On December 6, 2022, the Company entered into a Note Purchase Agreement (the "Note Purchase Agreement"), with Mr. Duggan and Dr. Zanganeh, pursuant to which the Company agreed to sell to each of Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the aggregate amount of $520,000. Pursuant to the Note Purchase Agreement, the Company issued to Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the amount of $400,000 (the "Duggan February Note") and $20,000 (the "Zanganeh Note"), respectively, which would mature and become due on February 15, 2023 and an unsecured promissory note to Mr. Duggan in the amount of $100,000 (the “Duggan September Note” and together with the Duggan February Note and the Zanganeh Note, the “December 2022 Notes”), which would mature and become due on September 15, 2023. The maturity dates of the December 2022 Notes could be extended one or more times at the Company’s election, but in no event to a date later than September 6, 2024. In addition, if the Company shall consummate a public offering, then upon the later to occur of (i) five business days after the Company receives the net cash proceeds therefrom or (ii) May 15, 2023, the Duggan February Note and the Zanganeh Note shall be prepaid by an amount equal to the lesser of (a) 100% of the amount of the net proceeds of such offering and (b) the outstanding principal amount on such Notes.

On January 19, 2023, the Company provided notice to extend the term of the Duggan February Note and Duggan September Note to a maturity date of September 6, 2024. Furthermore, on January 19, 2023, the Company and Mr. Duggan rectified the Duggan February Note and Duggan September Note in order to correctly reflect the parties’ intent that the Company may only prepay (i) the Duggan February Note following the completion of a public rights offering to be conducted by Summit in the approximate amount of $500,000, or a similar capital raise, in an amount equal to the lesser of (x) the net proceeds of the Rights Offering or such capital raise or (y) the full amount outstanding of the Duggan February Note, and (ii) Duggan September Note following the completion of a capital raising transaction subsequent to the 2023 Rights Offering in an amount equal to the lesser of (i) the net proceeds of such capital raise or (ii) the full amount outstanding of the Duggan September Note. Following the issuance of the two new Promissory Notes (the “Duggan Promissory Notes”), the Duggan February Note and Duggan September Note were marked as “cancelled” on their face and replaced in their entirety by the Duggan Promissory Notes (together with the Zanganeh Note, the "Notes").

On February 15, 2023, the $20,000 Zanganeh Note matured and the Company repaid the outstanding principal balance. In connection with the closing of the 2023 Rights Offering, the $400,000 Duggan Promissory Note matured and became due, and the Company satisfied all principal and accrued interest thereunder using a combination of a portion of the cash proceeds from the 2023 Rights Offering and the extinguishment of a portion of the amount due equal to the subscription price for shares subscribed by Mr Duggan in the 2023 Rights Offering.

The Notes accrue interest at an initial rate of 7.5%. All interest on the Notes was paid on the date of signing for the period through February 15, 2023. Such prepaid interest was paid in a number of shares of the Company’s common stock, par value $0.01 (“Common Stock”) equal to the dollar amount of such prepaid interest, divided by $0.7913 (the consolidated closing bid price immediately preceding the time the Company entered into the Note Purchase Agreement, plus $0.01), which was 9,720,291 shares. For all applicable periods following the February 15, 2023, interest shall accrue on the outstanding principal balance of the Notes at the US prime interest rate, as reported in the Wall Street Journal, plus 50 basis points, as adjusted monthly, for three months immediately following February 15, 2023, and thereafter at the US prime rate plus 300 basis points, as adjusted monthly.

Debt issuance costs associated with the Notes were $44 and were capitalized as part of the carrying value of the promissory notes payable to related parties. The Company incurred interest expense of $8,327 during the three months ended March 31, 2023, which included amortized imputed interest of $761. As of March 31, 2023, accrued interest of $999 payable on the Duggan September Note and as of December 31, 2022, accrued interest of $0, is included within accrued expenses in the condensed consolidated balance sheets.

Imputed interest is calculated as the difference between the expected interest payable and the deemed market rate of interest and is recorded as a debt discount at inception of the note payable with a credit to additional paid-in capital for notes payable to related parties. The debt discount is amortized to interest expense using an effective interest rate method. The effective interest rate of the Duggan February Note and Zanganeh Note was 8.9% and the effective interest rate of the Duggan September Note is 8.8%.

