Axcella Health (AXLA) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-38501
Entity Registrant Name	AXCELLA HEALTH INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3321056
Entity Address, Address Line One	840 Memorial Drive
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	320-2200
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	AXLA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		37,722,435
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0001633070
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 43,049	$ 71,590
Marketable securities	49,909	35,739
Prepaid expenses and other current assets	977	1,692
Total current assets	93,935	109,021
Property and equipment, net	334	360
Other assets	211	211
Total assets	94,480	109,592
Current liabilities:
Accounts payable	1,538	2,290
Accrued expenses and other current liabilities	4,604	5,494
Current portion of long-term debt	4,333	0
Total current liabilities	10,475	7,784
Long-term debt, net of current portion and discount	20,983	25,222
Other liabilities	1,364	1,205
Total liabilities	32,822	34,211
Commitments and contingencies (Note 10)	0	0
Stockholders' equity:
Common stock, $0.001 par value; 150,000,000 shares authorized, 38,109,416 and 38,022,273 shares issued and 37,690,435 and 37,603,292 shares outstanding at March 31, 2021 and December 31, 2020, respectively	38	38
Additional paid-in capital	349,449	347,990
Treasury stock, 418,981 shares at cost	0	0
Accumulated other comprehensive loss	(27)	(34)
Accumulated deficit	(287,802)	(272,613)
Total stockholders' equity	61,658	75,381
Total liabilities and stockholders' equity	$ 94,480	$ 109,592

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value (USD per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	150,000,000	150,000,000
Common stock issued (in shares)	38,109,416	38,022,273
Common stock outstanding (in shares)	37,690,435	37,603,292
Treasury stock at cost (in shares)	418,981	418,981

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 10,240	$ 10,335
General and administrative	4,256	4,125
Total operating expenses	14,496	14,460
Loss from operations	(14,496)	(14,460)
Other income (expense):
Interest income	35	257
Interest expense	(728)	(802)
Other income (expense), net	0	(4)
Total other income (expense), net	(693)	(549)
Net loss	$ (15,189)	$ (15,009)
Net loss per basic and diluted (USD per share)	$ (0.40)	$ (0.65)
Weighted average common shares outstanding, basic and diluted (in shares)	37,652,158	23,188,816
Comprehensive loss:
Net loss	$ (15,189)	$ (15,009)
Other comprehensive income (loss):
Unrealized gains on marketable securities	7	0
Comprehensive loss	$ (15,182)	$ (15,009)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (15,189)	$ (15,009)
Adjustment to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	64	131
Stock-based compensation	1,428	1,599
Non-cash interest expense	162	133
Other non-cash items	179	0
Changes in current assets and liabilities:
Prepaid expenses and other current assets	715	115
Accounts payable	(711)	(286)
Accrued expenses and other current liabilities	(793)	(3,214)
Net cash used in operating activities	(14,145)	(16,531)
Cash flows from investing activities:
Purchases of property and equipment	(50)	0
Purchases of marketable securities	(16,717)	0
Proceeds from maturities of marketable securities	2,375	0
Net cash used in investing activities	(14,392)	0
Cash flows from financing activities:
Public offering costs paid in the current period	(31)	0
Proceeds from exercise of common stock options	27	0
Net cash used in financing activities	(4)	0
Net decrease in cash and cash equivalents	(28,541)	(16,531)
Cash and cash equivalents, beginning of period	71,590	92,053
Cash and cash equivalents, end of period	43,049	75,522
Supplemental cash flow information:
Cash paid for interest	566	669
Purchases of property and equipment included in accounts payable and accrued expenses	$ 0	$ 59

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at beginning of period (in shares) at Dec. 31, 2019		23,607,797
Balance at beginning of period at Dec. 31, 2019	$ 60,224	$ 24	$ 276,286	$ 0	$ (216,086)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,599		1,599
Net loss	(15,009)				(15,009)
Balance at end of period (in shares) at Mar. 31, 2020		23,607,797
Balance at end of period at Mar. 31, 2020	46,814	$ 24	277,885	0	(231,095)
Balance at beginning of period (in shares) at Dec. 31, 2020		38,022,273
Balance at beginning of period at Dec. 31, 2020	75,381	$ 38	347,990	(34)	(272,613)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Costs incurred for the issuance of common stock	$ 4		4
Exercise of common stock options (in shares)	27,143	27,143
Exercise of common stock options	$ 27		27
Vesting of restricted stock units (in shares)		60,000
Stock-based compensation	1,428		1,428
Unrealized gain on marketable securities	7			7
Net loss	(15,189)				(15,189)
Balance at end of period (in shares) at Mar. 31, 2021		38,109,416
Balance at end of period at Mar. 31, 2021	$ 61,658	$ 38	$ 349,449	$ (27)	$ (287,802)

