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

Inclusion Criteria: * Female participants only, aged 18 or above * Participants with advanced solid tumors must have received prior adequate therapy in accordance with local practice for their tumor type and stage of disease, or, in the opinion of the Investigator, a clinical study is the best option for their next treatment based on response to and/or tolerability of prior therapy. * Metastatic or locoregionally recurrent disease and radiological or objective evidence of progression on or after the last systemic therapy prior to starting IMP. * ECOG/WHO performance status 0 to 1, and a minimum life expectancy of 12 weeks. * At least one lesion that is measurable and/or non-measurable, as per RECIST v1.1 and that can be accurately assessed at baseline and is suitable for repeated assessment. Exclusion Criteria: * Intervention with any of the following: * Any cytotoxic chemotherapy, investigational agents, or other anti-cancer drugs for the treatment of advanced cancer from a previous treatment regimen or clinical study within 14 days or 5 half-lives (whichever is shorter) of the first dose of IMP (21 days for myelosuppressive therapies) other than GnRHa (eg, goserelin) and bone-stabilizing agents (eg, zoledronic acid, denosumab). * Any prescription or non-prescription drugs or other products, including herbal products, known to be moderate or strong inhibitors/inducers of CYP3A4/5 which cannot be discontinued prior to first dose of IMP and withheld throughout the study unt…