Catalytic-site competitive inhibitors
These occupy the enzyme's active catalytic pocket directly, blocking the natural substrate from binding or reacting — a mature, well-validated mechanism with many FDA-approved examples, such as imatinib at the ATP-binding site. The tradeoff: catalytic pockets are often highly conserved across related isoforms, giving low selectivity across the enzyme family, and resistance can emerge easily from mutations at key binding-region residues (gatekeeper residues).
Allosteric inhibitors
These bind at a site away from the active center, locking the protein into an inactive conformation instead of directly blocking the catalytic pocket — asciminib is a representative example. That avoids the crowded, conserved catalytic pocket and can achieve very high selectivity, but allosteric sites are harder to find in the first place, and conformational shifts at the target can themselves produce a new form of resistance.
Mutation-site specific inhibitors
These exploit a unique 3D geometry created by a specific mutation to design a molecule with maximum selectivity for the mutant protein while sparing the wild-type version. Vemurafenib, designed against the BRAF V600E mutation, is the classic example; Prelude Therapeutics' JAK2 JH2 inhibitor program targeting the V617F mutation is another public example of the same strategy. The catch: this approach depends heavily on having a high-resolution mutant crystal structure to design against.
Covalent inhibitors
These use a reactive group on the molecule to form an irreversible bond with a nearby residue — typically a cysteine — permanently inactivating the protein. Nirmatrelvir works this way. The risk is off-target reactivity causing irreversible toxicity, and the strategy depends on that cysteine being present at the right position — once EGFR's C797S mutation removes it, this approach stops working for that target entirely. One computational subtlety: covalent inhibitor modeling should treat the non-covalent part of the molecule as entering the pocket first, with the reaction happening afterward.