Crizotinib-Resistant ROS1 Mutations Reveal a Predictive Kinase Inhibitor Sensitivity Model for ROS1- and ALK-Rearranged Lung Cancers

Scientific Advances in Thoracic Oncology 2016

Lung cancer care is rapidly changing with advances in genomic testing, the development of next-generation targeted kinase inhibitors, and the continued broad study of immunotherapy in new settings and potential combinations. The International Association for the Study of Lung Cancer and the Journal of Thoracic Oncology publish this annual update to help readers keep pace with these important developments. Experts in thoracic cancer and care provide focused updates across multiple areas, including prevention and early detection, molecular diagnostics, pathology and staging, surgery, adjuvant therapy, radiotherapy, molecular targeted therapy, and immunotherapy for NSCLC, SCLC, and mesothelioma. Quality and value of care and perspectives on the future of lung cancer research and treatment have also been included in this concise review.

TKI-addicted ROS1-rearranged cells are destined to survival or death by the intensity of ROS1 kinase activity

ROS1 rearrangement is observed in 1–2% of non-small cell lung cancers (NSCLC). The ROS1 tyrosine kinase inhibitor (TKI) crizotinib has induced marked tumour shrinkage in ROS1-rearranged cancers. However, emergence of acquired resistance to TKI is inevitable within a few years. Previous findings indicate that cabozantinib overcomes secondary mutation–mediated crizotinib-resistance in ROS1-fusion-positive cells. Here we attempted to establish cabozantinib-resistant cells by N-ethyl-N-nitrosourea mutagenesis screening using CD74-ROS1–expressing Ba/F3 cells. Two resistant cell lines with CD74-ROS1 F2004V or F2075C mutations, which are homologous to ALK F1174 or F1245 mutations, survived in the presence of a low dose of ROS1-TKI. Removal of ROS1-TKI from these TKI-addicted cells induced excessive activation of ROS1 tyrosine kinase followed by apoptosis. We succeeded in recapturing the TKI-addicted phenotype using doxycycline-inducible CD74-ROS1 mutant over-expression in Ba/F3 cells, suggesting that excessive ROS1 oncogenic signaling itself induced apoptosis instead of cell growth. Phosphoproteomic analysis and high-throughput inhibitor screening revealed that excessive ROS1 signaling in the TKI-addicted cells phosphorylated or activated apoptosis-related molecules such as FAF1 or p38. Collectively, our findings partly clarify molecular mechanisms of excessive ROS1 oncogenic signaling that mediates paradoxical induction of apoptosis.

Open-Label, Multicenter, Phase II Study of Ceritinib in Patients With Non-Small-Cell Lung Cancer Harboring ROS1 Rearrangement

Purpose ROS1 rearrangement is a distinct molecular subset of non-small-cell lung cancer (NSCLC). We investigated the efficacy and safety of ceritinib in patients with ROS1-rearranged NSCLC. Patients and Methods We enrolled 32 patients with advanced NSCLC who tested positive for ROS1 rearrangement by fluorescent in situ hybridization. Ceritinib 750 mg was administered once daily. The primary end point was objective response rate. The secondary end points were disease control rate; duration of response; progression-free survival; overall survival; toxicity; and concordance among fluorescent in situ hybridization, immunohistochemistry, and next-generation sequencing. Results Between June 7, 2013, and February 1, 2016, 404 patients underwent ROS1 prescreening, and 32 patients with ROS1 rearrangement were enrolled. All patients except two were crizotinib-naïve. At the time of data cutoff, the median follow-up was 14.0 months, and 18 patients (56%) had discontinued treatment. Of the 32 patients enrolled, 28 were evaluable for response by independent radiologic review. Objective response rate was 62% (95% CI, 45% to 77%), with one complete response and 19 partial responses; duration of response was 21.0 months (95% CI, 17 to 25 months); and disease control rate was 81% (95% CI, 65% to 91%). The median progression-free survival was 9.3 months (95% CI, 0 to 22 months) for all patients and 19.3 months (95% CI, 1 to 37 months) for crizotinib-naïve patients. The median overall survival was 24 months (95% CI, 5 to 43 months). Of the eight patients with brain metastases, intracranial disease control was reported in five (63%; 95% CI, 31% to 86%). The most common adverse events (majority, grade 1 or 2) for all treated patients were diarrhea (78%), nausea (59%), and anorexia (56%). Conclusion Ceritinib demonstrated potent clinical activity in patients with ROS1-rearranged NSCLC who were heavily treated previously with multiple lines of chemotherapy.

