Tricida (TCDAQ) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Cover Page

Cover Page - $ / shares	9 Months Ended
	Sep. 30, 2021	Oct. 29, 2021	Dec. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-38558
Entity Registrant Name	TRICIDA, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3372526
Entity Address, Address Line One	7000 Shoreline Court
Entity Address, Address Line Two	Suite 201
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	429-7800
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	TCDA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		50,447,578
Common stock, par value (in USD per share)	$ 0.001		$ 0.001
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001595585
Current Fiscal Year End Date	--12-31

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 16,988	$ 137,857
Short-term investments	129,782	171,670
Prepaid expenses and other current assets	4,404	4,488
Total current assets	151,174	314,015
Long-term investments	0	22,757
Property and equipment, net	836	1,112
Operating lease right-of-use assets	12,576	13,801
Total assets	164,586	351,685
Current liabilities:
Accounts payable	3,261	3,508
Current operating lease liabilities	2,716	2,079
Accrued expenses and other current liabilities	19,754	28,671
Total current liabilities	25,731	34,258
Term Loan, net	0	76,638
Convertible Senior Notes, net	125,194	118,670
Non-current operating lease liabilities	11,759	13,046
Other long-term liabilities	0	202
Total liabilities	162,684	242,814
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.001 par value; 40,000,000 shares authorized, no shares issued or outstanding as of September 30, 2021 and December 31, 2020	0	0
Common stock, $0.001 par value; 400,000,000 shares authorized as of September 30, 2021 and December 31, 2020; 50,447,578 and 50,210,779 shares issued and outstanding as of September 30, 2021 and December 31, 2020, respectively	50	50
Additional paid-in capital	762,317	742,555
Accumulated other comprehensive income (loss)	(77)	64
Accumulated deficit	(760,388)	(633,798)
Total stockholders’ equity	1,902	108,871
Total liabilities and stockholders’ equity	$ 164,586	$ 351,685

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	40,000,000	40,000,000
Preferred stock, outstanding (in shares)	0	0
Preferred stock, shares issued, (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	50,447,578	50,210,779
Common stock, shares outstanding (in shares)	50,447,578	50,210,779

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 26,635	$ 42,996	$ 78,591	$ 121,134
General and administrative	9,052	29,273	28,497	81,217
Total operating expenses	35,687	72,269	107,088	202,351
Loss from operations	(35,687)	(72,269)	(107,088)	(202,351)
Other income (expense), net	6	907	155	4,395
Interest expense	(3,994)	(6,267)	(13,533)	(12,043)
Loss on early extinguishment of term loan	0	0	6,124	0
Loss before income taxes	(39,675)	(77,629)	(126,590)	(209,999)
Income tax benefit (expense)	0	(36)	0	50
Net loss	(39,675)	(77,665)	(126,590)	(209,949)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments, net of tax	(15)	(431)	(141)	239
Total comprehensive loss	$ (39,690)	$ (78,096)	$ (126,731)	$ (209,710)
Net loss per share, basic (in dollars per share)	$ (0.79)	$ (1.55)	$ (2.52)	$ (4.20)
Net loss per share, diluted (in dollars per share)	$ (0.79)	$ (1.55)	$ (2.52)	$ (4.20)
Weighted-average number of shares outstanding, basic (in shares)	50,434,879	50,120,086	50,326,474	49,974,388
Weighted-average number of shares outstanding, diluted (in shares)	50,434,879	50,120,086	50,326,474	49,974,388

CONDENSED STATEMENTS OF STOCKHO

CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		49,763,176
Beginning balance at Dec. 31, 2019	$ 263,883	$ 50	$ 632,647	$ 193	$ (369,007)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		150,056
Issuance of common stock under equity incentive plans	550		550
Stock-based compensation	8,374		8,374
Net unrealized gain (loss) on available-for-sale investments, net of tax	(232)			(232)
Net loss	(74,114)				(74,114)
Ending balance (in shares) at Mar. 31, 2020		49,913,232
Ending balance at Mar. 31, 2020	198,461	$ 50	641,571	(39)	(443,121)
Beginning balance (in shares) at Dec. 31, 2019		49,763,176
Beginning balance at Dec. 31, 2019	263,883	$ 50	632,647	193	(369,007)
Total Stockholders’ Equity
Net unrealized gain (loss) on available-for-sale investments, net of tax	239
Net loss	(209,949)
Ending balance (in shares) at Sep. 30, 2020		50,184,240
Ending balance at Sep. 30, 2020	160,773	$ 50	739,247	432	(578,956)
Beginning balance (in shares) at Mar. 31, 2020		49,913,232
Beginning balance at Mar. 31, 2020	198,461	$ 50	641,571	(39)	(443,121)
Total Stockholders’ Equity
Equity component of Convertible Senior Notes, net of underwriter discounts and issuance costs	79,498		79,498
Issuance of warrants in connection with Term Loan	112		112
Issuance of common stock under equity incentive plans (in shares)		126,355
Issuance of common stock under equity incentive plans	1,098		1,098
Stock-based compensation	9,079		9,079
Net unrealized gain (loss) on available-for-sale investments, net of tax	902			902
Net loss	(58,170)				(58,170)
Ending balance (in shares) at Jun. 30, 2020		50,039,587
Ending balance at Jun. 30, 2020	230,980	$ 50	731,358	863	(501,291)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		75,837
Issuance of common stock under equity incentive plans	234		234
Stock-based compensation	7,655		7,655
Net unrealized gain (loss) on available-for-sale investments, net of tax	(431)			(431)
Net loss	(77,665)				(77,665)
Ending balance (in shares) at Sep. 30, 2020		50,184,240
Ending balance at Sep. 30, 2020	$ 160,773	$ 50	739,247	432	(578,956)
Total Stockholders’ Equity
Issuance of common stock upon exercise of warrants in connection with Term Loan (in shares)		68,816
Beginning balance (in shares) at Dec. 31, 2020	50,210,779	50,210,779
Beginning balance at Dec. 31, 2020	$ 108,871	$ 50	742,555	64	(633,798)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		61,946
Issuance of common stock under equity incentive plans	115		115
Stock-based compensation	6,042		6,042
Net unrealized gain (loss) on available-for-sale investments, net of tax	(105)			(105)
Net loss	(53,362)				(53,362)
Ending balance (in shares) at Mar. 31, 2021		50,272,725
Ending balance at Mar. 31, 2021	$ 61,561	$ 50	748,712	(41)	(687,160)
Beginning balance (in shares) at Dec. 31, 2020	50,210,779	50,210,779
Beginning balance at Dec. 31, 2020	$ 108,871	$ 50	742,555	64	(633,798)
Total Stockholders’ Equity
Net unrealized gain (loss) on available-for-sale investments, net of tax	(141)
Net loss	$ (126,590)
Ending balance (in shares) at Sep. 30, 2021	50,447,578	50,447,578
Ending balance at Sep. 30, 2021	$ 1,902	$ 50	762,317	(77)	(760,388)
Beginning balance (in shares) at Mar. 31, 2021		50,272,725
Beginning balance at Mar. 31, 2021	61,561	$ 50	748,712	(41)	(687,160)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		156,009
Issuance of common stock under equity incentive plans	333		333
Stock-based compensation	6,609		6,609
Net unrealized gain (loss) on available-for-sale investments, net of tax	(21)			(21)
Net loss	(33,553)				(33,553)
Ending balance (in shares) at Jun. 30, 2021		50,428,734
Ending balance at Jun. 30, 2021	34,929	$ 50	755,654	(62)	(720,713)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		18,844
Issuance of common stock under equity incentive plans	14		14
Stock-based compensation	6,649		6,649
Net unrealized gain (loss) on available-for-sale investments, net of tax	(15)			(15)
Net loss	$ (39,675)				(39,675)
Ending balance (in shares) at Sep. 30, 2021	50,447,578	50,447,578
Ending balance at Sep. 30, 2021	$ 1,902	$ 50	$ 762,317	$ (77)	$ (760,388)

