Trethera Corporation (“Trethera”), a clinical stage biopharmaceutical company developing first-in-class therapies for cancer and autoimmune diseases, announced today that the final patient has enrolled in its Phase 1 dose escalation trial for the treatment of advanced solid tumors. Patients have tolerated escalating doses of Trethera’s lead drug candidate, TRE-515, from 40 mg up to 1,440 mg per day—a 36-fold increase—without any dose-limiting toxicities. TRE-515 inhibits deoxycytidine kinase (dCK), an enzyme critical to the nucleoside salvage pathway that is essential for the growth of abnormal cells in cancer and autoimmune diseases.

“This milestone brings us significantly closer to advancing TRE-515 as the first-to-market dCK inhibitor,” said Dr. Ken Schultz, Trethera’s Chief Executive Officer and Chief Medical Officer. “We remain on track to expand our clinical research in 2026, building on our recent FDA Fast Track designation in prostate cancer.”

Evidence of antitumor activity has been observed even at the lowest dose levels. Multiple patients in the first two cohorts (40 mg and 80 mg) demonstrated clinical benefit, including one who maintained disease control for over 250 days. The trial dosed 33 patients, with several remaining on therapy today, underscoring the favorable safety profile and durability of TRE-515.

The primary endpoints of the Phase 1 trial evaluate safety and tolerability of TRE-515 to determine its maximum tolerated dose. Secondary endpoints include establishing a recommended Phase 2 dose, characterizing pharmacokinetics and pharmacodynamics (PK/PD), and evaluating antitumor activity. The protocol also includes exploratory objectives to measure biomarkers of target engagement. Trethera will present its Phase 1 findings at a major upcoming scientific conference.

The Phase 1 trial was partially supported by a grant from the National Institutes of Health (NIH). During the trial, Trethera’s lead asset, TRE-515, also received:

• Multiple patents with US market exclusivity extended through February 2045,
• FDA Fast Track designation as a combination therapy with radiation to treat prostate cancer,
• $2.3M in new NIH grant funding to study TRE-515 as a prostate cancer therapy with radiation, and
• Two FDA Orphan Drug designations for Acute Disseminated Encephalomyelitis (ADEM) and Optic Neuritis.