vesting monthly thereafter for three-years. Vesting of each option is subject to such employee’s continued service with the Company through the applicable vesting dates. These stock options were granted outside of the 2017 Plan as an inducement material to each employee’s acceptance of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4).

A summary of option activity for employee awards under the 2009 Plan, the 2017 Plan and inducement grants for the three months ended March 31, 2020 is as follows:


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Number of	Exercise		Contractual	Intrinsic
	Shares	Price		Term	Value
				(Years)	(in thousands)
Outstanding at January 1, 2020	7,453,076	$	7.46	7.7	$	1,313
Granted	1,469,422		3.85
Exercised	(61,158)		2.71
Forfeited	(43,397)		6.36
Outstanding at March 31, 2020	8,817,943	$	6.90	7.9	$	30,866
Vested or expected to vest at March 31, 2020	8,817,943	$	6.90	7.9	$	30,866
Options exercisable at March 31, 2020	4,441,194	$	7.14	6.9	$	15,609

The Company records stock‑based compensation related to stock options granted at fair value. The Company utilizes the Black‑Scholes option‑pricing model to estimate the fair value of stock option grants and to determine the related compensation expense. The assumptions used in calculating the fair value of stock‑based payment awards represent management’s best estimates. The assumptions used in determining fair value of the stock options granted during the three months ended March 31, 2020 and 2019, are as follows:


	Three Months Ended March 31,
	2020			2019
Expected volatility	79%	–	80%	81%	–	82%
Risk-free interest rate	1.46%	–	1.73%	2.49%	–	2.56%
Expected dividend yield		0%			0%
Expected term (in years)	5.90	–	6.08	5.52	–	6.63

The Company derived the risk‑free interest rate assumption from the U.S. Treasury rates for U.S. Treasury zero‑coupon bonds with maturities similar to those of the expected term of the awards being valued. The Company based the assumed dividend yield on its expectation of not paying dividends in the foreseeable future. The Company calculated the weighted‑average expected term of options using the simplified method, as the Company lacks relevant historical data due to the Company’s limited operating experience. The estimated volatility is based upon the historical volatility of comparable companies with publicly available share prices. The impact of forfeitures on compensation expense is recorded as they occur.

During the three months March 31, 2020 and 2019, the weighted average grant‑date fair value of options granted was $3.85 and $3.71, respectively. The fair value is being expensed over the vesting period of the options on a straight‑line basis as the services are being provided. As of March 31, 2020 and 2019, there was $21.7 million and $25.2 million, respectively, of unrecognized compensation cost related to the stock options granted, which is expected to be expensed over a weighted‑average period of 2.77 years and 2.91 years, respectively. Stock‑based compensation expense was classified in the statements of operations as follows (in thousands):


	Three Months Ended
	March 31,
	2020		2019

Cost of product revenues	$	20	$	2
Research and development		723		607
Selling, general and administrative		1,754		1,864
Total	$	2,497	$	2,473

Stock-based compensation costs for the Company’s manufacturing employees related to INVELTYS manufactured since FDA approval totaled $0.1 million and $0.3 million for the three months ended March 31, 2020 and 2019, respectively, and has been capitalized into inventory as a component of overhead expense. Capitalized stock-based compensation is recognized as an expense when the related product is sold or expensed to selling, general and administrative expense when the related sample is issued.

Employee Stock Purchase Plan—In 2017, the Company approved the 2017 Employee Stock Purchase Plan, which was amended and restated in December 2018 (as amended, the “ESPP”). The ESPP reserved an aggregate of 223,341 shares of common stock and provides for an annual increase on the first day of each fiscal year, beginning on January 1, 2019 and ending on December 31, 2029, in an amount equal to the lowest of: (1) 893,441 shares of the Company’s common stock; (2) 1% of the total number of shares of the Company’s common stock outstanding on the first day of the applicable fiscal year; and (3) an amount determined by the Company’s board of directors.