NATURE OF BUSINESS

NATURE OF BUSINESS	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF BUSINESS	NATURE OF BUSINESS Axcella Health Inc. and subsidiaries ("Axcella," the "Company" or "we") is a biotechnology company that was incorporated in Delaware on August 27, 2008 and has a principal place of business in Cambridge, Massachusetts. The Company is focused on pioneering a new approach to treat complex diseases and improve health using endogenous metabolic modulator, or EMM, compositions. The Company's product candidates are comprised of multiple EMMs that are engineered in distinct combinations and ratios with the goal of simultaneously impacting multiple biological pathways. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, successful development of technology, obtaining additional funding, protection of proprietary technology, compliance with government regulations, risks of failure of preclinical studies, Clinical Studies and Clinical Trials, the need to obtain marketing approval for its product candidates, if required, and successfully market products, fluctuations in operating results, economic pressure impacting therapeutic pricing, dependence on key personnel, risks associated with changes in technologies, development by competitors of technological innovations and the ability to scale manufacturing to large scale production. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and any necessary regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The accompanying condensed consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has historically funded its operations with proceeds from sales of preferred and common stock and borrowings under a loan and security agreement. As of March 31, 2021, the Company had an accumulated deficit of $287.8 million. The Company expects to continue to generate operating losses in the foreseeable future. The Company expects that its cash, cash equivalents and marketable securities at March 31, 2021 will be sufficient to fund its operations for at least the next 12 months following the filing date of this Quarterly Report on Form 10-Q.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Furthermore, the accompanying condensed consolidated financial statements are unaudited and certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. As of March 31, 2021, the Company’s significant accounting policies and estimates, which are detailed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, have not changed, and the unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements as of and for the year ended December 31, 2020. The accompanying interim condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2021, the results of its operations for the three months ended March 31, 2021 and 2020, its cash flows for the three months ended March 31, 2021 and 2020, and its statements of stockholders’ equity for the three months ended March 31, 2021 and 2020. The results for the three months ended March 31, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2020, and the notes thereto, together with Management’s Discussion and Analysis of Financial Condition and Results of Operations, contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of Axcella Health Inc. and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the CEO, who is the chief operating decision maker, in making decisions on how to allocate resources and assess performance. The Company operates in one reportable business segment. Use of Estimates The preparation of the condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting period. The Company bases its estimates on historical experience, known trends and other market-specific or relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions. Cash and Cash Equivalents Cash and cash equivalents include cash held in banks and amounts held in interest-bearing money market accounts. Cash equivalents are carried at cost, which approximates their fair market value. The Company considers all highly liquid investments with a remaining maturity when purchased of three months or less to also be cash equivalents. Marketable Securities The Company’s marketable securities, which consisted of corporate debt obligations as of March 31, 2021, are classified as available-for-sale and are reported at fair value. Unrealized gains and losses on available-for-sale securities are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the condensed consolidated statements of operations and comprehensive loss. No such adjustments were necessary during the periods presented. Concentrations of Credit Risk The Company has no off-balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company’s cash equivalents and marketable securities as of March 31, 2021 consisted of bank deposits, money market funds that invest in U.S. treasury securities, and corporate obligations. We invest in high-quality financial instruments and our portfolio does not consist of any instrument with a maturity duration in excess of twenty-four months, which we believe limits our credit risk. In addition, the Company's investment policy includes guidelines on the quality of the institutions and financial instruments and defines the allowable investments that the Company believes minimizes the exposure to concentrations of credit risk. The Company has not experienced any credit losses and does not believe that it is subject to significant credit risk. Fair Value Measurements Certain assets and liabilities of the Company are carried at fair value. 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 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. The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the long-term debt approximates fair value as evidenced by the recent amendment to the Company's debt facility. 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 three months ended March 31, 2021, the Company’s only element of other comprehensive loss was unrealized gains (losses) on marketable securities. Net Loss Per Share Basic net loss per share attributable to common stockholders is calculated by dividing net loss by the weighted average shares outstanding during the period. Diluted net income (loss) per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period. All common stock equivalents have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. Accounting Pronouncements Issued and Not Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), as amended by various subsequently issued ASUs. The standard requires lessees to recognize an operating lease with a term greater than one year on their balance sheets as a right-of-use asset and corresponding lease liability, measured at the present value of the lease payments. The new standard will become effective for the Company on January 1, 2022. The Company expects to apply the modified retrospective approach as of the date of adoption such that prior periods will not be restated. The Company is evaluating the effect that adoption of the standard is expected to have on the Company’s condensed consolidated financial statements and related disclosures and will recognize a lease obligation and right of use asset for its existing operating leases with a lease term greater than one year upon adoption. The Company anticipates that the adoption of ASU 2016-02 will have a material impact on the Company’s financial position and the related footnote disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326) . The new standard adjusts the accounting for assets held at amortized cost basis, including marketable securities accounted for as available-for-sale. The standard eliminates the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. The Company is required to adopt this standard effective January 1, 2023 and the Company is evaluating the impact the guidance will have on its condensed consolidated financial statements.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The following tables present the Company’s assets that are measured at fair value on a recurring basis and indicate the level within the fair value hierarchy (in thousands): Fair Value Measurements at March 31, 2021 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 40,549 $ — $ — $ 40,549 Marketable securities: Corporate obligations — 49,909 — 49,909 Total $ 40,549 $ 49,909 $ — $ 90,458 Fair Value Measurements at December 31, 2020 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 69,118 $ — $ — $ 69,118 Marketable securities: Corporate obligations — 35,739 — 35,739 Total $ 69,118 $ 35,739 $ — $ 104,857