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net loss	$ (126,590)	$ (209,949)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	351	716
Non-cash operating lease costs	574	597
Amortization of premiums and accretion of discounts on investments, net	440	(264)
Accretion of Term Loan and Convertible Senior Notes	7,047	5,246
Loss on early extinguishment of Term Loan	6,124	0
Stock-based compensation	19,300	25,108
Changes in compound derivative liability	(202)	(699)
Other non-cash items	(29)	(50)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	105	(3,341)
Accounts payable	(245)	(4,113)
Accrued expenses and other liabilities	(8,871)	(2,069)
Net cash used in operating activities	(101,996)	(188,818)
Investing activities:
Purchases of investments	(136,345)	(276,958)
Proceeds from maturities of investments	200,409	268,015
Purchases of property and equipment	(76)	(1,197)
Net cash provided by (used in) investing activities	63,988	(10,140)
Financing activities:
Proceeds from issuance of common stock under equity incentive plans	462	1,897
Proceeds from Convertible Senior Notes, net	0	193,285
Repayment of leasehold improvement loan	(38)	(57)
Cash paid for early extinguishment of Term Loan	(83,285)	0
Proceeds from Term Loan, net	0	14,971
Net cash provided by (used in) financing activities	(82,861)	210,096
Net increase (decrease) in cash and cash equivalents	(120,869)	11,138
Cash and cash equivalents at beginning of period	137,857	18,574
Cash and cash equivalents at end of period	16,988	29,712
Supplemental disclosures
Cash paid for interest	5,274	4,137
Supplemental disclosures of non-cash investing and financing activities
Right-of-use assets obtained in exchange for lease obligations	0	5,820
Issuance of warrants related to Term Loan	0	112
Purchases of property and equipment included in accounts payable and accrued expenses	$ 0	$ 644

ORGANIZATION AND BASIS OF PRESE

ORGANIZATION AND BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BASIS OF PRESENTATION	ORGANIZATION AND BASIS OF PRESENTATION Organization —Tricida, Inc., or the Company, was incorporated in the state of Delaware on May 22, 2013. The Company is focused on the development and commercialization of its investigational drug candidate, veverimer (also known as TRC101), a non-absorbed, orally-administered polymer designed to treat metabolic acidosis and slow chronic kidney disease, or CKD, progression in patients with CKD. The Company has sustained operating losses and expects such annual losses to continue over the next several years. The Company’s ultimate success depends on the outcome of its research and development and commercialization activities for veverimer, for which it expects to incur additional losses in the future. Through September 30, 2021, the Company has relied primarily on the proceeds from equity offerings and debt financing to finance its operations. The Company believes that its existing cash, cash equivalents and investments are sufficient to fund its operations for the twelve-month period following the filing of this Quarterly Report on Form 10-Q. However, its existing cash, cash equivalents and investments are not likely to be sufficient to fund the operations of the Company following the end of 2022. The Company recognizes that it will need to raise additional capital to fully implement its business plan, and if market conditions are favorable or if the Company identifies specific strategic opportunities or needs, intends to do so through the issuance of equity, borrowings, or strategic alliances with partner companies. However, if such financing is not available at adequate levels, on reasonable terms or within a reasonable time frame, the Company will need to reevaluate its operating plans and could be required to significantly reduce operating expenses and delay, reduce the scope of or eliminate some of its development programs or its future commercialization efforts, out-license intellectual property rights to its investigational drug candidates and sell unsecured assets, or a combination of the above, any of which may have a material adverse effect on its business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all. Basis of Presentation —The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. The condensed financial statements as of and for the three and nine months ended September 30, 2021 and 2020 are unaudited, but include all adjustments, consisting only of normal recurring adjustments, which the Company considers necessary for a fair presentation of the financial position, operating results and cash flows for the periods presented. The condensed balance sheet as of December 31, 2020 has been derived from audited financial statements. Although the Company believes that the disclosures in these condensed financial statements are adequate to make the information presented not misleading, certain information and footnote information normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES There have been no material changes to the significant accounting policies discussed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. Recent Accounting Pronouncements Adopted Standards Effective January 1, 2021, the Company adopted, on a prospective basis, Accounting Standards Update, or ASU, No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , or ASU 2019-12, which simplifies the accounting for income taxes. The adoption of ASU 2019-12 did not have a significant impact on the Company's condensed financial statements. Standards Not Yet Effective In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40), or ASU 2020-06. ASU 2020-06 simplifies the accounting for convertible debt instruments and convertible preferred stock by removing the existing guidance in Accounting Standards Codification, or ASC, 470-20, Debt – Debt with Conversion and Other Options , or ASC 470-20, that requires entities to account for beneficial conversion features and cash conversion features in equity, separately from the host convertible debt or preferred stock. The guidance in ASC 470-20 applies to convertible instruments for which the embedded conversion features are not required to be bifurcated from the host contract and accounted for as derivatives. In addition, the amendments revise the scope exception from derivative accounting in ASC 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity, for freestanding financial instruments and embedded features that are both indexed to the issuer’s own stock and classified in stockholders’ equity, by removing certain criteria required for equity classification. These amendments are expected to result in more freestanding financial instruments qualifying for equity classification (and, therefore, not accounted for as derivatives), as well as fewer embedded features requiring separate accounting from the host contract. The amendments in ASU 2020-06 further revise the guidance in ASC 260, Earnings Per Share , to require entities to calculate diluted earnings per share, or EPS, for convertible instruments by using the if-converted method. In addition, entities must presume share settlement for purposes of calculating diluted EPS when an instrument may be settled in cash or shares. ASU 2020-06 is effective for public business entities for annual reporting periods, and interim reporting periods within those annual periods, beginning after December 15, 2021 on a prospective basis, and early adoption is permitted. The Company will adopt ASU 2020-06 effective January 1, 2022, and expects to use the modified retrospective method. On adoption, the Company expects to account for the Convertible Senior Notes as a single liability measured at amortized cost resulting in reduced non-cash interest expense due to the de-recognition of the remaining debt discount associated with the equity component.

