Safety and Pharmacokinetics of ODM-209

MAIN INCLUSION CRITERIA: * Written informed consent (IC) obtained. * Age ≥ 18 years. * ECOG performance status 0-1. * Adequate marrow, liver and kidney function. * Able to swallow study treatment. Main Prostate cancer specific inclusion criteria: * Histologically confirmed adenocarcinoma of the prostate. * Castration resistant prostate cancer with serum testosterone \< 50 ng/dl. * Metastatic disease. * Ongoing androgen deprivation therapy with GnRH analogue, or have had bilateral orchiectomy. * Have had treatment with at least one line of second generation androgen receptor targeting therapy and one line of chemotherapy. Main Breast cancer specific inclusion criteria: * Histologically confirmed breast carcinoma * ER positive, HER2-negative advanced breast cancer * Postmenopausal or pre/perimenopausal if amendable to be treated with GnRH agonist or antagonist. * Documented disease progression after treatment with at least 2 lines of systemic treatment for advanced breast cancer. Of these, at least one line must have been endocrine treatment in combination with a cdk4/6 inhibitor. MAIN EXCLUSION CRITERIA * History of pituitary dysfunction. * Known brain metastases or active leptomeningeal disease. * Active infection or other medical condition that would make corticosteroids contraindicated. * Hypotension or uncontrolled hypertension. * Clinically significant cardiovascular disease, e.g. myocardial infarction, arterial thrombotic events, or pulmonary embolism in the past six months, unstable angina, or congestive heart failure (New York Heart Association \[NYHA\] class II-IV). * Prolonged QTcF interval. * Use of any investigational drug 4 weeks prior to the start of the study treatment.