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[Formula presented] 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%

Ruxolitinib (Jakafi) is the one approved therapy for myelofibrosis (MF) based on reduction of splenomegaly and symptoms but JAK inhibition has not proven to significantly modify disease progression. There remains the need for novel therapies with distinct modes of action that can improve the patient experience of MF and impact progression. Lysine-specific demethylase, LSD1, is an epigenetic enzyme critical for self-renewal of malignant myeloid cells and differentiation of myeloid progenitors. LSD1 bound to GFI1b permits maturation of progenitors to megakaryocytes and enables their normal function. IMG-7289 (bomedemstat) is an orally available LSD1 inhibitor. In mouse models of myeloproliferative neoplasms (MPN), IMG-7289 reduced elevated peripheral cell counts, spleen size, inflammatory cytokines, mutant allele frequencies, and marrow fibrosis (Jutzi et al. 2018) supporting its clinical development. IMG-7289-CTP-102 is an ongoing, multi-center, open-label study that recently transitioned from a Phase 1/2a dose-range finding study to a Phase 2b study of IMG-7289 administered orally once-daily in adult patients with intermediate-2 or high-risk MF resistant to or intolerant of ruxolitinib. The key objectives are safety, PD, changes in spleen volume (MRI/CT) and total symptoms scores (TSS) using the MPN-SAF instrument. Inclusion criteria included a platelet count >=100K/muL. Bone marrow (BM) biopsies and imaging studies (both centrally-read) were conducted at baseline and during washout (post-Day 84). The MPN-SAF was self-administered weekly. Phase 1/2a patients were treated for 84 days followed by a washout of up to 28 days. Patients demonstrating clinical benefit could resume treatment for additional 12 week cycles. Dosing was individually tailored using platelet count as a biomarker of effective thrombopoiesis. Patients were started at a presumed sub-therapeutic dose of 0.25 mg/kg/d and up-titrated weekly until the platelet count rested between 50 and 100K/muL. This