SOHO State of the Art Updates and Next Questions: Is Combination Therapy Here for Myelofibrosis?

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm characterized by progressive cytopenias, splenomegaly, and constitutional symptoms. The hallmark of MF pathophysiology is constitutive activation of JAK/STAT signaling, which, in the majority of cases, is associated with an acquired mutation in one of three driver mutations, JAK2, CALR, or MPL. Our growing understanding of the molecular biology of MPNs has resulted in regulatory approval of four JAK inhibitors (JAKi), which have demonstrated efficacy in improving symptom burden and reducing spleen size. Despite clear benefits of JAKi therapy, including evidence of improved survival, these therapeutic interventions have not established an ability to modify disease in terms of resolution of bone marrow fibrosis or molecular remissions. Therefore, recent emphasis has been on the development of novel therapies with informed targets outside of the JAK/STAT signaling pathway. Moreover, combination approaches utilizing JAK and non-JAK targeting agents underscore the potential for disease modification along with deeper and more durable clinical responses. Emerging combination strategies and their clinical development will be reviewed here, including investigations that pair JAKi therapy with BCL-2 family inhibitors, BET inhibitors, restored p53 cell death signals, telomerase inhibitors, PIM1 kinase inhibitors, and mutant CALR targeted therapies. While several combination clinical trials suggest improved spleen and symptom responses and the possibility of disease modification, toxicity profiles and optimal sequencing remain areas of active investigation.