New drug TOS-358 targets Hard-to-Treat breast cancer in early trial
NCT ID NCT05683418
First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time
Summary
This early-stage trial tests a new drug called TOS-358 in women with advanced HR+ HER2- breast cancer that has a specific mutation in the PIK3CA gene. The study aims to find the safest dose and see if the drug works alone or with standard treatments like fulvestrant and CDK4/6 inhibitors. Up to 241 participants will be enrolled to check for side effects and tumor response.
What this could mean
Our plain-language read of the trial. This is informational only — not medical advice or a prediction.
- Active substance
- TOS-358 (a PI3K-alpha inhibitor drug)
- What this could lead to
- If successful, this could lead to a new treatment option for women with a specific type of advanced breast cancer that has a PIK3CA mutation.
- What could go wrong
- This is an early Phase 1 trial, so the drug may not be safe or effective. Side effects are unknown, and the study is small, so results may not apply to everyone.
This is an AI summary of the original study and may miss details. Read our disclaimer.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
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Study contacts
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Contact
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Locations
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Beth Israel Deaconess Medical Center
RECRUITINGBoston, Massachusetts, 02215, United States
Contact Email: •••••@•••••
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Clinica Universidad de Navarra
RECRUITINGPamplona, 31008, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Comprehensive Cancer Centers of Nevada
RECRUITINGLas Vegas, Nevada, 89169, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Dana-Farber Cancer Institute
RECRUITINGBoston, Massachusetts, 02215, United States
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Hospital Clinico San Carlos
RECRUITINGMadrid, 28040, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Hospital Clinico Universitario de Valencia
RECRUITINGValencia, 46010, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Instituto de Investigacion Oncologica Vall dHebron (VHIO) - EPON
RECRUITINGBarcelona, 08035, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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NEXT Oncology - Hospital Quironsalud Barcelona - PPDS
RECRUITINGBarcelona, 08023, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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NEXT Oncology - Hospital Quironsalud Madrid - PPDS
RECRUITINGPozuelo de Alarcón, 28223, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Northwestern Memorial Hospital
RECRUITINGChicago, Illinois, 60611, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
Contact Phone: •••-•••-•••• Email: •••••@•••••
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START Barcelona HM Nou Delfos
RECRUITINGBarcelona, 08023, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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START MADRID Hospital Universitario Fundacion Jimenez Diaz - EDOS
RECRUITINGMadrid, 28050, Spain
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Contact Phone: •••-•••-•••• Email: •••••@•••••
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START MADRID Hospital Universitario HM Sanchinarro - CIOCC
RECRUITINGMadrid, 28050, Spain
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Sarah Cannon Cancer Center
RECRUITINGNashville, Tennessee, 37203, United States
Contact
Contact Phone: •••-•••-•••• Email: •••••@•••••
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Texas Oncology - Flower Mound
RECRUITINGFlower Mound, Texas, 75028, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
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University of Pennsylvania
RECRUITINGPhiladelphia, Pennsylvania, 19106, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Contact Email: •••••@•••••
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Vanderbilt-Ingram Cancer Center
RECRUITINGNashville, Tennessee, 37232, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
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Virginia Cancer Specialists
RECRUITINGFairfax, Virginia, 22031, United States
Contact Phone: •••-•••-•••• Email: •••••@•••••
Contact Phone: •••-•••-•••• Email: •••••@•••••
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