CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Unaudited) - USD ($) $ in Thousands | Total | Initial Public Offering | Follow-on Offering | Common Stock | Common StockInitial Public Offering | Common StockFollow-on Offering | Additional Paid-In Capital | Additional Paid-In CapitalInitial Public Offering | Additional Paid-In CapitalFollow-on Offering | Accumulated Other Comprehensive Income | Accumulated Deficit | Redeemable Convertible Preferred Stock | Series C Preferred Stock |
Beginning balance at Dec. 31, 2018 | $ (108,422) | | | | | | $ 1,300 | | | | $ (109,722) | | |
Redeemable convertible preferred stock, beginning balance, shares at Dec. 31, 2018 | | | | | | | | | | | | 29,595,909 | |
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2018 | | | | | | | | | | | | $ 205,081 | |
Beginning balance, shares at Dec. 31, 2018 | | | | 3,208,924 | | | | | | | | | |
Issuance of common stock pursuant to stock option exercises | 14 | | | | | | 14 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 3,766 | | | | | | | | | |
Issuance of common stock pursuant to early exercised stock options, shares | | | | 13,640 | | | | | | | | | |
Vesting of early exercised stock options | 27 | | | | | | 27 | | | | | | |
Repurchases of early exercised stock, shares | | | | (1,948) | | | | | | | | | |
Stock-based compensation expense | 403 | | | | | | 403 | | | | | | |
Net loss | (10,131) | | | | | | | | | | (10,131) | | |
Ending balance at Mar. 31, 2019 | (118,109) | | | | | | 1,744 | | | | (119,853) | | |
Redeemable convertible preferred stock, ending balance, shares at Mar. 31, 2019 | | | | | | | | | | | | 29,595,909 | |
Redeemable convertible preferred stock, ending balance at Mar. 31, 2019 | | | | | | | | | | | | $ 205,081 | |
Ending balance, shares at Mar. 31, 2019 | | | | 3,224,382 | | | | | | | | | |
Beginning balance at Dec. 31, 2018 | (108,422) | | | | | | 1,300 | | | | (109,722) | | |
Redeemable convertible preferred stock, beginning balance, shares at Dec. 31, 2018 | | | | | | | | | | | | 29,595,909 | |
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2018 | | | | | | | | | | | | $ 205,081 | |
Beginning balance, shares at Dec. 31, 2018 | | | | 3,208,924 | | | | | | | | | |
Net unrealized gains (loss) on marketable securities | 54 | | | | | | | | | | | | |
Net loss | (33,068) | | | | | | | | | | | | |
Ending balance at Sep. 30, 2019 | (139,446) | | | | | | 3,290 | | | $ 54 | (142,790) | | |
Redeemable convertible preferred stock, ending balance, shares at Sep. 30, 2019 | | | | | | | | | | | | 39,600,423 | |
Redeemable convertible preferred stock, ending balance at Sep. 30, 2019 | | | | | | | | | | | | $ 305,114 | |
Ending balance, shares at Sep. 30, 2019 | | | | 3,301,886 | | | | | | | | | |
Beginning balance at Mar. 31, 2019 | (118,109) | | | | | | 1,744 | | | | (119,853) | | |
Redeemable convertible preferred stock, beginning balance, shares at Mar. 31, 2019 | | | | | | | | | | | | 29,595,909 | |
Redeemable convertible preferred stock, beginning balance at Mar. 31, 2019 | | | | | | | | | | | | $ 205,081 | |
Beginning balance, shares at Mar. 31, 2019 | | | | 3,224,382 | | | | | | | | | |
Issuance of Series C redeemable convertible preferred stock for cash at $10.03 per share, net of issuance costs | | | | | | | | | | | | | $ 89,935 |
Issuance of Series C redeemable convertible preferred stock for cash at $10.03 per share, net of issuance costs, shares | | | | | | | | | | | | | 8,991,731 |
Issuance of common stock pursuant to stock option exercises | 1 | | | | | | 1 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 1,391 | | | | | | | | | |
Issuance of common stock pursuant to early exercised stock options, shares | | | | 5,998 | | | | | | | | | |
Vesting of early exercised stock options | 35 | | | | | | 35 | | | | | | |
Repurchases of early exercised stock, shares | | | | (51,375) | | | | | | | | | |
Stock-based compensation expense | 506 | | | | | | 506 | | | | | | |
Net unrealized gains (loss) on marketable securities | (15) | | | | | | | | | (15) | | | |
Net loss | (10,119) | | | | | | | | | | (10,119) | | |
Ending balance at Jun. 30, 2019 | (127,701) | | | | | | 2,286 | | | (15) | (129,972) | | |
Redeemable convertible preferred stock, ending balance, shares at Jun. 30, 2019 | | | | | | | | | | | | 38,587,640 | |
Redeemable convertible preferred stock, ending balance at Jun. 30, 2019 | | | | | | | | | | | | $ 295,016 | |
Ending balance, shares at Jun. 30, 2019 | | | | 3,180,396 | | | | | | | | | |
Issuance of Series C redeemable convertible preferred stock for cash at $10.03 per share, net of issuance costs | | | | | | | | | | | | | $ 10,098 |
Issuance of Series C redeemable convertible preferred stock for cash at $10.03 per share, net of issuance costs, shares | | | | | | | | | | | | | 1,012,783 |
Issuance of common stock pursuant to stock option exercises | 99 | | | | | | 99 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 65,008 | | | | | | | | | |
Issuance of common stock pursuant to early exercised stock options, shares | | | | 81,222 | | | | | | | | | |
Vesting of early exercised stock options | 51 | | | | | | 51 | | | | | | |