The ESPP provides for two six-month offering periods each year; the first offering period begins on the first trading day on or after each January 1; the second offering period begins on the first trading day on or after each July 1. Under the ESPP, participating employees can authorize the Company to withhold a portion of their base pay during consecutive six-month payment periods for the purchase of shares of the Company’s common stock. At the conclusion of the period, participating employees can purchase shares of the Company’s common stock at 85% of the lesser of the closing price of the common stock on (i) the first business day of the plan period or (ii) the exercise date. The fair value of the purchase rights granted under the ESPP was estimated on the date of grant, using the Black-Scholes option-pricing model. During the year ended December 31, 2019, employees of the Company purchased an aggregate of 123,664 shares under the ESPP. The second offering period closed on December 31, 2019. In January 2020, employees of the Company purchased an aggregate 85,553 shares under the ESPP.

Reserved Shares—As of March 31, 2020 and December 31, 2019, the Company had reserved the following shares of common stock issuable upon exercise of rights under equity compensation plans, inducement stock option awards, and warrant rights to acquire common stock:


	March 31,	December 31,
	2020	2019

Warrant rights to acquire Common Stock	384,163	384,163
ESPP	523,860	438,307
Outstanding inducement stock option awards	709,500	705,500
2009 Plan	2,439,678	2,530,586
2017 Plan	5,904,299	4,429,849
Total	9,961,500	8,488,405

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2020
Income Taxes
Income Taxes	11. INCOME TAXES The Company did not record a provision or benefit for income taxes during the three months ended March 31, 2020 and 2019. The Company continues to maintain a full valuation allowance for its U.S. federal and state deferred tax assets. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its generation of limited revenue from product sales 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. Management reevaluates the positive and negative evidence at each reporting period. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. Under the provisions of Section 382 of the Internal Revenue Code of 1986, as amended, certain substantial changes in the Company’s ownership, including a sale of the Company, or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of net operating loss carryforwards, which could be used annually to offset future taxable income. The Company recently completed an analysis and determined that an ownership change had occurred prior to December 31, 2019 and that such change has materially limited the net operating loss carryforwards and research and development tax credits available to offset future tax liabilities. The Company may be further limited by any changes that may have occurred or may occur subsequent to December 31, 2019. The Company files its corporate income tax returns in the United States and Massachusetts, Alabama, California, Montana, Oklahoma, Illinois, Kentucky, Pennsylvania, New Hampshire, New York, North Carolina and Texas. All tax years since the date of incorporation remain open to examination by the major taxing jurisdictions (state and federal) to which the Company is subject, as carryforward attributes generated in years past may still be adjusted upon examination by the Internal Revenue Service (“IRS”) or other authorities if they have or will be used in a future period. The Company is not currently under examination by the IRS or any other jurisdictions for any tax year. As of March 31, 2020, and 2019, the Company had no uncertain tax positions. The Company’s policy is to recognize interest and penalties related to income tax matters as a component of income tax expense, of which no interest or penalties were recorded for the three months ended March 31, 2020 and 2019.

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2020
Commitments and Contingencies.
Commitments and Contingencies	12. COMMITMENTS AND CONTINGENCIES License Agreement—In 2009, the Company entered into an exclusive license agreement with The Johns Hopkins University (“JHU”), as amended in November 2012, May 2014, August 2014, October 2014 and June 2018, which licensed to the Company a portfolio of specified patent rights and remains in full force and effect. Pursuant to the terms of the agreement, as amended, the Company agreed to pay an initial license fee, minimum annual payments beginning in 2017, certain development and commercial milestone payments, royalties on product sales and reimburse all or a portion of the costs associated with the preparation, filing, prosecution and maintenance of the agreed‑upon patents and patent applications to JHU. After 2016 and until the first commercial sale of product, which occurred in January 2019, the minimum annual payment was $37,500. Upon the first commercial sale of INVELTYS, the annual minimum payment increased to $0.1 million. The Company is obligated to pay JHU low single‑digit running royalties based upon a percentage of net sales of the licensed products, which is applied to the annual minimum payment. The Company also has an obligation to pay JHU certain one‑time development and commercial milestone payments. During the three months ended March 31, 2020 the Company paid JHU $11,800 in royalty payments associated with the sale of INVELTYS. The Company recorded other expenses related to the JHU agreement of $45,632 and $0 for the three months ended March 31, 2020 and 2019, respectively. Litigation—The Company is not currently subject to any material legal proceedings. Other Commitments — The Company entered into a commercial supply agreement with Catalent Pharma Solutions, LLC to manufacture commercial supplies of INVELTYS and EYSUVIS, with annual minimum purchase requirements. The Company is only subject to the minimum purchase requirements for EYSUVIS upon receiving FDA approval for the product.

