Activating point mutations in Anaplastic Lymphoma Kinase (ALK) have positioned ALK as the only mutated oncogene tractable for targeted therapy in neuroblastoma. Cells with these mutations respond to lorlatinib in pre-clinical studies, providing the rationale for a first-in-child Phase 1 trial (NCT03107988) in patients with ALK-driven neuroblastoma. To track evolutionary dynamics and heterogeneity of tumors, and to detect early emergence of lorlatinib resistance, we collected serial circulating tumor DNA samples from patients enrolled on this trial. Here we report the discovery of off-target resistance mutations in 11 patients (27%), predominantly in the RAS-MAPK pathway. We also identify newly acquired secondary compound ALK mutations in 6 (15%) patients, all acquired at disease progression. Functional cellular and biochemical assays and computational studies elucidate lorlatinib resistance mechanisms. Our results establish the clinical utility of serial circulating tumor DNA sampling to track response and progression and to discover acquired resistance mechanisms that can be leveraged to develop therapeutic strategies to overcome lorlatinib resistance.

There are several large-scale efforts to compare the sensitivities of tumor cells to chemotherapeutic drugs and small-molecule pathway probes. However, to date, none of these profiling efforts systematically probed malignant peripheral nerve sheet tumors (MPNST). We initiated a database of drug sensitivities of MPNST as part of a course in high-throughput screening. We first developed a panel of 130 drugs highly relevant to neurofibromatosis (NF1 and NF2) that included a comprehensive set of MEK, RAF, RAS, FTI, PAK, ERK inhibitors, a representative set of drugs against many other cancer pathways including Wnt, Hedgehog, p53, EGF, HDAC, as well as classical cytotoxic agents such as doxorubicin and taxol. Many of the drugs in our panel are in clinical trials themselves, or closely related to drugs in trials for NF1. The drugs were tested against cells in 384-well plates at eight concentrations ranging from .004 μM to 10 μM. Cells were allowed to attach overnight, incubated for 72 hours with drugs, and then analyzed for ATP content using ATPlite. To date, we have profiled nine MPNST cell lines (ST88-14, ST88-3, 90-8, SNF02.2, STS26, T265, S462TY, SNF96.2, SNF94.3) and one NF2 Schwannoma cell line (HEI193). We also tested several cell lines that were tested in other screens so that we can compare our results to the other databases. The IC50 was calculated as a common measure of how effective each drug is using GraphPad Prism software. NF1 cells were distinguished from NF2 cells and STS26 cells (a spontaneous MPNST cell line derived from a patient who did not have NF1) by their strong sensitivity to MEK and Bromodomain inhibitors. Some drugs, including cytotoxic agents, Pak inhibitors, and HDAC inhibitors, were broadly toxic, inhibiting growth regardless of NF1 and NF2 status. None of the drugs in our panel exclusively inhibited HEI193 cells. With this study we initiated a database to archive the drug sensitivities of NF1 and NF2 cells that will be expanded in future versions of our course. Sponsored by Children's Tumor Foundation. Citation Format: Jianman Guo, Michael Grovola, Grace Coggins, Patrick Duggan, Jiale Huang, Claire Song, Gabriela Witek, Danny Lin, Hong Xie, David Schultz, Simon Berritt, Jeffrey Field. The NF1 and NF2 pharmacome project, a course in high-throughput screening to identify targets and profile the sensitivity of MPNST cells to candidate drugs [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr A29.

OBJECTIVES/GOALS: Neuroblastoma (NB) is an embryonal cancer of the sympathetic nervous system that affects mostly infants and young children. The complex genetic background present across NB patients results in diverse clinical response and difficulty in individualizing therapy. Currently, NB patients undergo a regimen of genotoxic chemotherapeutics, radiation therapy, and new immunotherapy that, while effective, has significant side effects, including excruciating pain. One promising avenue for targeted therapy in neuroblastoma focuses on anaplastic lymphoma kinase (ALK), a cell surface neural receptor tyrosine kinase. We previously identified activating point mutations within the tyrosine kinase domain of ALK as the primary cause of hereditary NB, and we and others subsequently showed that these same alterations are the most common somatic single-nucleotide mutations in the sporadic forms of the disease. Crizotinib, a first-generation small molecule ATP-competitive inhibitor of the ALK tyrosine kinase, showed limited anti-tumor activity in patients with relapsed NB harboring ALK F1174 and F1245 mutations. We have demonstrated that lorlatinib, a novel ATP-competitive ALK inhibitor, overcomes this de novo resistance in preclinical models of ALK-driven NB. Recent clinical trials with lorlatinib in patients with non-small cell lung cancer harboring an ALK fusion, and in patients with NB harboring ALK mutations show the emergence of multiple or compound ALK mutations as a mechanism of resistance. We postulate that these compound mutations disrupt the interaction between and ALK and cause resistance. In this study, we employ a computational approach to model mutated ALK in complex with lorlatinib as well as ATP to understand whether the new mutations alter the affinity or mode of lorlatinib/ATP binding to ALK, and thus cause suboptimal ALK inhibition. METHODS/STUDY POPULATION: We employ methods in computational structural biology and drug design, primarily based on molecular modeling, molecular dynamics (MD), and molecular docking. Based on existing crystal structures of wildtype ALK, we model the mutations and perform MD simulations in order to characterize the activation state of the protein as well as perform ensemble docking calculations to assess the binding affinities and modes in ALK-lorlatinib and ALK-ATP complexes. RESULTS/ANTICIPATED RESULTS: We expect that the compound mutations cause resistance to lorlatinib either by lowering protein affinity for the drug or increasing the affinity for ATP. Alternatively, the compound mutations may disrupt the protein activation state, in which case ALK may no longer be active, and another protein/pathway could be driving the resistance. DISCUSSION/SIGNIFICANCE OF IMPACT: The results of this study will enable the understanding of the mechanism of resistance to lorlatinib and facilitate the design of new ALK inhibitors, or help develop more optimal and mechanism-guided therapies aimed to overcome the resistance.