PRN1008 (rilzabrutinib, Sanofi) is an oral, reversible covalent Bruton’s tyrosine kinase (BTK) inhibitor in a Ph. III trial for immune thrombocytopenia. A simultaneously published inhibitor, PRN473, is in development as a topical treatment for atopic dermatitis. Following target discovery in 1993, and subsequent approval of the first [...]

The accelerated approvals of Ras(OFF)-targeting KRAS G12C inhibitors sotorasib and adagrasib, decades in the making, marked the beginning of a new phase of KRAS drug discovery. While an increasing number of follow-on KRAS inhibitors are emerging with similar mechanisms of action, Revolution Medicines’ 2023 Molecule of the Year Nominee, RMC-6291, is representative of a completely novel approach that could become a strong addition to the clinical toolbox for KRAS, but also serves as proof-of-concept for a new class of small molecule therapeutics entirely.

Pfizer’s ritlecitinib, a first-in-class, selective, oral covalent inhibitor of JAK3 and the TEC family of kinases, was FDA-approved in June 2023 for the treatment of severe alopecia areata. Ritlecitinib derives its JAK-family kinase selectivity from the covalent modification of a unique cysteine on JAK3. This annotation reviews the discovery of ritlecitinib, highlighting the interpretation of selectivity assays, the PK optimization, the evolution of the JAK3 therapeutic hypothesis, and how this 2023 Molecule of the Year nominee has become a classic case study for covalent drug discovery.

Sovleplenib (HMPL-523) is an orally bioavailable Syk inhibitor being developed by HUTCHMED and is currently in Ph. II and Ph. III clinical trials for several autoimmune diseases. Derived from an HTS hit and SAR optimization, the discovery story of sovleplenib serves as an excellent case study on how to design a next-generation Syk inhibitor devoid of off-target kinase activity, mitigated hERG activity, and more.

Jecure’s JT001 is a selective inhibitor of NLRP3 inflammasome and among the earlier compounds in this now highly competitive space. In 2018, Genentech bought Jecure Therapeutics for an undisclosed amount, gaining access to Jecure’s NLRP3 inhibitor JT001. While there are many other NLRP3 inhibitors now in the space, JT001 is an interesting example of an initial attempt to overcome liver toxicity with well-known NLRP3 inhibitor MCC950. However, the molecule ran into its own kidney toxicity issues, making this an intriguing toxicology case study.