R348

R348 is a novel Janus kinase 3 (JAK3) and spleen tyrosine kinase (Syk) inhibitor developed by Rigel Pharmaceuticals. This compound was formulated as an ophthalmic solution for topical use in dry eye disease and investigated for its immunomodulatory effects via inhibition of JAK3/Syk-dependent pathways. The mechanism involves blocking cytokine signaling critical to immune cell activation and inflammation. In preclinical models, R348 demonstrated efficacy in reducing acute cardiac allograft rejection by suppressing Th1/Th2 responses and inflammatory cytokines. Clinical development reached Phase 2 trials for dry eye disease but was discontinued after failing to meet efficacy endpoints. The active metabolite of the prodrug is known as R333.

Other names

5-Fluoro-N-(4-methyl-3-propionylaminosulfonylphenyl)-N'-(4-(prop-2-ynyloxy)phenyl)-2,4-pyrimidinediamine