13. RELATED PARTY TRANSACTIONS

Relationship with Factor Bioscience Inc.

Dr. Matt Angel, Ph.D., the Company’s President and Chief Executive Officer and a member of its Board of Directors, is also the majority owner, Chief Executive Officer, and chairman of Factor Bioscience LLC. Factor is a wholly-owned subsidiary of Factor Bioscience LLC. On February 3, 2026, the Company completed the Asset Purchase Agreement with Erigen and Factor, pursuant to which the Sellers agreed to sell and transfer to the Company all right, title, and interest in and to the Erigen Assets in exchange for an aggregate purchase price of 8,268,495 shares of our common stock, issued to Erigen on behalf of both Sellers. Erigen is a limited liability company and an affiliate of Factor. At the Erigen Closing, we issued 8,268,495 shares of

our common stock to Erigen, resulting in Dr. Angel and Lotus Capital BVI Limited (“Lotus”) holding approximately 37% and 26% of our common stock, respectively, immediately following the Erigen Closing.

In November 2025, Erigen entered into an Amended and Restated License and Collaboration Agreement (the “Restated Factor License Agreement”) with Factor, which was assigned to the Company in connection with the Erigen Closing pursuant to the Asset Purchase Agreement. Pursuant to the Restated Factor License Agreement, we are obligated to meet certain diligence milestones by specified dates and to use commercially reasonable efforts to develop and make commercially available at least one licensed product in the licensed territory. We are obligated to pay Factor Bioscience Limited, a wholly-owned subsidiary of Factor, up to $40 million in total upon achievement of certain development milestones for the programs and up to $620 million in total upon achievement of certain commercial milestones for the programs. In addition, we are required to pay Factor Bioscience Limited mid-single digit to high-teens royalties on net sales of licensed products on a country-by-country and licensed product-by-licensed product basis until expiration of the last to expire valid claim of certain licensed patents covering such licensed product in such country, subject to certain customary reductions, and low-to-mid double digit sublicense fees.

Further. in November 2025, Erigen entered into the Factor MSA, which was assigned to the Company in connection with the Erigen Closing pursuant to the Asset Purchase Agreement. In March 2026, the Board of Directors of the Company approved and authorized the execution of the Work Order under the Factor MSA for R&D services beginning April 2026. Under this agreement, the Company committed to pay Factor for services through March 31, 2027, primarily related to the clinical advancement of TPST-2003, TPST-3003, and TPST-4003. In April 2026, the Company paid Factor a deposit of $0.4 million under the Work Order of the Factor MSA, recorded to prepaid expenses and other current assets, to be applied to the final invoice under the Work Order.

On May 12, 2026, the Company entered into the Letter Agreement with Factor relating to certain payment obligations of the Company under the Factor MSA and Work Order. Pursuant to the Letter Agreement, Factor agreed to permanently waive its right to receive the first $2.1 million payable by the Company to Factor under the Factor MSA and the Work Order. Because Factor is a related party of the Company and the waiver was provided by an entity controlled by a principal stockholder of the Company to furnish capital to the Company, the $2.1 million waiver has been accounted for as a capital contribution. Accordingly, $1.7 million of services rendered under the Work Order through June 30, 2026 were recorded to research and development expense and additional paid-in capital, with no amounts payable by the Company to Factor. The remaining $0.4 million of services to be waived under the Letter Agreement will be recorded as research and development expenses and additional paid-in capital in the periods in which the related research and development services will be performed. No gain or other income was recognized in connection with the waiver.

In addition, under the Letter Agreement, Factor agreed to return to the Company $0.2 million of the previous deposit made by the Company under the Work Order. As of June 30, 2026, Factor had not returned that amount. Under the terms of the Letter Agreement, the Company is required to repay the $0.2 million upon raising aggregate gross proceeds of at least $5.0 million through a capital raise transaction. As of June 30, 2026, this repayment obligation remained contingent upon that financing condition, and approximately $0.4 million of the deposit, including the $0.2 million not yet returned, remained outstanding and continues to be classified as prepaid expenses and other current assets. As of June 30, 2026, other than the approximately $0.4 million deposit paid under the Work Order, there were no amounts due to or from Factor related to the Factor MSA and Work Order in the accompanying consolidated balance sheets.

Further, pursuant to the Asset Purchase Agreement, Factor has made the Funding Commitment to provide the Company with financial support as further disclosed in Note 1 under “—Acquisition of Erigen Assets.” As of June 30, 2026, $11.8 million of availability remained under the Funding Commitment, with no amounts due to or from Factor related to the Funding Commitment in the accompanying consolidated balance sheets.

The Company also entered into a private placement financing in March 2026, further disclosed in in Note 1 under “—Private Placement.” Pursuant to the Purchase Agreement, we sold an aggregate of 231,482 Shares, 231,482 Series A Warrants and 231,482 Series B Warrants to Factor in exchange for $0.5 million, before deducting placement agent fees and other offering expenses payable by us.

Legal Fee Settlement

Prior to the Erigen Closing, Erigen incurred approximately $0.4 million of legal fees with Wilson Sonsini Goodrich & Rosati (“WSGR”), which serves as intellectual property counsel to both the Company and Factor, in connection with due diligence and other matters predating the Asset Acquisition. These fees were not liabilities assumed by the Company under the Asset Purchase Agreement, and the Company had no contractual or legal obligation to pay them. In April 2026, WSGR redirected the outstanding invoices to the Company and requested payment. Because Erigen is affiliated with Factor, a related party of the Company, this matter was reviewed and approved by the Audit Committee of the Board of Directors as a related party transaction. In June 2026, the Company’s management agreed to settle the invoices on Erigen’s behalf in order to preserve the Company’s ongoing relationship with WSGR.

Because the obligation was not assumed under the Asset Purchase Agreement, was not required to complete the Erigen Closing, and resulted from a discretionary decision made after the Erigen Closing, the Company recognized the $0.4 million settlement as general and administrative expense during the three and six months ended June 30, 2026. The $0.4 million was recorded in accounts payable as of June 30, 2026.

Advisory Agreement with Andrew Fang

In March 2026, the Board of the Company approved and authorized the execution of an advisory agreement dated April 1, 2026 (the “Advisory Agreement”), with YQ Advisors Limited (“YQ”) pursuant to which YQ will provide various business development and corporate development activities to us at an hourly rate of (i) $1,250 for services provided by Andrew Fang and (ii) $250 for services provided by other YQ service providers, up to a maximum aggregate amount of $720,000 per year. The agreement has a term of 12 months, unless extended by mutual written agreement of the parties. Mr. Fang is the son of Bangxia Yang, the beneficial owner of Lotus, a greater than 5% holder of our common stock.

Services under the arrangement began April 2026. During the three months ended June 30, 2026, the Company incurred $0.2 million in advisory fees as general and administrative expense under the Advisory Agreement. As of June 30, 2026, $0.1 million had been paid and $0.1 million remained in accounts payable.