• Informed Consent: provision of signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.

• Age greater than or equal to 18 years. Members of all races and ethnic groups will be included.

• Participants must have histologically confirmed non-metastatic adenocarcinoma of the prostate

• (a) Any one of the following three high risk features:

‣ Gleason sum \>7 (ISUP Grade Group \>3)

⁃ Clinical stage T3 (resectable), per AJCC Cancer Staging Manual, 8th ed.

⁃ PSA \> 20 ng/ml oSubjects who meet high risk criteria solely by PSA (i.e., stage \<T3 AND Gleason sum less than or equal to 7) must have a progression-free probability after radical prostatectomy that is less than or equal to 50% at 5 years as estimated by the Memorial Sloan Kettering (MSK) pre-radical prostatectomy nomogram: https://www.mskcc.org/nomograms/prostate/pre\_op (b) Subjects not meeting high risk criteria that have the following combination may be screened for inclusion:

⁃ Gleason score 4+3=7 (ISUP Grade Group 3) AND

⁃ Estimated progression-free probability after radical prostatectomy that is less than or equal to 50% at 5 years by MSK nomogram

• No definitive evidence of metastasis on nuclear bone scan (required on all subjects)

• No evidence of lymph nodes \> 2 cm in diameter on pelvic CT scan (scan only required in patients with a PSA \> 20 ng/ml)

• Prostatectomy with extended lymph node dissection planned as primary therapy.

‣ The subject had a discussion with a clinician about other options, such as radiotherapy, and elected to undergo surgical treatment.

⁃ The subject has been offered consultation with radiation oncology and declined consultation or radiation treatment, or determined it was not in best medical interest

• Be willing to provide tissue from a diagnostic biopsy core or excisional biopsy of a tumor lesion obtained up to 6 months/180 days prior to initiation of treatment on Day 1. Subjects for whom samples cannot be provided (e.g., inaccessible or subject safety concern) may submit an older archived specimen only upon agreement from the Sponsor-Investigator.

• Tumor tissue must be provided for biomarker analysis. PTEN IHC staining must be less than or equal to 10% as determined by the central lab. If insufficient tumor tissue content is provided for analysis, acquisition of additional archived tumor tissue (block and /or slides) for the biomarker analysis is required.

⁃ Have a performance status of 0 or 1 on the ECOG Performance Scale with no deterioration over the previous 2 weeks prior to baseline or day of first dosing.

⁃ Life expectancy of greater than 10 years per the treating physician.

⁃ Minimum body weight of 45 kg with minimum Body Mass Index (BMI) of 18.5

⁃ Non-sterile men who are not totally sexually abstinent (i.e., refraining from heterosexual intercourse during the entire period of risk associated with study interventions) and intend to be sexually active with a women of childbearing potential partner must use a condom upon entering the study and until 16 weeks after the last dose of capivasertib. Contraception should be considered in females' partners of men taking capivasertib who are of childbearing potential

⁃ Able and willing to swallow and retain oral medication

⁃ Demonstrate adequate organ function as defined by laboratory parameters including ANC, platelets, hemoglobin, transaminases, albumin, hemoglobin A1C, CrCl or eGFR, PTT and INR (unless anticoagulated, then therapeutic range is acceptable). All screening labs should be performed within 30 days of treatment initiation