NCT05683418 · Totus Medicines
A Study to Evaluate the Safety and Tolerability of TOS-358 in Women With HR+ HER2- Breast Cancer
What this study is about
The goal of this clinical trial is to evaluate the safety and effectiveness 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.
View original scientific 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: 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.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
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
Where
- Chicago, Illinois
- Boston, Massachusetts
- Las Vegas, Nevada
- Philadelphia, Pennsylvania
- Nashville, Tennessee
- Flower Mound, Texas
- Fairfax, Virginia
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Apr 22, 2026 · Source of record for eligibility and locations