ROS1 Tyrosine Kinase Inhibitors Research Articles

Abstract 1111: MYC promotes tyrosine kinase inhibitor resistance in ROS1 fusion positive lung cancers

Abstract Targeted therapy of ROS1 fusion-driven non-small cell lung cancer (NSCLC) with the tyrosine kinase inhibitor (TKI), crizotinib, has achieved notable clinical success. Despite these promising results, resistance to therapy poses a significant challenge. 47-92% of crizotinib-resistant tumors have a wild-type ROS1 kinase domain suggesting that concurrent aberrations in bypass signaling pathways contribute to sustained cancer growth even in the presence of ROS1 inhibition. Bypass resistance pathways are not well-characterized in ROS1 fusion-driven cancers; hence there is a dearth of secondary therapeutic strategies. To identify recurrent genomic alterations that co-occur with ROS1 fusions and could potentially impinge on sensitivity to crizotinib and other emerging ROS1 TKIs, we interrogated MSK-IMPACT datasets and found that 10% of patients with ROS1-fusion have concurrent MYC copy number amplification (CNA). We hypothesized that c-Myc overexpression compensates for the loss of ROS1 signaling due to ROS1 TKI treatment. Here we dissected the role of c-Myc overexpression in diminishing ROS1 TKI sensitivity using two models: 1) a MYC-amplified and crizotinib-resistant patient-derived ROS1-fusion NSCLC cell line (LUAD0006) and 2) a CRISPR-Cas9 engineered human bronchial epithelial EZR-ROS1 cell line (HBEC-ER) exhibiting sensitivity to ROS1 TKI. We validated LUAD0006 ROS1 TKI-resistance using cell viability assays and confirmed MYC CNA and protein overexpression with fluorescence in situ hybridization and immunoblotting, respectively. Live cell imaging assays revealed that ROS1-TKI or c-Myc knockdown via shRNA alone were insufficient to inhibit LUAD0006 cell growth; however combined ablation of ROS1 kinase activity and c-Myc expression significantly suppressed cell proliferation. Gain of function experiments using HBEC-ER revealed that these cells acquire functional resistance to multiple ROS1 TKIs upon expression of a degradation-resistant c-Myc T58A mutant. Notably, immunoblotting confirmed 50-fold overexpression of c-Myc T58A relative to endogenous c-Myc in unmodified cells. We also performed RNA sequencing and reverse-phase protein array (RPPA) analysis of LUAD0006 cells treated with or without crizotinib and found that targets related to cell cycle, apoptosis, and metabolism were differentially expressed. Finally, we found that CDK4/6 and BET bromodomain inhibitors re-sensitized LUAD0006 cells to crizotinib, demonstrating the importance of c-Myc to the survival of these TKI-resistant cells. Taken together, we demonstrate that CNA or post-translational stabilization that leads to c-Myc overexpression confers resistance to crizotinib and other emerging ROS1 TKIs. These patients will likely benefit from a combination therapeutic strategy that targets both ROS1 and c-Myc. Citation Format: Sudarshan R. Iyer, Igor Odintsov, Adam J. Schoenfeld, Hiroki Sato, Evan Siau, Alexander Drilon, Gregory J. Riely, Romel Somwar, Marc Ladanyi, Monika A. Davare. MYC promotes tyrosine kinase inhibitor resistance in ROS1 fusion positive lung cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1111.

