On December 12, 2022 Imago BioSciences, Inc. ("Imago") (Nasdaq: IMGO), a clinical-stage biopharmaceutical company discovering and developing new medicines for the treatment of myeloproliferative neoplasms (MPNs) and other bone marrow diseases, reported positive data from its ongoing global Phase 2 clinical study evaluating bomedemstat in patients with essential thrombocythemia (ET) who have failed at least one standard of care (Press release, Imago BioSciences, DEC 12, 2022, View Source [SID1234625118]).

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The data were presented in an oral presentation session during the 64th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition (ASH) (Free ASH Whitepaper) taking place 10-13 December 2022. A Phase 2 data set with a cut-off date of 29 April 2022 was previously presented at the 30th European Hematology Association (EHA) (Free EHA Whitepaper) Annual Meeting and congress (EHA) (Free EHA Whitepaper) in June 2022.

Updated Highlights (available data as of 18 October 2022)

Of the 62 Patients treated with bomedemstat for more than 24 weeks:
100% (62/62) achieved platelet count reduction to ≤ 400 x 109/L.
95% (59/62) achieved platelet count reduction to ≤ 400 x 109/L in the absence of thromboembolic events.
89% (25/28) of the 28 patients treated with bomedemstat for at least 48 weeks achieved a durable response by week 48, defined as platelet count of ≤ 400 x 109/L for ≥ 12 weeks.
Of the 12 patients with baseline Total Symptom Scores (TSS) greater than 20:
75% (9/12) showed a decrease in TSS.
67% (8/12) showed improvements ≥ 10 points.
Platelet response rate was 100% across all genotypes identified in the study (JAK2V617F, CALR, MPL, triple negative and no mutations). Further, 67% (20/30) patients demonstrated a net decrease in mutation allele frequencies including both CALR and JAK2.
100% (5/5) patients with baseline loss of heterozygosity and follow-up samples demonstrated a reduction in homozygous mutant granulocytes and mutant allele frequencies.
"We are delighted to share the most recent data from our ongoing Phase 2 study of bomedemstat in patients with ET, which has notably achieved platelet count reductions to below 400 x 109/L in every patient treated for at least 24 weeks," said Hugh Young Rienhoff, Jr., M.D., Chief Executive Officer of Imago BioSciences. "We are intrigued by the observation in granulocytes that patients homozygous for a driver mutation at baseline showed at follow-up a significant reduction in the proportion of homozygous cells, some reduced to the limit of detection, regardless of the driver mutation. The impact of bomedemstat on mutant stem cell population is currently being assayed. Additionally, we recently conducted an End-of-Phase 2 meeting with the FDA where we aligned on a strategy for the bomedemstat Phase 3 registrational program in ET."

Safety and Tolerability

Bomedemstat was generally well-tolerated with no safety signals identified per the Safety Advisory Board.
The most common adverse events (AEs)(>20%) regardless of causality were dysgeusia, constipation, thrombocytopenia, arthralgia, fatigue, contusion and diarrhea.
There were 38 reported serious adverse events (SAEs), 7 of which were deemed drug-related by the investigator in 5% (4/73) of patients.
20 patients have discontinued treatment, with 10 due to AEs, 1 death from aspiration pneumonia unrelated to bomedemstat, 7 due to withdrawal of consent, 1 due to investigator decision, and 1 due to disease progression.
Details on the Imago ASH (Free ASH Whitepaper) Oral Presentation

Oral Presentation Title: "A Phase 2 Study of the LSD1 Inhibitor Bomedemstat (IMG-7289) for the Treatment of Essential Thrombocythemia (ET)"
Session Name: Myeloproliferative Syndromes: Clinical and Epidemiological: Novel Therapies and Surrogate Endpoints in ET and PV
Presentation Date/Time: Monday, December 12, 2022, at 11:45 AM ET
Location: Ernest N. Morial Convention Center, 217-219
Presenting Author: Harinder Gill, Queen Mary Hospital University of Hong Kong