FAIR VALUE MEASUREMENTS AND FAI

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS The fair value of the Company’s financial assets and liabilities are determined in accordance with the fair value hierarchy established in the FASB's ASC Topic 820, Fair Value Measurements and Disclosures, or Topic 820. Topic 820 defines fair value 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. The fair value hierarchy of Topic 820 requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels: Level 1 —Observable inputs, such as quoted prices in active markets; Level 2 —Inputs, other than the quoted prices in active markets, which are observable either directly or indirectly such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life; and Level 3 —Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Our financial instruments consist primarily of cash and cash equivalents, short-term and long-term investments, accounts payable and the Convertible Senior Notes. Cash, cash equivalents and investments are reported at their respective fair values on the Company's condensed balance sheets. Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds and U.S. Treasury securities as Level 1. When quoted market prices are not available for a specific security, then the Company estimates fair value by using quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Where applicable, these models incorporate expected future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to benchmark yields, reported trades and broker/dealer quotes. Where applicable the market approach utilizes prices and information from market transactions for similar or identical assets. The Company classifies U.S. government agency securities, commercial paper and corporate debt securities as Level 2. The Company's short-term and long-term investments are classified as available-for-sale. The following tables set forth the value of the Company's financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy by significant investment category as of September 30, 2021 and December 31, 2020. September 30, 2021 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 1,332 $ — $ — $ 1,332 $ 1,332 $ — $ — Level 1: Money market funds 12,656 — — 12,656 12,656 — — U.S. Treasury securities 6,020 1 — 6,021 — 6,021 — Subtotal 18,676 1 — 18,677 12,656 6,021 — Level 2: U.S. government agency securities 29,068 2 — 29,070 — 29,070 — Commercial paper 97,679 14 (2) 97,691 3,000 94,691 — Subtotal 126,747 16 (2) 126,761 3,000 123,761 — Total assets measured at fair value $ 146,755 $ 17 $ (2) $ 146,770 $ 16,988 $ 129,782 $ — December 31, 2020 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 2,011 $ — $ — $ 2,011 $ 2,011 $ — $ — Level 1: Money market funds 25,862 — — 25,862 25,862 — — U.S. Treasury securities 8,157 1 (1) 8,157 — 8,157 — Subtotal 34,019 1 (1) 34,019 25,862 8,157 — Level 2: U.S. government agency securities 64,370 15 (3) 64,382 — 41,625 22,757 Commercial paper 159,183 16 (6) 159,193 97,989 61,204 — Corporate debt securities 72,546 134 (1) 72,679 11,995 60,684 — Subtotal 296,099 165 (10) 296,254 109,984 163,513 22,757 Total assets measured at fair value $ 332,129 $ 166 $ (11) $ 332,284 $ 137,857 $ 171,670 $ 22,757 There were no gross realized gains and gross realized losses for the three and nine months ended September 30, 2021 and 2020. All available-for-sale investments held as of September 30, 2021 have a maturity of one year of less. The following table presents a reconciliation of financial liabilities related to the compound derivative liability associated with the Loan and Security Agreement, or Term Loan, with Hercules Capital Inc., or Hercules, measured at fair value on a recurring basis using Level 3 unobservable inputs for the nine months ended September 30, 2021 and 2020. The key valuation assumptions used were the discount rate and the probability of the occurrence of certain events. In conjunction with early extinguishment of the Term Loan on March 12, 2021, the Company extinguished the compound derivative liability associated with the Term Loan. Nine Months Ended September 30, (in thousands) 2021 2020 Fair value at beginning of period $ 202 $ 977 Change in fair value — (699) Extinguishment of compound derivative liability upon extinguishment of Term Loan (202) — Fair value at end of period $ — $ 278 The estimated fair value of the Convertible Senior Notes was $90.7 million as of September 30, 2021 measured using Level 3 inputs. The key valuation assumptions used consist of the discount rate of 21.8% and volatility of 87.0%.

BORROWINGS

BORROWINGS	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
BORROWINGS	BORROWINGS Term Loan On March 12, 2021, the Company repaid the outstanding principal of $75.0 million and fees in the amount of $8.3 million to Hercules under the Term Loan. The Company recognized a loss on early debt extinguishment of $6.1 million which represents the remaining unamortized issuance costs. In conjunction with early extinguishment of the Term Loan on March 12, 2021, the Company extinguished the compound derivative liability associated with the Term Loan. Convertible Senior Notes On May 22, 2020, the Company issued $200.0 million aggregate principal amount of 3.50% convertible senior notes due 2027, or the Convertible Senior Notes. The Convertible Senior Notes are convertible into cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock at the Company’s election at an initial conversion rate of 30.0978 shares of the Company’s common stock per $1,000 principal amount of the Convertible Senior Notes, which is equivalent to an initial conversion price of approximately $33.23 per share of the Company’s common stock. The conversion rate is subject to customary adjustments for certain events as described in the Indenture. It is the Company’s current intent to settle conversions through combination settlement, which involves repayment of the principal portion in cash and any excess of the conversion value over the principal amount in shares of its common stock. As of September 30, 2021, the “if-converted value” did not exceed the remaining principal amount of the Convertible Senior Notes. At issuance, the Convertible Senior Notes were bifurcated into liability and equity components and accounted for separately. The carrying amount of the liability component was calculated to be $117.7 million by measuring the fair value of similar debt instruments that do not have an associated convertible feature. The carrying amount of the equity component, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the Convertible Senior Notes. The carrying amount of the equity component was calculated to be $82.3 million and was recorded in additional paid-in capital. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The allocation of proceeds into the equity component resulted in a debt discount for the Convertible Senior Notes that is amortized to interest expense at an effective interest rate of 13.5% over the effective life of the Convertible Senior Notes of 7.0 years, using the effective interest method. The following table presents the carrying amount of the liability and equity components of the Convertible Senior Notes as of September 30, 2021. (in thousands) September 30, Liability component: Principal $ 200,000 Unamortized discount - equity component (71,170) Unamortized underwriter discounts and issuance costs (3,636) Net carrying amount $ 125,194 Equity component, net of underwriter discounts and issuance costs $ 79,498 The remaining unamortized debt discount is being amortized over approximately 5.7 years which is also the remaining life of the Senior Convertible Notes. The following table presents the interest expense related to the Convertible Senior Notes for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Contractual interest expense $ 1,750 $ 1,750 $ 5,250 $ 2,508 Amortization of debt discount 2,175 1,930 6,334 2,767 Amortization of underwriter discounts and issuance costs 69 50 192 72 Total interest expense $ 3,994 $ 3,730 $ 11,776 $ 5,347

