Acrylamide Bioisosterism: Alkenyl Aromatic Heterocycles as Reactivity-Tunable Warheads for Covalent BTK Inhibitors

Cysteine-targeted covalent inhibitors have traditionally used a few electrophilic warheads, with Michael acceptors being the most common. However, their stability and selectivity in physiological conditions require enhancement. Inspired by the principles of bioisosterism, we have developed an innovative class of tunable electrophilic warheads by substituting the conventional acrylamide moiety in covalent inhibitors with alkenyl aromatic heterocycles. This approach aimed to enhance selectivity and reactivity. We synthesized a library of these warheads and integrated them into the BTK inhibitor ibrutinib. The resulting compounds showed strong and selective BTK inhibition, effectively blocking B-cell receptor signaling and cancer cell growth. Key derivatives specifically bound to the Cys481 residue of BTK, as confirmed by mass spectrometry and cellular tests. A lead compound demonstrated good pharmacokinetics and significant antitumor effects in a mouse model, highlighting this bioisosteric strategy as a promising avenue for covalent drug development.