OncoMatch/Clinical Trials/NCT05683418
A Study to Evaluate the Safety and Tolerability of TOS-358 in Women With HR+ HER2- Breast Cancer
Is NCT05683418 recruiting? Yes, currently enrolling (Sep 2026). This Phase 1 trial studies multiple treatments including TOS-358 and Fulvestrant for hr+/her2-negative breast cancer.
Treatment: TOS-358 · Fulvestrant · Palbociclib · Ribociclib — 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)
Check if I qualifyExtracted eligibility criteria
Treatments studied
Targeted therapy
Endocrine / hormonal
Other
Cancer type
Breast Carcinoma
Biomarker criteria
Required: PIK3CA mutation
Known PIK3CA mutations or amplifications as determined at a CAP/CLIA-certified or equivalently accredited diagnostic laboratory using a validated test
Required: PIK3CA amplification
Known PIK3CA mutations or amplifications as determined at a CAP/CLIA-certified or equivalently accredited diagnostic laboratory using a validated test
Excluded: PTEN mutation
PTEN mutations
Performance status
ECOG 0–1(Restricted strenuous activity)
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
Demographics
Prior therapy
Lab requirements
Blood counts
Adequate bone marrow function within 14 days prior to first dose of investigational product
Kidney function
Adequate kidney function within 14 days prior to first dose of investigational product
Liver function
Adequate liver function within 14 days prior to first dose of investigational product
Adequate bone marrow, liver, and kidney function within 14 days prior to first dose of investigational product
Structured fields extracted by AI. May contain errors — verify against the official protocol.
US trial sites
- Northwestern Memorial Hospital · Chicago, Illinois
- Beth Israel Deaconess Medical Center · Boston, Massachusetts
- Dana-Farber Cancer Institute · Boston, Massachusetts
- Comprehensive Cancer Centers of Nevada · Las Vegas, Nevada
- University of Pennsylvania · Philadelphia, Pennsylvania
Showing up to 5 US sites.
See all sites on ClinicalTrials.gov →Frequently asked questions
Is NCT05683418 currently recruiting?
Yes, this trial is currently recruiting patients.
Does this trial require PIK3CA?
Yes, PIK3CA mutation is a required biomarker for enrollment.
Does this trial require PIK3CA?
Yes, PIK3CA amplification is a required biomarker for enrollment.
Are patients with PTEN alterations eligible?
No. PTEN mutation is an exclusion criterion.
Is this trial open to male patients?
No. This trial enrolls female patients only.
Could you qualify for this trial?
Enter your biomarker results to see how this trial's eligibility criteria match your specific cancer profile.
Check if I qualifyRelated pages