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Study identifier: NCT05683418 Synced from ClinicalTrials.gov · July 29, 2026
● Recruiting

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

Condition: HR+/HER2-negative Breast Cancer  ·  Sponsor: Totus Medicines

PhasePhase 1
Planned participants241
Who can joinFemale, 18 Years to no upper limit
Healthy volunteersNo

About this study

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)

This description comes directly from the study's public registry record.

Talk to the study team

Clinical Trials  ·  Please e-mail  ·  clinicaltrials@totusmedicines.com

Always discuss trial participation with your own doctor first.

Locations (18)

Northwestern Memorial HospitalChicago, Illinois, United StatesRecruiting
Beth Israel Deaconess Medical CenterBoston, Massachusetts, United StatesRecruiting
Dana-Farber Cancer InstituteBoston, Massachusetts, United StatesRecruiting
Comprehensive Cancer Centers of NevadaLas Vegas, Nevada, United StatesRecruiting
University of PennsylvaniaPhiladelphia, Pennsylvania, United StatesRecruiting
Sarah Cannon Cancer CenterNashville, Tennessee, United StatesRecruiting
Vanderbilt-Ingram Cancer CenterNashville, Tennessee, United StatesRecruiting
Texas Oncology - Flower MoundFlower Mound, Texas, United StatesRecruiting
Virginia Cancer SpecialistsFairfax, Virginia, United StatesRecruiting
NEXT Oncology - Hospital Quironsalud Barcelona - PPDSBarcelona, SpainRecruiting
START Barcelona HM Nou DelfosBarcelona, SpainRecruiting
Instituto de Investigacion Oncologica Vall dHebron (VHIO) - EPONBarcelona, SpainRecruiting

+ 6 more locations — full list on the registry record.

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Source record: clinicaltrials.gov/study/NCT05683418