Totus Medicines to Present Updated Phase 1 Data for Novel Covalent PI3Kα Inhibitor TOS-358 at ESMO TAT Congress
核心洞察
Totus Medicines will present updated Phase 1 clinical data for TOS-358, a next-generation covalent PI3Kα (搜索) inhibitor, at the ESMO Targeted Anticancer Therapies Congress in Paris on March 16, 2026.
The presentation will include safety data from over 50 patients and efficacy results from 20 heavily pretreated patients with confirmed PI3Kα (搜索) mutations across breast cancer (搜索), endometrial adenocarcinoma (搜索), and head and neck squamous cell carcinoma (搜索).
TOS-358 achieves greater than 95% continuous target engagement at clinically relevant doses and represents the first and only covalent PI3Kα (搜索) inhibitor currently in clinical development.
Totus Medicines announced that updated Phase 1 clinical data for TOS-358, a next-generation covalent PI3Kα (搜索) inhibitor, will be presented at the European Society for Medical Oncology (ESMO) Targeted Anticancer Therapies Congress in Paris on March 16, 2026. The oral presentation will be delivered by Antonio Giordano, MD, PhD, Clinical Director of the Center for Cancer Therapeutic Innovation and Breast Cancer (搜索) Pathways Medical Director at Dana-Farber Cancer Institute.
Novel Mechanism and Target Engagement
TOS-358 is an oral, highly selective, pan-mutant, covalent PI3Kα (搜索) inhibitor that achieves greater than 95% continuous target engagement at clinically relevant doses for deep and durable inhibition of PI3K-AKT (搜索) signaling. The drug represents the first and only covalent PI3Kα inhibitor currently in clinical development, positioning it as a potential best-in-class therapy in this space.
The therapeutic targets PI3Kα (搜索) driver mutations, which are present in approximately 40% of ER-positive/HER2-negative breast cancer (搜索) patients, 50% of endometrial adenocarcinoma (搜索) patients, and a meaningful subset of head and neck squamous cell carcinoma (搜索) (HNSCC (搜索)) patients. This broad applicability across multiple solid tumor types underscores the clinical potential of the approach.
Clinical Data Overview
The upcoming presentation will include comprehensive safety data from more than 50 patients enrolled in the ongoing Phase 1 study. Additionally, efficacy results will be presented from a monotherapy-evaluable cohort of 20 patients with confirmed PI3Kα (搜索) mutations at specific positions including E345, E542, E545, or H1047.
The patient population represents a challenging treatment scenario, as participants were heavily pretreated, including those who had progressed on prior PI3K, AKT, or mTOR pathway therapies. This context makes any demonstrated efficacy particularly noteworthy, as it suggests potential activity even in treatment-resistant disease.
Company Platform and Pipeline
Totus Medicines operates as a clinical-stage precision medicines company, leveraging its proprietary AI-powered OmniDEL platform, which utilizes DNA-encoded covalent library technology to discover novel covalent small molecules against previously undrugged or difficult to drug targets. The company is advancing TOS-358 into Phase 1b clinical development across selected solid tumor indications.
Beyond TOS-358, the company's pipeline includes a lead preclinical program targeting IRF5, described as a key genetically validated but previously undrugged target across multiple inflammatory and immunological indications. This diversified approach demonstrates the platform's potential to address multiple therapeutic areas with historically challenging targets.
Clinical Significance
According to the company, TOS-358 has demonstrated efficacy, response, and long-term disease control with class-leading tolerability across breast, endometrial, and head and neck cancers in early clinical development. The covalent binding mechanism may offer advantages in terms of sustained target inhibition compared to reversible inhibitors, potentially translating to improved clinical outcomes.
The March presentation at ESMO TAT will provide the medical community with updated insights into the drug's performance in this heavily pretreated patient population, offering important data points for the future development strategy of this novel therapeutic approach.