How do you approach therapy for a fit adult with relapsed AML with CNS involvement after allogeneic stem cell transplantation?

Agree with Dr. @Dr. First Last. If on immunosuppression, would stop immunosuppression. HIDAC q12 hours x 5-6 days reinduction is a regimen that can be used for relapsed AML. There is some data in adding venetoclax to chemo induction and should be considered.

If starting venetoclax single agent to add...

I would use intrathecal Cytarabine for immediate control, then a high dose AraC based regimen. Ultimately, prognosis is very poor, but consideration of research protocols could be discussed, or Car_T protocols if CNS disease is controlled eventually.