CASH, CASH EQUIVALENTS, AND MAR

CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES	CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES As of March 31, 2021, and December 31, 2020, cash, cash equivalents and marketable securities by security type consisted of the following (in thousands): March 31, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents $ 43,049 $ — $ — $ 43,049 Corporate obligations 49,936 5 (32) 49,909 Total $ 92,985 $ 5 $ (32) $ 92,958 December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents $ 71,590 $ — $ — $ 71,590 Corporate obligations 35,773 1 (35) 35,739 Total $ 107,363 $ 1 $ (35) $ 107,329 The fair values of cash equivalents and marketable securities by contractual maturity were as follows (in thousands): Contractual Maturities March 31, December 31, Mature in one year or less $ 64,114 $ 86,338 Mature in two years or less 26,344 18,519 Total $ 90,458 $ 104,857 Marketable securities with maturities beyond one year are classified as short-term marketable securities in the condensed consolidated balance sheets due to their highly liquid nature and because they represent the Company’s investments that are available for current operations. All cash equivalents mature within three months or less. Operating cash of $2.5 million and $2.5 million is excluded from the above table as of March 31, 2021 and December 31, 2020, respectively.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment consist of the following (in thousands): March 31, December 31, Laboratory equipment $ 3,060 $ 3,022 Leasehold improvements 564 564 Office and computer equipment 111 111 Furniture and fixtures 122 122 Property and equipment 3,857 3,819 Less: accumulated depreciation and amortization (3,523) (3,459) Property and equipment, net $ 334 $ 360

ACCRUED EXPENSES AND OTHER CURR

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, Accrued employee compensation and benefits $ 832 $ 2,998 Accrued external research and development expenses 3,245 1,870 Accrued professional fees and other 527 626 Total accrued expenses and other current liabilities $ 4,604 $ 5,494

DEBT FINANCING

DEBT FINANCING	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
DEBT FINANCING	DEBT FINANCING Long-term debt consisted of the following (in thousands): March 31, December 31, Principal amount of long-term debt $ 26,000 $ 26,000 Debt discount (271) (308) Deferred financing fees (413) (470) Current portion of long-term debt (4,333) — Long-term debt, net of current portion and discount $ 20,983 $ 25,222 In January 2018, the Company entered into a Loan and Security Agreement. Under the Loan and Security Agreement, t he Company granted the lender a first priority security interest in all assets of the Company, excluding intellectual property and granted a negative pledge on such intellectual property. The interest rate is LIBOR plus 8.50% per annum. On August 28, 2020, the Loan and Security Agreement was further amended to, among other things; (i) extend the date on which repayment of principal commences until November 2021, (ii) provide for further extensions of the date on which repayment of principal commences to February 2022 and May 2022, provided that certain specified regulatory and clinical milestones are satisfied by the Company, (iii) increase the final payment fee from 5.35% to 6.35% and (iv) add a 0.2% floor to the LIBOR rate. The Company achieved two of the specified regulatory and clinical milestones and the date on which repayment of principal commences was extended to February 2022. The monthly principal payments of $2.2 million will be paid over a period of 12 months . The interest rate was 8.70% as of March 31, 2021 . The Company's debt facility includes a terminal interest fee obligation totaling $1.7 million, which is due with the final principal payment of the loan and has been modified from time to time as the facilities were amended. The Company is accruing the terminal fee obligation over the term of the facility. The carrying value of the terminal interest fee was $1.1 million and $1.1 million at March 31, 2021 and December 31, 2020, respectively. The scheduled principal maturity of the long-term debt as of March 31, 2021 is as follows (in thousands): Year Ending December 31, 2021 $ — 2022 23,833 2023 2,167 $ 26,000

