Inclusion Criteria:  Participants with documented evidence of locally advanced inoperable or metastatic solid tumours who have exhausted standard of care options and may be suitable to receive capivasertib monotherapy treatment with tumours harbouring a protocol specified alteration in the PIK3CA/AKT/PTEN genes determined by local testing. Eastern Cooperative Oncology Group/World Health Organization performance status 0 to 1 and with minimum life expectancy for 12 weeks. Participant should have at least one lesion that can be assessed by computed tomography/magnetic resonance imaging or plain X-ray at baseline Body mass index within the range 18 to 30 kg/m^2  Exclusion Criteria:  Participants are excluded from the study if any of the following criteria apply:  Radiotherapy with a wide field of radiation within 4 weeks of the first dose of capivasertib and/or radiotherapy with a limited field of radiation for palliation within 2 weeks prior to study intervention initiation. Participants with diabetes mellitus type I or diabetes mellitus type II (irrespective of management). Undergone a major surgery within 4 weeks of the first dose of capivasertib. Any unresolved toxicities from prior therapies higher than CTCAE grade 2 or any unresolved toxicity that may interfere with PK assessment at the time of study intervention initiation. Participants with spinal cord compression or brain metastases. Participants with severe or uncontrolled systemic diseases, active bleeding diatheses, or active infection. Previous allogeneic bone marrow transplant or solid organ transplant. Known immunodeficiency syndrome.