Checkpoint inhibition of PD-L1 and CTLA-4 in a child with refractory acute leukemia.

Children with multiple relapsed or refractory leukemia have dismal survival. Research has identified engagement of immune checkpoint receptors (e.g., PD-1, PD-L1 and CTLA-4) as a mechanism for treatment resistance. For adult cancer, inhibitors of PD-1 (nivolumab) and CTLA-4 (ipilimumab) have shown promise with response rates ranging from 7 to 40%. In vitro studies using acute myeloid leukemia cell lines have shown that acute myeloid leukemia blasts may similarly utilize the PD-1/PD-L1 axis to evade an anticancer immune response. We report the first case of a pediatric patient with multiple relapsed/refractory leukemia treated with nivolumab, ipilimumab and 5-azacytidine who tolerated therapy with brief improvement of symptoms.