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The Company has contractual obligations relating to its Convertible Senior Notes, operating lease, manufacturing and service contracts, and other research and development activities. The following table aggregates the Company’s material expected contractual obligations and commitments as of September 30, 2021. September 30, 2021 (in thousands) Total 2021 (4) 2022 - 2023 2024 - 2025 Thereafter Convertible Senior Notes (1) $ 242,000 $ 3,500 $ 14,000 $ 14,000 $ 210,500 Lease obligations (2) 17,999 705 5,780 6,131 5,383 Manufacturing and service contracts (3) 591,046 20,428 82,164 114,930 373,524 Total contractual obligations and commitments $ 851,045 $ 24,633 $ 101,944 $ 135,061 $ 589,407 (1) Comprised of interest payable and principal repayment due under the Convertible Senior Notes' Indenture. (2) Comprised of rent payments under the amended lease for the Company's offices and laboratory space executed on August 14, 2019. (3) The purchase obligations are comprised of the Company's non-cancelable purchase commitments under the Supply Agreement with Patheon. These amounts are based on forecasts that may include estimates of future market demand, quantity discounts and manufacturing efficiencies. (4) Remaining three months. Other Commitments On October 4, 2019, the Company and Patheon Austria GmbH & Co KG, or Patheon, entered into a multi-year Manufacturing and Commercial Supply Agreement as amended by Amendment No. 1 dated March 30, 2021, and Amendment No. 2 dated August 26, 2021, collectively the Supply Agreement, under which Patheon agreed to manufacture and supply veverimer to support the Company's commercialization efforts. Patheon has also agreed to manufacture and supply veverimer to support the Company’s drug development and clinical trial activities. Under the Supply Agreement, the Company is obligated to make certain purchases of API. The Company and Patheon are also parties to a Master Development/Validation Services and Clinical/Launch Supply Agreement, or the MDA, pursuant to which Patheon agreed to manufacture and supply veverimer. Certain manufacturing activities previously governed by the MDA are now subject to the Supply Agreement, whereas other ongoing manufacturing activities under the MDA will continue to be governed by the MDA until such activities are complete. The Supply Agreement may be terminated by either party following an uncured material breach by the other party, in the event the other party becomes insolvent or subject to bankruptcy proceedings, or in connection with a force majeure event that continues beyond 12 months. In addition, the Supply Agreement may be terminated by the Company upon the occurrence of certain regulatory events or actions, including: (i) if the Company does not obtain regulatory approval for veverimer by a specified date or (ii) if the Company terminates its commercialization of veverimer or fails to launch veverimer by a specified date. The Company’s obligation to purchase veverimer is subject to minimum and maximum annual commitments, with the minimum commitments subject to modest reduction in certain circumstances. Patheon has agreed to make facility improvements under the Supply Agreement and will be the exclusive owner of the purchased equipment and facility improvements. Patheon may manufacture other products with the facility improvements when not occupied by manufacturing veverimer. Under the Supply Agreement, the Company has agreed to reimburse Patheon up to a specified amount for plant modifications. These payments will be expensed to research and development prior to FDA approval of veverimer. The Company also enters into other contracts in the normal course of business with contract research organizations, contract development and manufacturing organizations and other service providers and vendors. These contracts generally provide for termination on short notice and are cancellable contracts and accordingly, are not included in the contractual obligations and disclosures summarized above. Contingencies On January 6, 2021, a putative securities class action was filed in the U.S. District Court for the Northern District of California against the Company and its CEO and CFO, Pardi v. Tricida, Inc., et al., 21-cv-00076 (the "Securities Class Action"). In April 2021, the court appointed Jeffrey Fiore as lead plaintiff and Block & Leviton LLP as lead plaintiffs’ counsel. In June 2021, the lead plaintiff filed an amended complaint which alleges that during the period between June 28, 2018 through February 25, 2021, the Company and its senior officers violated federal securities laws, including under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder, through alleged public misrepresentations and/or omissions of material facts concerning the Company's NDA for veverimer and the likelihood and timing of approval of veverimer by the FDA. The amended complaint makes claims against the Company and its CEO. In July 2021, the defendants filed a motion to dismiss the amended complaint and a hearing on the defendants' motion is currently scheduled for December 2021. No damages amount is specified in the Securities Class Action. On February 15, 2021, a derivative action was filed in the District of Delaware, brought by and on behalf of Tricida, Inc. as a Nominal Defendant, against the Company’s directors as well as its CEO and CFO, Ricks v. Alpern et al., Case No, 1:21-cv-000205 (the "Ricks Derivative Case"). The Ricks Derivative Case is based on the allegations of the Securities Class Action and asserts that by allowing the Company and senior executives to make the allegedly false and misleading statements at issue in the Securities Class Action, the defendants breached their fiduciary duties and wasted corporate assets. Additionally, the complaint asserts claims against the senior officers for violation of Sections 10(b) and 21D of the Securities Exchange Act of 1934. No damages amount is specified in the Ricks Derivative Case. On April 8, 2021 a second derivative action was filed in the District of Delaware, brought by and on behalf of Tricida, Inc. as a Nominal Defendant, against the Company’s directors as well as its CEO and CFO, Goodman v. Klaerner et al., Case No, 1:21-cv-00510 (the “Goodman Derivative Case”). As with the Ricks Derivative Case, the Goodman Derivative Case is based on the allegations of the Securities Class Action and asserts that by allowing the Company and senior executives to make the allegedly false and misleading statements at issue in the Securities Class Action, the defendants breached their fiduciary duties. Additionally, the complaint asserts claims against the senior officers for violation of Sections 10(b) and 21D of the Securities Exchange Act of 1934. No damages amount is specified in the Goodman Derivative Case. On May 27, 2021, a third derivative action was filed in the District of Delaware, brought by and on behalf of Tricida, Inc. as a Nominal Defendant, against the Company’s directors as well as its CEO and CFO, Verica v. Veitinger et al., Case No, 1:21-cv-00759 (the "Verica Derivative Case" and collectively with the Goodman Derivative Case and Ricks Derivative Case, the "Derivative Cases"). As with the Goodman Derivative Case and Ricks Derivative Case, the Verica Derivative Case is based on the allegations of the Securities Class Action and asserts that by allowing the Company and senior executives to make the allegedly false and misleading statements at issue in the Securities Class Action, the defendants breached their fiduciary duties. Additionally, the complaint asserts claims for violations of Sections 14(a) and 20(a) of the Securities Exchange Act of 1934 and for unjust enrichment and waste of corporate assets. No damages amount is specified in the Verica Derivative Case. The Derivative Cases have been consolidated by order of the District of Delaware Court and lead plaintiffs' counsel has been appointed. Pursuant to an agreement between the parties, the Delaware court issued an order on October 12, 2021 staying the consolidated derivative case pending final resolution of any motions to dismiss filed in the Securities Class Action. A consolidated derivative complaint has not yet been filed. As of September 30, 2021, the Company has not provided for a loss contingency in its condensed financial statements relating to the Securities Class Action and the Derivative Cases since it is not probable that a loss has been incurred. The Company does not believe that any ultimate liability resulting from any of these claims will have a material adverse effect on its results of operations, financial position, or liquidity. However, the Company cannot give any assurance regarding the ultimate outcome of these claims, and their resolution could be material to operating results for any particular period. Further, while there are no other material legal proceedings that the Company is

RESTRUCTURING

RESTRUCTURING	9 Months Ended
	Sep. 30, 2021
Restructuring and Related Activities [Abstract]
RESTRUCTURING	RESTRUCTURING Third Quarter 2020 Restructuring In August 2020, the Company received a Complete Response Letter, or CRL, from the FDA related to its NDA for veverimer. Due to the resulting delay in regulatory approval and commercialization of veverimer, on September 10, 2020, the Compensation Committee of the Board of Directors approved the Tricida, Inc. 2020 Reduction in Force Severance Benefit Plan, or 2020 Restructuring Plan. On September 18, 2020, the Company implemented a restructuring, or Third Quarter 2020 Restructuring, under the 2020 Restructuring Plan to streamline the organization and preserve capital that included the elimination of approximately 21.5% of the Company's workforce and other cost reductions. Following is a summary of accrued restructuring costs related to the Third Quarter 2020 Restructuring as of September 30, 2021 and December 31, 2020. (in thousands) Severance and Benefits Costs Contract Termination Costs Total Balance at January 1, 2020 $ — $ — $ — Charges 2,524 136 2,660 Cash payments made (2,456) (137) (2,593) Non-cash and other adjustments (6) 1 (5) Balance at December 31, 2020 62 — 62 Non-cash and other adjustments (62) — (62) Balance at September 30, 2021 $ — $ — $ — Fourth Quarter 2020 Restructuring On October 25, 2020, the Company's Board of Directors approved and on October 28, 2020, the Company implemented a restructuring under the 2020 Restructuring Plan, or Fourth Quarter 2020 Restructuring, to reduce operating costs and better align its workforce with the needs of its business following the completion of the Type A meeting with the FDA in October 2020. The Fourth Quarter 2020 Restructuring resulted in the elimination of approximately 60.0% of the Company's workforce and included one-time termination severance payments and other employee-related costs, and exit costs including contract termination costs and accelerated depreciation of capitalized software. Following is a summary of accrued restructuring costs related to the Fourth Quarter 2020 Restructuring as of September 30, 2021 and December 31, 2020. (in thousands) Severance and Benefits Costs Contract Termination Costs Other Associated Costs Total Balance at January 1, 2020 $ — $ — $ — $ — Charges 7,338 3,077 679 11,094 Cash payments made (3,555) (2,032) — (5,587) Non-cash and other adjustments — (34) (679) (713) Balance at December 31, 2020 3,783 1,011 — 4,794 Cash payments made (4,013) (727) — (4,740) Non-cash and other adjustments 230 (84) — 146 Balance at September 30, 2021 $ — $ 200 $ — $ 200 Restructuring costs of $0.1 million were recorded in operating expenses in our condensed statements of operations and comprehensive loss for the nine months ended September 30, 2021.

