Zero dose-limiting toxicities. That is the safety result Trethera Corporation reports for TRE-515, an oral drug it is testing in patients with advanced solid tumors, at doses up to 720 mg.
The figure comes from an ongoing Phase 1, open-label, first-in-human dose-escalation study, registered as NCT05055609. Trethera says it has already gathered nearly 1,000 biomarker samples from that trial.
What the drug does
TRE-515 is a small-molecule inhibitor of deoxycytidine kinase, or dCK. The enzyme sits in the deoxyribonucleoside salvage pathway, a route that fast-dividing cells use to get the raw material for copying DNA. Cells with weak de novo synthesis lean on it harder. Block dCK, the company argues, and those cells lose supply.
The company calls the drug first in class.
A study in healthy volunteers
In August 2025 the US Food and Drug Administration cleared a second trial, this one in healthy adults. It will enroll up to 72 people and test how food changes the drug’s blood levels and a biomarker called dC. If eating turns out not to matter much, future patients might not have to fast before a dose.
The healthy-volunteer numbers will also give the company a baseline for dC in people without disease, to set against the readings from tumor patients.
“FDA clearance of our healthy volunteer protocol, combined with promising data from our ongoing oncology trial, underscores the strong safety profile of TRE-515 and positions Trethera to explore its full potential across a broad range of disease conditions,” said Ken Schultz, MD, chairman and CEO of Trethera, in a press release.
Beyond cancer
Trethera is also looking at autoimmune and inflammatory disease. In February 2025 the company announced a study in the journal Immunology in which TRE-515 cut the overactive T and B cells that drive multiple sclerosis in mice, and eased disease severity there. The effect was aimed at the harmful cells rather than the wider immune system. Nobody has shown the same in people.
The company says it is exploring Crohn’s disease, ALS and lupus, and that the FDA has already granted designations for optic neuritis and acute disseminated encephalomyelitis.
Everything so far is early. The oncology data speak to safety and dosing, not to whether tumors shrink. Consult your doctor for medical advice.
Sources
- Trethera & UCLA Publish Data on TRE-515 in Mice with MS
- FDA Clears TRE-515 Healthy Volunteer Study, Advancing Biomarker-Driven Oncology | Targeted Onc – Immunotherapy, Biomarkers, and Cancer Pathways
