Theseus Pharma decimated on termination of THE-630 development

14 July 2023

After markets closed on Thursday, US clinical-stage biotech Theseus Pharmaceuticals (Nasdaq: THRX) announced that it is discontinuing enrollment in the ongoing Phase I/II study and terminating development of its lead candidate THE-630 in patients with gastrointestinal stromal tumors (GIST).

The news saw the firm’s shares plummet 67% to $3.15 in early trading this morning.

Theseus previously released initial dose escalation data from the ongoing phase 1/2 trial, which employs a standard 3 + 3 dose escalation design, on May 25, 2023. As of the April 21, 2023 data cutoff date, 23 patients had been dosed through Cohort 6 (18 mg) and two patients had been enrolled in Cohort 7 (27mg). As of May 25, those two patients in Cohort 7 had cleared the dose–limiting toxicity (DLT) observation period without experiencing a DLT.

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