A Study to Evaluate the Safety and Tolerability of TOS-358 in Women With HR+ HER2- Breast Cancer

Summary

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)

Eligibility

Key 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
* Fasting plasma glucose \<= 140 mg/dL AND hemoglobin A1c (HbA1c) \<= 7.0%
* Available archived or fresh tumor tissue sample for detection of PIK3CA mutation by central laboratory test

Key Exclusion Criteria

* Has an established diagnosis of diabetes mellitus type 1 or has uncontrolled diabetes mellitus type 2
* Known active central nervous system (CNS) metastases
* PTEN mutations

Conditions6

Interventions4

Locations9 sites

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