The purpose of this study is to evaluate whether high-dose testosterone followed by targeted radioligand therapy (TRT) is effective in treating metastatic castration resistant prostate cancer. Participants will be asked to spend about 6 months in this study. Participants will take study drug for 3.5 months.

Inclusion Criteria:

• Participants must have histologically or cytologically confirmed prostate cancer that has progressed to mCRPC with no grade 2 or above cancer related symptoms.
• Participants need to have either PSA or imaging progression at castrate level of serum testosterone (i.e. <50ng/dl). The definition of PSA progression and the definitions of imaging progression on measurable or non-measurable lesions will be based on the prostate cancer working group 3 (PCWG3) criteria. Patients with symptomatic oligo progression (1-3 sites), the symptoms need to be improved to grade 1 or less with palliative local therapy prior to study enrollment.
• Participants need to have a positive PSMA PET scan and deem eligible for PSMA-617.
• Allowable prior therapies: Prior treatment with one line of ARPI. Patients need to be on ARPI for at least 4 weeks to be considered one line of therapy. Prior treatment with sipuleucel-T for mCRPC. Prior treatment with docetaxel in the castration sensitive setting.
• ECOG performance status 0-1.
• Participants must have adequate organ and marrow functions.
• Participants with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial.
• Participants with h/o myocardial infarction or history of congestive heart failure, need to have estimated left ventricle ejection fraction above 40% either on echocardiogram or MUGA scan within 6 months of study enrollment.
• Non-sterilized men who are sexually active with a female partner of childbearing potential treated or enrolled on this protocol must agree to use adequate contraception prior to the study, for the duration of study participation, and for 6 weeks after last dose of enzalutamide or docetaxel administration.
• Ability to understand and the willingness to sign a written informed consent document or have a legally authorized representative sign on the subject's behalf. Stated willingness to comply with all study procedures and availability for the duration of the study.

Exclusion Criteria:

• Metastatic prostate cancer with known epidural, liver or brain metastases.
• No history of cord compression.
• Treatment with radiation within 30 days prior to the first dose of Tc400.
• Receiving any other investigation agents. Prior treatment with investigation agents need to have a washout period of 4 weeks prior to enrollment.
• Participants with uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, delayed healing of wounds, ulcers, or bone fractures, or psychiatric illness/social situations that would limit compliance with study requirements.