CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands |
12 Months Ended |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
| Cash flows from operating activities: |
|
|
|
| Net loss |
$ (163,458)
|
$ (89,195)
|
$ (43,847)
|
| Adjustments to reconcile net loss to net cash used in operating activities: |
|
|
|
| Stock-based compensation expense |
41,271
|
27,528
|
17,903
|
| Depreciation and amortization expense |
2,995
|
1,263
|
447
|
| Change in fair value of preferred stock warrant liability |
|
2,187
|
785
|
| Accretion of discount on investments |
(2,320)
|
(329)
|
|
| Loss on disposal of property and equipment |
335
|
|
|
| Non-cash interest expense |
289
|
86
|
42
|
| Changes in operating assets and liabilities: |
|
|
|
| Prepaid expenses and other current assets |
2,655
|
(9,037)
|
(647)
|
| Operating lease, right-of-use-asset |
4,991
|
|
|
| Other assets |
2
|
(74)
|
|
| Accounts payable |
(1,037)
|
4,938
|
1,110
|
| Accrued expenses and other current liabilities |
6,503
|
4,307
|
2,247
|
| Deferred rent |
|
(15)
|
22
|
| Operating lease liabilities |
(2,670)
|
|
|
| Net cash used in operating activities |
(110,444)
|
(58,341)
|
(21,938)
|
| Cash flows from investing activities: |
|
|
|
| Purchases of property, plant and equipment |
(40,657)
|
(14,952)
|
(2,251)
|
| Purchases of investments |
(319,133)
|
(160,972)
|
|
| Sales and maturities of investments |
227,155
|
64,285
|
|
| Net cash used in investing activities |
(132,635)
|
(111,639)
|
(2,251)
|
| Cash flows from financing activities: |
|
|
|
| Proceeds from issuance of convertible preferred stock, net of issuance costs |
|
100,986
|
120,067
|
| 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 the sale of restricted common stock |
|
|
100
|
| Proceeds from repayment of promissory note |
|
246
|
|
| Payments of debt issuance costs |
|
(285)
|
(11)
|
| Repurchase of unvested restricted common stock |
(122)
|
|
|
| Proceeds from borrowings under loan and security agreement |
25,000
|
25,000
|
1,500
|
| Payment of long-term debt |
|
(5,500)
|
|
| Proceeds from issuance of common stock upon exercise of stock options |
2,413
|
64
|
37
|
| Net cash provided by financing activities |
27,291
|
374,829
|
121,693
|
| Net increase (decrease) in cash, cash equivalents and restricted cash |
(215,788)
|
204,849
|
97,504
|
| Cash, cash equivalents and restricted cash at beginning of period |
309,421
|
104,572
|
7,068
|
| Cash, cash equivalents and restricted cash at end of period |
93,633
|
309,421
|
104,572
|
| Supplemental cash flow information: |
|
|
|
| Cash paid for interest, net of interest capitalized |
2,961
|
385
|
265
|
| Cash paid for leases |
5,375
|
|
|
| Supplemental disclosure of non-cash investing and financing information: |
|
|
|
| Lease assets obtained in exchange for new operating lease liabilities |
49,799
|
|
|
| Purchases of property, plant and equipment included in accounts payable or accrued expenses |
3,095
|
1,550
|
9
|
| Amounts capitalized under build-to-suit 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
|
|
| Issuance of preferred stock warrant in connection with loan and security agreement |
|
|
14
|
| Accretion of Series A redeemable convertible preferred stock to redemption value |
|
|
$ 656
|
| Debt issuance costs included in accounts payable and accrued expenses |
|
$ 489
|
|