NET LOSS PER SHARE

NET LOSS PER SHARE	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (In thousands, except share and per share amounts) 2021 2020 2021 2020 Numerator: Net loss $ (39,675) $ (77,665) $ (126,590) $ (209,949) Denominator: Weighted-average common shares outstanding 50,434,879 50,121,784 50,326,474 49,977,339 Less: weighted-average shares subject to repurchase — (1,698) — (2,951) Weighted-average number of shares used in basic and diluted net loss per share 50,434,879 50,120,086 50,326,474 49,974,388 Net loss per share, basic and diluted $ (0.79) $ (1.55) $ (2.52) $ (4.20) Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive. September 30, 2021 2020 Warrants to purchase common stock 31,352 31,352 Assumed conversion of Convertible Senior Notes 6,019,560 6,019,560 Common stock subject to repurchase — 1,260 Stock options and RSUs issued and outstanding 11,142,994 9,894,957 Total potential common shares excluded from the computation of diluted net loss per share 17,193,906 15,947,129

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Equity Incentive Plans The following table summarizes stock option activity under the 2013 Equity Incentive Plan and the 2018 Equity Incentive Plan, or 2018 Plan, for the nine months ended September 30, 2021. Shares Weighted- Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Balance at December 31, 2020 8,030,415 $ 19.25 7.1 $ 10,137 Granted 4,792,580 6.71 Granted due to Exchange Offer 621,406 3.88 Exercised (125,431) 1.43 Forfeited or canceled (908,212) 25.92 Canceled due to Exchange Offer (1,419,182) 30.25 Balance at September 30, 2021 10,991,576 $ 11.15 7.9 $ 5,721 Vested and expected to vest at September 30, 2021 9,725,705 $ 11.20 7.8 $ 5,682 Exercisable at September 30, 2021 4,921,902 $ 16.17 6.8 $ 5,243 The following table summarizes restricted stock units, or RSUs, activity under the 2018 Plan for the nine months ended September 30, 2021. Shares Weighted- Unvested balance at December 31, 2020 90,020 $ 16.88 Granted 98,418 4.92 Vested (34,020) 25.40 Forfeited (3,000) 11.71 Unvested balance at September 30, 2021 151,418 $ 7.30 Stock Option Exchange Program On July 16, 2021, the Company commenced a tender offer to its employees, excluding executive officers, to exchange eligible stock options for replacement stock options with modified terms, or Exchange Offer. Pursuant to the Exchange Offer, the Company offered employees who held outstanding stock options under the 2018 Plan with an exercise price equal to or greater than $20.00 per share, or eligible options, the opportunity to tender each eligible option in exchange for a new replacement stock option with modified terms, or new options. The Exchange Offer expired on August 12, 2021. Pursuant to the Exchange Offer, employees elected to exchange outstanding stock options to purchase an aggregate of 1,419,182 shares of common stock for new options to purchase 621,406 shares of common stock. The new options have an exercise price of $3.88 per share, which was the closing price per share of the Company’s common stock on the grant date of August 16, 2021. As a result, 797,776 shares of common stock returned to the 2018 Plan reserve and became available for future issuance under the 2018 Plan. Each new option granted in exchange for a vested option will vest in full on the 1-year anniversary following the grant date of the new option. Each new option granted in exchange for an unvested option will vest one-third on the one-year anniversary following the grant date of the new option and followed by equal monthly installments over the remaining two year period. Each new option has a maximum term of 7 years and was granted as a nonqualified stock option under the 2018 Plan. The exchange of stock options was treated as a modification for accounting purposes. The incremental expense of $0.3 million for the new options was calculated using the Black-Scholes option pricing model and will be recognized over the new service period. The unamortized expense remaining on the exchanged options as of the modification date of August 16, 2021, will continue to be recognized over the remainder of the original requisite service period. Employee Stock Purchase Plan In June 2018, the Company's Board of Directors and stockholders approved the Tricida Inc. Employee Stock Purchase Plan, or ESPP. The ESPP allowed eligible employees to have up to 15.0% of their eligible compensation withheld and used to purchase common stock, subject to a maximum of $25,000 worth of stock purchased in a calendar year or no more than 2,500 shares in an offering period, whichever is less. An offering period consisted of a six-month purchase period, with a look back feature to our stock price at the commencement of the offering period. Eligible employees could purchase the Company’s common stock at the end of the offering period at 85.0% of the lower of the closing price of the Company's common stock on The Nasdaq Global Select Market on the first and last days of the offering periods. In June 2021, the Compensation Committee of the Company's Board of Directors approved modifications to the ESPP, including extending the offering period from six months to 24 months with four six-month purchase periods within each offering period, adjusted the purchase dates from June 30 and December 31 of each calendar year to May 31 and November 30, respectively and increased the maximum number of shares available for purchase during each purchase period to 10,000. The initial number of shares of common stock available for issuance under the ESPP, was 800,000. Unless the Company's Board of Directors provides otherwise, beginning on January 1, 2019, the maximum number of shares which shall be made available for sale under the ESPP will automatically increase on the first trading day in January of each calendar year during the term of the ESPP by an amount equal to the lesser of (i) 1.0% of the total number of shares issued and outstanding on December 31 of the immediately preceding calendar year, (ii) 800,000 shares or (iii) an amount determined by the Board of Directors. The Company issued 77,348 shares under the ESPP, representing approximately $0.3 million in employee contributions, for the nine months ended September 30, 2021. Stock-Based Compensation The following table presents stock-based compensation expense as reported in the Company’s condensed statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Research and development $ 2,819 $ 2,937 $ 7,948 $ 9,261 General and administrative 3,830 4,718 11,352 15,847 Total $ 6,649 $ 7,655 $ 19,300 $ 25,108 The following table presents stock-based compensation expense by award type as reported in the Company’s condensed statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Stock options $ 6,210 $ 7,284 $ 17,902 $ 24,211 RSUs 246 238 929 459 ESPP 193 133 469 438 Total $ 6,649 $ 7,655 $ 19,300 $ 25,108

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation —The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. The condensed financial statements as of and for the three and nine months ended September 30, 2021 and 2020 are unaudited, but include all adjustments, consisting only of normal recurring adjustments, which the Company considers necessary for a fair presentation of the financial position, operating results and cash flows for the periods presented. The condensed balance sheet as of December 31, 2020 has been derived from audited financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted Standards Effective January 1, 2021, the Company adopted, on a prospective basis, Accounting Standards Update, or ASU, No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , or ASU 2019-12, which simplifies the accounting for income taxes. The adoption of ASU 2019-12 did not have a significant impact on the Company's condensed financial statements. Standards Not Yet Effective In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40), or ASU 2020-06. ASU 2020-06 simplifies the accounting for convertible debt instruments and convertible preferred stock by removing the existing guidance in Accounting Standards Codification, or ASC, 470-20, Debt – Debt with Conversion and Other Options , or ASC 470-20, that requires entities to account for beneficial conversion features and cash conversion features in equity, separately from the host convertible debt or preferred stock. The guidance in ASC 470-20 applies to convertible instruments for which the embedded conversion features are not required to be bifurcated from the host contract and accounted for as derivatives. In addition, the amendments revise the scope exception from derivative accounting in ASC 815-40, Derivatives and Hedging – Contracts in Entity’s Own Equity, for freestanding financial instruments and embedded features that are both indexed to the issuer’s own stock and classified in stockholders’ equity, by removing certain criteria required for equity classification. These amendments are expected to result in more freestanding financial instruments qualifying for equity classification (and, therefore, not accounted for as derivatives), as well as fewer embedded features requiring separate accounting from the host contract. The amendments in ASU 2020-06 further revise the guidance in ASC 260, Earnings Per Share , to require entities to calculate diluted earnings per share, or EPS, for convertible instruments by using the if-converted method. In addition, entities must presume share settlement for purposes of calculating diluted EPS when an instrument may be settled in cash or shares. ASU 2020-06 is effective for public business entities for annual reporting periods, and interim reporting periods within those annual periods, beginning after December 15, 2021 on a prospective basis, and early adoption is permitted. The Company will adopt ASU 2020-06 effective January 1, 2022, and expects to use the modified retrospective method. On adoption, the Company expects to account for the Convertible Senior Notes as a single liability measured at amortized cost resulting in reduced non-cash interest expense due to the de-recognition of the remaining debt discount associated with the equity component.

