PKC412 Inhibits the ZNF198-FGFR1 Fusion Tyrosine Kinase and Is Efficacious in Treatment of t(8;13)(p11;q12) Associated Stem Cell Myeloproliferative Disease.

Human stem cell leukemia-lymphoma syndrome usually presents as a myeloproliferative disease (MPD) that evolves to acute myeloid leukemia and/or lymphoma. The syndrome associated with t(8;13)(p11;q12) results in expression of the ZNF198-FGFR1 fusion tyrosine kinase. Current empirically-derived cytotoxic chemotherapy is inadequate treatment of this disease. We hypothesized that small molecule inhibitors of the ZNF198-FGFR1 fusion would have therapeutic efficacy. We characterized the transforming activity of ZNF198-FGFR1 in hematopoietic cells in vitro and in vivo. Expression of ZNF198-FGFR1 in primary murine hematopoietic cells caused a myeloproliferative syndrome in mice that recapitulated the human MPD phenotype. Transformation in these assays, and activation of the downstream effector molecules PLCγ, STAT5 and PI3K/AKT, required the proline-rich, but not the zinc-finger domains of ZNF198. A small molecule tyrosine kinase inhibitor, PKC412 (N-benzoyl-staurosporine) effectively inhibited ZNF198-FGFR1 tyrosine kinase activity and activation of downstream effector pathways, and inhibited proliferation of ZNF198-FGFR1 transformed Ba/F3 cells. Furthermore, treatment with PKC412 resulted in statistically significant prolongation of survival in the murine model of ZNF198-FGFR1 induced myeloproliferative disease. Based in part on these data, PKC412 was administered to a patient with t(8;13)(p11;q12) and was efficacious in treatment of progressive myeloproliferative disease with organomegaly. Therefore, PKC412 may be a useful therapy for treatment of human stem cell leukemia-lymphoma syndrome.