This is a PhaseI, open-label study, Dose-Escalation Study, where tolerated doses will be escalated to the next doses with the safety, tolerability, and PK being evaluated in metastatic castration-resistant prostate cancer (mCRPC) patients. Tumor assessment and PSA values will be evaluated during the study as an additional point.

Inclusion Criteria:

1. Men aged 18 years and older.
2. Histologically confirmed diagnosis of prostate cancer
3. Castrate level of testosterone in blood serum < 1,7 nmol/l or < 50 ng/dl
4. PSA level at screening > 2 ng/ml
5. Progression of metastatic CRPC after the chemical castration with gonadotropin-releasing hormone (GnRH) analogue or after the chemical castration and subsequent chemotherapy.
6. The patient's ECOG performance status of 0 - 2
7. Patients previously treated with docetaxel chemotherapy should have received 2 or less prior lines of chemotherapy for mCRPC
8. The expected survival time of not less than 12 weeks

Exclusion Criteria:

1. Prior anticancer therapy:

   • Treatment with chemotherapeutic agents or radiotherapy within 4 weeks prior to screening or preserved toxicities of ≥ II grade according to CTCAE scale, related to prior anticancer therapy (excluding alopecia)
   • Prior antiandrogen therapy: flutamide within 4 weeks prior to screening or bicalutamide within 6 weeks prior to screening
   • Exposure to bisphosphonates is allowed only if the treatment started prior to screening

2. Clinically significant cardiovascular system diseases:

3. Clinically significant central nervous system diseases:

4. History of other significant concomitant diseases which, in the Investigator's opinion, may cause a disease recurrence (i.e. uncontrolled diabetes mellitus)

5. Prior or concomitant therapy:

   • Exposure to drugs which may cause a convulsive state within 4 weeks prior to screening
   • Exposure to treatment with characteristics of CYP3A4 or CYP2D6 inhibitors within 4 weeks prior to screening
   • Exposure to treatment relating to the Class I risk of QT-interval prolongation; exposure to treatment relating to the Class II risk of QT-interval prolongation is allowed if the patient have received not less than 5 half-life periods of flat-dosed treatment