Mechanisms of resistance to EGFR TKIs and related treatment strategies Rafal Dziadziuszko Medical University of Gdańsk, Poland 16th European Congress „Perspectives in Lung Cancer” Torino, 06 – 07 March 2014

Disclosure Astra-Zeneca Roche Boehringer-Ingelheim Pfizer Clovis Oncology

Currently used EGFR TKIs Gefitinib and erlotinib (reversible, 1st generation EGFR TKIs) Afatinib and dacomitinib* (irreversible, 2nd generation EGFR TKIs) CO-1686* and AZD9291* (Irreversible, 3rd generation mutation-specific EGFR TKIs) * Investigational

When should we exepect relapse?

Progression-free survival First-line trials of EGFR tyrosine kinase inhibitors vs. chemotherapy in pts with EGFR mutations EGFR TKI Comparator N (Total) EGFR mut-positive Response rate (%) Progression-free survival (months) IPASS1,2 Gefitinib Carboplatin/ paclitaxel 1217 261 71 vs 47 p=0.0001 9.5 vs 6.3 HR 0.48 (0.36‒0.64) First-SIGNAL3 Gemcitabine/ cisplatin 309 42 85 vs 38 p=0.002 8.0 vs 6.3 HR 0.54 (0.27–1.10) NEJ0024 224 74 vs 31 p<0.001 10.8 vs 5.4 HR 0.30 (0.22–0.41) WJTOG-34055 Cisplatin/ docetaxel 172 62 vs 32 p<0.0001 9.2 vs 6.3 HR 0.5 (0.34–0.71) OPTIMAL6 Erlotinib Gemcitabine/ carboplatin 154 83 vs 36 13.1 vs 4.6 HR 0.16 (0.10–0.26) EURTAC7 Chemotherapy 173 58 vs 15 9.7 vs 5.2 HR 0.37 (0.25–0.54) LUX-LUNG 38 Afatinib Pemetrexed/ cisplatin 345 56 vs 23 p<0.0001 11.1 vs 6.9 HR 0.58 (0.43–0.78) LUX-LUNG 69 364 67 vs 23 p<0.0001 11.0 vs 5.6 HR 0.28 (0.20–0.39) 1. Mok T et al., N Engl J Med 2009;361:947–957; 2. Fukuoka M et al., J Clin Oncol 2011; 29:2866‒2874; 3. Han J-Y et al., J Clin Oncol 2012; 30:1122‒128; 4. Maemondo M et al., N Engl J Med 2010;362:2380–2388; 5. Mitsudomi T et al., Lancet Oncol 2010;:121–128; 6. Zhou C et al., Lancet Oncol 2011;12:735‒742; 7. Rosell R et al., Lancet Oncol 2012;13:239–246; 8. Yang JC et al., J Clin Oncol 2012;30 (Suppl. 16):LBA 7500, Wu Y et al., Lancet 2014; 15:213. NR = not reported

PFS in LUX-Lung 3 and 6 trials Afatinib PFS in LUX-Lung 3 and 6 trials LUX-Lung 31 (n=345) Afatinib vs Pem/Cis LUX-Lung 62 (n=364) Afatinib vs Gem/Cis Median PFS 11.1 vs 6.9 11.0 vs 5.6 HR for PFS 0.58, P<0.001 0.28, P<0.0001 12-month PFS3 47% vs 22% 47% vs 2% 1.0 47% 2% 47% 22% 0.8 0.6 Afatinib LUX-Lung 6 Gem/cis LUX-Lung 6 PFS (probability) 0.4 Afatinib LUX-Lung 3 Pem/cis LUX-Lung 3 0.2 0.0 3 6 9 12 15 18 21 24 27 Months Number at risk: Afatinib (LL3) 230 180 151 120 77 50 31 10 3 0 Pem/cis (LL3) 115 72 41 21 11 7 3 2 0 0 Afatinib (LL6) 242 208 166 126 89 60 35 12 4 0 Gem/cis (LL6) 122 70 25 8 1 0 0 0 0 0 1. Sequist et al. J Clin Oncol. 2013;31:3327; 2. Wu et al. Lancet Oncol. 2014;15:213.

NSCLC M+: EGFR-TKI acquired resistance Baseline Tumor regression Progression (median 10 months) Disease Flare: ~25% of patients: Hospitalization and/or death attributable to disease progression after discontinuation of gefitinib or erlotinib and before initiation of study drug Slide courtesy Prof. F. Cappuzzo

What are acquired resistance mechanisms to EGFR TKIs?

