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A Study to Evaluate the Safety and Tolerability of TOS-358 in Women With HR+ HER2- Breast Cancer
Trial Status: active
The goal of this clinical trial is to evaluate the safety and efficacy of TOS-358 in
women with HR+ HER2- metastatic breast cancer whose tumors have a mutation in PIK3CA and
who meet all other study enrollment criteria. The main questions it aims to answer are:
1. Phase 1a: what is the maximum tolerated dose and recommended dose for phase 2?
2. Phase 1a: how safe and tolerable is TOS-358 at different dose levels when taken
orally once or twice per day?
3. Phase 1b: how safe and effective is TOS-358 when given with standard of care
medicines for HR+HER2- metastatic breast cancer (fulvestrant and CDK4/6i)
Inclusion Criteria
Locally advanced, recurrent, or metastatic HR +/HER2- breast cancer
Up to 3 prior lines of therapy for metastatic disease
Willing and able to provide written informed consent for this study
Adults ≥ 18 years old at time of consent
Known PIK3CA mutations or amplifications as determined at a CAP/CLIA-certified or equivalently accredited diagnostic laboratory using a validated test
Measurable or evaluable disease by RECIST 1.1
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
Life expectancy ≥ 6 months, as determined by the investigator
Adequate bone marrow, liver, and kidney function within 14 days prior to first dose of investigational product
