This is a phase I, open-label, multicentre study of AZD8186 administered orally in patients with advanced castrate-resistant prostate cancer (CRPC), squamous non-small cell lung cancer (sqNSCLC), triple negative breast cancer (TNBC) and known PTEN-deficient/mutated or PIK3CB mutated/amplified advanced solid malignancies. The study design allows an escalation of dose with intensive safety monitoring to ensure the safety of the patients.