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Statements of Cash Flows - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2019
Cash Flows from Operating Activities |  |  |
Net loss | $ (88,644) | $ (47,264) |
Adjustments to reconcile net loss to net cash used in operating activities: |  |  |
Stock-based compensation | 11,371 | 5,932 |
Operating lease right-of-use asset amortization | 1,378 | 1,331 |
Depreciation | 578 | 601 |
Net amortization of premium (accretion of discount) on marketable securities | 1,321 | (155) |
Loss on early repayment of debt |  | 585 |
Amortization of debt issuance costs and accretion of debt discount |  | 22 |
Change in deferred tax asset |  | 1,404 |
Changes in operating assets and liabilities: |  |  |
Research and development tax incentive receivable | (854) | (517) |
Receivable from collaboration partner - related party | (212) | 3,966 |
Prepaid expenses and other assets | (2,632) | (1,566) |
Accounts payable | (2,285) | 32 |
Payable to collaboration partner - related party | (1,611) | 815 |
Accrued expenses and other payables | 14,393 | 3,130 |
Deferred revenue - related party | (12,236) | (20,653) |
Operating lease liability | (1,493) | (1,450) |
Other liabilities |  | 170 |
Net cash used in operating activities | (80,926) | (53,617) |
Cash Flows from Investing Activities |  |  |
Purchase of marketable securities | (255,902) | (147,600) |
Proceeds from maturities of marketable securities | 213,080 | 131,383 |
Purchases of property and equipment | (905) | (346) |
Net cash used in investing activities | (43,727) | (16,563) |
Cash Flows from Financing Activities |  |  |
Proceeds from public offering of common stock, net of issuance costs | 123,995 | 105,478 |
Proceeds from issuance of common stock upon exercise of stock options and purchases under employee stock purchase plan | 3,944 | 2,486 |
Tax withholding payments related to net settlement of restricted stock units | (189) |  |
Issuance costs related to long-term debt |  | (14) |
Proceeds from at-the-market offering, net of issuance costs |  | 23,219 |
Early repayment of long-term debt |  | (10,524) |
Net cash provided by financing activities | 127,750 | 120,645 |
Effect of exchange rate changes on cash, cash equivalents and restricted cash | (148) | 154 |
Net increase in cash, cash equivalents and restricted cash | 2,949 | 50,619 |
Cash, cash equivalents and restricted cash, beginning of period | 117,818 | 33,466 |
Cash, cash equivalents and restricted cash, end of period | 120,767 | 84,085 | $ 33,466
Supplemental Disclosure of Non-Cash Financing and Investing Information: |  |  |
Purchases of property and equipment in accounts payable and accrued liabilities | 24 | 27 |
Public Offering | Accrued liabilities and other payables |  |  |
Supplemental Disclosure of Non-Cash Financing and Investing Information: |  |  |
Issuance costs related to common stock offering | $ 191 | 25 |
Public Offering | Prepaid expenses and other assets |  |  |
Supplemental Disclosure of Non-Cash Financing and Investing Information: |  |  |
Issuance costs related to common stock offering |  |  | $ 125
At-the-market offering | Accrued liabilities and other payables |  |  |
Supplemental Disclosure of Non-Cash Financing and Investing Information: |  |  |
Issuance costs related to common stock offering |  | 17 |
At-the-market offering | Prepaid expenses and other assets |  |  |
Supplemental Disclosure of Non-Cash Financing and Investing Information: |  |  |
Issuance costs related to common stock offering |  | $ 191 |

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