Abstract 1794: AP26113 is a dual ALK/EGFR inhibitor: Characterization against EGFR T790M in cell and mouse models of NSCLC (2012)

Abstract Background: The EGFR T790M gatekeeper mutation accounts for ∼50% of resistance observed in patients treated with first generation inhibitors that target activated variants of EGFR. Multiple irreversible T790M inhibitors are in development but can exhibit skin and GI toxicity due to co-inhibition of native (endogenous) EGFR, suggesting that T790M-selective agents will be required. Previously, we have identified AP26113 as a potent ALK inhibitor that maintains activity against crizotinib-resistant variants, including the L1196M gatekeeper mutant. Here we further characterize AP26113's activity as a reversible inhibitor of activated and T790M-mutant EGFR. Methods: The activity of AP26113 against native EGFR, or activated forms (delE746_A750 [DEL]) with or without a T790M resistance mutation, was examined in NSCLC as well as engineered Ba/F3 cell lines. EGFR activity was assessed by measuring levels of phosphorylated EGFR, in vitro proliferation measured by MTS assay, and in vivo tumor growth measured in mouse xenografts following daily oral dosing. Results: AP26113 did not inhibit native EGFR phosphorylation in a NSCLC cell line (H358) or in engineered Ba/F3 cells (IC50s &amp;gt;3000 nM). In contrast, potent activity was observed against activated forms of EGFR, with or without the T790M mutation. In Ba/F3 cells expressing EGFR-DEL, AP26113 inhibited EGFR phosphorylation and viability with IC50s of 75 and 114 nM, respectively. In Ba/F3 cells expressing EGFR-DEL/T790M, AP26113 inhibited EGFR phosphorylation and viability with IC50s of 15 and 281 nM, respectively. In a NSCLC line expressing EGFR-DEL (HCC827), AP26113 inhibited EGFR phosphorylation with an IC50 of 62 nM and cell growth with a GI50 of 165 nM. In HCC827 cells expressing EGFR-DEL/T790M AP26113 inhibited EGFR phosphorylation with an IC50 of 59 nM and cell growth with a GI50 of 245 nM. AP26113 also exhibited similar potency against HCC827 cells expressing either EGFR-DEL or EGFR-DEL/T790M in a xenograft model, with daily oral doses of 25 mg/kg or greater leading to tumor regression in both models. Anti-tumor activity that was associated with inhibition of EGFR phosphorylation was also seen in a Ba/F3 EGFR-DEL/T790M tumor model. Conclusions: AP26113 is a potent, reversible inhibitor of activated and T790M-mutant EGFR that does not inhibit the native enzyme. Importantly, orally efficacious doses in mice against activated and T790M-mutant EGFR are similar to those active against crizotinib-resistant ALK variants, suggesting that AP26113 is a dual ALK/mutant EGFR inhibitor with potential to target these two well-defined and important subsets of NSCLC. Based on these data, we recently initiated a Phase 1/2 clinical trial of AP26113 (NCT01449461, www.clinicaltrials.gov) in ALK and EGFR+ NSCLC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1794. doi:1538-7445.AM2012-1794