A First-in-human Dose Escalation and Expansion Study to Evaluate the Safety, and Tolerability of AZD8421 Alone or in Combination in Participants With Selected Advanced or Metastatic Solid Tumors

This is a first in-human study of AZD8421 administered to participants with advanced or metastatic solid tumors. The study will evaluate the safety, tolerability, preliminary efficacy, pharmacokinetics, and pharmacodynamics of AZD8421 alone and in combination with selected targeted anti-cancer drugs. AZD8421 monotherapy (M1) will evaluate the safety, tolerability and pharmacokinetics of AZD8421 as monotherapy to identify a recommended Phase II dose (RP2D) in participants with ER+ HER2- advanced breast cancer previously treated with a CDK4/6i (Parts A and B) and participants with metastatic high-grade serous ovarian cancer previously treated with a platinum-based chemotherapy in the metastatic setting (Part B). AZD8421 combination therapy (M2) will evaluate the safety, tolerability, and pharmacokinetics of different formulations of AZD8421 in combination with a CDK4/6 inhibitor (one or more of abemaciclib, ribociclib and palbociclib) and camizestrant (next generation oral SERD; referred to throughout as 'camizestrant') in participants with ER+ HER2- advanced breast cancer previously treated with a CDK4/6 inhibitor.