A Study of PRT2527 in Participants With Advanced Solid Tumors

Inclusion Criteria: * Tumor types under study 1. Selected sarcomas with a documented gene fusion 2. Castrate resistant prostate cancer (CRPC) 3. Hormone receptor positive (HR+), HER2 negative (HER2-) breast cancer 4. Non-small cell lung cancer (NSCLC) 5. MYC amplified solid tumors * Must have measurable disease per RECIST 1.1; participants with CRPC or sarcoma may have nonmeasurable but evaluable disease * Eastern Cooperative Oncology Group (ECOG) Performance Score of 0 or 1 * Adequate organ function * Must provide tumor tissue sample to the central laboratory for biomarker analysis * Participants must have recovered from the effects of prior cancer-related therapy, radiotherapy, or surgery to ≤ Grade 1 Exclusion Criteria: * Primary malignancies of the CNS, or uncontrolled CNS metastases, including impending spinal cord compression * have a corrected QT interval \>480 msec from prior or baseline * have impaired cardiac function or clinically significant cardiac disease * Treatment with strong inhibitors or inducers of CYP3A4 * Prior exposure to a CDK9 inhibitor * History of another malignancy except for: 1. Curatively treated malignancy with no known active disease 2. Curatively treated non-melanoma skin cancer without evidence of disease 3. Curatively treated carcinoma in situ without evidence of disease * have undergone major surgery within 2 weeks prior to Week 1 Day 1 * have had chemotherapy, biologic therapy, targeted therapy, immunotherapy, extended-field radiotherapy, or investigational agents within 5 half-lives or 28 days (whichever is shorter) prior to administration of the first dose of study drug on Week 1 Day 1.