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2020
Subsequent Events
Subsequent Events	13. SUBSEQUENT EVENTS The Company has evaluated all events and transactions that occurred after the balance sheet date through the date of this filing. During this period, the Company did not have any material subsequent events that impacted its condensed consolidated financial statements or disclosures.

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2020
Summary of Significant Accounting Policies
Recent Accounting Pronouncements	Recent Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”). ASU 2018-13 is intended to improve the effectiveness of disclosures in the notes to financial statements related to fair value measurements in Topic 820. This ASU will become effective for annual periods beginning after December 15, 2019, including interim periods within that period, and early adoption is permitted. The ASU was effective on January 1, 2020 and the adoption of ASU 2018-13 did not have a material effect on the Company’s condensed consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software -Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”). ASU 2018-15 aligns the accounting for implementation costs incurred in a hosting arrangement that is a service contract with the guidance on capitalizing costs associated with developing or obtaining internal-use software. This ASU became effective for annual periods beginning after December 15, 2019, including interim periods within that period, and early adoption is permitted. The ASU was effective on January 1, 2020 and the adoption of ASU 2018-15 did not have a material effect on the Company’s condensed consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 significantly changes the impairment model for most financial assets and certain other instruments. ASU 2016-13 will require immediate recognition of estimated credit losses expected to occur over the remaining life of many financial assets, which will generally result in earlier recognition of allowances for credit losses on loans and other financial instruments. In November 2019, the FASB issued ASU 2019-10, Financial Instruments - Credit Losses (Topic 326), Derivatives and Hedging (Topic 815),

Revenue (Tables)

3 Months Ended

Mar. 31, 2020

Revenue and Trade Receivables

Schedule of co-pay assistance program

The following table summarizes activity in each of the Company’s product revenue provision and allowance categories for the three months ended March 31, 2020:


	Trade Discounts,
	Allowances and				Rebates and
	Chargebacks (1)		Product Returns (2)		Incentives (3)

Balance at December 31, 2019	$	1,783	$	180		10,044
Provision related to current period sales		725		—		4,576
Changes in estimate related to prior period sales		2		(66)		93
Credit/payments made		(1,114)		—		(8,090)
Balance at March 31, 2020	$	1,396	$	114	$	6,623

(1)

(2)

(3)

Inventory (Tables)

3 Months Ended

Mar. 31, 2020

Inventory

Schedule of Inventory


	March 31,		December 31,
	2020		2019

Raw materials	$	1,387	$	1,387
Work in progress		3,541		4,166
Finished goods		4,165		2,873
Total inventory	$	9,093	$	8,426

Accrued Expenses (Tables)

3 Months Ended

Mar. 31, 2020

Accrued Expenses

Schedule of accrued expenses

	March 31,		December 31,
	2020		2019

Compensation and benefits	$	4,080	$	6,502
Accrued revenue reserves (1)		6,737		9,482
Development costs		984		1,600
Professional services		1,417		760
Commercial cost		408		930
Contract manufacturing		620		630
Other		465		1,025
Accrued expenses	$	14,711	$	20,929

(1) There were additional revenue reserves included in accounts payable of $0 and $0.7 million, as of March 31, 2020 and December 31, 2019, respectively.

Lease (Tables)

3 Months Ended

Mar. 31, 2020

Lease

Schedule of components of lease expense and related cash flows

The components of lease expense and related cash flows were as follows (in thousands):


	Three Months Ended March 31,
	2020		2019
Lease cost
Operating lease cost	$	1,185	$	1,102
Variable lease cost		410		124
Total lease cost	$	1,595	$	1,226

Operating cash outflows from operating leases	$	1,444	$	743

Debt (Tables)

3 Months Ended

Mar. 31, 2020

Debt

Schedule of carrying value of debt

The components of the carrying value of the debt as of March 31, 2020, and December 31, 2019 are detailed below (in thousands):


	March 31,		December 31,
	2020		2019
Principal loan balance	$	75,000	$	75,000
Unamortized debt discount and issuance cost		(3,782)		(3,999)
Cumulative accretion of exit fee		220		183
Long-term debt, net	$	71,438	$	71,184

