A Phase I/IIa, First-in-human, Open-label, Dose Escalation and Expansion Study to Evaluate the Safety, Pharmacokinetics, Pharmacodynamics and Preliminary Efficacy 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 hi…