SHP2 inhibition displays efficacy as a monotherapy and in combination with JAK2 inhibition in preclinical models of myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocytosis, and primary myelofibrosis, are clonal hematopoietic neoplasms driven by mutationally activated signaling by the JAK2 tyrosine kinase. Although JAK2 inhibitors can improve MPN patients' quality of life, they do not induce complete remission as disease-driving cells persistently survive therapy. ERK activation has been highlighted as contributing to JAK2 inhibitor persistent cell survival. As ERK is a component of signaling by activated RAS proteins and by JAK2 activation, we sought to inhibit RAS activation to enhance responses to JAK2 inhibition in preclinical MPN models. We found the SHP2 inhibitor RMC-4550 significantly enhanced growth inhibition of MPN cell lines in combination with the JAK2 inhibitor ruxolitinib, effectively preventing ruxolitinib persistent growth, and the growth and viability of established ruxolitinib persistent cells remained sensitive to SHP2 inhibition. Both SHP2 and JAK2 inhibition diminished cellular RAS-GTP levels, and their concomitant inhibition enhanced ERK inactivation and increased apoptosis. Inhibition of SHP2 inhibited the neoplastic growth of MPN patient hematopoietic progenitor cells and exhibited synergy with ruxolitinib. RMC-4550 antagonized MPN phenotypes and increased survival of an MPN mouse model driven by MPL-W515L. The combination of RMC-4550 and ruxolitinib, which was safe and tolerated in healthy mice, further inhibited disease compared to ruxolitinib monotherapy, including extending survival. Given SHP2 inhibitors are undergoing clinical evaluation in patients with solid tumors, our preclinical findings suggest that SHP2 is a candidate therapeutic target with potential for rapid translation to clinical assessment to improve current targeted therapies for MPN patients.

Bendamustine and rituximab as frontline therapy in extranodal marginal zone lymphoma: a single-institution experience.

Extranodal marginal zone lymphoma (EMZL) encompasses 70% of cases of marginal zone lymphoma. Frontline bendamustine and rituximab (BR) were derived from trials involving other indolent non-Hodgkin's lymphomas. Only one trial has evaluated frontline BR prospectively in EMZL. This retrospective study reports outcomes among EMZL patients receiving frontline BR. Twenty-five patients were included with a median age of 69 years (40-81). Five (20.0%) patients had stage I/II disease, and 20 (80.0%) had stage III/IV disease. The median number of cycles was 6.0 (3.0-6.0). Maintenance rituximab was administered to 10 (41.7%) individuals. Overall response rate (ORR) was 100.0% (60.0% complete response, 40.0% partial response). Medians of overall survival and progression-free survival were not reached. The estimated 2-year progression-free survival was 85.2% and overall survival was 100.0%. Four (16.6%) patients had infections related to treatment; 3 (12.0%) transformed to diffuse large B-cell lymphoma; 5 (20.8%) had a relapse or progression of EMZL; and 3 (12.0%) died unrelated to BR. BR is an efficacious and well-tolerated front-line regimen for EMZL with response data consistent with existing literature.