A Study of LY3405105 in Participants With Advanced Cancer

A Phase 1a/1b Study of LY3405105 Administered to Patients With Advanced Solid Tumors

The main purpose of this study is to investigate the safety of LY3405105 in participants with advanced cancer. The study has two parts phase 1a and phase 1b. Participants will only enroll in one part.

Inclusion Criteria:

Phase 1 a:

• Have histological or cytological evidence of a diagnosis of a solid tumor cancer that is advanced and/or metastatic
• Have available archived tissue for exploratory biomarker analysis
• Have adequate organ function
• Have discontinued all previous treatments for cancer and recovered from their side effects
• Are able to swallow capsules/tablets

Phase 1 b:

• Cohort 1: Triple-negative breast cancer (TNBC).
• Cohort 2: Clear cell ovarian cancer, endometrioid ovarian cancer, or endometrioid endometrial carcinoma with a LOF mutation in one or more of the following genes: ARID1A, KMT2C (MLL3), KMT2D (MLL2), or KDM6A (UTX).
• Cohort 3: Soft tissue sarcoma or sarcomatoid/rhabdoid malignancy with loss of expression of INI1, BRG1, or BRM by immunohistochemistry or a LOF mutation in one or more of the following genes: ARID1A, SMARCA2, SMARCA4, or SMARCB1. Participants aged ≥ 12 years with a body weight of ≥ 40 kilogram (kg) are acceptable for Cohorts 3. Participants with synovial sarcoma and a confirmed SS18-SSX gene fusion are also eligible.
• Cohort 4: Epithelioid sarcoma with INI1 loss of expression by immunohistochemistry or SMARCB1 LOF mutation. Participants aged ≥ 12 years with a body weight of ≥ 40 kilogram (kg) are acceptable for Cohorts 4.
• Cohort 5: Bladder cancer with a LOF mutation in one or more of the following genes: ARID1A, KMT2C (MLL3), KMT2D (MLL2), or KDM6A (UTX).

Exclusion Criteria:

• Have symptomatic central nervous system (CNS) malignancy or metastasis
• Have symptomatic human immunodeficiency virus (HIV), Hepatitis A, B, or C
• Have congestive heart failure
• Are breastfeeding