CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
| Cash flows from operating activities: |
|
|
|
| Net loss |
$ (167,731)
|
$ (163,458)
|
$ (89,195)
|
| Adjustments to reconcile net loss to net cash used in operating activities: |
|
|
|
| Stock-based compensation expense |
33,665
|
41,271
|
27,528
|
| Depreciation and amortization expense |
5,691
|
2,995
|
1,263
|
| Change in fair value of preferred stock warrant liability |
|
|
2,187
|
| Amortization (accretion) of premium (discount) on investments |
266
|
(2,320)
|
(329)
|
| Loss on disposal of property and equipment |
|
335
|
|
| Non-cash interest expense |
349
|
289
|
86
|
| Changes in operating assets and liabilities: |
|
|
|
| Prepaid expenses and other current assets |
992
|
2,655
|
(9,037)
|
| Operating lease, right-of-use-asset |
5,539
|
4,991
|
|
| Other assets |
46
|
2
|
(74)
|
| Accounts payable |
(1,369)
|
(1,037)
|
4,938
|
| Accrued expenses and other current liabilities |
(96)
|
6,107
|
4,307
|
| Other long-term liabilities |
283
|
396
|
(15)
|
| Operating lease liabilities |
(5,283)
|
(2,670)
|
|
| Net cash used in operating activities |
(127,648)
|
(110,444)
|
(58,341)
|
| Cash flows from investing activities: |
|
|
|
| Purchases of property, plant and equipment |
(5,497)
|
(40,657)
|
(14,952)
|
| Purchases of investments |
(122,671)
|
(319,133)
|
(160,972)
|
| Sales and maturities of investments |
228,600
|
227,155
|
64,285
|
| Net cash provided by (used in) investing activities |
100,432
|
(132,635)
|
(111,639)
|
| Cash flows from financing activities: |
|
|
|
| Proceeds from issuance of convertible preferred stock, net of issuance costs |
|
|
100,986
|
| Proceeds from initial public offering of common stock, net of commissions and underwriting discounts |
|
|
257,866
|
| Payments of initial public offering costs |
|
|
(3,548)
|
| Proceeds from repayment of promissory note |
|
|
246
|
| Payments of debt issuance costs |
|
|
(285)
|
| Repurchase of unvested restricted common stock |
|
(122)
|
|
| Proceeds from borrowings under loan and security agreement |
25,000
|
25,000
|
25,000
|
| Payment of long-term debt |
|
|
(5,500)
|
| Proceeds from issuance of common stock upon exercise of stock options |
1,484
|
2,413
|
64
|
| Net cash provided by financing activities |
26,484
|
27,291
|
374,829
|
| Net decrease in cash, cash equivalents and restricted cash |
(732)
|
(215,788)
|
204,849
|
| Cash, cash equivalents and restricted cash at beginning of period |
93,633
|
309,421
|
104,572
|
| Cash, cash equivalents and restricted cash at end of period |
92,901
|
93,633
|
309,421
|
| Supplemental cash flow information: |
|
|
|
| Cash paid for interest, net of interest capitalized |
3,822
|
2,961
|
385
|
| Cash paid for leases |
8,486
|
5,375
|
|
| Lease assets obtained in exchange for new operating lease liabilities |
496
|
49,799
|
|
| Lease asset derecognized upon lease cancellation |
982
|
|
|
| Supplemental disclosure of non-cash investing and financing information: |
|
|
|
| Purchases of property, plant and equipment included in accounts payable or accrued expenses |
$ 317
|
3,095
|
1,550
|
| Amounts capitalized under build-to-suit lease transaction |
|
|
45,142
|
| Proceeds from issuance of common stock upon exercise of stock options in other current assets |
|
$ 32
|
|
| Reclassification of warrant liability to additional paid-in capital |
|
|
3,053
|
| Conversion of preferred stock to common stock upon closing of the initial public offering |
|
|
240,776
|
| Debt issuance costs included in accounts payable and accrued expenses |
|
|
$ 489
|