Totus Medicines presented Phase 1a clinical data for TOS-358 at ESMO TAT 2026 in Paris. In the efficacy cohort, the company reported a clinical benefit rate of 50%, disease control rate of 75%, overall response rate of 15%, at least 20% tumor shrinkage in 40% of patients and 45% of patients remained on treatment for 24 weeks or longer.
The data were presented by Dr Antonio Giordano of Dana Farber Cancer Center. The company noted disease control rates of 67% in patients resistant to PI3K AKT mTOR pathway therapies and 100% in patients intolerant to such therapies.
The company claims that TOS-358 demonstrated a differentiated safety profile, with no bone marrow, hepatic, renal or ocular toxicities, no rash and no stomatitis or mucositis, and that less than 5% of patients required medication for nausea or diarrhea. The company reported that hyperglycemia was generally low-grade and manageable, with 3.6% (2 of 54 patients) requiring ongoing insulin.
A Phase 1b trial was initiated in January 2026 to evaluate combinations with fulvestrant and CDK4/6 inhibitors, with initial combination data expected at future scientific meetings.
