Clinical Trial

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

MOA: TOS-358 is a covalent inhibitor of WT and mutant PI3Kα and has much better toxicity profile compared to other inhibitors in this class

Key Eligibility:

• HR+/HER2- LA/rec or MBC with PIK3CA mutations (central testing) and
  measurable disease per RECIST v1.1
  • Response evaluable disease allowed
  • Tumor tissue must be provided for detection of PIK3CA mutation by central
    testing. Blood samples might be acceptable upon sponsor approval
• Must have received CDK4/6i in the adjuvant or metastatic setting or must be
  able to receive it on protocol AND
• Must not have received any prior chemotherapy (including ADC) in the
  metastatic setting AND
• No more than 3 prior lines of tx in total in the metastatic setting
• Prior PI3Kα inhibitor is allowed
  • If pt had PD on PI3K inhibitor, tissue or liquid biopsy submission following
    PD or at screening is required to verify resistance mutation(s)
• Pt receiving SERD at the time of consent may remain on it while receiving
  study tx.
• Pt may remain on CDK4/6i if enrolling to Phase 1b breast cancer group 2
• PTEN mutation or deletions and AKT activating mutations are excluded