Home › Trials › NCT05683418

Evaluating TOS-358 for safety in adults with certain solid tumors

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

Phase 1 Interventional Totus Medicines · NCT05683418

This study is testing a new medication called TOS-358 to see if it's safe for adults with certain types of solid tumors, like specific breast and head and neck cancers.

Quick facts

PhasePhase 1
Study typeInterventional
Enrollment241 (estimated)
Ages18 Years and up
SexFemale
SponsorTotus Medicines Industry-sponsored
Locations18 sites (Chicago, Illinois and 17 other locations)
Trial IDNCT05683418 on ClinicalTrials.gov

What this trial studies

This clinical trial aims to assess the safety and tolerability of TOS-358 in adults diagnosed with specific solid tumors, including HR+/HER2-negative breast cancer, squamous cell carcinoma of the head and neck, urothelial carcinoma, and endometrial cancer. The study is divided into two parts: a dose-finding phase to determine the maximum tolerated dose and a dose expansion phase to evaluate safety in tumor-specific cohorts. Participants will receive TOS-358 orally, either once or twice daily, until disease progression or unacceptable toxicity occurs.

Who should consider this trial

Good fit: Ideal candidates include adults aged 18 and older with advanced, recurrent, or metastatic solid tumors that are HR+/HER2-negative and have known PIK3CA mutations.

Not a fit: Patients without PIK3CA mutations or those with tumors not specified in the study may not benefit from this treatment.

Why it matters

Potential benefit: If successful, this study could provide a new treatment option for patients with specific solid tumors that have PIK3CA mutations.

How similar studies have performed: Other studies targeting PIK3CA mutations have shown promise, indicating potential for success with this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
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

Where this trial is running

Chicago, Illinois and 17 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions HR+/HER2-negative Breast CancerPI3K-alphabreast cancermetastatic breast cancerPIK3CAhormone receptor positive breast cancer
Last reviewed 2026-06-09 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.