A Phase 2 Study of the LSD1 Inhibitor Img-7289 (bomedemstat) for the Treatment of Advanced Myelofibrosis
Authors: Gill Harinder , Yacoub Abdulraheem , Pettit Kristen M. , Bradley Terrence , Gerds Aaron T. , Tatarczuch Maciej , Shortt Jake , Curtin Natasha Joan , Rossetti James M. , Burbury Kate , Mead Adam J. , Göthert Joachim R. , Koschmieder Steffen , Jones Amber , Peppe Jennifer , Natsoulis Georges , Hong Wan-Jen , Stevenson William S. , Ewing Joanne , Harrison Claire N. , Vannucchi Alessandro , Watts Justin , Ross David M , Talpaz Moshe , Rienhoff Hugh Young 
Published: November 2021

There is an unmet need for novel therapies with distinct modes of action to offer clinical benefit for patients with myelofibrosis (MF) who become resistant or intolerant to JAK inhibitors. Lysine-specific demethylase-1 (LSD1) is a histone demethylase critical for self-renewal potential of malignant myeloid cells for hematopoietic differentiation, e.g., LSD1 licenses maturation of megakaryocytes, one cell type critical to the pathogenesis of MF. Bomedemstat is an orally active LSD1 inhibitor that in mouse models of MPNs reduced peripheral cell counts, splenomegaly, inflammatory cytokines, marrow fibrosis, mutant cell burden and overall survival (Jutzi et al. 2018). IMG-7289-CTP-102 is a global, open-label Phase 1/2 study evaluating bomedemstat dosed once daily in MF patients (NCT03136185). Data from this ongoing study are presented.

Key eligibility criteria include IPSS int.-1 or -2 or high-risk patients refractory or resistant to, inadequately controlled by or intolerant of available approved therapy, or in the Investigator's judgment, are not candidates for available approved therapy, peripheral blast count ≤10%, absolute neutrophil count ≥0.5 x 10 9/L, and platelet count ≥100 x 10 9/L. Key objectives are safety and reduction of spleen volume (SVR) by MRI/CT and total symptoms scores (TSS) using the MPN-SAF instrument. Serial bone marrow (BM) biopsies and imaging studies are read centrally. Of 261 genes recurrently mutated in AML/MPN/MDS, germline and somatic baseline and follow-up sequencing is conducted to quantify existing or new mutant alleles frequencies (MAF). Dosing is individually tailored using platelet count as a biomarker of bomedemstat activity on megakaryocyte function, targeting a range between 50-100 x 10 9/L and titrating as needed.

At data cutoff (15 July 2021), the study is fully enrolled with 89 patients: 49% primary MF, 30% post-essential thrombocythemia-MF, 21% post-polycythemia vera-MF. Median age is 68 (35-88) with 52% males. Prior treatment with ruxolitinib was reported in 81% (72/89), 43% (38/89) had also received up to 3 different treatments. 30% of patients (25/83) had received ≥1 RBC transfusion prior to dosing. By IPSS, 54% were high-risk, 40% int.-2, and 6% int.-1. At screening (N=88), sequencing to an average depth of &gt;1000, JAK2 was mutated in 70%, CALR in 22%, and MPL in 7%; 64% had ≥2 mutations of which 66% had high-molecular risk mutations in ASXL1, IDH1/2, EZH2 and/or SRSF2.

The median duration of treatment is 17 weeks (2-102). Of all enrolled patients for whom data is available (evaluable) at 24 weeks for TSS with baseline value ≥20, 89% recorded a reduction in TSS (mean change -36%; -81% to 21%) with 39% reporting ≥50% reduction. Of all patients evaluable for SVR at 24 weeks (N=27), 78% had a reduction in spleen volume from baseline (mean SVR: -4%; -41% to 107%) with 37% showing ≥20% SVR. Of evaluable patients (N=29), 86% had stable (∆&lt;±1.0 g/dL) or improved hemoglobin (&gt;1.0 g/dL). Of patients evaluable for BM fibrosis scoring post-baseline (N=29), 17% improved by 1 grade and 66% were stable. Serially sequencing 43 patients, MAFs in one or more alleles were reduced in 42% with 1 patient in complete molecular remission, and stable in 44%. Clones with JAK2 and/or ASXL1 mutations were most frequently reduced. MAF reduction also correlated with efficacy: SV and/or TSS were improved in patients in whom MAFs were also decreased. No new mutations were identified in any patient. No patient transformed to AML during this study.