Abstract 1098: Activation of YAP1 confers ROS1 inhibitor resistance in ROS1-rearranged lung cancer

Abstract ROS1 gene arrangements occur in approximately 1% to 2% of non-small cell lung cancers. Crizotinib, the ROS1-tyrosine kinase inhibitor (TKI), has been approved for ROS1-rearranged lung cancer based on its dramatic therapeutic effect, but cures are usually not achieved. We have been focused on relationships between Yes associated protein1 (YAP1) and resistance to molecular target drugs. YAP1, a main mediator of the Hippo pathway, promotes cell proliferation and epithelial-mesenchymal transition and is associated with drug resistance in some cancer types. We previously demonstrated that YAP1 mediates survival against alectinib therapy in anaplastic lymphoma kinase-rearranged lung cancer cells. Then, in this study, we evaluated the role of YAP1 as an initial survival mechanism from lorlatinib in ROS1-rearranged lung cancer. We established a patient-derived EZR-ROS1-rearranged lung cancer cell line (KTOR71) from pleural effusion of a patient who acquired resistance to crizotinib. Subsequently, we conducted functional analysis of YAP1 involvement in drug-resistance, using this patient-derived cell line. DNA sequencing confirmed that KTOR71 cells harbored EZR-ROS1 fusion and ROS1 S1986F mutation, which is known crizotinib resistance mutation. KTOR71 cells were sensitive to lorlatinib, while resistant to crizotinib in cell viability assay (CVA). Nuclear localization of YAP1, which is an activation marker of YAP1, was assessed using immunofluorescence staining. In KTOR71 cells, YAP1 was activated after lorlatinib exposure. Then, to evaluate functional role of YAP1 in the initial survival against lorlatinib, the genetic inhibition of YAP1 in KTOR71 cells were performed using small interfering RNA (siRNA). Silencing of YAP1 by siRNA enhanced sensitivity to lorlatinib in KTOR71 cells in CVA. Furthermore, to confirm this functional role of YAP1 in vivo, we established the KTOR71 cell-derived xenograft model. The combination therapy with lorlatinib and verteporfin, an inhibitor of YAP1-TEAD interaction, sustained tumor remission significantly compared with lorlatinib monotherapy in vivo. Finally, we found that AKT was reactivated with activation of YAP1 and silencing of YAP1 by siRNA suppressed this AKT reactivation. These results suggest that YAP1 may be a potential drug target for ROS1-rearranged lung cancer. Citation Format: Masatoshi Yamazoe, Hiroaki Ozasa, Tetsuya Ohgimoto, Kazutaka Hosoya, Hitomi Ajimizu, Tomoko Funazo, Yuto Yasuda, Takahiro Tsuji, Hironori Yoshida, Ryo Itotani, Yuichi Sakamori, Young Hak Kim, Hirai Toyohiro. Activation of YAP1 confers ROS1 inhibitor resistance in ROS1-rearranged lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1098.

Abstract 3003: MET mediates entrectinib resistance in ROS1 gene fusion positiveNSCLC

Abstract ROS1 gene fusions are predominantly found in non-small cell lung cancer (NSCLC), and ROS1 gene fusion-positive (ROS1+) tumors comprise 1-2% of all diagnosed lung adenocarcinomas. Currently, there are two ROS1 tyrosine kinase inhibitors (TKIs) which are US FDA approved, crizotinib and entrectinib, both of which generate tumor response rates in excess of 70% and demonstrate prolonged disease control. However, acquired resistance to TKIs is inevitable, and has been reported in ROS1+ NSCLC tumors or cancer cell models by our group and others and include ROS1 kinase domain mutations (e.g., L1951R, S1986Y/F, F2004V, L2026M, and G2032R), activation of bypass signaling pathways (e.g., EGFR, RAS, or KIT), or phenotypic transformation (such as epithelial to mesenchymal transition). In order to better understand mechanisms of acquired TKI resistance in ROS1 NSCLC, our lab utilized primary, patient-derived cancer cell models harboring these rare oncogenic kinase rearrangements. Herein, using a patient-derived NSCLC cancer cell line (CUTO28) harboring a TPM3-ROS1 fusion, we derived an entrectinib-resistant cell line (CUTO28-ER) through in vitro culture under drug selection. In these CUTO28-ER cells, we identified: (1) MET-mediated bypass signaling as an acquired resistance mechanism to entrectinib, (2) upregulation of MET signaling is accomplished via MET gene amplification, and (3) resistance could be overcome by the dual ROS1/MET inhibitor crizotinib. To our knowledge, this is the first reported case of MET-mediated acquired resistance in a ROS1+ cancer. This cell line model finding was supported by another primary, patient-derived cell line (CUTO38) harboring a CD74-ROS1 fusion; this cell line was derived from a NSCLC patient following disease progression on entrectenib in the clinic. CUTO38 is resistant to entrectinib in vitro and displays elevated MET expression, MET activation with increased phosphorylation, and dependence on MET for cell proliferation and survival. Notably, MET activation in CUTO38 was not generated by gene amplification, MET exon 14 splicing, MET gene fusion, or autocrine HGF expression, suggesting alternate means of MET activation. These findings suggest that interrogation of MET gene amplification or other MET biomarkers should be performed in ROS1+ NSCLC patients who experience disease progression on entrectinib or other ROS1 TKIs that do not inhibit MET, since there are clinically available MET inhibitors, some of which are dual ROS1/MET inhibitors, that may overcome drug resistance in these patients. Citation Format: Logan Tyler, Anh Le, Hala Nijmeh, Robert Doebele. MET mediates entrectinib resistance in ROS1 gene fusion positiveNSCLC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3003.

