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New drug TOS-358 targets Hard-to-Treat breast cancer in early trial

NCT ID NCT05683418

Disease control Sponsor: Totus Medicines Source: ClinicalTrials.gov ↗

What the study statuses mean

This study's is highlighted.

Recruitment status, easiest to join first

Recruiting now This study
This trial is taking on new participants right now.
Not yet recruiting
Registered, but not yet taking participants.
By invitation only
Not open to general applications. Only people the study team invites can take part.
Paused
Paused for now. It may or may not start again.
Ongoing
Running, but no longer taking on new participants.
Completed
The trial has finished. Results may not be published yet.
Stopped early
Stopped early, before it reached the end. That can be for many reasons, including safety.
Cancelled
Cancelled before anyone took part.

Expanded access (not trials)

Expanded access
Not a trial. This treatment can be requested outside a study, case by case, for people who qualify.
Expanded access (paused)
Not a trial. The treatment can normally be requested outside a study, but is unavailable right now.
Expanded access (ended)
Not a trial. The treatment could once be requested outside a study, but no longer can.
Approved
The treatment has been approved, so it is available normally rather than through this programme.

When the status isn't known

Details not published
The full record has not been published yet, so there is little to show here.
Status unknown
This status has not been confirmed recently, so it may be out of date.

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.

Study facts

What this study's own registry entry says, in plain language.

Phase

Phase 1

The first testing in people. Mainly checks safety and dose, usually in a small group.

Participants

About 241 people

The number the study aims to enrol. It can still change while the study runs.

Started

Feb 2023

Expected to finish

Dec 2027

An estimate. End dates often move.

Lead sponsor

A company

The lead sponsor is a pharmaceutical, biotech, or medical-device company.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

18 years and older

Sex

Female participants only

Healthy volunteers

Not accepted

This study is not open to healthy volunteers. The entry requirements below say who it is open to.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

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

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Conditions

The condition(s) this trial relates to.

breast neoplasm hereditary sensory and autonomic neuropathy hormone receptor-positive breast cancer

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

HR+/HER2-negative breast cancer

How to take part

Only the study team decides who joins. These are the ways to reach them.

  1. The study's own enquiry address

    This study publishes an address for enquiries. See it below .

  2. The places running it

    18 sites in 2 countries. The list below names each one and where it is.

  3. The official record

    ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.

    Open the record ↗

  4. A doctor treating you

    A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.

Contacts and locations

Locations

  • Beth Israel Deaconess Medical Center

    RECRUITING

    Boston, Massachusetts, 02215, United States

  • Clinica Universidad de Navarra

    RECRUITING

    Pamplona, 31008, Spain

  • Comprehensive Cancer Centers of Nevada

    RECRUITING

    Las Vegas, Nevada, 89169, United States

  • Dana-Farber Cancer Institute

    RECRUITING

    Boston, Massachusetts, 02215, United States

  • Hospital Clinico San Carlos

    RECRUITING

    Madrid, 28040, Spain

  • Hospital Clinico Universitario de Valencia

    RECRUITING

    Valencia, 46010, Spain

  • Instituto de Investigacion Oncologica Vall dHebron (VHIO) - EPON

    RECRUITING

    Barcelona, 08035, Spain

  • NEXT Oncology - Hospital Quironsalud Barcelona - PPDS

    RECRUITING

    Barcelona, 08023, Spain

  • NEXT Oncology - Hospital Quironsalud Madrid - PPDS

    RECRUITING

    Pozuelo de Alarcón, 28223, Spain

  • Northwestern Memorial Hospital

    RECRUITING

    Chicago, Illinois, 60611, United States

  • START Barcelona HM Nou Delfos

    RECRUITING

    Barcelona, 08023, Spain

  • START MADRID Hospital Universitario Fundacion Jimenez Diaz - EDOS

    RECRUITING

    Madrid, 28050, Spain

  • START MADRID Hospital Universitario HM Sanchinarro - CIOCC

    RECRUITING

    Madrid, 28050, Spain

  • Sarah Cannon Cancer Center

    RECRUITING

    Nashville, Tennessee, 37203, United States

  • Texas Oncology - Flower Mound

    RECRUITING

    Flower Mound, Texas, 75028, United States

  • University of Pennsylvania

    RECRUITING

    Philadelphia, Pennsylvania, 19106, United States

    Contact Email: •••••@•••••

  • Vanderbilt-Ingram Cancer Center

    RECRUITING

    Nashville, Tennessee, 37232, United States

  • Virginia Cancer Specialists

    RECRUITING

    Fairfax, Virginia, 22031, United States

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