The most common non-hematologic AEs reported by patients were diarrhea and dysgeusia, each at 28% (25/89). There have been 13 related SAEs with 3 Grade 2, 9 Grade 3 and 1 Grade 4 (thrombocytopenia). Thirty-nine patients remain on study. Early terminations (&lt;24 weeks) due to AEs occurred in 13 (15%) patients with 5 related to bomedemstat, and 15 discontinued for other reasons. There have been no safety signals, DLTs, or deaths related to drug.

In a patient population with advanced disease, a heavy mutation burden and limited treatment options, once-daily bomedemstat as monotherapy had an acceptable tolerability profile, relieved symptoms, reduced spleen volume and improved anemia without any significant safety signals. Additionally, reductions in the allele frequency of both driver and high molecular risk mutations were observed and correlated with improved efficacy metrics.

The study is now fully enrolled and additional data will be presented.

Disclosures

Yacoub: Cara: Current equity holder in publicly-traded company; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; ACCELERON PHARMA: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Dynavex: Current equity holder in publicly-traded company; Seattle Genetics: Honoraria, Speakers Bureau; Ardelyx: Current equity holder in publicly-traded company; Hylapharm: Current equity holder in publicly-traded company. Bradley: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Gerds: AbbVie: Consultancy; CTI BioPharma: Research Funding; Sierra Oncology: Consultancy; Celgene/Bristol Myers Squibb: Consultancy; PharmaEssentia Corporation: Consultancy; Constellation: Consultancy; Novartis: Consultancy. Shortt: Amgen: Research Funding; Astex: Research Funding; BMS: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. Mead: Abbvie: Consultancy, Honoraria; Celgene/BMS: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Speakers Bureau. Göthert: AOP Orphan Pharmaceuticals: Honoraria, Other: Travel reimbursement; zr pharma&: Honoraria; Proteros Biostructures: Consultancy; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel reimbursement; Incyte: Consultancy, Honoraria, Other: Travel reimbursement; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel reimbursement. Koschmieder: Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Shire: Honoraria, Other; Ariad: 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; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Abbvie: Other: Travel support; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Baxalta: Membership on an entity's Board of Directors or advisory committees, Other; Image Biosciences: Other: Travel support; Alexion: Other: Travel support; CTI: Membership on an entity's Board of Directors or advisory committees, Other; Karthos: Other: Travel support; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; AOP Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding. Jones: Imago BioSciences: Current Employment, Current equity holder in publicly-traded company. Peppe: Imago BioSciences: Current Employment, Current equity holder in publicly-traded company. Natsoulis: Imago BioSciences: Current Employment, Current equity holder in publicly-traded company. Hong: Imago BioSciences: Current Employment, Current equity holder in publicly-traded company; Genentech, Inc.: Ended employment in the past 24 months. Harrison: BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Galacteo: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: 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; CTI BioPharma: 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; Keros: 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; Sierra Oncology: Honoraria; Incyte Corporation: Speakers Bureau; AOP Orphan Pharmaceuticals: 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; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Constellation Pharmaceuticals: Research Funding; Gilead Sciences: 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. Vannucchi: Incyte: 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; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Watts: Rafael Pharmaceuticals: Consultancy; Genentech: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Aptevo Therapeutices: Research Funding. Ross: Keros Therapeutics: Consultancy, Honoraria; Bristol Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Talpaz: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Constellation: Membership on an entity's Board of Directors or advisory committees; Imago: Consultancy; Celgene: Consultancy; Takeda: Other: Grant/research support . Rienhoff: Imago BioSciences: Current Employment, Current equity holder in publicly-traded company.