Term Loan	12 Months Ended
Dec. 31, 2022
Debt Disclosure [Abstract]
Term Loan	6. Term Loan Loan and Security Agreement In April 2020, the Company entered into a Loan and Security Agreement, (the “Loan Agreement”) with the lenders referred to therein, and Silicon Valley Bank (“SVB”), as collateral agent. The Loan Agreement provided for (i) a secured term A loan facility (the “Term A Loan Facility”) of up to $10.0 million and (ii) a secured term B loan facility (the “Term B Loan Facility”) of up to $5.0 million that became available upon the satisfaction of certain milestones, each of which was available to be drawn through May 31, 2021. The term loan is secured by certain assets of the Borrowers (as defined in the Loan Agreement), including substantially all of the assets of the Company, excluding the Company’s intellectual property. The term loan contains customary representations, warranties, affirmative covenants and also certain restrictive covenants. In April 2020, in connection with the execution of the Loan Agreement, the Company issued SVB a warrant to purchase 25,000 shares of the Company’s common stock with a warrant exercise price of $22.06 per share that is immediately exercisable and expires on June 30, 2025, as amended. The fair value of the warrant at the issuance date was determined by using the Black-Scholes option-pricing model and the fair value allocated to the warrant of $0.6 million met the requirements for equity classification within additional paid-in capital. Additionally, the Company incurred $0.2 million in closing costs, which together with the value of the warrants, were recorded as debt issuance costs. In May 2021, the parties further amended the Loan Agreement (as amended, the “2021 Loan Agreement”). The 2021 Loan Agreement increased the Term A Loan Facility to up to $20.0 million, which was fully drawn as of December 2021. The Term B Loan Facility of up to $5.0 million was available to be drawn upon on achievement of certain additional milestones, on or before September 30, 2022, which expired unused. The 2021 Loan Agreement provided for interest-only payments until October 1, 2022, which could be extended to April 1, 2023, if on or before September 30, 2022, the Company received net cash proceeds of at least $75.0 million from the sale of its equity securities. In July 2022, the Company met the net cash proceeds requirement (see Note 7) and on September 1, 2022, the interest-only period was extended to April 1, 2023. Consecutive monthly payments of principal and interest commence on April 1, 2023 and continue through September 1, 2024, the maturity date of the term loan. The term loan bears interest at the greater of (i) 4.25% and (ii) the sum of (a) the Prime Rate as reported in The Wall Street Journal plus (b) 1.00%. The interest rate on the term loan was 4.25% at inception and 8.50% as of December 31, 2022. In addition, a final payment fee of 5.0% of the principal amount of the loan is due when the term loan becomes due or upon prepayment of the term loan. If the Company elects to prepay the loan, there is also a prepayment fee of between 1.0% and 3.0% of the principal amount of the term loan depending on the timing of prepayment. In May 2021, in connection with the execution of the 2021 Loan Agreement, the Company issued SVB a warrant to purchase 33,923 shares of the Company’s common stock with a warrant exercise price of $19.12 per share that is immediately exercisable and expires on May 28, 2031. The Company determined the fair value of the warrant at the issuance date by using the Black-Scholes option-pricing model with the following assumptions: risk-free interest rate of 1.6%, no dividends, expected volatility of 98.6% and expected term of 10.0 years. Upon issuance, the fair value of the warrant of $0.6 million was recorded as a debt issuance cost and met the requirements for equity classification within additional paid-in capital in the consolidated balance sheets. In addition, closing costs incurred were not material. In connection with Term B Loan Facility, if funded, the Company was to issue an additional warrant to purchase 11,305 shares of the Company’s common stock with the exercise price at the Company’s stock price at the time of issuance. However, the Term Loan B Facility expired unused and therefore no additional warrant was issued. The 2021 Loan Agreement was accounted for as a modification to a credit facility. The related debt issuance costs incurred in May 2021, including the fair value of the warrant, together with the remaining unamortized debt issuance costs related to the Loan Agreement of $0.4 million were recorded as deferred assets and recognized on a straight-line basis as interest expense over the availability of the draw period. As of December 31, 2021, all amounts were drawn under the Term Loan A Facility such that all debt issuance costs were recorded as a debt discount. The carrying value of the debt discount, together with the final payment fee, are recognized using the effective interest method. In September 2022, the parties agreed the extension of the interest-only period was met as a result of the July 2022 public offering (see Note 7), which was accounted for as a debt modification. A new effective interest rate equating to the revised cash flows of the carrying amount of the original debt was applied prospectively. The Company did not incur any costs in relation to the extension. In January 2023, the Company executed a loan and security agreement with new lenders (the “2023 Loan Agreement”) and repaid its outstanding obligations under the 2021 Loan Agreement (see Note 11). As the Company had the intent and ability to refinance amounts due under the 2021 Loan Agreement pursuant to the terms of the 2023 Loan Agreement, as of December 31, 2022, the current portion of the outstanding principal obligation under the 2021 Loan Agreement was classified as long-term. As of December 31, 2022, the Company’s total obligations under the 2021 Loan Agreement were $19.7 million classified as term loan, non-current, net and $0.5 million classified as other non-current liability related to the final payment fee. The term loan, non-current, net is comprised of the outstanding principal amount of $20.0 million net of $0.3 million of unamortized debt discount.

