This is an investigator-initiated phase II single arm trial, combining neoadjuvant apalutamide (ARN509) with radical prostatectomy, in the treatment of D'Amico intermediate to high risk organ-confined prostate cancer. Apalutamide has shown efficacy in castrate resistant prostate cancer in phase II studies and are now in phase III trials combined with radiation in organ confined disease.

The primary study objectives include assessment of (i) oncological efficacy as determined by tumour downstaging and achievement of nadir PSA The secondary study objectives include(i) determination of adverse effects related to apalutamide and surgical complication rates (ii) human prostate tissue effect of apalutamide

The study will recruit thirty eligible participants who will receive 12 weeks of oral apalutamide 240mg daily. This will be followed by standard-of-care radical prostatectomy. The total trial duration is 26 weeks.

This is a phase II single arm study looking at the efficacy of 12 weeks of neoadjuvant apalutamide (ARN 509), combined with standard-of-care radical prostatectomy, for D'Amico intermediate to high risk prostate cancer patients. The phases of the study will include: screening, treatment and follow-up phases.

Safety will be monitored throughout the study.

Inclusion Criteria:

• histologically diagnosed primary adenocarcinoma of the prostate gland
• non-metastatic D'Amico intermediate to high risk patients undergoing radical prostatectomy as primary definitive therapy
• no known hypersensitivity to the study drug
• able to swallow study drug as whole tablets

Exclusion Criteria:

• presence of small cell, neuroendocrine or ductal differentiation at needle biopsy
• individuals with prior pelvic irradiation therapy for any form of pelvic malignancy
• patients with psychiatric conditions requiring anti-psychotic therapy, or preventing the provision of informed consent
• renal impairment with serum creatinine more than twice the upper limit of normal
• Other prior malignancy less than or equal to 5 years prior to recruitment
• ECOG performance status 2 or poorer