Molecular mechanisms of therapy resistance in solid tumors: chasing "moving" targets

The goal of personalized cancer therapy is to treat tumors based on genomic aberrations that drive their survival and progression. Most patients who receive targeted therapies typically develop resistance and disease progression within a year's time. This review focuses on the heterogeneous mechanisms of therapy resistance to tyrosine kinase inhibitors, endocrine/hormone therapy and checkpoint blockade using non-small cell lung cancer, breast and castration-resistant prostate cancer, and melanoma as classical examples, respectively. In addition, testing for resistance mechanisms and therapeutic approaches to overcoming resistance is addressed.

Overcoming On-Target Resistance to Tyrosine Kinase Inhibitors in Lung Cancer

Advances in genomics, an improved understanding of malignant transformation, and the development of potent small molecule inhibitors capable of targeting key kinases have led to the adoption of genotype-guided approaches for the treatment of advanced cancers. As regulators of complex signaling networks, tyrosine kinases are among the most attractive targets. Moreover, insight into the conserved three-dimensional structures of these kinases and their mechanism of activation has facilitated the development of selective tyrosine kinase inhibitors (TKIs). TKIs have shown robust clinical activity in many different oncogene-addicted cancers; however, resistance invariably develops. In a significant proportion of patients, resistance results from acquired genetic alterations within the kinase target that allow cancer cells to escape TKI-mediated growth suppression. In this review, we discuss clinically observed and preclinical on-target resistance events in oncogene-driven solid tumors and describe current and future therapeutic strategies to overcome this type of resistance.

Mechanisms of Resistance to Target Therapies in Non-small Cell Lung Cancer

Targeted therapies are revolutionizing the treatment of advanced non-small cell lung cancer (NSCLC). The discovery of key oncogenic events mainly in lung adenocarcinoma, like EGFR mutations or ALK rearrangements, has changed the treatment landscape while improving the prognosis of lung cancer patients. Inevitably, virtually all patients initially treated with targeted therapies develop resistance because of the emergence of an insensitive cellular population, selected by pharmacologic pressure. Diverse mechanisms of resistance, in particular to EGFR, ALK and ROS1 tyrosine-kinase inhibitors (TKIs), have now been discovered and may be classified in three different groups: (1) alterations in the target (such as EGFR T790M and ALK or ROS1 mutations); (2) activation of alternative pathways (i.e. MET amplification, KRAS mutations); (3) phenotype transformation (to small cell lung cancer, epithelial-mesenchymal transition). These basic mechanisms are informing the development of novel therapeutic strategies to overcome resistance in the clinic. Novel-generation molecules include osimertinib, for EGFR-T790M-positive patients, and new ALK-TKIs. Nevertheless, the possible concomitant presence of multiple resistance mechanisms, as well as their heterogeneity among cells and disease localizations, makes research in this field particularly arduous. In this chapter, available evidence and perspectives concerning precise mechanisms of escape to pharmacological inhibition in oncogene-addicted NSCLC are reported for single targets, including but not limited to EGFR and ALK.

Stratified Treatment in Lung Cancer

Even though great efforts have been made to improve chemotherapy-based treatment approaches for lung cancer, the prognosis of patients with advanced and metastasized disease remains particularly poor. In recent years, a growing number of genetic aberrations driving lung cancer have been identified. Targeted inhibition of some of these aberrations, most prominently mutated EGFR and ALK, by tyrosine kinase inhibitors has dramatically increased efficacy and tolerability of systemic lung cancer treatment in subsets of patients. However, the duration of response is limited due to the acquisition of molecular mechanisms of resistance to targeted treatment. Modern next-generation inhibitors aim to break resistance. A deep understanding of the mechanisms of treatment failure is imperative to the development of new approaches. In this review, we focus on the current status of stratified therapy in lung cancer and highlight new, potentially promising treatment approaches.