A Phase 1, Open-label Study to Evaluate the Pharmacokinetics and Safety of ASP5541 in Chinese Participants With Advanced Prostate Cancer
In this study, ASP5541 will be given to Chinese men with prostate cancer. It will be given together with prednisone and androgen deprivation therapy (ADT). Prednisone is a steroid, and ADT is already given to the men as their standard of care for prostate cancer. The main aims of the study are to check the safety of ASP5541, when given with prednisone and ADT, and to check how ASP5541 moves through the bodies of Chinese men. The men will receive ASP5541 as an injection into a muscle (intramuscular injection) at the side of the hip. They will all receive the same dose of ASP5541. The men will be given prednisone and ADT according to their label. The men will continue to receive ASP5541 with prednisone and ADT until their cancer gets worse or the doctor decides the men should stop study treatment.
• Participant is diagnosed with histologically or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine differentiation or small cell features.
• Participant has Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, or ECOG performance status of 2 if due to bone pain.
• Participant must have an estimated life expectancy of ≥ 12 months with metastatic hormone-sensitive prostate cancer (mHSPC) or ≥ 6 months with metastatic castration-resistant prostate cancer (mCRPC).
• Participant is able to understand and comply with all study requirements and procedures.
• Participant has been diagnosed with mCRPC or mHSPC documented by metastatic lesions on a bone scan, computed tomography (CT), magnetic resonance imaging (MRI) or prostate-specific membrane antigen positron emission tomography (PSMA-PET).
• Participant is receiving ongoing androgen deprivation therapy (ADT) with a gonadotropin-releasing hormone (GnRH) analogue or has a history of bilateral orchiectomy (i.e., surgical or medical castration). Participant with mHSPC must have started castration therapy (medical or surgical) at least 14 days prior to Cycle 1 Day 1 (C1D1).
∙ Note: Participant who has not had a bilateral orchiectomy must have a plan to maintain effective GnRH analogue therapy for the duration of the study.
• If the participant has mCRPC, participant has evidence of disease progression defined as 1 or more of the following criteria at study entry:
‣ Evidence of radiographic progression of disease prior to first dose and following the most recent prostate cancer treatment, defined as progressive disease on CT/MRI per Response Evaluation Criteria in Solid Tumours (RECIST) v1.1 or on a bone scan per PCWG3.
⁃ PSA progression defined as an increase in PSA of at least 25% and ≥ 1 ng/mL above the nadir, confirmed by a second value 1 week later, and with at least 1 of the measurements within 90 days prior to screening. PSA nadir is defined as the lowest PSA during or after the most recent treatment.
• If the participant has mCRPC, participant has a serum testosterone level \< 1.73 nmol/L (\< 50 ng/dL) at the Screening visit.
• Male participant must agree to use contraception with female partner(s) of childbearing potential (including breastfeeding partner) throughout the treatment period and for 7 months after final ASP5541 administration.
• Male participant must agree to remain abstinent or use a condom with pregnant partner(s) for the duration of the pregnancy throughout the investigational period and for 7 months after final ASP5541 administration.
• Male participant must not donate sperm during the treatment period and for 7 months after final ASP5541 administration.
• Participant has adequate ventrogluteal muscle mass for an intramuscular injection.
• Participant agrees not to participate in another interventional study while receiving ASP5541 in the present study.