Pharmacologic inhibition of PI3K p110δ in mutant Shp2E76K-expressing mice

Juvenile myelomonocytic leukemia is a childhood malignancy that lacks effective chemotherapies and thus has poor patient outcomes. PI3K p110 delta has been found to promote hyperproliferation of cells expressing mutant Shp2. In this study, we tested the efficacy of a PI3K delta inhibitor in mice expressing the Shp2 gain-of-function mutation, E76K. We found that in vivo treatment of mice led to significantly decreased splenomegaly, reduced frequency of bone marrow progenitor cells, and increased terminally differentiated peripheral blood myeloid cells. The survival of drug-treated mice was significantly prolonged compared to vehicle-treated controls, although mice from both groups ultimately succumbed to a similar myeloid cell expansion. PI3K delta inhibitors are currently used to treat patients with relapsed lymphoid malignancies, such as chronic lymphocytic leukemia. The current findings provide evidence for using PI3K delta inhibitors as a treatment strategy for JMML and potentially other myeloid diseases.