Schedule of maturities of long-term debt

The annual principal payments due under the Athyrium Credit Facility as of March 31, 2020 were as follows (in thousands):


Years Ending December 31,
2020 (remaining nine months)	$	—
2021		—
2022		16,665
2023		33,330
2024		25,005
Total	$	75,000

Warrants (Tables)

3 Months Ended

Mar. 31, 2020

Warrants

Schedule of outstanding warrants


					Shares Exercisable at
	Exercise		Expiration	Exercisable	March 31,	December 31,
Issued	Price		Date	From	2020	2019
2013	$	7.50	April 2021	July 2017	82,816	82,816
2014	$	7.50	November 2024	July 2017	16,000	16,000
2016	$	8.27	October 2026	September 2017	14,512	14,512
2018	$	12.18	October 2025	October 2018	184,660	184,660
2018	$	12.18	October 2025	(1)	—	—
					297,988	297,988

As of March 31, 2020, and December 31, 2019, warrants outstanding to acquire 86,175 shares of common stock are not exercisable and are only exercisable upon draw down of the Term Loan B.

Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Stock-based Compensation

Summary of option activity for employee and non employee awards


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
	Number of	Exercise		Contractual	Intrinsic
	Shares	Price		Term	Value
				(Years)	(in thousands)
Outstanding at January 1, 2020	7,453,076	$	7.46	7.7	$	1,313
Granted	1,469,422		3.85
Exercised	(61,158)		2.71
Forfeited	(43,397)		6.36
Outstanding at March 31, 2020	8,817,943	$	6.90	7.9	$	30,866
Vested or expected to vest at March 31, 2020	8,817,943	$	6.90	7.9	$	30,866
Options exercisable at March 31, 2020	4,441,194	$	7.14	6.9	$	15,609

Schedule of assumptions used in determining fair value of the stock options granted


	Three Months Ended March 31,
	2020			2019
Expected volatility	79%	–	80%	81%	–	82%
Risk-free interest rate	1.46%	–	1.73%	2.49%	–	2.56%
Expected dividend yield		0%			0%
Expected term (in years)	5.90	–	6.08	5.52	–	6.63

Schedule of stock based compensation expense


	Three Months Ended
	March 31,
	2020		2019

Cost of product revenues	$	20	$	2
Research and development		723		607
Selling, general and administrative		1,754		1,864
Total	$	2,497	$	2,473

Schedule of reserved common stock shares upon exercise of rights under equity compensation plans


	March 31,	December 31,
	2020	2019

Warrant rights to acquire Common Stock	384,163	384,163
ESPP	523,860	438,307
Outstanding inducement stock option awards	709,500	705,500
2009 Plan	2,439,678	2,530,586
2017 Plan	5,904,299	4,429,849
Total	9,961,500	8,488,405

Nature of business (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Nature of business and basis of presentation
Accumulated deficit	$ (317,411)	$ (295,456)

Summary of Significant Accounting Policies - Basis of Presentation and Stock Split (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Summary of Significant Accounting Policies
Net loss attributable to common stockholders	$ (21,955)	$ (25,388)
Cash used in operations	$ (19,880)	$ (31,170)

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Adjustment to revenue	$ 354	$ 241
Allowance for bad debts	0	$ 800
Sales discounts and contractual fee for service arrangements
Allowance for bad debts	$ 1,400

Revenue - Co-pay Assistance Program (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Trade Discounts, Allowances and Chargebacks
Beginning balance	$ 1,783
Provision related to current period sales	725
Changes in estimate related to prior period sales	2
Credit/payments made	(1,114)
Ending balance	1,396
Product Returns
Beginning balance	180
Changes in estimate related to prior period sales	(66)
Ending balance	114
Rebates And Incentives
Beginning balance	10,044
Provision related to current period sales	4,576
Changes in estimate related to prior period sales	93
Credit/payments made	(8,090)
Ending balance	$ 6,623

Revenue - Accounts Receivable, net (Details) - USD ($) $ in Millions	Mar. 31, 2020	Mar. 31, 2019
Allowance for doubtful accounts	$ 0.0	$ 0.8
Sales discounts and contractual fee for service arrangements
Allowance for doubtful accounts	$ 1.4

Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Inventory
Raw Materials	$ 1,387	$ 1,387
Work in Progress	3,541	4,166
Finished Goods	4,165	2,873
Total inventory	9,093	8,426
Inventory	5,272	4,648
Long-term inventory	$ 3,821	$ 3,778

Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Compensation and benefits	$ 4,080	$ 6,502
Accrued revenue reserves	6,737	9,482
Development costs	984	1,600
Professional services	1,417	760
Commercial cost	408	930
Contract manufacturing	620	630
Other	465	1,025
Accrued expenses	14,711	20,929
Accounts payable
Accrued revenue reserves	$ 0	$ 700

Lease (Details) $ in Thousands	3 Months Ended
Lease (Details) $ in Thousands	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Nov. 15, 2018
Leases
Restricted cash	$ 12,584	$ 12,575	$ 12,582
Variable lease cost	$ 410	124
Remaining lease term	1 year 10 months 24 days
Number of vehicles leased under a master fleet lease agreement \| item	65
Term of vehicle lease	3 years
Amount borrowed	$ 500
Lease cost
Operating lease cost	1,185	1,102
Variable Lease, Cost	410	124
Total lease cost	1,595	1,226
Operating cash outflows from operating leases	1,444	743
Operating Lease, Right-of-Use Asset	$ 29,308		$ 29,781
Watertown Lease
Leases
Lease term	13 years
Restricted cash	$ 2,000
Discount rate (as a percent)				9.90%
Variable lease cost	$ 400	100
Remaining lease term	11 years 7 months 6 days
Lease cost
Variable Lease, Cost	$ 400	$ 100

Debt (Details) - USD ($) $ in Thousands	3 Months Ended
Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019	Oct. 01, 2018
Debt instruments
Amount borrowed	$ 500
Interest expense	$ 2,128	$ 2,094
Term Loan A
Debt instruments
Interest rate (as a percent)			9.875%
Aggregate principal amount			$ 75,000
Term Loan B
Debt instruments
Aggregate principal amount			$ 35,000

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Debt - Athyrium Credit Facility (Details) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	Oct. 01, 2018 USD ($) $ / shares shares	Mar. 31, 2020 USD ($) item $ / shares shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)
Debt instruments
Warrant exercisable \| shares		297,988		297,988
Interest expense		$ 2,128	$ 2,094
Warrants 2018
Debt instruments
Exercise Price \| $ / shares		$ 12.18
Warrant exercisable \| shares		184,660		184,660
Remaining warrant exercisable upon condition \| shares		86,175		86,175
Athyrium Credit Facility
Debt instruments
Aggregate principal amount	$ 110,000	$ 75,000			$ 75,000
Cumulative accretion of exit fee		$ 220			183
Present value of prepayments if prepayment occurs prior to the second anniversary (as a percent)	105.00%
Prepayments if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary (as a percent)	3.00%
Prepayments if prepayment occurs on or after the third anniversary (as a percent)	2.00%
Prepayments if prepayment occurs after the fourth anniversary (as a percent)	0.00%
Additional interest rate upon an event of default accrued (as a percent)	3.00%
Total interest rate (as a percent)	12.875%
Number of features of embedded derivative \| item		2
Number of derivatives \| item		1
Financial covenant amount	$ 10,000
Restricted Cash and Cash Equivalents		$ 10,000		$ 10,000
Debt issuance costs		3,782			$ 3,999
Interest expense		2,100
Amortization of debt discount		200
Contractual coupon interest		$ 1,900
Athyrium Credit Facility \| Warrants 2018
Debt instruments
Warrant to purchase shares of common stock \| shares	270,835
Exercise Price \| $ / shares	$ 12.18456
Warrant exercisable \| shares	184,660
Remaining warrant exercisable upon condition \| shares	86,175
Initial fair value of the Warrant	$ 1,900
Term Loan A
Debt instruments
Aggregate principal amount	$ 75,000
Interest rate (as a percent)	9.875%
Exit fee of the total principal payments (as a percent)	1.00%
Cumulative accretion of exit fee	$ 700
Term Loan B
Debt instruments
Aggregate principal amount	$ 35,000

Debt - Carrying Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2018
Debt instruments
Long-term debt, net	$ 71,438	$ 71,184
Athyrium Credit Facility
Debt instruments
Principal Loan Balance	75,000		$ 75,000	$ 110,000
Unamortized debt discount and issuance cost	(3,782)		(3,999)
Accretion of exit fee	220		183
Long-term debt, net	$ 71,438		$ 71,184

