Theseus Logo LR 2023Theseus Pharmaceuticals announced yesterday the discontinuation of enrollment in the Phase 1/2 study and terminating the development of THE-630 for GIST patients with advanced or metastatic GIST. The company reported dose-limiting toxicities relating to hand-foot skin reaction. Theseus had previously released an initial dose escalation on May 25 of this year, but by July 10 made the decision to terminate development of the drug. Patients currently enrolled will continue to receive THE-630 until treatment discontinuation criterion is met.

As for the future of GIST treatments, Theseus announced new program targeting KIT for patients with early-line GIST. Theseus has continued an extensive medicinal chemistry effort to target KIT which has led to the discovery of a series of chemically distinct, highly selective, pan-variant KIT inhibitors for the treatment of early-line GIST. The company plans to nominate a development candidate from this series in the first half of 2024.

“We are disappointed that we will not be able to achieve the target exposure for pan-variant inhibition with THE-630, as we continue to believe a therapy with potent activity against all major classes of activating and resistance mutations in KIT has the potential to confer significant clinical benefit, given the unmet need in GIST. On behalf of the entire Theseus team, I would like to thank the patients, their caregivers, and the investigators and site staff who participated in this study. We remain committed to helping GIST patients with plans to nominate a new, highly selective pan-variant KIT inhibitor candidate for GIST in the first half of 2024.”   –  Tim Clackson, Ph.D., President & Chief Executive Officer, Theseus Pharmaceuticals

Theseus’ full press release is available to read here.

“We are disappointed to hear about the discontinuation of the THE-630 study. While we understand may be discouraging news, we are hopeful that the next pan-variant candidate drug at Theseus will be a better molecule with less toxicity for our GIST patient community.”  –  Sara Rothschild, Executive Director, The Life Raft Group

If you have any questions about the THE-630 clinical trial or any other clinical trials, please contact The Life Raft Group at