ROS1-dependent cancers - biology, diagnostics and therapeutics.

The proto-oncogene ROS1 encodes a receptor tyrosine kinase with an unknown physiological role in humans. Somatic chromosomal fusions involving ROS1 produce chimeric oncoproteins that drive a diverse range of cancers in adult and paediatric patients. ROS1-directed tyrosine kinase inhibitors (TKIs) are therapeutically active against these cancers, although only early-generation multikinase inhibitors have been granted regulatory approval, specifically for the treatment of ROS1 fusion-positive non-small-cell lung cancers; histology-agnostic approvals have yet to be granted. Intrinsic or extrinsic mechanisms of resistance to ROS1 TKIs can emerge in patients. Potential factors that influence resistance acquisition include the subcellular localization of the particular ROS1 oncoprotein and the TKI properties such as the preferential kinase conformation engaged and the spectrum of targets beyond ROS1. Importantly, the polyclonal nature of resistance remains underexplored. Higher-affinity next-generation ROS1 TKIs developed to have improved intracranial activity and to mitigate ROS1-intrinsic resistance mechanisms have demonstrated clinical efficacy in these regards, thus highlighting the utility of sequential ROS1 TKI therapy. Selective ROS1 inhibitors have yet to be developed, and thus the specific adverse effects of ROS1 inhibition cannot be deconvoluted from the toxicity profiles of the available multikinase inhibitors. Herein, we discuss the non-malignant and malignant biology of ROS1, the diagnostic challenges that ROS1 fusions present and the strategies to target ROS1 fusion proteins in both treatment-naive and acquired-resistance settings.

MAPK Pathway Alterations Correlate with Poor Survival and Drive Resistance to Therapy in Patients with Lung Cancers Driven by ROS1 Fusions.

ROS1 tyrosine kinase inhibitors (TKI) provide significant benefit in lung adenocarcinoma patients with ROS1 fusions. However, as observed with all targeted therapies, resistance arises. Detecting mechanisms of acquired resistance (AR) is crucial to finding novel therapies and improve patient outcomes. ROS1 fusions were expressed in HBEC and NIH-3T3 cells either by cDNA overexpression (CD74/ROS1, SLC34A2/ROS1) or CRISPR-Cas9-mediated genomic engineering (EZR/ROS1). We reviewed targeted large-panel sequencing data (using the MSK-IMPACT assay) patients treated with ROS1 TKIs, and genetic alterations hypothesized to confer AR were modeled in these cell lines. Eight of the 75 patients with a ROS1 fusion had a concurrent MAPK pathway alteration and this correlated with shorter overall survival. In addition, the induction of ROS1 fusions stimulated activation of MEK/ERK signaling with minimal effects on AKT signaling, suggesting the importance of the MAPK pathway in driving ROS1 fusion-positive cancers. Of 8 patients, 2 patients harbored novel in-frame deletions in MEK1 (MEK1delE41_L54) and MEKK1 (MEKK1delH907_C916) that were acquired after ROS1 TKIs, and 2 patients harbored NF1 loss-of-function mutations. Expression of MEK1del or MEKK1del, and knockdown of NF1 in ROS1 fusion-positive cells activated MEK/ERK signaling and conferred resistance to ROS1 TKIs. Combined targeting of ROS1 and MEK inhibited growth of cells expressing both ROS1 fusion and MEK1del. We demonstrate that downstream activation of the MAPK pathway can mediate of innate acquired resistance to ROS1 TKIs and that patients harboring ROS1 fusion and concurrent downstream MAPK pathway alterations have worse survival. Our findings suggest a treatment strategy to target both aberrations.