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY 2019 Stock Option and Incentive Plan The 2019 Stock Option and Incentive Plan (the "2019 Plan") provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards and cash-based awards to the Company's officers, employees, directors and consultants. The number of shares available for future issuance under the 2019 Plan was 1,173,347 shares as of March 31, 2021. 2019 Employee Stock Purchase Plan The 2019 Employee Stock Purchase Plan (the "2019 ESPP") provides participating employees with the opportunity to purchase shares of common stock. The number of shares available for future issuance under the 2019 ESPP was 666,207 shares as of March 31, 2021. Stock-Based Compensation Expense In connection with all share-based payment awards, total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 410 $ 716 General and administrative 1,018 883 Total stock-based compensation expense $ 1,428 $ 1,599 Fair Value of Stock Options The fair value of each option issued to employees was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended 2021 2020 Risk-free interest rate 0.76 % 1.64 % Expected option life (in years) 6.02 6.11 Expected dividend yield — % — % Expected volatility 97.2 % 72.5 % Stock Option Activity The following table summarizes the Company’s stock option activity for the three months ended March 31, 2021: Number of Shares Weighted Weighted Intrinsic Outstanding as of January 1, 2021 4,919,960 $ 6.37 Granted 1,682,976 6.31 Exercised (27,143) 1.00 Canceled (536,960) 7.74 Outstanding as of March 31, 2021 6,038,833 $ 6.26 7.58 $ 1,659 Exercisable as of March 31, 2021 3,051,583 $ 6.44 6.08 $ 1,275 Vested or expected to vest as of March 31, 2021 5,988,833 $ 6.22 7.50 $ 1,625 The intrinsic value of options exercised during the three months ended March 31, 2021 was $117,000. The intrinsic value of options exercised during the same period in 2020 was nominal. The weighted-average grant date fair value of the options granted during the three months ended March 31, 2021 and 2020, was $4.81 and $2.69 per share, respectively. As of March 31, 2021, there was $12.1 million of unrecognized compensation expense that is expected to be recognized over a weighted-average period of approximately 2.85 years. Restricted Stock Units The fair values of restricted stock units are based on the market value of our stock on the date of grant. The following table summarizes the Company's restricted stock unit activity for the three months ended March 31, 2021: Number of Shares Weighted Average Outstanding as of January 1, 2021 347,587 $ 4.04 Granted 120,916 6.41 Vested (60,000) 4.98 Forfeited — — Outstanding as of March 31, 2021 408,503 $ 4.60

NET LOSS PER SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three Months Ended 2021 2020 Options to purchase common stock 6,038,833 5,443,078 Unvested restricted stock units 408,503 162,967 Shares issuable under employee stock purchase plan 22,870 — 6,470,206 5,606,045

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Other Commitments We enter into contracts in the normal course of business with contract research organizations ("CROs"), contract manufacturing organizations ("CMOs") and other third parties for preclinical research studies, Clinical Studies, Clinical Trials and testing and manufacturing services. These contracts do not contain minimum purchase commitments and are cancelable upon prior written notice. Payments due upon cancellation consist only of payments for services provided or expenses incurred, including non-cancelable obligations of service providers, up to the date of cancellation. Legal Proceedings