Debt - Future annual principal payments (Details) - Athyrium Credit Facility $ in Thousands	Mar. 31, 2020 USD ($)
Maturities of long-term debt
2022	$ 16,665
2023	33,330
2024	25,005
Total	$ 75,000

Warrants (Details) - $ / shares	3 Months Ended	12 Months Ended
Warrants (Details) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Preferred stock warrants
Shares Exercisable	297,988	297,988
Warrants 2013
Preferred stock warrants
Exercise Price	$ 7.50
Shares Exercisable	82,816	82,816
Warrants 2014
Preferred stock warrants
Exercise Price	$ 7.50
Shares Exercisable	16,000	16,000
Warrants 2016
Preferred stock warrants
Exercise Price	$ 8.27
Shares Exercisable	14,512	14,512
Warrants 2018
Preferred stock warrants
Exercise Price	$ 12.18
Shares Exercisable	184,660	184,660
Shares Exercisable upon condition	86,175	86,175

Equity Financings (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended	12 Months Ended
	Apr. 03, 2020	Mar. 11, 2020	Oct. 05, 2018	Aug. 27, 2018	Mar. 31, 2020	Dec. 31, 2019
Equity Offerings
Net proceeds					$ 130,754
Underwriters discount and offering costs					8,100
Underwriter's option
Equity Offerings
Issuance of common stock	979,371	2,400,000
Period granted		30 days
Price per share	$ 7.89
Net proceeds	$ 7,200
Shelf
Equity Offerings
Share authorized value (shelf)	$ 18,300				$ 26,100
Registration period				3 years
Sales agreement			$ 50,000
Shelf \| Maximum
Equity Offerings
Additional authorized value of securities				$ 250,000
2020 Offering
Equity Offerings
Issuance of common stock	16,979,371	16,000,000
Price per share		$ 7.89
Net proceeds	$ 125,400	$ 118,200
ATM
Equity Offerings
Issuance of common stock					2,352,671	2,592,934
Net proceeds					$ 12,500	$ 13,100

Stock-based Compensation - Narrative (Details) - shares	3 Months Ended	12 Months Ended
Stock-based Compensation - Narrative (Details) - shares	Mar. 31, 2020	Dec. 31, 2017	Dec. 31, 2019
Stock-based compensation
Common stock available for future grant	9,961,500		8,488,405
2017 Equity Incentive Plan
Stock-based compensation
Common stock available for future grant	138,513
2017 Equity Incentive Plan \| Maximum
Stock-based compensation
Common stock available for future grant	2,439,678
2017 Equity Incentive Plan \| Minimum
Stock-based compensation
Common stock available for future grant		3,573,766
Percentage of aggregate number of common shares reserved for future issuance (as a percent)		4.00%
2009 plan
Stock-based compensation
Common stock available for future grant	2,439,678		2,530,586
Number of shares outstanding	8,817,943		7,453,076
Employee and Non-Employee Stock Options
Stock-based compensation
Common stock available for future grant	709,500		705,500
Employee and Non-Employee Stock Options \| 2009 plan
Stock-based compensation
Options Expiry Term	10 years
Vesting Period	4 years
Performance Stock Options
Stock-based compensation
Number of shares outstanding	0
ESPP
Stock-based compensation
Common stock available for future grant	523,860		438,307

Stock-based Compensation - Inducement Stock Option Awards (Details) - Non-statutory Stock Options - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Options Expiry Term	4 years
Vesting Period	3 years
Granted (in shares)	4,000	85,500
Percentage of vesting of share-based compensation awards on the one year anniversary of the grant date	25.00%
Anniversary of the share-based compensation arrangement	1 year
Percentage of vesting of share-based compensation awards after the year anniversary of the grant date	75.00%

