Carrying out clinical trials of salbutamol hydrochloride combined with immunotherapy and castration for the treatment of prostate cancer is of great significance. Firstly, it can verify the efficacy and safety of this combination in the treatment of prostate cancer, providing a scientific basis for its clinical application. Secondly, through clinical trials, the mechanism of action of salbutamol hydrochloride combined with immunotherapy can be further studied. Finally, this clinical trial can further expand the treatment strategies for prostate cancer.

This study is a single-arm clinical trial. Eligible patients will be included in the group receiving farsufilide hydrochloride combined with immunotherapy. After enrollment, in addition to the routine androgen deprivation therapy, they will also receive farsufilide hydrochloride (10mg intravenous infusion) on days 1-5, and PD-1 monoclonal antibody (Tirapibep, 3mg/kg, intravenous infusion) on day 5. The treatment will be repeated every 21 days for a total of 4 times.

Inclusion Criteria:

1. Age ≥ 18 years and < 85 years;
2. Patients who have failed at least one chemotherapy regimen containing docetaxel and one standard novel endocrine therapy;
3. Diagnosed with CRPC, defined as: after continuous castration therapy, the castration level of testosterone is < 50 ng/ml; disease progression within 12 weeks before enrollment: PSA levels increase consecutively for 3 times at intervals of 1 week, and serum PSA ≥ 2 ng/ml; evaluated as soft tissue progression according to RECIST criteria, or ≥ 2 new lesions on bone scan;
4. Imaging evidence indicates bone metastatic disease and/or measurable non-bone metastatic disease (lymph nodes or internal organs); Expected survival period ≥ 3 months; All patients voluntarily signed the informed consent form and were able to cooperate with treatment and follow-up;

Exclusion Criteria:

1. Severe cardiovascular and cerebrovascular diseases;
2. Abnormal liver function: Total bilirubin in blood is less than 1.5 times the upper limit of normal value, and the ratio of blood ALT to AST is less than 2 times the upper limit of normal value;
3. Abnormal kidney function: Serum creatinine is less than 1.5 mg/dl or the creatinine clearance rate is greater than or equal to 60 cc/min;
4. Those allergic to the used drugs;
5. Those with tumors in other parts;
6. Abnormal thyroid function: Blood FT4 and/or TT4 levels are higher or lower than the normal value (normal blood FT4 level is 9-25 pmol/L (0.7-1.9 ng/dl), normal blood TT4 level is 64-154 nmol/L (5-12 ug/dl));
7. Cortisol deficiency: Serum cortisol at 8 a.m. is less than 140 nmol/L (5 ug/dL).