RELATED-PARTY TRANSACTIONS

RELATED-PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2021
Related Party Transactions [Abstract]
RELATED-PARTY TRANSACTIONS	RELATED-PARTY TRANSACTIONSIn August 2019, the Company entered into a consulting agreement with the chairman of the Company's Board of Directors to provide various consulting services to the Company. The total cash expense under the agreement for the three months ended March 31, 2021 and 2020 was $0.1 million and $0.1 million, respectively. As of March 31, 2021, there were no amounts payable to the chairman for costs related to the consulting agreement. In March 2021, the consulting agreement was modified so that the chairman would no longer receive cash compensation for his consulting services and would instead be compensated solely via equity compensation. The aggregate grant date fair value of the equity awarded to the chairman in 2021 and 2020 for his consulting services was $0.6 million and $0.2 million, respectively. The grant date fair value is calculated in accordance with FASB ASC Topic 718.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTSThe Company has evaluated subsequent events for financial statement purposes occurring through the date these condensed consolidated financial statements were issued and determined that there are no material recognized or unrecognized subsequent events requiring disclosure.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Furthermore, the accompanying condensed consolidated financial statements are unaudited and certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. As of March 31, 2021, the Company’s significant accounting policies and estimates, which are detailed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, have not changed, and the unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements as of and for the year ended December 31, 2020. The accompanying interim condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2021, the results of its operations for the three months ended March 31, 2021 and 2020, its cash flows for the three months ended March 31, 2021 and 2020, and its statements of stockholders’ equity for the three months ended March 31, 2021 and 2020.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of Axcella Health Inc. and its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation.
Segment Information	Segment InformationOperating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the CEO, who is the chief operating decision maker, in making decisions on how to allocate resources and assess performance. The Company operates in one reportable business segment.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting period. The Company bases its estimates on historical experience, known trends and other market-specific or relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates as there are changes in circumstances, facts and experience. Actual results may differ from those estimates or assumptions.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash held in banks and amounts held in interest-bearing money market accounts. Cash equivalents are carried at cost, which approximates their fair market value. The Company considers all highly liquid investments with a remaining maturity when purchased of three months or less to also be cash equivalents.
Marketable Securities	Marketable Securities The Company’s marketable securities, which consisted of corporate debt obligations as of March 31, 2021, are classified as available-for-sale and are reported at fair value. Unrealized gains and losses on available-for-sale securities are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity. Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss. The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the condensed consolidated statements of operations and comprehensive loss. No such adjustments were necessary during the periods presented.
Concentrations of Credit Risk	Concentrations of Credit Risk The Company has no off-balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company’s cash equivalents and marketable securities as of March 31, 2021 consisted of bank deposits, money market funds that invest in U.S. treasury securities, and corporate obligations. We invest in high-quality financial instruments and our portfolio does not consist of any instrument with a maturity duration in excess of twenty-four months, which we believe limits our credit risk. In addition, the Company's investment policy includes guidelines on the quality of the institutions and financial instruments and defines the allowable investments that the Company believes minimizes the exposure to concentrations of credit risk. The Company has not experienced any credit losses and does not believe that it is subject to significant credit risk.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities of the Company are carried at fair value. 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 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. The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the long-term debt approximates fair value as evidenced by the recent amendment to the Company's debt facility.
Comprehensive Loss	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 three months ended March 31, 2021, the Company’s only element of other comprehensive loss was unrealized gains (losses) on marketable securities.
Net Loss Per Share	Net Loss Per ShareBasic net loss per share attributable to common stockholders is calculated by dividing net loss by the weighted average shares outstanding during the period. Diluted net income (loss) per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period. All common stock equivalents have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented.
Accounting Pronouncements Issued and Not Adopted	Accounting Pronouncements Issued and Not Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), as amended by various subsequently issued ASUs. The standard requires lessees to recognize an operating lease with a term greater than one year on their balance sheets as a right-of-use asset and corresponding lease liability, measured at the present value of the lease payments. The new standard will become effective for the Company on January 1, 2022. The Company expects to apply the modified retrospective approach as of the date of adoption such that prior periods will not be restated. The Company is evaluating the effect that adoption of the standard is expected to have on the Company’s condensed consolidated financial statements and related disclosures and will recognize a lease obligation and right of use asset for its existing operating leases with a lease term greater than one year upon adoption. The Company anticipates that the adoption of ASU 2016-02 will have a material impact on the Company’s financial position and the related footnote disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326) . The new standard adjusts the accounting for assets held at amortized cost basis, including marketable securities accounted for as available-for-sale. The standard eliminates the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. The Company is required to adopt this standard effective January 1, 2023 and the Company is evaluating the impact the guidance will have on its condensed consolidated financial statements.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Assets Measured at Fair Value	The following tables present the Company’s assets that are measured at fair value on a recurring basis and indicate the level within the fair value hierarchy (in thousands): Fair Value Measurements at March 31, 2021 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 40,549 $ — $ — $ 40,549 Marketable securities: Corporate obligations — 49,909 — 49,909 Total $ 40,549 $ 49,909 $ — $ 90,458 Fair Value Measurements at December 31, 2020 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 69,118 $ — $ — $ 69,118 Marketable securities: Corporate obligations — 35,739 — 35,739 Total $ 69,118 $ 35,739 $ — $ 104,857