Stock-based Compensation - Stock Options (Details) - 2009 plan - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Number of Shares
Outstanding at the beginning of the period (in shares)	7,453,076
Granted (in shares)	1,469,422
Exercised (in shares)	(61,158)
Forfeited	(43,397)
Outstanding at the end of the period (in shares)	8,817,943	7,453,076
Vested and expected to vest (in shares)	8,817,943
Options exercisable (in shares)	4,441,194
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 7.46
Granted (in dollars per share)	3.85
Exercised (in dollars per share)	2.71
Forfeited (in dollars per share)	6.36
Outstanding at the end of the period (in dollars per share)	6.90	$ 7.46
Vested and expected to vest (in dollars per share )	6.90
Options exercisable (in dollars per shares)	$ 7.14
Weighted Average Remaining Contractual Term
Weighted average period	7 years 10 months 24 days	7 years 8 months 12 days
Vested and expected to vest	7 years 10 months 24 days
Options exercisable	6 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding at the beginning of the period (in dollars)	$ 1,313
Outstanding at the end of the period (in dollars)	30,866	$ 1,313
Vested and expected to vest (in dollars)	30,866
Options exercisable (in dollars)	$ 15,609

Stock-based Compensation - Fair Value Assumptions (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Assumptions used in determining fair value of the stock options granted
Expected volatility (minimum)	79.00%	81.00%
Expected volatility (maximum)	80.00%	82.00%
Risk-free interest rate (minimum)	1.46%	2.49%
Risk-free interest rate (maximum)	1.73%	2.56%
Expected dividend yield	0.00%	0.00%
Minimum
Assumptions used in determining fair value of the stock options granted
Expected term (in years)	5 years 10 months 24 days	5 years 6 months 7 days
Maximum
Assumptions used in determining fair value of the stock options granted
Expected term (in years)	6 years 29 days	6 years 7 months 17 days

Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Weighted average grant date fair value of options granted	$ 3.85	$ 3.71
2009 plan
Stock-based compensation
Unrecognized compensation expense	$ 21.7	$ 25.2
Weighted average expense recognition period	2 years 9 months 7 days	2 years 10 months 28 days

Stock-based Compensation - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Stock based compensation expense	$ 2,497	$ 2,473
Cost of product revenues
Stock-based compensation
Stock based compensation expense	20	2
Research and development
Stock-based compensation
Stock based compensation expense	723	607
Selling, general and administrative
Stock-based compensation
Stock based compensation expense	$ 1,754	$ 1,864

Stock-based Compensation - Compensation expense - INVELTYS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Stock based compensation expense	$ 2,497	$ 2,473
Inventories \| INVELTYS
Stock-based compensation
Stock based compensation expense	$ 100	$ 300

Stock-based Compensation - Employee Stock Purchase Plan (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2020 shares	Mar. 31, 2020 USD ($) item shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 shares	Dec. 31, 2018 shares
Stock-based compensation
Stock-based compensation expense \| $		$ 2,584	$ 2,738
2017 Employee Stock Purchase Plan
Stock-based compensation
Shares Authorized					223,341
Employee basic pay holding period		6 months
Number of offering periods \| item		2
Percentage of market value at which employee may purchase stock		85.00%
Issuance under employee stock purchase plan (in shares)	85,553			123,664
2017 Employee Stock Purchase Plan \| Maximum
Stock-based compensation
Shares Authorized		893,441
Threshold percentage of share available to grant		1.00%

Stock-based Compensation - Reserved Shares (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Stock-based compensation
Common stock shares reserved for future issuance	9,961,500	8,488,405
2017 Employee Stock Purchase Plan
Stock-based compensation
Common stock shares reserved for future issuance	5,904,299	4,429,849
ESPP
Stock-based compensation
Common stock shares reserved for future issuance	523,860	438,307
Employee and Non-Employee Stock Options
Stock-based compensation
Common stock shares reserved for future issuance	709,500	705,500
Warrants
Stock-based compensation
Common stock shares reserved for future issuance	384,163	384,163
2009 plan
Stock-based compensation
Common stock shares reserved for future issuance	2,439,678	2,530,586

Income Taxes (Details) - USD ($)	3 Months Ended
Income Taxes (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2019
Income Taxes
Income tax expense	$ 0	$ 0
Uncertain tax positions	0	0
Interest or penalties recorded	$ 0	$ 0

Commitments and Contingencies - License Agreement (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Contingencies
Research and development expenses	$ 5,434,000	$ 6,959,000
The Johns Hopkins University (“JHU”)
Contingencies
Minimum annual payment	37,500
License fee, if the company achieves the first commercial sale	100,000
First commercial sale milestone	11,800
Research and development expenses	$ 45,632	$ 0