Aqcuired resistance Pharmacological Biological Compliance Absorption Distribution Metabolism Excretion Biological Alterations in drug target Bypass signaling Phenotypic changes Downstream signaling

Absorption and metabolism - examples Administration of proton-pump inhibitor omeprazole with erlotinib decreases erlotinib exposure (AUC) and maximal concentration (Cmax) by 46% and 61%, respectively. Ketoconazol administration with erlotinib increases erlotinib exposure by 86% through inhibition of CYP3A4 Smoking leads to two-fold lower steady-state concentrations of erlotinib through induction of CYPA1 and CYPA2

Drug distribution – CNS as a sanctuary site Mean CSF CSF penetration concentration Gefitinib 3.7ng/mL 1.13% Erlotinib 28.7ng/mL 2.77% Up to 20% of patients develop symptomatic CNS progression while on gefitinib or erlotinib Togashi Y et al., Cancer Chemother Pharmacol 2012 11

Comprehensive review of EGFR TKI pharmacology

Biological mechanisms of resistance

Biological mechanisms of resistance Alterations in drug target Bypass signaling Phenotypic changes Downstream signaling Camidge, D. R. et al. (2014) Acquired resistance to TKIs in solid tumours: learning from lung cancer Nat. Rev. Clin. Oncol. doi:10.1038/nrclinonc.2014.104

Biological mechanisms of resistance - Implication for subsequent therapies - Alterations in drug target - Bypass signaling - Phenotypic changes - Downstream signaling Yu, H. et al. Clin Cancer Res. 20: 5898, 2014

Biological mechanisms of resistance T790M resistance mutations (~40-60%) EGFR T790M+ cells are usually present as a minor clone in the initial tumor specimen Clinical progression is related to clonal selection and outgrowth of EGFR T790M+ population of cells Substitution of a bulky methionine residue for threonine at gatekeeper 790 position is believed to cause steric interference with binding of first-generation TKIs to ATP-binding pocket of EGFR tyrosine kinase.

Prognostic significance of T790M resistance mutations at progression on gefitinib or erlotinib – PFS and OS Oxnard G et al., Clin Cancer Res 17: 1616; 2011

Prognostic significance of T790M resistance mutations at progression on gefitinib or erlotinib – overall survival Hata A et al., Cancer 119: 4325; 2013

Biological mechanisms of resistance MET amplification (~5 - 25%) MET encodes hepatocyte frowth factor (HGF) receptor Amplification of MET is observed in ~ 5 – 25% of EGFR M+ tumors with acquired resistance to gefitinib or erlotinib Activation of MET through enhanced ligand stimulation appears to have similar effect

Biological mechanisms of resistance MET amplification Engelman J et al., Science 2007; 10.1126/science.1141478

Biological mechanisms of resistance MET amplification Suda et al., Clin Cancer Res. 16:5489; 2010

Biological mechanisms of resistance HGF plasma levels Tanaka H et al., Int J Cancer 129:1410; 2011

Biological mechanisms of resistance HER2 amplification (~8-13%) Takezawa K et al., Cancer Discov. 2: 922; 2012

Biological mechanisms of resistance Transformation to SCLC (~2-14%) Observed in absence of SCLC component in pre-treatment biopsy SCLC at progression on EGFR TKI retained initial EGFR mutations and were responsive to platinum-etoposide Exact molecular mechanism unknown (Myc amplification?) Sequist LV et al., Sci Transl Med. 2011;3:75ra26

Biological mechanisms of resistance Epithelial-to mesenchymal (EMT) transition (<10%?) Typical phenotype: loss of E-cadherin and beta-catenin, gain of vimentin and N-cadherin as evaluated by immunohistochemistry Postulated molecular mechanisms: NOTCH-1 upregulation, TGF-beta overexpression, MET or AXL activation Sequist LV et al., Sci Transl Med. 2011;3:75ra26; Cortot and Janne, Eur Resp Rev 2013; 22:565

Biological mechanisms of resistance to afatinib Preclinical and clinical data are scarce but indicate that T790M resistance mutation is also a resistance mechanism for afatinib Other reports suggest transition to high-grade neuroendocrine histology Kim Y et al. Mol Cancer Ther 2012;11:784

How accurate is clinical detection of mechanisms of resistance?

Accuracy of T790M status assessment at progression In 169 patients with acquired resistance to 1st and 2nd generation EGFR TKIs, 60 patients underwent more than 1 biopsy at progression T790M mutation status was discordant in 15/60 (=25%) of these patients Piotrowska Z, et al. Chicago Multidisciplinary Symposium in Thoracic Oncology 2014. Abstract 11

EGFR T790M mutation detection in plasma of lung cancer patients

Plasma EGFR mutation data from a phase I/II trial of rociletinib (CO-1686) EGFR mutation detection by NSCLC disease classification (n = 73) Dziadziuszko R, Karlovich C et al., AACR 2014 abstract 5587

Best Overall Response: SD Plasma EGFR mutation data from a phase I/II trial of rociletinib (CO-1686) Patient A (600 mg QD) Best Overall Response: SD Dziadziuszko R, Karlovich C et al., AACR 2014 abstract 5587

Best Overall Response: SD Plasma EGFR mutation data from a phase I/II trial of rociletinib (CO-1686) Patient B (400 mg TID) Best Overall Response: SD Dziadziuszko R, Karlovich C et al., AACR 2014 abstract 5587

Take-home messages Acquired resistance to EGFR TKIs develops through pharmacological and biological mechanisms Understanding of clinical pharmacology (ADME) of EGFR TKIs is essential for practictioners Most common mechanisms of biological resistance include T790M gatekeeper mutation, MET and HER2 amplification, SCLC and EMT transformation, and PIK3CA mutations. Different mechanisms may be present in different metastatic sites Plasma EGFR mutation detection and monitoring, including T790M, is close to clinical application

Take-home messages Diehl F. Nat Med 14:985; 2008