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.

The Bristol Myers Squibb (BMS) HPK1 kinase inhibitor, “compound 24” is an oral tool compound intended for cancer immunotherapy, with >50x selectivity against family members including GLK. The starting point was an IRAK4 kinase inhibitor identified from historical kinome selectivity data. A homology-model based on MST1 was used for [...]

Zilucoplan is a macrocyclic peptide-containing drug with 15 amino acids in total, targeting the challenging-to-drug C5 complement protein and formulated for self-administered once-daily SC injection. In Sept. 2023, zilucoplan received its first global approval in Japan, followed in Oct. 2023 by FDA approval for gMG patients who are AChR antibody-positive, making zilucoplan the first drug derived from mRNA display for cyclic peptides to be approved. This case study discusses how zilucoplan was discovered and why it’s an important scientific milestone for the industry.

Kymera's KT-474 is the first oral degrader to demonstrate activity in clinical trials outside cancer and Sanofi recently started a Ph. II trial with the molecule in AD, restoring life to IRAK4 as an immunology target. This article highlights why Kymera’s KT-474 program is scientifically notable, including how it differentiates from small molecule inhibitors, potential competitiveness with biologics, the first reported cryo-EM ternary complex of a heterobifunctional degrader, and why this 2023 Molecule of the Year Nominee will likely be considered a “landmark in drug discovery” for some time.

Zunsemetinib (ATI-450, CDD-450) is a p38α- MK2 complex inhibitor discovered by Confluence Technologies and developed by Confluence spinout, Aclaris Therapeutics. The molecule has a unique molecular glue-like mechanism of action that held promise in immunology, but sadly recent results have led to its discontinuation. This article reviews the target, its mechanism, and why it mattered.