FAIR VALUE MEASUREMENTS AND F_2

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIALINSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Cash and financial assets re-measured on a recurring basis by hierarchy	The following tables set forth the value of the Company's financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy by significant investment category as of September 30, 2021 and December 31, 2020. September 30, 2021 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 1,332 $ — $ — $ 1,332 $ 1,332 $ — $ — Level 1: Money market funds 12,656 — — 12,656 12,656 — — U.S. Treasury securities 6,020 1 — 6,021 — 6,021 — Subtotal 18,676 1 — 18,677 12,656 6,021 — Level 2: U.S. government agency securities 29,068 2 — 29,070 — 29,070 — Commercial paper 97,679 14 (2) 97,691 3,000 94,691 — Subtotal 126,747 16 (2) 126,761 3,000 123,761 — Total assets measured at fair value $ 146,755 $ 17 $ (2) $ 146,770 $ 16,988 $ 129,782 $ — December 31, 2020 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 2,011 $ — $ — $ 2,011 $ 2,011 $ — $ — Level 1: Money market funds 25,862 — — 25,862 25,862 — — U.S. Treasury securities 8,157 1 (1) 8,157 — 8,157 — Subtotal 34,019 1 (1) 34,019 25,862 8,157 — Level 2: U.S. government agency securities 64,370 15 (3) 64,382 — 41,625 22,757 Commercial paper 159,183 16 (6) 159,193 97,989 61,204 — Corporate debt securities 72,546 134 (1) 72,679 11,995 60,684 — Subtotal 296,099 165 (10) 296,254 109,984 163,513 22,757 Total assets measured at fair value $ 332,129 $ 166 $ (11) $ 332,284 $ 137,857 $ 171,670 $ 22,757
Reconciliation of liabilities using Level 3 unobservable inputs	The following table presents a reconciliation of financial liabilities related to the compound derivative liability associated with the Loan and Security Agreement, or Term Loan, with Hercules Capital Inc., or Hercules, measured at fair value on a recurring basis using Level 3 unobservable inputs for the nine months ended September 30, 2021 and 2020. The key valuation assumptions used were the discount rate and the probability of the occurrence of certain events. In conjunction with early extinguishment of the Term Loan on March 12, 2021, the Company extinguished the compound derivative liability associated with the Term Loan. Nine Months Ended September 30, (in thousands) 2021 2020 Fair value at beginning of period $ 202 $ 977 Change in fair value — (699) Extinguishment of compound derivative liability upon extinguishment of Term Loan (202) — Fair value at end of period $ — $ 278

BORROWINGS (Tables)

BORROWINGS (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of component carrying values of convertible senior notes	The following table presents the carrying amount of the liability and equity components of the Convertible Senior Notes as of September 30, 2021. (in thousands) September 30, Liability component: Principal $ 200,000 Unamortized discount - equity component (71,170) Unamortized underwriter discounts and issuance costs (3,636) Net carrying amount $ 125,194 Equity component, net of underwriter discounts and issuance costs $ 79,498
Schedule of interest expense on convertible debt	The following table presents the interest expense related to the Convertible Senior Notes for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Contractual interest expense $ 1,750 $ 1,750 $ 5,250 $ 2,508 Amortization of debt discount 2,175 1,930 6,334 2,767 Amortization of underwriter discounts and issuance costs 69 50 192 72 Total interest expense $ 3,994 $ 3,730 $ 11,776 $ 5,347

COMMITMENT AND CONTINGENCIES (T

COMMITMENT AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Material expected contractual obligations and commitments	The following table aggregates the Company’s material expected contractual obligations and commitments as of September 30, 2021. September 30, 2021 (in thousands) Total 2021 (4) 2022 - 2023 2024 - 2025 Thereafter Convertible Senior Notes (1) $ 242,000 $ 3,500 $ 14,000 $ 14,000 $ 210,500 Lease obligations (2) 17,999 705 5,780 6,131 5,383 Manufacturing and service contracts (3) 591,046 20,428 82,164 114,930 373,524 Total contractual obligations and commitments $ 851,045 $ 24,633 $ 101,944 $ 135,061 $ 589,407 (1) Comprised of interest payable and principal repayment due under the Convertible Senior Notes' Indenture. (2) Comprised of rent payments under the amended lease for the Company's offices and laboratory space executed on August 14, 2019. (3) The purchase obligations are comprised of the Company's non-cancelable purchase commitments under the Supply Agreement with Patheon. These amounts are based on forecasts that may include estimates of future market demand, quantity discounts and manufacturing efficiencies. (4) Remaining three months.

RESTRUCTURING AND RELATED ACTIV

RESTRUCTURING AND RELATED ACTIVITIES (Tables)	9 Months Ended
	Sep. 30, 2021
Restructuring and Related Activities [Abstract]
Summary of accrued restructuring costs	Following is a summary of accrued restructuring costs related to the Third Quarter 2020 Restructuring as of September 30, 2021 and December 31, 2020. (in thousands) Severance and Benefits Costs Contract Termination Costs Total Balance at January 1, 2020 $ — $ — $ — Charges 2,524 136 2,660 Cash payments made (2,456) (137) (2,593) Non-cash and other adjustments (6) 1 (5) Balance at December 31, 2020 62 — 62 Non-cash and other adjustments (62) — (62) Balance at September 30, 2021 $ — $ — $ — Following is a summary of accrued restructuring costs related to the Fourth Quarter 2020 Restructuring as of September 30, 2021 and December 31, 2020. (in thousands) Severance and Benefits Costs Contract Termination Costs Other Associated Costs Total Balance at January 1, 2020 $ — $ — $ — $ — Charges 7,338 3,077 679 11,094 Cash payments made (3,555) (2,032) — (5,587) Non-cash and other adjustments — (34) (679) (713) Balance at December 31, 2020 3,783 1,011 — 4,794 Cash payments made (4,013) (727) — (4,740) Non-cash and other adjustments 230 (84) — 146 Balance at September 30, 2021 $ — $ 200 $ — $ 200

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Basic and diluted net loss per share	The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (In thousands, except share and per share amounts) 2021 2020 2021 2020 Numerator: Net loss $ (39,675) $ (77,665) $ (126,590) $ (209,949) Denominator: Weighted-average common shares outstanding 50,434,879 50,121,784 50,326,474 49,977,339 Less: weighted-average shares subject to repurchase — (1,698) — (2,951) Weighted-average number of shares used in basic and diluted net loss per share 50,434,879 50,120,086 50,326,474 49,974,388 Net loss per share, basic and diluted $ (0.79) $ (1.55) $ (2.52) $ (4.20)
Antidilutive securities excluded from computation	The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive. September 30, 2021 2020 Warrants to purchase common stock 31,352 31,352 Assumed conversion of Convertible Senior Notes 6,019,560 6,019,560 Common stock subject to repurchase — 1,260 Stock options and RSUs issued and outstanding 11,142,994 9,894,957 Total potential common shares excluded from the computation of diluted net loss per share 17,193,906 15,947,129

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Stock Option Activity	The following table summarizes stock option activity under the 2013 Equity Incentive Plan and the 2018 Equity Incentive Plan, or 2018 Plan, for the nine months ended September 30, 2021. Shares Weighted- Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Balance at December 31, 2020 8,030,415 $ 19.25 7.1 $ 10,137 Granted 4,792,580 6.71 Granted due to Exchange Offer 621,406 3.88 Exercised (125,431) 1.43 Forfeited or canceled (908,212) 25.92 Canceled due to Exchange Offer (1,419,182) 30.25 Balance at September 30, 2021 10,991,576 $ 11.15 7.9 $ 5,721 Vested and expected to vest at September 30, 2021 9,725,705 $ 11.20 7.8 $ 5,682 Exercisable at September 30, 2021 4,921,902 $ 16.17 6.8 $ 5,243
Schedule of Restricted Stock Activity	The following table summarizes restricted stock units, or RSUs, activity under the 2018 Plan for the nine months ended September 30, 2021. Shares Weighted- Unvested balance at December 31, 2020 90,020 $ 16.88 Granted 98,418 4.92 Vested (34,020) 25.40 Forfeited (3,000) 11.71 Unvested balance at September 30, 2021 151,418 $ 7.30
Schedule of Stock-based Compensation Expense	The following table presents stock-based compensation expense as reported in the Company’s condensed statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Research and development $ 2,819 $ 2,937 $ 7,948 $ 9,261 General and administrative 3,830 4,718 11,352 15,847 Total $ 6,649 $ 7,655 $ 19,300 $ 25,108 The following table presents stock-based compensation expense by award type as reported in the Company’s condensed statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020. Three Months Ended Nine Months Ended (in thousands) 2021 2020 2021 2020 Stock options $ 6,210 $ 7,284 $ 17,902 $ 24,211 RSUs 246 238 929 459 ESPP 193 133 469 438 Total $ 6,649 $ 7,655 $ 19,300 $ 25,108