On July 25, 2022 the Company entered into a first amendment, dated July 19, 2022, to its initial sublease agreement with Maky Zanganeh and Associates, Inc. ("MZA") consisting of 4,500 square feet of office space at 2882 Sand Hill Road, Menlo Park, California entered into on March 26, 2021. The sublease term, which was set to expire on September 30, 2022, was extended for a period of thirty-nine months from October 1, 2022 through December 31, 2025. The rent payable under the terms of the sublease is equivalent to the proportionate share of the net payable by MZA to the third-party landlord, based on the square footage of office space sublet by the Company, and no mark-up has been applied. During the three months ended March 31, 2023, payments of $189, were made pursuant to the first amendment to the Sublease Agreement. During the three months ended March 31, 2022, payments of $179, were made pursuant to the initial Sublease Agreement.

On July 29, 2022, the Company entered into a second amendment, dated August 1, 2022, to its existing sublease agreement with MZA, described above. The second amendment was effective as of August 1, 2022 and expires on December 31, 2025. The second amendment includes an additional 1,277 square feet (the "Expansion Premises") of office space at 2882 Sand Hill Road, Menlo Park, California. The rent payable under the terms of the sublease is equivalent to the proportionate share of the net payable by MZA to the third-party landlord, based on the square footage of office space sublet by the Company, and no mark-up has been applied. During the three months ended March 31, 2023, payments of $54, were made pursuant to the second amendment to the Sublease Agreement.

On March 10, 2022, the Company entered into a Note Purchase Agreement (the "March 2022 Note"), with Mr. Duggan, pursuant to which Mr. Duggan loaned the Company $25,000 in exchange for the issuance by the Company of an unsecured promissory note in the amount of $25,000. The March 2022 Note accrued interest at a rate per annum equal to the prime rate as reported in the Wall Street Journal, which was 3.25% as of the effective date and 4.75% as of June 30, 2022. The March 2022 Note, including accrued interest, became due upon the earlier of (i) the consummation of a registered public offering with net proceeds of no less than $25,000 or (ii) 18 months from the date of issuance of the March 2022 Note, and was repaid on August 10, 2022.

In August 2022, the Company announced the closing and final results of its previously announced rights offering. The 2022 Rights Offering commenced on July 18, 2022, and the associated subscription rights expired on August 8, 2022. Aggregate gross proceeds received from the rights offering were $100,000 from the sale of 103,092,783 shares of common stock. Mr. Robert W. Duggan and Dr. Maky Zanganeh fully subscribed to their respective basic subscription rights and oversubscribed, at a price of $0.97 per share. Issuance costs were $111. In connection with the closing of the 2022 Rights Offering, the March 2022 Note matured and became due, and the Company repaid all principal and accrued interest thereunder using a portion of the proceeds from the 2022 Rights Offering on August 10, 2022.

On December 6, 2022, the Company entered into a Note Purchase Agreement (the "Note Purchase Agreement"), with Mr. Duggan and Dr. Zanganeh, pursuant to which the Company agreed to sell to each of Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the aggregate amount of $520,000. Pursuant to the Note Purchase Agreement, the Company issued to Mr. Duggan and Dr. Zanganeh unsecured promissory notes in the amount of $400,000 (the "Duggan February Note") and $20,000 (the "Zanganeh Note"), respectively, which would mature and become due on February 15, 2023 and an unsecured promissory note to Mr. Duggan in the amount of $100,000 (the “Duggan September Note” and together with the Duggan February Note and the Zanganeh Note, the “December 2022 Notes”), which will mature and become due on September 15, 2023. The maturity dates of the December 2022 Notes could be extended one or more times at the Company’s election, but in no event to a date later than September 6, 2024. In addition, if the Company shall consummate a public offering, then upon the later to occur of (i) five business days after the Company receives the net cash proceeds therefrom or (ii) May 15, 2023, the Duggan February Note and the Zanganeh Note shall be prepaid by an amount equal to the lesser of (a) 100% of the amount of the net proceeds of such offering and (b) the outstanding principal amount on such notes.

