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

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

Discovery of a Noncovalent, Mutant-Selective Epidermal Growth Factor Receptor Inhibitor

Inhibitors targeting the activating mutants of the epidermal growth factor receptor (EGFR) have found success in the treatment of EGFR mutant positive non-small-cell lung cancer. A secondary point mutation (T790M) in the inhibitor binding site has been linked to the acquired resistance against those first generation therapeutics. Herein, we describe the lead optimization of a series of reversible, pan-mutant (L858R, del_746–750, T790M/L858R, and T790M/del_746–750) EGFR inhibitors. By use of a noncovalent double mutant (T790M/L858R and T790M/del_746–750) selective EGFR inhibitor (<b>2</b>) as a starting point, activities against the single mutants (L858R and del_746–750) were introduced through a series of structure-guided modifications. The in vitro ADME-PK properties of the lead molecules were further optimized through a number of rational structural changes. The resulting inhibitor (<b>21</b>) exhibited excellent cellular activity against both the single and double mutants of EGFR, demonstrating target engagement in vivo and ADME-PK properties that are suitable for further evaluation. The reversible, noncovalent inhibitors described complement the covalent pan-mutant EGFR inhibitors that have shown encouraging results in recent clinical trials