Repurchases of early exercised stock, shares | | | | (24,740) | | | | | | | | | |
Stock-based compensation expense | 854 | | | | | | 854 | | | | | | |
Net unrealized gains (loss) on marketable securities | 69 | | | | | | | | | 69 | | | |
Net loss | (12,818) | | | | | | | | | | (12,818) | | |
Ending balance at Sep. 30, 2019 | (139,446) | | | | | | 3,290 | | | 54 | (142,790) | | |
Redeemable convertible preferred stock, ending balance, shares at Sep. 30, 2019 | | | | | | | | | | | | 39,600,423 | |
Redeemable convertible preferred stock, ending balance at Sep. 30, 2019 | | | | | | | | | | | | $ 305,114 | |
Ending balance, shares at Sep. 30, 2019 | | | | 3,301,886 | | | | | | | | | |
Beginning balance at Dec. 31, 2019 | $ (152,574) | | | | | | 4,738 | | | 74 | (157,386) | | |
Redeemable convertible preferred stock, beginning balance, shares at Dec. 31, 2019 | 39,600,423 | | | | | | | | | | | 39,600,423 | |
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2019 | $ 305,109 | | | | | | | | | | | $ 305,109 | |
Beginning balance, shares at Dec. 31, 2019 | | | | 3,292,124 | | | | | | | | | |
Conversion of redeemable convertible preferred stock into common stock | 305,109 | | | $ 4 | | | 305,105 | | | | | $ (305,109) | |
Conversion of redeemable convertible preferred stock into common stock, shares | | | | 39,600,423 | | | | | | | | (39,600,423) | |
Issuance of common stock upon offering, net of offering costs | | $ 250,697 | | | $ 2 | | | $ 250,695 | | | | | |
Issuance of common stock upon offering, net of offering costs, shares | | | | | 16,100,000 | | | | | | | | |
Issuance of common stock pursuant to stock option exercises | 27 | | | | | | 27 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 11,097 | | | | | | | | | |
Vesting of early exercised stock options | 47 | | | | | | 47 | | | | | | |
Stock-based compensation expense | 1,567 | | | | | | 1,567 | | | | | | |
Net unrealized gains (loss) on marketable securities | (38) | | | | | | | | | (38) | | | |
Net loss | (19,519) | | | | | | | | | | (19,519) | | |
Ending balance at Mar. 31, 2020 | 385,316 | | | $ 6 | | | 562,179 | | | 36 | (176,905) | | |
Ending balance, shares at Mar. 31, 2020 | | | | 59,003,644 | | | | | | | | | |
Beginning balance at Dec. 31, 2019 | $ (152,574) | | | | | | 4,738 | | | 74 | (157,386) | | |
Redeemable convertible preferred stock, beginning balance, shares at Dec. 31, 2019 | 39,600,423 | | | | | | | | | | | 39,600,423 | |
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2019 | $ 305,109 | | | | | | | | | | | $ 305,109 | |
Beginning balance, shares at Dec. 31, 2019 | | | | 3,292,124 | | | | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | 447,966 | | | | | | | | | | | | |
Net unrealized gains (loss) on marketable securities | $ 137 | | | | | | | | | | | | |
Net loss | (73,955) | | | | | | | | | | | | |
Ending balance at Sep. 30, 2020 | $ 505,070 | | | $ 7 | | | 736,193 | | | 211 | (231,341) | | |
Redeemable convertible preferred stock, ending balance, shares at Sep. 30, 2020 | 0 | | | | | | | | | | | | |
Ending balance, shares at Sep. 30, 2020 | | | | 66,324,753 | | | | | | | | | |
Beginning balance at Mar. 31, 2020 | $ 385,316 | | | $ 6 | | | 562,179 | | | 36 | (176,905) | | |
Beginning balance, shares at Mar. 31, 2020 | | | | 59,003,644 | | | | | | | | | |
Issuance of common stock pursuant to stock option exercises | 86 | | | | | | 86 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 21,578 | | | | | | | | | |
Vesting of early exercised stock options | 39 | | | | | | 39 | | | | | | |
Repurchase of common stock, shares | | | | (9,354) | | | | | | | | | |
Stock-based compensation expense | 2,017 | | | | | | 2,017 | | | | | | |
Net unrealized gains (loss) on marketable securities | 255 | | | | | | | | | 255 | | | |
Net loss | (27,215) | | | | | | | | | | (27,215) | | |
Ending balance at Jun. 30, 2020 | 360,498 | | | $ 6 | | | 564,321 | | | 291 | (204,120) | | |
Ending balance, shares at Jun. 30, 2020 | | | | 59,015,868 | | | | | | | | | |
Issuance of common stock upon offering, net of offering costs | | | $ 167,767 | | | $ 1 | | | $ 167,766 | | | | |
Issuance of common stock upon offering, net of offering costs, shares | | | | | | 6,900,000 | | | | | | | |
Issuance of common stock pursuant to stock option exercises | 1,390 | | | | | | 1,390 | | | | | | |
Issuance of common stock pursuant to stock option exercises, shares | | | | 415,291 | | | | | | | | | |
Vesting of early exercised stock options | 46 | | | | | | 46 | | | | | | |
Repurchase of common stock, shares | | | | (6,406) | | | | | | | | | |
Stock-based compensation expense | 2,670 | | | | | | 2,670 | | | | | | |
Net unrealized gains (loss) on marketable securities | (80) | | | | | | | | | (80) | | | |
Net loss | (27,221) | | | | | | | | | | (27,221) | | |
Ending balance at Sep. 30, 2020 | $ 505,070 | | | $ 7 | | | $ 736,193 | | | $ 211 | $ (231,341) | | |
Redeemable convertible preferred stock, ending balance, shares at Sep. 30, 2020 | 0 | | | | | | | | | | | | |
Ending balance, shares at Sep. 30, 2020 | | | | 66,324,753 | | | | | | | | | |