Phase 1b trial of IRAK 1/4 inhibition for low-risk myelodysplastic syndrome refractory/resistant to prior therapies.

person Guillermo Garcia-Manero The University of Texas MD Anderson Cancer Center, Houston, TX info_outline Guillermo Garcia-Manero, Lewis R. Silverman, Mikkael A. Sekeres, Lucy Yan

Authors person Guillermo Garcia-Manero The University of Texas MD Anderson Cancer Center, Houston, TX info_outline Guillermo Garcia-Manero, Lewis R. Silverman, Mikkael A. Sekeres, Lucy Yan Organizations The University of Texas MD Anderson Cancer Center, Houston, TX, Icahn School of Medicine at Mount Sinai, New York, NY, University of Miami Miller School of Medicine, Miami, FL, Rigel Pharmaceuticals, Inc., South San Francisco, CA Abstract Disclosures Research Funding Rigel Pharmaceuticals, Inc. (Contact person: Leslie Todd) Background: Chronic stimulation of both the interleukin-1 receptor (IL-1R) and toll-like receptors (TLRs) in myeloid progenitors is thought to promote a proinflammatory environment in the bone marrow that causes persistent cytopenia in patients with low-risk myelodysplastic syndrome (LR-MDS). The serine/threonine kinases IRAK1 and IRAK4 are critical for the signaling downstream of IL-1R and most TLRs promote production of proinflammatory cytokines and NLRP3 inflammasome-driven pyroptosis, leading to bone marrow inflammation and cell death. IRAK1/4 is a potential target for inhibition for the treatment of LR-MDS by decreasing inflammation and cell death within the bone marrow, allowing for restoration of hematopoiesis. R289 is a prodrug for R835, a potent and selective inhibitor of IRAK1 and IRAK4 kinases. The safety and pharmacokinetic properties of R289/R835 were evaluated in a phase 1 study in healthy volunteers (Study C-906289-001). R289 was well tolerated with no serious or severe adverse events (AEs) reported. Most AEs were mild and transient; the most common AEs (mild/moderate) were headache and GI disturbance. Overall, the study supported the further evaluation of R289. An open-label, phase 1b study to determine the tolerability and preliminary efficacy of R289 for patients with LR-MDS refractory to prior therapies is currently enrolling patients. Methods: The R289 phase 1b open label, single arm, multi-center study (NCT05308264) includes a dose escalation phase (up to 24 patients) and a dose expansion phase (up to 10 patients). Inclusion criteria for both phases: patients ≥18 years with a definitive diagnosis of LR-MDS. Exclusion criteria include prior MDS treatment(s) within 4 weeks of study treatment. Dose Escalation Phase: A 3+3 dose escalation design will be used to determine the maximum tolerated dose (MTD). An initial R289 dose of 250 mg qd, will be given orally, with or without food, progressing to 1 g qd with dose limiting toxicity (DLT) assessed at each dose level. The DLT evaluation period will be 28 days. After completion, patients without DLTs may remain at their respective dose levels if clinical benefit continues without toxicity. Dose Expansion Phase: R289 will be administered to up to 10 additional patients with LR-MDS at a dose not exceeding the MTD in the dose escalation phase. The primary endpoint is safety and tolerability of R289. Secondary endpoints include preliminary efficacy and pharmacokinetics of R289. Statistical analyses will be primarily descriptive. The trial is currently ongoing at 9 US sites. Clinical trial information: NCT05308264.

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