CASH, CASH EQUIVALENTS, AND M_2

CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Schedule of Cash, Cash Equivalents, and Marketable Securities by Security Type	As of March 31, 2021, and December 31, 2020, cash, cash equivalents and marketable securities by security type consisted of the following (in thousands): March 31, 2021 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents $ 43,049 $ — $ — $ 43,049 Corporate obligations 49,936 5 (32) 49,909 Total $ 92,985 $ 5 $ (32) $ 92,958 December 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents $ 71,590 $ — $ — $ 71,590 Corporate obligations 35,773 1 (35) 35,739 Total $ 107,363 $ 1 $ (35) $ 107,329
Schedule of Fair Values of Cash Equivalents and Marketable Securities by Contractual Maturities	The fair values of cash equivalents and marketable securities by contractual maturity were as follows (in thousands): Contractual Maturities March 31, December 31, Mature in one year or less $ 64,114 $ 86,338 Mature in two years or less 26,344 18,519 Total $ 90,458 $ 104,857

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	Property and equipment consist of the following (in thousands): March 31, December 31, Laboratory equipment $ 3,060 $ 3,022 Leasehold improvements 564 564 Office and computer equipment 111 111 Furniture and fixtures 122 122 Property and equipment 3,857 3,819 Less: accumulated depreciation and amortization (3,523) (3,459) Property and equipment, net $ 334 $ 360

ACCRUED EXPENSES AND OTHER CU_2

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, Accrued employee compensation and benefits $ 832 $ 2,998 Accrued external research and development expenses 3,245 1,870 Accrued professional fees and other 527 626 Total accrued expenses and other current liabilities $ 4,604 $ 5,494

DEBT FINANCING (Tables)

DEBT FINANCING (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Summary of Long-term Debt	Long-term debt consisted of the following (in thousands): March 31, December 31, Principal amount of long-term debt $ 26,000 $ 26,000 Debt discount (271) (308) Deferred financing fees (413) (470) Current portion of long-term debt (4,333) — Long-term debt, net of current portion and discount $ 20,983 $ 25,222
Schedule of Principal Maturities of Long-term Debt	The scheduled principal maturity of the long-term debt as of March 31, 2021 is as follows (in thousands): Year Ending December 31, 2021 $ — 2022 23,833 2023 2,167 $ 26,000

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Schedule of Stock-based Compensation Expense Recognized	In connection with all share-based payment awards, total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 410 $ 716 General and administrative 1,018 883 Total stock-based compensation expense $ 1,428 $ 1,599
Schedule of Fair Value Assumptions for Stock Options	The fair value of each option issued to employees was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended 2021 2020 Risk-free interest rate 0.76 % 1.64 % Expected option life (in years) 6.02 6.11 Expected dividend yield — % — % Expected volatility 97.2 % 72.5 %
Schedule of Stock Option Activity	The following table summarizes the Company’s stock option activity for the three months ended March 31, 2021: Number of Shares Weighted Weighted Intrinsic Outstanding as of January 1, 2021 4,919,960 $ 6.37 Granted 1,682,976 6.31 Exercised (27,143) 1.00 Canceled (536,960) 7.74 Outstanding as of March 31, 2021 6,038,833 $ 6.26 7.58 $ 1,659 Exercisable as of March 31, 2021 3,051,583 $ 6.44 6.08 $ 1,275 Vested or expected to vest as of March 31, 2021 5,988,833 $ 6.22 7.50 $ 1,625
Schedule of Restricted Stock Unit Activity	The following table summarizes the Company's restricted stock unit activity for the three months ended March 31, 2021: Number of Shares Weighted Average Outstanding as of January 1, 2021 347,587 $ 4.04 Granted 120,916 6.41 Vested (60,000) 4.98 Forfeited — — Outstanding as of March 31, 2021 408,503 $ 4.60

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Three Months Ended 2021 2020 Options to purchase common stock 6,038,833 5,443,078 Unvested restricted stock units 408,503 162,967 Shares issuable under employee stock purchase plan 22,870 — 6,470,206 5,606,045

NATURE OF BUSINESS (Details)

NATURE OF BUSINESS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (287,802)	$ (272,613)

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended
	Mar. 31, 2021segment
Accounting Policies [Abstract]
Number of operating segments	1

