EMERYVILLE, Calif. — February 12, 2026 — Leads & Copy — Totus Medicines will present updated Phase 1 clinical data from its ongoing study of TOS-358 at the European Society for Medical Oncology (ESMO) Targeted Anticancer Therapies (TAT) Congress in Paris in March 2026, the company announced today.
The presentation will be an oral session and will include safety data from more than 50 patients and efficacy results from a monotherapy-evaluable cohort of 20 patients with confirmed PI3Ka mutations at positions E345, E542, E545, or H1047. Patients in the study were heavily pretreated, including those who had progressed on prior PI3K, AKT, or mTOR pathway therapies.
TOS-358 is described as an oral, highly selective, pan-mutant, covalent PI3Ka inhibitor designed to achieve over 95% continuous target engagement at clinically relevant doses for deep and durable inhibition of PI3K-AKT signaling.
PI3Ka driver mutations are reportedly present in approximately 40% of ER-positive/HER2-negative breast cancer, 50% of endometrial adenocarcinoma, and a meaningful subset of head and neck squamous cell carcinoma (HNSCC) patients.
Totus Medicines is advancing TOS-358 as a potential best-in-class PI3Ka inhibitor into Ph1b clinical development across selected solid tumor indications.
Antonio Giordano, MD, PhD, Clinical Director of the Center for Cancer Therapeutic Innovation and Breast Cancer Pathways Medical Director at Dana-Farber Cancer Institute, will be the presenter. The presentation is scheduled for Monday, March 16, 2026, at 16:20.
Totus Medicines is a clinical-stage, precision medicines company focused on discovering novel covalent small molecules against previously undrugged or difficult to drug targets, based on its proprietary AI-powered OmniDEL platform (DNA-encoded covalent library technology). The company’s lead program, TOS-358, is described as the first and only covalent PI3Ka inhibitor in clinical development, and has reportedly shown efficacy, response and long-term disease control with class-leading tolerability in breast, endometrial and head & neck cancers. The company’s lead pre-clinical program is targeting IRF5, a key genetically validated but previously undrugged target across multiple I&I indications.
Source: Totus Medicines