On January 19, 2023, the Company provided notice to extend the term of the Duggan February Note and Duggan September Note to a maturity date of September 6, 2024. Furthermore, on January 19, 2023, the Company and Mr. Duggan rectified the Duggan February Note and Duggan September Note in order to correctly reflect the parties’ intent that the Company may only prepay (i) the Duggan February Note following the completion of a public rights offering to be conducted by Summit in the approximate amount of $500,000, or a similar capital raise, in an amount equal to the lesser of (x) the net proceeds of the 2023 Rights Offering or such capital raise or (y) the full amount outstanding of the Duggan February Note, and (ii) Duggan September Note following the completion of a capital raising transaction subsequent to the 2023 Rights Offering in an amount equal to the lesser of (i) the net proceeds of such capital raise or (ii) the full amount outstanding of the Duggan September Note. Following the issuance of the two new Promissory Notes, the Duggan Promissory Notes, the Duggan February Note and Duggan September Note were marked as “cancelled” on their face and replaced in their entirety by the Duggan Promissory Notes.

On February 15, 2023, the $20,000 Zanganeh Note, matured and the Company repaid the outstanding principal balance. In connection with the closing of the 2023 Rights Offering, the $400,000 Duggan Promissory Note, matured and became due, and the Company satisfied all principal and accrued interest thereunder using a combination of a portion of the cash proceeds from the 2023 Rights Offering and the extinguishment of a portion of the amount due equal to the subscription price for shares subscribed by Mr Duggan in the 2023 Rights Offering (as defined above).

The Notes accrue interest at an initial rate of 7.5%. All interest on the Notes was paid on the date of signing for the period through February 15, 2023. Such prepaid interest was paid in a number of shares of the Company’s Common Stock equal to the dollar amount of such prepaid interest, divided by $0.7913 (the consolidated closing bid price immediately preceding the time the Company entered into the Note Purchase Agreement, plus $0.01), which was 9,720,291 shares. For all applicable periods following the February 15, 2023, interest shall accrue on the outstanding principal balance of the Notes at the United States prime interest rate, as reported in the Wall Street Journal, plus 50 basis points, as adjusted monthly, for three months immediately following February 15, 2023, and thereafter at the United States prime rate plus 300 basis points, as adjusted monthly.

Upon the closing of the License Agreement, the Board of Directors (the “Board”) of the Company appointed Dr. Yu (Michelle) Xia to serve as a member of the Board pursuant to the terms of the License Agreement. Dr. Xia is the founder of Akeso, Inc., and has been the chairwoman, president and CEO of the Company since its inception in 2012. For details on the License Agreement, see Note 8. Furthermore, in connection with the License Agreement, the Company also entered into a Supply Agreement with Akeso, pursuant to which Summit agreed to purchase a certain portion of drug substance for clinical and commercial supply (the “Supply Agreement”). During the three months ended March 31, 2023, the transactions pursuant to the Supply Agreement were in the ordinary course of business.

On December 6, 2022, the Company announced a rights offering for its existing shareholders to participate in the purchase of additional shares of its Common Stock for $1.05 per share. The 2023 Rights Offering commenced on February 7, 2023 and the associated subscription rights expired on March 1, 2023. Aggregate gross proceeds from the 2023 Rights Offering were $500,000 from the sale of 476,190,471 shares of the Company's common stock and issuance costs were $619. Mr. Duggan and Dr. Zanganeh fully subscribed to their respective basic subscription rights at a price of $1.05 per share. To satisfy the $395,314 subscription price for the shares subscribed by Mr Duggan in the 2023 Rights Offering, Mr Duggan agreed with the Company to extinguish a portion of the amount due and payable to him by the Company at the closing of the 2023 Rights Offering pursuant to the $400,000 Duggan Promissory Note in an amount equal to the subscription price.

On March 17, 2023, the Company filed a registration statement on Form S-3 to register for resale the following shares of the Company's common stock at $0.01 par value: (i) 10,000,000 shares of Common Stock issued on January 17, 2023 in connection with the License Agreement with Akeso pursuant to which the Company issued Akeso such shares; and (ii) the 9,346,434 and 373,857 shares of Common Stock issued in December 2022 to the Company's CEO, Robert Duggan and Co-CEO, Dr. Mahkam Zanganeh, respectively, as payment of prepaid interest in connection with the Note Purchase Agreement dated December 6, 2022 between Robert Duggan, Dr. Mahkam Zanganeh and the Company. On April 27, 2023, the SEC issued the Company a Notice of Effectiveness for the registration statement on Form S-3.