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets, Fair Value Disclosure [Abstract]
Corporate obligations	$ 92,958	$ 107,329
Corporate obligations
Assets, Fair Value Disclosure [Abstract]
Money market funds	43,049	71,590
Corporate obligations	49,909	35,739
Fair Value, Recurring
Assets, Fair Value Disclosure [Abstract]
Money market funds	40,549	69,118
Total	90,458	104,857
Fair Value, Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Money market funds	40,549	69,118
Total	40,549	69,118
Fair Value, Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Money market funds	0	0
Total	49,909	35,739
Fair Value, Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Money market funds	0	0
Total	0	0
Fair Value, Recurring | Corporate obligations
Assets, Fair Value Disclosure [Abstract]
Corporate obligations	49,909	35,739
Fair Value, Recurring | Corporate obligations | Level 1
Assets, Fair Value Disclosure [Abstract]
Corporate obligations	0	0
Fair Value, Recurring | Corporate obligations | Level 2
Assets, Fair Value Disclosure [Abstract]
Corporate obligations	49,909	35,739
Fair Value, Recurring | Corporate obligations | Level 3
Assets, Fair Value Disclosure [Abstract]
Corporate obligations	$ 0	$ 0

CASH, CASH EQUIVALENTS, AND M_3

CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES - Schedule of Cash, Cash Equivalents, and Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Line Items]
Amortized Cost	$ 43,049	$ 71,590
Corporate obligations	92,985	107,363
Gross Unrealized Gains	5	1
Gross Unrealized Losses	(32)	(35)
Estimated Fair Value	92,958	107,329
Corporate obligations
Cash and Cash Equivalents [Line Items]
Corporate obligations	49,936	35,773
Gross Unrealized Gains	5	1
Gross Unrealized Losses	(32)	(35)
Cash and cash equivalents	43,049	71,590
Estimated Fair Value	$ 49,909	$ 35,739

CASH, CASH EQUIVALENTS, AND M_4

CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES - Schedule of Fair Values of Cash Equivalents and Marketable Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Mature in one year or less	$ 64,114	$ 86,338
Mature in two years or less	26,344	18,519
Total	$ 90,458	$ 104,857

CASH, CASH EQUIVALENTS, AND M_5

CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Operating cash	$ 2.5	$ 2.5
Sale of marketable securities	$ 0	$ 0

PROPERTY AND EQUIPMENT - Summar

PROPERTY AND EQUIPMENT - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,857	$ 3,819
Less: accumulated depreciation and amortization	(3,523)	(3,459)
Property and equipment, net	334	360
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment	3,060	3,022
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	564	564
Office and computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	111	111
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	$ 122	$ 122

PROPERTY AND EQUIPMENT - Narrat

PROPERTY AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 64	$ 131

ACCRUED EXPENSES AND OTHER CU_3

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued employee compensation and benefits	$ 832	$ 2,998
Accrued external research and development expenses	3,245	1,870
Accrued professional fees and other	527	626
Total accrued expenses and other current liabilities	$ 4,604	$ 5,494

DEBT FINANCING - Summary of Lon

DEBT FINANCING - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Principal amount of long-term debt	$ 26,000	$ 26,000
Debt discount	(271)	(308)
Deferred financing fees	(413)	(470)
Current portion of long-term debt	(4,333)	0
Long-term debt, net of current portion and discount	$ 20,983	$ 25,222

DEBT FINANCING - Narrative (Det

DEBT FINANCING - Narrative (Details) - USD ($) $ in Millions	Aug. 28, 2020	Feb. 28, 2022	Jan. 31, 2018	Mar. 31, 2021	Dec. 31, 2020	Oct. 31, 2018
2018 Facility | LIBOR | Secured Debt
Line of Credit Facility [Line Items]
Basis spread on interest rate			8.50%
Amended 2018 Facility | Secured Debt
Line of Credit Facility [Line Items]
Increase in final payment fee percent	5.35%
Final payment fee percent	6.35%
Amended 2018 Facility | Line of Credit
Line of Credit Facility [Line Items]
Terminal fee						$ 1.7
Terminal fee, at carrying value				$ 1.1	$ 1.1
Amended 2018 Facility | LIBOR | Secured Debt
Line of Credit Facility [Line Items]
Basis spread on interest rate floor				0.20%
Interest rate during period				8.70%
Forecast | Amended Two Thousand Twenty Facility | Line of Credit
Line of Credit Facility [Line Items]
Principal periodic payments		$ 2.2

