Study of OP-3136 in Advanced or Metastatic Solid Tumors

Key Inclusion Criteria:

• Participants with advanced or metastatic ER+HER2- breast cancer, mCRPC, or NSCLC (Part 1) or advanced or metastatic ER+HER2- BC or mCRPC (Part 2).

• Part 1 (Dose escalation): Participants must have a tumor that is unresectable ormetastatic and for which life prolonging measures do not exist or availabletherapies are intolerable or no longer effective.

• Part 2 (Dose Expansion in ER+ HER2- mBC): Participants must have received up to 3prior lines of endocrine therapy (one of which must be in combination with CDK4/6inhibitor) and up to 1 prior line of chemotherapy or an antibody-drug conjugate.

• Part 2 (Dose Expansion in mCRPC): Participants must have received up to 4 lines ofprior systemic therapy for prostate cancer. Prior therapy must include treatmentwith an androgen receptor pathway inhibitor(s).

Key Exclusion Criteria:

• Prior therapy with KAT6A/B inhibitor in any treatment setting.

• Participants with advanced/metastatic, symptomatic, visceral spread, that are atrisk of life-threatening complications in the short term.

• Known active or symptomatic central nervous system (CNS) metastases, carcinomatousmeningitis, leptomeningeal disease, or a spinal cord compression that requireCNS-specific treatment, or participants who did not demonstrate clinical andradiologic stability during the last 2 months prior to the first dose of studytreatment or require or are currently on steroid therapy for CNS metastases.

• History of cerebral vascular disease, including transient ischemic attack, within 6months prior to the first dose of study treatment.

• History of or ongoing impaired cardiac function or clinically significant cardiacdisease within 6 months prior to the first dose of study treatment.

Note: Additional inclusion/exclusion criteria may apply.