Abstract LB-232: Potent, novel small molecule inhibitors targeting EGFR L858R/T790M mutation for non-small cell lung cancer
Authors: Sivanandhan Dhanalakshmi , Parikh Payal K. , Sheshachalam Avinash , V Chandregowda , Bhakthavatchalam Rajagopal , Gupta Manish , Giri Sanjeev , V Krishnakumar 
Published: May 2015

Abstract
Introduction: EGFR targeted therapies like Tarceva are very effective initially for non-small cell lung cancer (NSCLC) harboring EGFR activating mutations; but patients eventually develop resistance to these first line inhibitors and in about 50% of the cases, resistance is due to a secondary mutation T790M,leading to decreased affinity of these drugs. In such cases, drugs targeting this secondary mutation will be quite beneficial in improving the quality of life. Also, such drugs could potentially delay the onset of resistance in patients with EGFR activating mutation. In this context, we’ve developed a series of potent small molecule inhibitors (Pyrimidine derivatives) that target EGFR-activating (Exon 19 del and L858R) and resistance mutations and are very selective against wild type EGFR.
Methods: TR-FRET Biochemical assay was performed for assessing the in-vitro enzymatic potency. Cell based mechanistic and functional assays like EGFR autophos assay, cell proliferation and apoptotic assays were used to assess the cellular potency of these inhibitors. HCC827 and xenograft models were used to assess in vivo target engagement and efficacy.
Results: One of the compounds from this series, JIEM-0186, had an IC50 of 0.004 uM against EGFR T790M mutation in the in vitro TR-FRET assay. In cells carrying EGFR activating mutation (HCC827), this compound showed an IC50 of 0.012 uM that is comparable to Tarceva (0.005 uM). In H1975 cells carrying the EGFRT790M mutation, JIEM-0186 had a potency of 0.009 uM in inhibiting cell proliferation. Further JIEM-0186 showed remarkable selectivity against cells carrying wild type EGFR (&gt;200 fold). Afatinib, a pan EGFR inhibitor, has been shown to have an IC50 of 0.09 uM against EGFRT790M with comparable potency on cells carrying wild type EGFR (Li et al., 2008). JIEM-0186 also showed very good selectivity for EGFR over other kinases. In in vivo pharmacokinetics (PK) studies in mice, JIEM-0186 showed good exposure and half life for adequate target coverage. JIEM-0186 showed excellent target engagement in inhibiting EGFR autophos in H1975 xenograft with an ED80 of about 40 mg/kg. JIEM-0186 also showed strong efficacy in H1975 xenograft accounting for 61, 71 and 86 % tumor growth inhibition at 12.5, 25 and 50 mg/kg, BID, PO dosing compared to vehicle control. In mice, MTD of JIEM-0186 was higher than 1000 mg/kg and was well tolerated upon consecutive dosing at 100 mg/kg, PO for 14 days. We are currently evaluating additional compounds from this and another series with similar potency and better PK properties as potential back-ups.
Conclusion: JIEM-0186 and other compounds from this series have the promise to be developed as novel, efficacious and selective small molecule inhibitors for NSCLC with EGFR-activating and resistant mutations, which is still a high unmet medical need.
Citation Format: Dhanalakshmi Sivanandhan, Payal K. Parikh, Avinash Sheshachalam, Chandregowda V, Rajagopal Bhakthavatchalam, Manish Gupta, Sanjeev Giri, Krishnakumar V. Potent, novel small molecule inhibitors targeting EGFR L858R/T790M mutation for non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-232. doi:10.1158/1538-7445.AM2014-LB-232