Tests TOS-358 with standard drugs in breast cancer with a PIK3CA mutation
Tests the drug TOS-358 in women with a type of metastatic breast cancer.
Plain-language title generated from the registry record
Registry title: A Study to Evaluate the Safety and Tolerability of TOS-358 in Women With HR+ HER2- Breast Cancer
Key facts
- Where
- Barcelona, Madrid, Pamplona, Pozuelo de Alarcón, and Valencia, SpainSee the 10 sites
- Phase
- Phase 1
AI summary: who the study is looking for
From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.
The trial is looking for adult women with HR+/HER2- breast cancer that is advanced, has come back or has spread, and whose tumor has a PIK3CA change.
- Age
- 18 years or older
- Sex
- Women only
- Disease stage
- Locally advanced, recurrent or metastatic HR+/HER2- breast cancer that can be measured or evaluated by RECIST 1.1
- Earlier treatment
- Up to 3 prior lines of therapy for metastatic disease
- Biomarker or test result
- Known PIK3CA mutation or amplification found by a certified laboratory test; tumor tissue must be available for a central lab test
Main reasons for not taking part
- Type 1 diabetes or uncontrolled type 2 diabetes
- Known active central nervous system (CNS) metastases
- PTEN mutations
- Fasting plasma glucose above 140 mg/dL (7.8 mmol/L) or HbA1c above 7.0% (53 mmol/mol)
Read by machine on 12 November 2026.
Where in Spain
- Hospital HM Nou DelfosBarcelona, SpainTaking people
- Hospital Quirónsalud BarcelonaBarcelona, SpainTaking people
- Vall d'Hebron Institute of OncologyBarcelona, SpainTaking people
- Clinica Universidad de NavarraMadrid, SpainTaking people
- Hospital Clínico San CarlosMadrid, SpainTaking people
- Hospital Universitario Fundación Jiménez DíazMadrid, SpainTaking people
- Hospital Universitario HM SanchinarroMadrid, SpainTaking people
- Clínica Universidad de navarraPamplona, SpainTaking people
- Hospital Universitario Quironsalud MadridPozuelo de Alarcón, SpainTaking people
- Hospital Clinico Universitario de ValenciaValencia, SpainTaking people
Questions to ask the study team
- How often do I need to come in, and for how long each time?
- Are travel costs paid?
- Can I keep my own doctor?
- What happens if I want to stop?
Contact the study team: see the registry record → Contacts and Locations
Print a page for my doctorTrial details
- Who runs it
- Totus Medicines
- Trial code
- NCT05683418EU 2023-505346-26-01
- Record updated
- 22 April 2026
- Original description
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:Read full original descriptionShow less
A Study to Evaluate the Safety and Tolerability of the Covalent Phosphoinositide-3-Kinase (PI3K)-Alpha Inhibitor, TOS-358, in Adult Subjects With Select Solid Tumors
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: 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.
Exclusion: 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.