A Randomized Open-Label, Phase 3 Study to Evaluate Imetelstat Versus Best Available Therapy (BAT) in Patients with Intermediate-2 (Int-2) or High-Risk Myelofibrosis (MF) Refractory to Janus Kinase Inhibitor (JAKi)

Abstract

MF is a life-threatening myeloproliferative neoplasm. The JAKi ruxolitinib and fedratinib are the only FDA approved treatment options for MF. Despite benefits reported with ruxolitinib in the front-line setting, a high proportion of patients (pts) discontinue treatment (Abdelrahman 2015), and the median overall survival (OS) is 13-16 months (Kuykendall 2018; Newberry 2017; Schain 2019; Palandri 2019; Mcnamara 2019), highlighting a great unmet need for pts non-responsive to a JAKi treatment. Imetelstat, a first-in-class telomerase inhibitor, has shown meaningful clinical improvement in IMbark, a Phase 2 study in pts with Int-2 or high-risk MF who have relapsed after or are refractory to JAKi (Mascarenhas EHA 2020, ASH 2020). Treatment with imetelstat 9.4 mg/kg resulted in 32.2% symptom response (total symptom score [TSS] reduction ≥50%) at Week 24 and median OS of 28.1 months with overall study follow up of 42 months. Dose-dependent inhibition of telomerase with imetelstat resulted in on-target activity that correlated with clinical benefits; dose-dependent reduction in variant allele frequency of MF driver mutations indicated targeting of the underlying malignant clone. The Phase 2 results support continued study of imetelstat 9.4 mg/kg in a Phase 3 randomized controlled study. Study MYF3001 (IMpactMF; NCT04576156) is an open label, randomized (2:1), multicenter, Phase 3 study of imetelstat compared with BAT in ~320 pts with Int-2 or high-risk MF refractory to JAKi treatment. Pts will be randomized to receive imetelstat 9.4 mg/kg IV every 21 days or investigator selected BAT (including hydroxyurea, thalidomide, interferon, danazol, hypomethylating agents, chemotherapy, or other non-JAKi containing therapy as appropriate). Eligible pts will be stratified based on a) Int-2 or high-risk per Dynamic International Prognostic Scoring System; b) platelet count at entry (platelets ≥ 75 and < 150 x 10 9/L vs ≥ 150 x 10 9/L). Pts who meet progressive disease criteria and discontinue BAT may be eligible to crossover to imetelstat. The primary endpoint is OS, and one interim analysis is planned when >70% of death events have occurred. Secondary endpoints include symptom and spleen response rates at Week 24, progression-free survival, clinical response assessment per modified 2013 International Working Group - Myeloproliferative Neoplasms Research and Treatment criteria, time to and duration of response, reduction in degree of bone marrow fibrosis, safety, pharmacokinetics, and patient-reported outcomes. Biomarkers and mutation analyses will be performed to evaluate the impact of imetelstat on reduction/depletion of malignant clones. Approximately 180 sites are planned in North and South America, Europe, Middle East, Australia, and Asia. The study is open for enrollment. Disclosures Mascarenhas: Promedior: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Constellation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kartos: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Prelude: Consultancy; Geron: Consultancy, Research Funding; Geron: Consultancy; Galecto: Consultancy; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; CTI Biopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forbius: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merus: Research Funding. Harrison: Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sierra Oncology: Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte Corporation: Speakers Bureau; AOP Orphan Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Constellation Pharmaceuticals: Research Funding; Galacteo: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Geron: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Promedior: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Keros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kiladjian: Taiho Oncology, Inc.: Research Funding; AOP Orphan: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: 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; PharmaEssentia: Other: Personal fees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Komrokji: BMSCelgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Geron: Consultancy; Taiho Oncology: Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees; Acceleron: Consultancy; AbbVie: Consultancy; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Koschmieder: Abbvie: Other: Travel support; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Shire: Honoraria, Other; CTI: Membership on an entity's Board of Directors or advisory committees, Other; Alexion: Other: Travel support; AOP Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Geron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Image Biosciences: Other: Travel support; Baxalta: Membership on an entity's Board of Directors or advisory committees, Other; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Karthos: Other: Travel support. Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Berry: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Sherman: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Dougherty: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Sun: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Huang: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Wan: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Feller: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Rizo: Geron Corp: Current Employment, Current equity holder in publicly-traded company. Verstovsek: Incyte Corporation: Consultancy, Research Funding; Protagonist Therapeutics: Research Funding; CTI BioPharma: Research Funding; NS Pharma: Research Funding; Ital Pharma: Research Funding; Promedior: Research Funding; PharmaEssentia: Research Funding; Roche: Research Funding; Gilead: Research Funding; Genentech: Research Funding; Celgene: Consultancy, Research Funding; Blueprint Medicines Corp: Research Funding; AstraZeneca: Research Funding; Novartis: Consultancy, Research Funding; Sierra Oncology: Consultancy, Research Funding; Constellation: Consultancy; Pragmatist: Consultancy. OffLabel Disclosure: Imetelstat, a first-in-class telomerase inhibitor, is undergoing clinical development but is not approved for treatment of MF

Emerging Pathogenetic Mechanisms and New Drugs for Anemia in Myelofibrosis and Myelodysplastic Syndromes

“…However, treatment with imetelstat was associated with grade 3 or higher neutropenia (in 68%) and thrombocytopenia (in 62%) [85]. Recently, in 2024, imetelstat received FDA approval for LR-MDS, relapsed or refractory to ESAs, while investigations are ongoing in MF [86,87].…”

Emerging Pathogenetic Mechanisms and New Drugs for Anemia in Myelofibrosis and Myelodysplastic Syndromes

“…However, treatment with imetelstat was associated with grade 3 or higher neutropenia (in 68%) and thrombocytopenia (in 62%) [85]. Recently, in 2024, imetelstat received FDA approval for LR-MDS, relapsed or refractory to ESAs, while investigations are ongoing in MF [86,87].…”

Emerging Pathogenetic Mechanisms and New Drugs for Anemia in Myelofibrosis and Myelodysplastic Syndromes

“…However, treatment with imetelstat was associated with grade 3 or higher neutropenia (in 68%) and thrombocytopenia (in 62%) [85]. Recently, in 2024, imetelstat received FDA approval for LR-MDS, relapsed or refractory to ESAs, while investigations are ongoing in MF [86,87].…”

Emerging Pathogenetic Mechanisms and New Drugs for Anemia in Myelofibrosis and Myelodysplastic Syndromes

“…However, treatment with imetelstat was associated with grade 3 or higher neutropenia (in 68%) and thrombocytopenia (in 62%) [85]. Recently, in 2024, imetelstat received FDA approval for LR-MDS, relapsed or refractory to ESAs, while investigations are ongoing in MF [86,87].…”