Term Loan

12 Months Ended

Dec. 31, 2022

6. Term Loan

Loan and Security Agreement

In April 2020, the Company entered into a Loan and Security Agreement, (the “Loan Agreement”) with the lenders referred to therein, and Silicon Valley Bank (“SVB”), as collateral agent. The Loan Agreement provided for (i) a secured term A loan facility (the “Term A Loan Facility”) of up to $10.0 million and (ii) a secured term B loan facility (the “Term B Loan Facility”) of up to $5.0 million that became available upon the satisfaction of certain milestones, each of which was available to be drawn through May 31, 2021. The term loan is secured by certain assets of the Borrowers (as defined in the Loan Agreement), including substantially all of the assets of the Company, excluding the Company’s intellectual property. The term loan contains customary representations, warranties, affirmative covenants and also certain restrictive covenants.

In April 2020, in connection with the execution of the Loan Agreement, the Company issued SVB a warrant to purchase 25,000 shares of the Company’s common stock with a warrant exercise price of $22.06 per share that is immediately exercisable and expires on June 30, 2025, as amended. The fair value of the warrant at the issuance date was determined by using the Black-Scholes option-pricing model and the fair value allocated to the warrant of $0.6 million met the requirements for equity classification within additional paid-in capital. Additionally, the Company incurred $0.2 million in closing costs, which together with the value of the warrants, were recorded as debt issuance costs.

In May 2021, the parties further amended the Loan Agreement (as amended, the “2021 Loan Agreement”). The 2021 Loan Agreement increased the Term A Loan Facility to up to $20.0 million, which was fully drawn as of December 2021. The Term B Loan Facility of up to $5.0 million was available to be drawn upon on achievement of certain additional milestones, on or before September 30, 2022, which expired unused. The 2021 Loan Agreement provided for interest-only payments until October 1, 2022, which could be extended to April 1, 2023, if on or before September 30, 2022, the Company received net cash proceeds of at least $75.0 million from the sale of its equity securities. In July 2022, the Company met the net cash proceeds requirement (see Note 7) and on September 1, 2022, the interest-only period was extended to April 1, 2023. Consecutive monthly payments of principal and interest commence on April 1, 2023 and continue through September 1, 2024, the maturity date of the term loan. The term loan bears interest at the greater of (i) 4.25% and (ii) the sum of (a) the Prime Rate as reported in The Wall Street Journal plus (b) 1.00%. The interest rate on the term loan was 4.25% at inception and 8.50% as of December 31, 2022. In addition, a final payment fee of 5.0% of the principal amount of the loan is due when the term loan becomes due or upon prepayment of the term loan. If the Company elects to prepay the loan, there is also a prepayment fee of between 1.0% and 3.0% of the principal amount of the term loan depending on the timing of prepayment.

In May 2021, in connection with the execution of the 2021 Loan Agreement, the Company issued SVB a warrant to purchase 33,923 shares of the Company’s common stock with a warrant exercise price of $19.12 per share that is immediately exercisable and expires on May 28, 2031. The Company determined the fair value of the

warrant at the issuance date by using the Black-Scholes option-pricing model with the following assumptions: risk-free interest rate of 1.6%, no dividends, expected volatility of 98.6% and expected term of 10.0 years. Upon issuance, the fair value of the warrant of $0.6 million was recorded as a debt issuance cost and met the requirements for equity classification within additional paid-in capital in the consolidated balance sheets. In addition, closing costs incurred were not material. In connection with Term B Loan Facility, if funded, the Company was to issue an additional warrant to purchase 11,305 shares of the Company’s common stock with the exercise price at the Company’s stock price at the time of issuance. However, the Term Loan B Facility expired unused and therefore no additional warrant was issued.

The 2021 Loan Agreement was accounted for as a modification to a credit facility. The related debt issuance costs incurred in May 2021, including the fair value of the warrant, together with the remaining unamortized debt issuance costs related to the Loan Agreement of $0.4 million were recorded as deferred assets and recognized on a straight-line basis as interest expense over the availability of the draw period. As of December 31, 2021, all amounts were drawn under the Term Loan A Facility such that all debt issuance costs were recorded as a debt discount. The carrying value of the debt discount, together with the final payment fee, are recognized using the effective interest method.

In September 2022, the parties agreed the extension of the interest-only period was met as a result of the July 2022 public offering (see Note 7), which was accounted for as a debt modification. A new effective interest rate equating to the revised cash flows of the carrying amount of the original debt was applied prospectively. The Company did not incur any costs in relation to the extension.

In January 2023, the Company executed a loan and security agreement with new lenders (the “2023 Loan Agreement”) and repaid its outstanding obligations under the 2021 Loan Agreement (see Note 11). As the Company had the intent and ability to refinance amounts due under the 2021 Loan Agreement pursuant to the terms of the 2023 Loan Agreement, as of December 31, 2022, the current portion of the outstanding principal obligation under the 2021 Loan Agreement was classified as long-term. As of December 31, 2022, the Company’s total obligations under the 2021 Loan Agreement were $19.7 million classified as term loan, non-current, net and $0.5 million classified as other non-current liability related to the final payment fee. The term loan, non-current, net is comprised of the outstanding principal amount of $20.0 million net of $0.3 million of unamortized debt discount.