DEBT FINANCING - Maturities of

DEBT FINANCING - Maturities of Long-term Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
2021	$ 0
2022	23,833
2023	2,167
Principal amount of long-term debt	$ 26,000	$ 26,000

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value, options exercised	$ 117
Weighted-average grand date fair value of options granted in the period (USD per share)	$ 4.81	$ 2.69
Unrecognized compensation expense related to unvested stock options	$ 12,100
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, recognition period	2 years 10 months 6 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, recognition period	2 years 1 month 24 days
Unrecognized compensation expense related to unvested stock RSUs	$ 1,500
Stock Option And Incentive Plan 2019 | Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for future issuance (in shares)	1,173,347
Employee Stock Purchase Plan 2019 | Stock options | Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for future issuance (in shares)	666,207

STOCKHOLDERS' EQUITY - Summary

STOCKHOLDERS' EQUITY - Summary of Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 1,428	$ 1,599
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	410	716
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 1,018	$ 883

STOCKHOLDERS' EQUITY - Stock Op

STOCKHOLDERS' EQUITY - Stock Option Valuation Fair Value Measurement Inputs (Details) - Stock options	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.76%	1.64%
Expected option life (in years)	6 years 7 days	6 years 1 month 9 days
Expected dividend yield	0.00%	0.00%
Expected volatility	97.20%	72.50%

STOCKHOLDERS' EQUITY - Summar_2

STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)$ / sharesshares
Number of Shares
Number of shares outstanding at beginning of period (in shares) | shares	4,919,960
Shares granted (in shares) | shares	1,682,976
Shares exercised (in shares) | shares	(27,143)
Shares canceled (in shares) | shares	(536,960)
Number of shares outstanding at end of period (in shares) | shares	6,038,833
Shares exercisable (in shares) | shares	3,051,583
Shares vested or expected to vest (in shares) | shares	5,988,833
Weighted Average Exercise Price
Weighted average exercise price of shares outstanding at beginning of period (USD per share) | $ / shares	$ 6.37
Weighted-average exercise price of shares granted (USD per share) | $ / shares	6.31
Weighted-average exercise price of shares exercised (USD per share) | $ / shares	1
Weighted-average exercise price of shares canceled (USD per share) | $ / shares	7.74
Weighted average exercise price of shares outstanding at end of period (USD per share) | $ / shares	6.26
Weighted-average exercise price of shares exercisable (USD per share) | $ / shares	6.44
Weighted-average exercise price of shares vested or expected to vest (USD per share) | $ / shares	$ 6.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining life of shares outstanding (in years)	7 years 6 months 29 days
Weighted average remaining life of shares exercisable (in years)	6 years 29 days
Weighted average remaining life of shares vested or expected to vest (in years)	7 years 6 months
Intrinsic value of shares outstanding | $	$ 1,659
Intrinsic value of shares exercisable | $	1,275
Intrinsic value of shares vested or expected to vest | $	$ 1,625

STOCKHOLDERS' EQUITY - Summar_3

STOCKHOLDERS' EQUITY - Summary of Restricted Stock Units (Details) - RSUs	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Shares
RSUs outstanding at beginning of period (in shares) | shares	347,587
RSUs granted (in shares) | shares	120,916
RSUs vested (in shares) | shares	(60,000)
RSUs forfeited (in shares) | shares	0
RSUs outstanding at end of period (in shares) | shares	408,503
Weighted Average Grant Date Fair Value per Share
Weighted average exercise price of RSUs outstanding at beginning of period (USD per share) | $ / shares	$ 4.04
Weighted-average exercise price of RSUs granted (USD per share) | $ / shares	6.41
Weighted-average exercise price of RSUs vested (USD per share) | $ / shares	4.98
Weighted-average exercise price of RSUs forfeited (USD per share) | $ / shares	0
Weighted average exercise price of RSUs outstanding at end of period (USD per share) | $ / shares	$ 4.60

NET LOSS PER SHARE - Summary of

NET LOSS PER SHARE - Summary of Anti-dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share (in shares)	6,470,206	5,606,045
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share (in shares)	6,038,833	5,443,078
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share (in shares)	408,503	162,967
Shares issuable under employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share (in shares)	22,870	0

RELATED-PARTY TRANSACTIONS (Det

RELATED-PARTY TRANSACTIONS (Details) - Related Party Consulting Agreement - Board of Directors Chairman - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Related Party Transaction [Line Items]
Related party costs	$ 100,000	$ 100,000
Due to related parties	0
Grant date fair value of equity awarded	$ 600,000	$ 200,000