Noncovalent Mutant Selective Epidermal Growth Factor Receptor Inhibitors: A Lead Optimization Case Study

Abstract

Because of their increased activity against activating mutants, first-generation epidermal growth factor receptor (EGFR) kinase inhibitors have had remarkable success in treating non-small-cell lung cancer (NSCLC) patients, but acquired resistance, through a secondary mutation of the gatekeeper residue, means that clinical responses only last for 8-14 months. Addressing this unmet medical need requires agents that can target both of the most common double mutants: T790M/L858R (TMLR) and T790M/del(746-750) (TMdel). Herein we describe how a noncovalent double mutant selective lead compound was optimized using a strategy focused on the structure-guided increase in potency without added lipophilicity or reduction of three-dimensional character. Following successive rounds of design and synthesis it was discovered that cis-fluoro substitution on 4-hydroxy- and 4-methoxypiperidinyl groups provided synergistic, substantial, and specific potency gain through direct interaction with the enzyme and/or effects on the proximal ligand oxygen atom. Further development of the fluorohydroxypiperidine series resulted in the identification of a pair of diastereomers that showed 50-fold enzyme and cell based selectivity for T790M mutants over wild-type EGFR (wtEGFR) in vitro and pathway knock-down in an in vivo xenograft model.

Design, synthesis, and evaluation of A-ring-modified lamellarin N analogues as noncovalent inhibitors of the EGFR T790M/L858R mutant

“…[16][17][18] Thus, new EGFR-TKIs that do not rely on covalent bond formation with Cys797 for potency are needed. [19][20][21] Lamellarins are DOPA-derived marine natural products with a unique polyaromatic structure (Fig. 2).…”

The marine-derived pachycladin diterpenoids as novel inhibitors of wild-type and mutant EGFR

“…This may explain the negligible effect of these mutations on 1 ’s EGFR inhibitory activity in kinase assays. Although non-covalent inhibition of T790M mutant sounds like attractive strategy for overcoming the acquired drug resistance whilst lacking the confounding off-target toxicity due to irreversible EGFR inhibition, brigatinib has been the only known non-covalent EGFR T790M inhibitor [57]. Unfortunately, brigatinib is a dual anaplastic lymphoma kinase (ALK)/EGFR inhibitor and the primary focus of its clinical applications appears to be in ALK-driven lung cancers [57].…”

“…Although non-covalent inhibition of T790M mutant sounds like attractive strategy for overcoming the acquired drug resistance whilst lacking the confounding off-target toxicity due to irreversible EGFR inhibition, brigatinib has been the only known non-covalent EGFR T790M inhibitor [57]. Unfortunately, brigatinib is a dual anaplastic lymphoma kinase (ALK)/EGFR inhibitor and the primary focus of its clinical applications appears to be in ALK-driven lung cancers [57]. These data renders 1 as one of the novel reversible EGFR T790M mutant inhibitors known to date, with possible therapeutic potential to prevent relapse and recurrences in EGFR-dependent malignancy patients after the successful completion of gefitinib or erlotinib regimen.…”

Targeting EGFRL858R/T790M and EGFRL858R/T790M/C797S resistance mutations in NSCLC: Current developments in medicinal chemistry

“…For this reason, the aminopyrimidine noncovalent mutant-selective EGFR T790M inhibitors were further optimized by Heald et al with the aim of increasing the inhibitory potency without added lipophilicity. 87 One of the most potent compounds, 26e (Figure 21), bearing a cis-fluorohydroxypiperidine, a hydroxyethyl group, and a trifluoropropyl group displayed surprising potency against EGFR T790M/L858R and EGFR T790M/del (746-750) , with 125-fold selectivity over EGFR WT and promising efficacy in a xenograft model. In order to improve the activity against the activating single and double mutants of EGFR, the substituted piperidine was replaced by an N-alkylsulfonylpyrazole, leading to one of the most potent compounds 26f.…”