Published OnlineFirst October 20, 2020; DOI: 10.1158/1078-0432.CCR-20-2278 CLINICAL CANCER RESEARCH | RESEARCH BRIEFS: CLINICAL TRIAL BRIEF REPORT Overcoming MET-Dependent Resistance to Selective RET Inhibition in Patients with RET Fusion–Positive Lung Cancer by Combining Selpercatinib with Crizotinib A C Ezra Y. Rosen1, Melissa L. Johnson2, Sarah E. Clifford3, Romel Somwar4, Jennifer F. Kherani5, Jieun Son3, Arrien A. Bertram3, Monika A. Davare6, Eric Gladstone4, Elena V. Ivanova7, Dahlia N. Henry5, Elaine M. Kelley3, Mika Lin3, Marina S.D. Milan3, Binoj C. Nair5, Elizabeth A. Olek5, Jenna E. Scanlon3, Morana Vojnic4, Kevin Ebata5, Jaclyn F. Hechtman4, Bob T. Li1,8, Lynette M. Sholl9, Barry S. Taylor10, Marc Ladanyi4, Pasi A. Janne€ 3, S. Michael Rothenberg5, Alexander Drilon1,8, and Geoffrey R. Oxnard3 ABSTRACT ◥ Purpose: The RET proto-oncogene encodes a receptor tyrosine Results: MET amplification was identified in posttreatment kinase that is activated by gene fusion in 1%–2% of non–small biopsies in 4 patients with RET fusion–positive NSCLC treated with cell lung cancers (NSCLC) and rarely in other cancer types. selpercatinib. In at least one case, MET amplification was clearly Selpercatinib is a highly selective RET kinase inhibitor that has evident prior to therapy with selpercatinib. We demonstrate that recently been approved by the FDA in lung and thyroid cancers increased MET expression in RET fusion–positive tumor cells causes with activating RET gene fusions and mutations. Molecular resistance to selpercatinib, and this can be overcome by combining mechanisms of acquired resistance to selpercatinib are poorly selpercatinib with crizotinib. Using SPPs, selpercatinib with crizo- understood. tinib were given together generating anecdotal evidence of clinical Patients and Methods: We studied patients treated on the first- activity and tolerability, with one response lasting 10 months. in-human clinical trial of selpercatinib (NCT03157129) who were Conclusions: Through the use of SPPs, we were able to offer found to have MET amplification associated with resistance to combination therapy targeting MET-amplified resistance iden- selpercatinib. We validated MET activation as a targetable mediator tified on the first-in-human study of selpercatinib. These data of resistance to RET-directed therapy, and combined selpercatinib suggest that MET dependence is a recurring and potentially with the MET/ALK/ROS1 inhibitor crizotinib in a series of single targetable mechanism of resistance to selective RET inhibition patient protocols (SPP). in advanced NSCLC. Introduction patient selection. While several combination therapies are approved (e.g., MEK inhibition with BRAF inhibition in BRAF-mutant mela- Combination targeted therapy represents a compelling strategy for þ noma; CDK4/6 inhibition with endocrine therapy in ER breast overcoming drug resistance in metastatic cancer. However, the clinical cancer; refs. 1–4), no drug combination has yet met the standard of development of combination approaches has been challenging due to regulatory approval for effective treatment of resistance to targeted toxicity from combining two agents and the need for appropriate kinase inhibitors (TKI) in genotype-selected patients. Because resis- tance to targeted TKIs is universal, effective strategies to overcome acquired resistance are key to prolonging clinical benefit. To that end, 1Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York. 2Department of Medicine, Sarah Cannon Cancer Center, Nashville, combination approaches remain a compelling investigational strategy – Tennessee. 3Lowe Center for Thoracic Oncology, Dana-Farber Cancer Institute, in oncogene-dependent non small cell lung cancer (NSCLC) with Boston, Massachusetts. 4Department of Pathology, Memorial Sloan Kettering several clinical trials ongoing (5–8). Cancer Center, New York, New York. 5Loxo Oncology, Inc., a wholly owned The RET proto-oncogene encodes a receptor tyrosine kinase which 6 subsidiary of Eli Lilly and Company, Stamford, Connecticut. Oregon Health and is activated by gene fusion in 1%–2% of NSCLC and rarely in many 7 Science University, Portland, Oregon. Belfer Center for Applied Cancer Science, other tumor types. RET gene fusions are bona fide cancer drivers and Dana-Farber Cancer Institute, Boston, Massachusetts. 8Weill Cornell Medical College, New York, New York. 9Department of Pathology, Brigham and they display the key characteristics of oncogene addiction preclini- Women’s Hospital, Boston, Massachusetts. 