CD4 and myeloproliferative neoplasm: Considering the reported on-target suppressive effects of Ruxo on MPN-associated splenomegaly that could ensue potential toxicity on mature T cells52, we assessed the abundance of CD4+ and CD8+ T cells in the spleens and did not observe overt reduction (Supplementary Fig. 6i), suggesting negligible toxicity from this short-term Ruxo therapy.