Phase 1/2 Study to Evaluate EP0062 as Monotherapy and in Combination in Patients With Advanced or Metastatic AR+/HER-2-/ER+ Breast Cancer

Required: AR overexpression (≥ 10% AR nuclei staining by central immunohistochemistry (IHC) using the Ventana assay (Module A); ≥ 30% AR nuclei staining by central IHC using the Ventana assay (Modules B and C))

Biopsy-proven AR+ breast cancer * For Module A, AR+ breast cancer is defined as ≥ 10% AR nuclei staining by central immunohistochemistry (IHC) using the Ventana assay * For Modules B and C, AR+ breast cancer is defined as ≥ 30% AR nuclei staining by central IHC using the Ventana assay

Required: ESR1 overexpression

Biopsy-proven ER+ breast cancer

Required: HER2 (ERBB2) wild-type (IHC 0 or 1+; if IHC 2+, FISH negative (HER2/CEP17 ratio <2.0))

HER2-negative breast cancer, defined as negative by fluorescence in situ hybridisation (FISH) or IHC score of 0 or 1+. If IHC is equivocal at 2+, a negative FISH test (HER2/Amplification of the centromeric region of chromosome 17)CEP17 ratio of <2.0) is required

Cannot have received: chemotherapy

Any chemotherapy within 21 days prior to the first dose of study drug

Cannot have received: investigational anti-cancer drug

Any non-chemotherapy investigational anti-cancer drug < 5 half-lives (28 days for biologics) or < 14 days for small-molecule therapeutics or if half-life is not known

Cannot have received: endocrine therapy (tamoxifen, aromatase inhibitor)

Tamoxifen and aromatase inhibitors within 14 days prior to the first dose of study drug

Cannot have received: Selective Estrogen Receptor Degrader (fulvestrant)

Fulvestrant or other investigational Selective Estrogen Receptor Degraders (SERDs) within 21 days prior to first dose of study drug

Cannot have received: selected combination agent

Prior treatment with selected combination agent