FAIR VALUE MEASUREMENTS AND F_3

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Marketable securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	$ 16,988	$ 137,857
Level 2:
Short-term investments	129,782	171,670
Long-term investments	0	22,757
Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	16,988	137,857
Total assets measured at fair value
Amortized Cost	146,755	332,129
Gross Unrealized Gains	17	166
Gross Unrealized Losses	(2)	(11)
Estimated Fair Value	146,770	332,284
Cash | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	1,332	2,011
Level 1:
Estimated Fair Value	1,332	2,011
Cash and Cash Equivalents | Cash | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	1,332	2,011
Short-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Short-term investments	129,782	171,670
Long-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Long-term investments	0	22,757
Level 1: | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	18,676	34,019
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	(1)
Estimated Fair Value	18,677	34,019
Short-term investments	6,021	8,157
Long-term investments	0	0
Level 1: | Money market funds | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	12,656	25,862
Level 1:
Estimated Fair Value	12,656	25,862
Level 1: | U.S. Treasury securities | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	6,020	8,157
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	(1)
Estimated Fair Value	6,021	8,157
Short-term investments	6,021	8,157
Long-term investments	0	0
Level 1: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	12,656	25,862
Level 1: | Cash and Cash Equivalents | Money market funds | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	12,656	25,862
Level 1: | Cash and Cash Equivalents | U.S. Treasury securities | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	0	0
Level 2: | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	126,747	296,099
Gross Unrealized Gains	16	165
Gross Unrealized Losses	(2)	(10)
Estimated Fair Value	126,761	296,254
Level 2: | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Amortized Cost	29,068	64,370
Gross Unrealized Gains	2	15
Gross Unrealized Losses	0	(3)
Estimated Fair Value	29,070	64,382
Level 2: | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Amortized Cost	97,679	159,183
Gross Unrealized Gains	14	16
Gross Unrealized Losses	(2)	(6)
Estimated Fair Value	97,691	159,193
Level 2: | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Amortized Cost		72,546
Gross Unrealized Gains		134
Gross Unrealized Losses		(1)
Estimated Fair Value		72,679
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	3,000	109,984
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Estimated Fair Value	0	0
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Estimated Fair Value	3,000	97,989
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Estimated Fair Value		11,995
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Short-term investments	123,761	163,513
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Short-term investments	29,070	41,625
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Short-term investments	94,691	61,204
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Short-term investments		60,684
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Long-term investments	0	22,757
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Long-term investments	0	22,757
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Long-term investments	$ 0	0
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Long-term investments		$ 0

FAIR VALUE MEASUREMENTS AND F_4

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross realized gains and gross realized losses on available-for-sale securities	$ 0	$ 0	$ 0	$ 0
Convertible Senior Notes | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value	$ 90,700,000		$ 90,700,000
Convertible Senior Notes | Discount rate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation assumptions as a percentage	0.218		0.218
Convertible Senior Notes | Volatility | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation assumptions as a percentage	0.870		0.870

FAIR VALUE MEASUREMENTS AND F_5

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Reconciliation of liabilities measured using Level 3 (Details) - Fair Value, Inputs, Level 3 - Derivative Financial Instruments, Liabilities [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of period	$ 202	$ 977
Change in fair value	(202)	(699)
Fair value at end of period	$ 0	$ 278

BORROWINGS - Additional informa

BORROWINGS - Additional information (Details) - USD ($)	Mar. 12, 2021	May 22, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Loss on early extinguishment of Term Loan			$ 0	$ 0	$ 6,124,000	$ 0
Fifth amendment to term loan | Tranche Five
Debt Instrument [Line Items]
Repayments of long-term loan	$ 75,000,000
Fees paid on repayment of term loan	8.3 million
Loss on early extinguishment of Term Loan	$ 6,100,000
Senior Notes | 3.50% Due 2027
Debt Instrument [Line Items]
Debt aggregate principal amount		$ 200,000,000
Debt interest rate		0.035%
Conversion rate (in shares)		3009.78%
Principal amount		$ 1,000
Conversion price (in dollars per share)		$ 33.23
Carrying amount of liability component		$ 117,700,000	125,194,000		125,194,000
Equity component, net of underwriter discounts and issuance costs		$ (82,300,000)	$ (79,498,000)		$ (79,498,000)
Effective interest rate		13.50%
Amortization period		7 years			5 years 8 months 12 days

BORROWINGS - Convertible Debt C

BORROWINGS - Convertible Debt Carrying Value (Details) - Senior Notes - 3.50% Due 2027 - USD ($) $ in Thousands	Sep. 30, 2021	May 22, 2020
Debt Instrument [Line Items]
Principal	$ 200,000
Unamortized discount - equity component	(71,170)
Unamortized underwriter discounts and issuance costs	(3,636)
Net carrying amount	125,194	$ 117,700
Equity component, net of underwriter discounts and issuance costs	$ 79,498	$ 82,300

BORROWINGS - Interest Expense (

BORROWINGS - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Total interest expense	$ 3,994	$ 6,267	$ 13,533	$ 12,043
Senior Notes | 3.50% Due 2027
Debt Instrument [Line Items]
Contractual interest expense	1,750	1,750	5,250	2,508
Amortization of debt discount	2,175	1,930	6,334	2,767
Amortization of underwriter discounts and issuance costs	69	50	192	72
Total interest expense	$ 3,994	$ 3,730	$ 11,776	$ 5,347

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	Sep. 30, 2021USD ($)
Lease obligations
Total	$ 17,999
2021	705
2022 - 2023	5,780
2024 - 2025	6,131
Thereafter	5,383
Manufacturing and service contracts
Total	591,046
2021	20,428
2022 - 2023	82,164
2024 - 2025	114,930
Thereafter	373,524
Total contractual obligations and commitments
Total	851,045
2021	24,633
2022 - 2023	101,944
2024 - 2025	135,061
Thereafter	589,407
Senior Notes
Convertible Senior Notes [Abstract]
Total	242,000
2021	3,500
2022 - 2023	14,000
2024 - 2025	14,000
Thereafter	$ 210,500

RESTRUCTURING - Additional Info

RESTRUCTURING - Additional Information (Details) - USD ($) $ in Millions	Oct. 28, 2020	Sep. 18, 2020	Sep. 30, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring costs			$ 0.1
Third Quarter 2020 Restructuring
Restructuring Cost and Reserve [Line Items]
Percent of company's workforce eliminated		21.50%
Fourth Quarter 2020 Restructuring
Restructuring Cost and Reserve [Line Items]
Percent of company's workforce eliminated	60.00%

RESTRUCTURING - Third Quarter 2

RESTRUCTURING - Third Quarter 2020 Restructuring (Details) - Third Quarter 2020 Restructuring - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restructuring Reserve [Roll Forward]
Beginning balance	$ 62	$ 0
Charges		2,660
Cash payments made		(2,593)
Non-cash and other adjustments	(62)	(5)
Ending balance	0	62
Severance and Benefits Costs
Restructuring Reserve [Roll Forward]
Beginning balance	62	0
Charges		2,524
Cash payments made		(2,456)
Non-cash and other adjustments	(62)	(6)
Ending balance	0	62
Contract Termination Costs
Restructuring Reserve [Roll Forward]
Beginning balance	0	0
Charges		136
Cash payments made		(137)
Non-cash and other adjustments	0	1
Ending balance	$ 0	$ 0

