SIR9900

SIR9900 is a potent, selective, and CNS-penetrable small molecule inhibitor of receptor-interacting serine/threonine kinase 1 (RIPK1), developed by Sironax Ltd. It is designed to treat a range of neurodegenerative, autoimmune, and inflammatory conditions by modulating RIPK1-mediated necroptosis and inflammatory signaling. The drug has demonstrated high blood-brain barrier permeability, with a cerebrospinal fluid to unbound plasma ratio of 1.15, making it a candidate for central nervous system disorders such as Alzheimer's disease, multiple sclerosis, and amyotrophic lateral sclerosis (ALS). In Phase 1 clinical trials, SIR9900 showed favorable safety and tolerability, achieving approximately 90% peripheral target engagement and sustained RIPK1 inhibition.