On October 27, 2023, Theseus Pharmaceuticals, Inc. (the Company) provided written notice to ARIAD Pharmaceuticals, Inc. (ARIAD) of its termination of the License Agreement, dated June 13, 2018, between the Company and ARIAD (the ?ARIAD License Agreement?), which termination will be effective in accordance with the terms of the termination for convenience clause of such agreement. The Company previously announced in July 2023 that it was discontinuing enrollment in the ongoing Phase 1/2 study and terminating development of THE-630 in patients with gastrointestinal stromal tumors. THE-630 is derived from intellectual property licensed to the Company under the ARIAD License Agreement and is therefore subject to the ARIAD License Agreement.

In connection with the termination of development of THE-630, the Company is terminating the ARIAD License Agreement. The Company did not use any intellectual property licensed to the Company, or any biological materials provided to the Company, under the ARIAD License Agreement to develop any of the Company?s other programs. Under the ARIAD License Agreement, the Company acquired an exclusive, transferable (subject to certain restrictions), sublicensable (subject to certain conditions), worldwide license, under certain of ARIAD?s patent rights, know-how and compounds and a certain ARIAD chemical library, to develop, use, manufacture, market and commercialize certain compounds, and products that contain such compounds, that are therapeutically useful for the treatment of diseases and disorders in humans, including with respect to KIT. The Company is not subject to any termination penalties related to the termination of the ARIAD License Agreement.