RESTRUCTURING - Fourth quarter

RESTRUCTURING - Fourth quarter 2020 Restructuring (Details) - Fourth Quarter 2020 Restructuring - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Restructuring Reserve [Roll Forward]
Beginning balance	$ 4,794	$ 0
Charges		11,094
Cash payments made	(4,740)	(5,587)
Non-cash and other adjustments	146	(713)
Ending balance	200	4,794
Severance and Benefits Costs
Restructuring Reserve [Roll Forward]
Beginning balance	3,783	0
Charges		7,338
Cash payments made	(4,013)	(3,555)
Non-cash and other adjustments	230	0
Ending balance	0	3,783
Contract Termination Costs
Restructuring Reserve [Roll Forward]
Beginning balance	1,011	0
Charges		3,077
Cash payments made	(727)	(2,032)
Non-cash and other adjustments	(84)	(34)
Ending balance	200	1,011
Other Associated Costs
Restructuring Reserve [Roll Forward]
Beginning balance	0	0
Charges		679
Cash payments made	0	0
Non-cash and other adjustments	0	(679)
Ending balance	$ 0	$ 0

NET LOSS PER SHARE - Basic and

NET LOSS PER SHARE - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (39,675)	$ (33,553)	$ (53,362)	$ (77,665)	$ (58,170)	$ (74,114)	$ (126,590)	$ (209,949)
Denominator:
Weighted average common shares outstanding (in shares)	50,434,879			50,121,784			50,326,474	49,977,339
Less: weighted average shares subject to repurchase (in shares)	0			(1,698)			0	(2,951)
Weighted-average number of shares outstanding, diluted (in shares)	50,434,879			50,120,086			50,326,474	49,974,388
Weighted-average number of shares outstanding, basic (in shares)	50,434,879			50,120,086			50,326,474	49,974,388
Net loss per share, diluted (in dollars per share)	$ (0.79)			$ (1.55)			$ (2.52)	$ (4.20)
Net loss per share, basic (in dollars per share)	$ (0.79)			$ (1.55)			$ (2.52)	$ (4.20)

NET LOSS PER SHARE - Antidiluti

NET LOSS PER SHARE - Antidilutive securities (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	17,193,906	15,947,129
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	31,352	31,352
Assumed conversion of Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	6,019,560	6,019,560
Common stock subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	1,260
Stock options and RSUs issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	11,142,994	9,894,957

STOCK-BASED COMPENSATION - Addi

STOCK-BASED COMPENSATION - Additional information (Details)	Aug. 16, 2021USD ($)$ / sharesshares	Jun. 30, 2021shares	Jun. 30, 2018USD ($)purchasePeriodshares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Jul. 16, 2021$ / shares	Dec. 31, 2020$ / sharesshares	Jan. 01, 2019shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock outstanding eligible for conversion				10,991,576		10,991,576			8,030,415
Exercise price of options | $ / shares				$ 19.25		$ 19.25			$ 11.15
Stock-based compensation expense | $				$ 6,649,000	$ 7,655,000	$ 19,300,000	$ 25,108,000
Employee stock purchase price, percentage of market or closing price			85.00%
Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	33.33%
Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	2.78%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $	$ 300,000			6,210,000	7,284,000	17,902,000	24,211,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $				$ 246,000	$ 238,000	$ 929,000	$ 459,000
The 2018 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price (equal to or greater than) | $ / shares								$ 20
The 2018 Equity Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock outstanding eligible for conversion	1,419,182
Shares of common stock returned to 2018 plan reserve	797,776
Award expiration period (in years)	7 years
ESPP | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of employee pay to be withheld for employee stock purchase plan			15.00%
Maximum share value of employee pay allowed to be withheld for ESPP | $			$ 25,000
Maximum annual shares purchased by employee (in shares)		10,000	2,500
Annual increase in number of shares authorized (in shares)										800,000
Employee purchase plan offering period (in months)		24 months	6 months
Number of purchase periods within offering period | purchasePeriod			4
Duration of purchase period within ESPP stock offering period		6 months
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)										800,000
Annual percentage increase in number of shares authorized										1.00%
Shares issued under employee stock purchase plan						(77,348)
ESPP cash contributions | $						$ 300,000
Stock Option Exchange Program | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares converted to new options	621,406
Exercise price of options | $ / shares	$ 3.88
Award vesting period (in years)	1 year

STOCK-BASED COMPENSATION - Sche

STOCK-BASED COMPENSATION - Schedule of stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Shares
Beginning balance (in shares)	8,030,415
Granted (in shares)	4,792,580
Exercised (in shares)	(125,431)
Forfeited (in shares)	(908,212)
Ending balance (in shares)	10,991,576	8,030,415
Outstanding options, vested and expected to vest (in shares)		9,725,705
Outstanding options, exercisable (in shares)		4,921,902
Weighted- Average Exercise Price
Beginning balance (in USD per share)	$ 11.15
Granted (in USD per share)	6.71
Exercised (in USD per share)	1.43
Forfeited (in USD per share)	25.92
Ending balance (in USD per share)	$ 19.25	$ 11.15
Vested and expected to vest (in dollars per share)		11.20
Exercisable (in dollars per share)		$ 16.17
Weighted average remaining contractual term	7 years 1 month 6 days	7 years 10 months 24 days
Weighted average remaining contractual term, vested and expected to vest (in years)		7 years 9 months 18 days
Weighted average remaining contractual term, exercisable		6 years 9 months 18 days
Aggregate intrinsic value	$ 10,137	$ 5,721
Aggregate intrinsic value, vested and expected to vest		5,682
Aggregate intrinsic value, exercisable		$ 5,243
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock outstanding eligible for conversion	10,991,576	8,030,415
Exercise price of options	$ 19.25	$ 11.15
Weighted average remaining contractual term	7 years 1 month 6 days	7 years 10 months 24 days
Aggregate intrinsic value	$ 10,137	$ 5,721
Granted (in shares)	4,792,580
Granted (in USD per share)	$ 6.71
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	125,431
Exercised (in USD per share)	$ 1.43
Outstanding options, forfeited (in shares)	908,212
Forfeited (in USD per share)	$ 25.92
Outstanding options, vested and expected to vest (in shares)		9,725,705
Vested and expected to vest (in dollars per share)		$ 11.20
Weighted average remaining contractual term, vested and expected to vest (in years)		7 years 9 months 18 days
Aggregate intrinsic value, vested and expected to vest		$ 5,682
Outstanding options, exercisable (in shares)		4,921,902
Exercisable (in dollars per share)		$ 16.17
Weighted average remaining contractual term, exercisable		6 years 9 months 18 days
Aggregate intrinsic value, exercisable		$ 5,243
Stock Option Exchange Program
Shares
Granted (in shares)	621,406
Forfeited (in shares)	(1,419,182)
Weighted- Average Exercise Price
Granted (in USD per share)	$ 3.88
Forfeited (in USD per share)	$ 30.25
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	621,406
Granted (in USD per share)	$ 3.88
Outstanding options, forfeited (in shares)	1,419,182
Forfeited (in USD per share)	$ 30.25

STOCK-BASED COMPENSATION - Sc_2

STOCK-BASED COMPENSATION - Schedule of restricted stock activity (Details) - RSUs - $ / shares	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Shares
Unvested beginning balance (in shares)	151,418	90,020
Granted (in shares)	98,418
Vested (in shares)	(34,020)
Forfeited (in shares)	(3,000)
Unvested ending balance (in shares)	151,418
Weighted- Average Grant Date Fair Value
Unvested beginning balance, (in dollars per share)	$ 16.88	$ 7.30
Granted (in dollars per share)	4.92
Vested (in dollars per share)	25.40
Forfeitures (in dollars per share)	11.71
Unvested ending balance (in dollars per share)	$ 16.88

STOCK-BASED COMPENSATION - Sc_3

STOCK-BASED COMPENSATION - Schedule of stock-based compensation (Details) - USD ($) $ in Thousands	Aug. 16, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 6,649	$ 7,655	$ 19,300	$ 25,108
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 300	6,210	7,284	17,902	24,211
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		246	238	929	459
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		193	133	469	438
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		2,819	2,937	7,948	9,261
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 3,830	$ 4,718	$ 11,352	$ 15,847