A covalent fragment-based strategy targeting a novel cysteine to inhibit activity of mutant EGFR kinase.

Several generations of ATP-competitive anti-cancer drugs that inhibit the activity of the intracellular kinase domain of the epidermal growth factor receptor (EGFR) have been developed over the past twenty years. The first-generation of drugs such as gefitinib bind reversibly and were followed by a second-generation such as dacomitinib that harbor an acrylamide moiety that forms a covalent bond with C797 in the ATP binding pocket. Resistance emerges through mutation of the T790 gatekeeper residue to methionine, which introduces steric hindrance to drug binding and increases the Km for ATP. A third generation of drugs, such as osimertinib were developed which were effective against T790M EGFR in which an acrylamide moiety forms a covalent bond with C797, although resistance has emerged by mutation to S797. A fragment-based screen to identify new starting points for an EGFR inhibitor serendipitously identified a fragment that reacted with C775, a previously unexploited residue in the ATP binding pocket for a covalent inhibitor to target. A number of acrylamide containing fragments were identified that selectively reacted with C775. One of these acrylamides was optimized to a highly selective inhibitor with sub-1 µM activity, that is active against T790M, C797S mutant EGFR independent of ATP concentration, providing a potential new strategy for pan-EGFR mutant inhibition.

The discovery and optimisation of pyrido[2,3-d]pyrimidine-2,4-diamines as potent and selective inhibitors of mTOR kinase.

We describe a novel series of potent inhibitors of the kinase activity of mTOR. The compounds display good selectivity relative to other PI3K-related kinase family members and, in cellular assays, inhibit both mTORC1 and mTORC2 complexes and exhibit good antiproliferative activity.

Arylpiperazines displaying preferential potency against chloroquine-resistant strains of the malaria parasite Plasmodium falciparum.

Arylpiperazines in which the terminal secondary amino group is unsubstituted were found to display a mefloquine-type antimalarial behavior in being significantly more potent against the chloroquine-resistant (W2 and FCR3) strains of Plasmodium falciparum than against the chloroquine-sensitive (D10 and NF54) strains. Substitution of the aforementioned amino group led to a dramatic drop in activity across all strains as well as abolition of the preferential potency against resistant strains that was observed for the unsubstituted counterparts. The data suggest that unsubstituted arylpiperazines are not well-recognized by the chloroquine resistance mechanism and may imply that they act mechanistically differently from chloroquine. On the other hand, 4-aminoquinoline-based heteroarylpiperazines in which the terminal secondary amino group is also unsubstituted, were found to be equally active against the chloroquine-resistant and chloroquine-sensitive strains, suggesting that chloroquine cross-resistance is not observed with these two 4-aminoquinolines. In contrast, two 4-aminoquinoline-based heteroarylpiperazines are positively recognized by the chloroquine resistance mechanism. These studies provide structural features that determine the antimalarial activity of arylpiperazines for further development, particularly against chloroquine-resistant strains.