Phase 1/2 Study of ETX-636 in Participants With Advanced Solid Tumors

Prior treatment

• Has received treatment with any local or systemic anticancer therapy or investigational anticancer agent within 14 days prior to start of treatment.
• Has toxicities from previous anticancer therapies that have not resolved to baseline levels with the exception of alopecia and peripheral neuropathy.
• Has had radiotherapy outside the target tumor lesions within 14 days prior to start of treatment.

Other illness

• Has symptomatic brain or spinal metastases or a known or suspected history of untreated or uncontrolled central nervous system (CNS) involvement.
• Has an established diagnosis of diabetes mellitus type 1 or has uncontrolled diabetes mellitus type 2.

Age

• Has history (within ≤2 years before screening) of a solid tumor or hematological malignancy that is histologically distinct from the cancers being studied.

• Metastatic or locally advanced and unresectable solid tumor that has progressed on or after at least one available therapy.
• Tumor harboring an activating PIK3CA mutation detected in either tumor tissue or ctDNA.
• At least 1 measurable lesion or evaluable disease per RECIST v1.1.
• An ECOG performance status score of 0 or 1.
• Adequate organ function.
  • Additional key inclusion criterion for Parts B and C:
  • \- Confirmed metastatic or locally advanced HR+/HER2- breast cancer not amenable to surgical resection with curative intent and must have received at least 1 prior CDK4/6 inhibitor and at least 1 prior anti-estrogen therapy.