Momelotinib's Spleen, Symptom and Anemia Efficacy Is Maintained in Intermediate/High Risk Myelofibrosis Patients with Thrombocytopenia

Momelotinib (MMB), a JAK1, JAK2 and ACVR1 inhibitor, has demonstrated clinically comparable splenic and symptomatic benefits to ruxolitinib (RUX), the standard-of-care JAK1/JAK2 inhibitor for myelofibrosis (MF), a condition marked by splenomegaly, constitutional symptoms and progressive anemia and thrombocytopenia. MMB also uniquely restores iron homeostasis and red blood cell production, reduces or eliminates the need for transfusions and improves or maintains platelet (PLT) counts. Consistent with MMB’s differentiated biological profile, low myelosuppressive potential and favorable hematological tolerability, prolonged, near-maximal MMB dose intensity can be maintained regardless of underlying PLT values. In contrast, RUX’s hematological toxicity profile necessitates attenuated starting doses for thrombocytopenic (TCP) patients with PLTs A retrospective analysis of spleen, symptom and TI response rates at week 24 was conducted in the TCP and ITT groups from SIMPLIFY-1 (S1), a double-blind Phase 3 study in intermediate/high risk MF patients randomized 1:1 to MMB or RUX over a 24-week treatment period, and SIMPLIFY-2 (S2), a Phase 3 study comparing MMB to best available therapy (BAT) in previously RUX-exposed MF patients. A baseline PLTs ≥50 × 109/L was required in S1, while there was no lower PLT limit for S2. Most subjects randomized to BAT (88%) received RUX during the 24-week randomized period. In S1, 9.5% and 24% of 432 subjects randomized had a PLT count of In S2, 44% of 156 subjects randomized had a PLT count of These retrospective analyses of data from the two Phase 3 SIMPLIFY studies demonstrate that MMB efficacy is maintained in TCP patients and is comparable to that observed in the broader JAKi-naive and previously JAKi-treated ITT populations in S1 and S2. These data contrast with RUX data from S1 where the SRR was markedly decreased and the TSS moderately decreased in TCP patients, consistent with reduced RUX dose intensity and higher rates of early discontinuation in this subset. Consequently, for patients in S1 with low PLTs, MMB and RUX demonstrated similar symptomatic benefit, while MMB had a more favorable profile for splenic volume reduction and TI. Response rates for the three parameters in the MMB arm of S2 were comparable between the TCP and ITT groups. Response rates in the control arm were low and not substantially different between the TCP and ITT groups, with most patients receiving very low dose intensity of RUX. Together, the findings of comparable spleen, symptom and TI response in the TCP and ITT groups treated with MMB suggest that the compound could become the optimal JAK inhibitor therapy for intermediate/high risk MF patients with underlying disease-related or prior RUX-induced thrombocytopenia. Disclosures Kiladjian: Novartis: Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; AOP Orphan: Membership on an entity’s Board of Directors or advisory committees; AbbVie: Membership on an entity’s Board of Directors or advisory committees. Platzbecker: Amgen: Honoraria, Research Funding; Geron: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding. Mayer: Principia Biopharma: Research Funding; AbbVie: Research Funding. Illes: Novartis, Janssen, Pfizer, Roche;: Other: Travel, Accommodations, Expenses; Takeda, Seattle Genetics: Research Funding; Celgene, Janssen, Novartis,Roche, Takeda: Consultancy; Janssen, Celgene, Takeda, Novartis Pharma SAS, Pfizer Pharmaceuticals Israel, Roche;: Consultancy, Honoraria. Vannucchi: AbbVie: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Celgene/BMS: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Blueprint: Membership on an entity’s Board of Directors or advisory committees; Incyte: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Nagy: MorphoSys AG: Patents & Royalties. Yoon: Novartis: Consultancy, Honoraria; Janssen: Consultancy; F. Hoffmann-La Roche: Other: All authors received support for third-party writing assistance, furnished by Scott Battle, PhD, provided by F. Hoffmann-La Roche, Basel, Switzerland., Research Funding; Amgen: Consultancy, Honoraria; Kyowahako Kirin: Research Funding; YuhanPharma: Research Funding. Von Bubnoff: Novartis: Membership on an entity’s Board of Directors or advisory committees, Other: Clinical biomarker research, steering committee, Patents & Royalties: Research support, Research Funding; Astra Zeneca: Honoraria, Other: Lectures, Patents & Royalties: Astra Zeneca. Verstovsek: Promedior: Research Funding; PharmaEssentia: Research Funding; AstraZeneca: Research Funding; Celgene: Consultancy, Research Funding; Protagonist Therapeutics: Research Funding; CTI Biopharma Corp: Research Funding; Sierra Oncology: Consultancy, Research Funding; Gilead: Research Funding; Genentech: Research Funding; Incyte Corporation: Consultancy, Research Funding; Roche: Research Funding; Novartis: Consultancy, Research Funding; ItalPharma: Research Funding; Blueprint Medicines Corp: Research Funding; NS Pharma: Research Funding. Klencke: Sierra Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Donahue: Sierra Oncology Inc.: Current Employment, Current equity holder in publicly-traded company. Mesa: Incyte: Research Funding; Bristol Myers Squibb: Research Funding; AbbVie: Research Funding; Sierra Oncology: Consultancy; Novartis: Consultancy; LaJolla Pharmaceutical Company: Consultancy; Samus Therapeutics: Research Funding; Promedior: Research Funding; Genentech: Research Funding; CTI BioPharma: Research Funding.