R289 is an investigational, oral, inhibitor of interleukin receptor-associated kinases 1 and 4 (IRAK1/4), being studied as a potentially differentiated approach to treating lower-risk MDS

SOUTH SAN FRANCISCO, CA, USA I December 15, 2022 I Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced it dosed the first patient in its Phase 1b study of R289, an IRAK1/4 dual inhibitor, in patients with lower-risk myelodysplastic syndromes (MDS) who are refractory or resistant to prior therapies.

“R289’s dual inhibition of IRAK1 and IRAK4 has the potential to provide a more robust suppression of the pro-inflammatory environment that causes lower-risk MDS by blocking inflammatory cytokine production,” said Wolfgang Dummer, M.D., Ph.D., Rigel’s chief medical officer. “The initiation of our Phase 1b study demonstrates our continued ability and commitment to bringing innovative, investigational candidates for hematology-oncology indications into the clinic. We believe R289 may represent a promising new approach to treating patients with lower-risk MDS and look forward to investigating R289 further in this Phase 1b study.”

Rigel’s open-label, Phase 1b study of R289 is expected to enroll approximately 22 patients with lower-risk MDS who are refractory or resistant to prior therapies (NCT05308264). The primary objective of the study is safety, with secondary and exploratory objectives to assess preliminary efficacy and characterize the pharmacokinetic (PK) and pharmacodynamic (PD) profile of R289. The safety and efficacy data from this Phase 1b study, along with the safety and PK/PD data from the completed first-in-human (FIH) study in heathy volunteers, are intended to be used to determine the recommended Phase 2 dose for future clinical development of R289 targeting lower-risk MDS.  

About R2891
R289 is a prodrug of R8351, an IRAK1/4 dual inhibitor, which has been shown in preclinical studies to block inflammatory cytokine production in response to toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) family signaling. TLRs and IL-1Rs play a critical role in the innate immune response and dysregulation of these pathways can lead to various inflammatory conditions. Chronic stimulation of both these receptor systems is thought to cause the pro-inflammatory environment in the bone marrow responsible for persistent cytopenias in lower-risk MDS patients2.

About Rigel
Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) is a biotechnology company dedicated to discovering, developing and providing novel small molecule drugs that significantly improve the lives of patients with hematologic disorders, cancer and rare immune diseases. Founded in 1996, Rigel is based in South San Francisco, California. For more information on Rigel, the Company’s marketed product and pipeline of potential products, visit www.rigel.com

1. R289 and R835 are investigational compounds not approved by the FDA
2. Sallman, DA et al. Unraveling the Pathogenesis of MDS: The NLRP3 Inflammasome and Pyroptosis Drive the MDS Phenotype. Front Oncol. June 16, 2016. DOI: https://doi.org/10.3389/fonc.2016.0015

SOURCE: Rigel Pharmaceuticals