How would you sequence therapies for a patient with chemotherapy-naive metastatic castration-resistant prostate cancer who is MSI-H on tissue-based NGS?

Yes, I absolutely would use Pembrolizumab (200 mg IV q3wk, or 400 mg IV q6wk) in a MSI-high patient with mCRPC who has not yet received chemotherapy. However, I would probably postpone this until after the patient has progressed on one novel AR-directed therapy. I think that the "sweet spot" for using immune checkpoint inhibition in these patients is just after failure of one NHT but before use of taxane chemotherapy for mCRPC. My enthusiasm to use PD-1 blockade would be further increased if the...