10Department of Epidemiology and cally (9). Selpercatinib is a highly selective and potent anti-RET TKIs Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York. which has recently reported durable responses in lung and thyroid fi Note: Supplementary data for this article are available at Clinical Cancer cancers, and these responses were maintained regardless of the speci c Research Online (http://clincancerres.aacrjournals.org/). RET alteration or prior TKI use, and also in the setting of the RET V804 “gatekeeper” mutation (10). Selpercatinib was recently approved by E.Y. Rosen and M.L. Johnson contributed equally to this article. A. Drilon and G.R. Oxnard contributed equally to this article. the FDA for use in these cancers. Mechanisms of acquired resistance to treatment with selective RET inhibitors are not well understood. While Corresponding Author: Alexander Drilon, Memorial Sloan Kettering Cancer a secondary mutation in the RET kinase domain has recently been Center, 530 East 74th Street, New York, NY 10021. Phone: 646-888-4206; fi Fax: 646-888–4263; E-mail: [email protected] reported (11), activation of bypass tracts, such as MET ampli cation, also represent a recurring mechanism of resistance to driver genotypes Clin Cancer Res 2020;XX:XX–XX in NSCLC (12, 13). Here we piloted combination therapy to target doi: 10.1158/1078-0432.CCR-20-2278 MET amplification detected in 4 patients with RET-positive NSCLC Ó2020 American Association for Cancer Research. (of a total 79 patients with NSCLC enrolled at all three sites) with AACRJournals.org | OF1 Downloaded from clincancerres.aacrjournals.org on September 28, 2021. © 2020 American Association for Cancer Research. Published OnlineFirst October 20, 2020; DOI: 10.1158/1078-0432.CCR-20-2278 Rosen et al. Preclinical RET-dependent models Translational Relevance RET fusion–positive human bronchioepithelial (HBEC-RET) Molecular mechanisms of acquired resistance to selpercatinib, a cell lines expressing a CCDC6-RET fusion were engineered to highly selective and potent RET kinase inhibitor, are poorly overexpress MET and a patient-derived organoid was also estab- understood. We identified MET amplification as a recurrent lished. These models were subsequently studied to investigate mechanism of resistance to targeted therapy in patients with the role of MET in selpercatinib resistance (see Supplementary non–small cell lung cancer (NSCLC) treated with selpercatinib. Methods). We show that MET amplification is sufficient to cause selpercatinib resistance in vitro, and that the addition of the MET/ALK/ROS1 SPPs of selpercatinib and crizotinib inhibitor crizotinib can rescue this phenotype. We then utilize a Each SPP was sponsored by LOXO and drafted in collaboration series of single-patient protocols to treat these patients with between LOXO and the site primary investigator. Each protocol combination therapy, and this combination treatment showed enrolled a single patient after review by the FDA and approval by clinical activity, with one response lasting 10 months. These data the site IRB. Dosing was individualized per patient and dose escalation suggest that MET dependence is a recurring and potentially was permitted as tolerated up to the established tolerable dose for each targetable mechanism of resistance to selective RET inhibition in drug. Patients initiated combination therapy directly after demon- advanced NSCLC. Prospective clinical trials are needed to validate strating resistance to prior targeted therapy (Table 1; Supplementary these findings and to identify effective combination therapies to Fig. S1). treat acquired resistance to selpercatinib. Results MET-dependent resistance to selpercatinib in patients with resistance to selpercatinib. This was made possible through the use of advanced NSCLC multiple single-patient protocols (SPP) which allowed for the quick Case 1 delivery of potentially effective combination therapy to patients with The first patient was a 36-year-old female former smoker with clear unmet clinical need. stage IV NSCLC metastatic to bone, heavily pretreated. Molecular testing identified a RET rearrangement by break-apart FISH (83% of cells) as well as MET copy-number gain (CNG) by FISH (6 copies). Patients and Methods She initiated treatment with alectinib, an ALK TKI with some Analysis of resistance to selpercatinib degree of anti-RET activity preclinically (14), and progressed in Patients were included in this analysis if they had received less than 2 months. Next-generation sequencing (NGS) analysis of selpercatinib (LOXO-292) for RET-positive NSCLC on the first- plasma circulating cell-free tumor DNA (cfDNA) then identified an in-human study of selpercatinib (NCT03157128) and exhibited EML4-RET fusion (AF 14%; ref. 15). She started treatment with evidence of MET amplification following drug resistance. All selpercatinib and experienced a clinical response (decreased tumor- patients provided written informed consent wherever necessary. related pain