A Study to Investigate the Effect of Capivasertib on the Pharmacokinetics of Oral Dextromethorphan (CYP2D6 Substrate) in Healthy Participants

Main Inclusion Criteria: * Have a Body Mass Index (BMI) between 18 and 30 kg/m2 inclusive and weigh at least 50 kg. * All females must have a negative pregnancy test at the Screening Visit and on admission to the Clinical Unit. * Females of non-childbearing potential must be confirmed at the screening visit (postmenopausal or documentation of irreversible surgical sterilisation). * Male participants must have documentation of vasectomy done 6 months prior to screening visit. Participants must be willing to use one barrier method of contraception (condom) during sexual intercourse with a female partner of childbearing potential from the time of first study intervention administration until 16 weeks after the last dose of capivasertib. Main Exclusion Criteria: * History of any clinically important disease or disorder * History or presence of gastrointestinal, hepatic or renal disease. * Any clinically important illness, medical/surgical procedure (excluding placement of vascular access), or significant traumatic injury within 4 weeks of the first administration of study intervention or an anticipated need for major surgery during the study. * Any clinically significant skin abnormalities that are chronic or currently active. * Abnormal hepato-renal and bone marrow organ function laboratory values. * Any clinically important abnormalities in clinical chemistry, haematology, or urinalysis. * Any clinically significant abnormalities in glucose metabolism. * Any positive result on screening for serum HBsAg OR anti-HBc antibody, indicative of active hepatitis B, hepatitis C, or human immunodeficiency virus (HIV) * Current smokers or those who have smoked or used other nicotine/nicotine-containing products within the previous 3 months prior to Screening Visit. * Known or suspected history of alcohol or drug abuse or excessive intake of alcohol. * Use of drugs with enzyme inducing properties 3 weeks prior to the first administration of study intervention. * Use of strong inhibitors of Cytochrome P450 3A4 (CYP3A4) or strong/moderate inducers of CYP3A4 within 2 weeks prior to first dose of capivasertib. * Concurrent use of herbal or natural products intended as treatment or prophylaxis that may interact with capivasertib. * Participants who have previously received capivasertib. * Any clinically significant abnormal findings in vital signs and 12-lead electrocardiogram (ECG). * History of severe allergy/hypersensitivity