Cases of ROS1-rearranged lung cancer: when to use crizotinib, entrectinib, lorlatinib, and beyond?

ROS1-rearranged (also known as ROS1 fusion-positive) non-small-cell lung cancer is an uncommon but distinct molecular subgroup seen in approximately 1–2% of cases. Oncogene addiction due to constitutive ROS1 tyrosine kinase activation has allowed development of molecularly targeted therapies with remarkable anti-tumor activity. Both crizotinib and entrectinib, multitargeted tyrosine kinase inhibitors (TKIs) have now received approval by the FDA for treatment of patients with advanced ROS1-rearranged lung cancers; however, the clinical efficacy and safety of these drugs have been derived from expansion cohorts of single-arm phase I or basket clinical trials with relatively small populations of this clinically and molecularly distinct subgroup. Both drugs lead to high objective response rates (approximately 70–80%) and have manageable side effects, although only entrectinib has potent intracranial efficacy. Lorlatinib is an oral brain-penetrant ALK/ROS1 TKI with activity in both TKI-naïve and some crizotinib-resistant settings (albeit with limited potency against the crizotinib/entrectinib-resistant ROS1-G2032R mutation). We describe cases of advanced ROS1-rearranged lung cancer receiving crizotinib, entrectinib, and/or lorlatinib in first and later line treatment settings to dissect the current state of evidence supporting management decisions for these patients. The next generation ROS1 TKIs (repotrectinib and DS-6051b), owing to their broad activity against kinase mutations including ROS1-G2032R in preclinical studies, hold promise to transform the current treatment paradigm and permit even further gains with regards to long-term outcomes in this subset of patients.

Resistance to lorlatinib in ROS1 fusion-positive non-small cell lung cancer.

9611 Background: Lorlatinib is a potent, brain-penetrant ROS1/ALK tyrosine kinase inhibitor (TKI), which has demonstrated efficacy in advanced ROS1 fusion-positive (ROS1+) non-small cell lung cancer (NSCLC), including in patients (pts) previously treated with crizotinib. Despite initial benefit, however, most pts experience disease progression on lorlatinib. Mechanisms of resistance to lorlatinib in ROS1+ NSCLC are poorly understood. Methods: We analyzed repeat tumor biopsies derived from advanced ROS1+ lung cancer pts progressing on lorlatinib. Next-generation sequencing (NGS, n = 17) or whole exome sequencing (n = 1) was performed to detect mutations, indels, and copy number alterations. Results: Sixteen pts underwent a total of 18 repeat tumor biopsies after progression on lorlatinib. Fourteen had received prior crizotinib; two received prior crizotinib and entrectinib. Median duration of therapy on lorlatinib was 13.5 months (95% CI, 8.3-18.4). Among the 18 cases analyzed by sequencing, 7 (38.9%) harbored a ROS1 resistance mutation, including G2032R (4/18, 22.2%), S1986F/L2000V (1/18, 5.6%), L2086F (1/18, 5.6%), and G2032R/S1986F/L2086F (1/18, 5.6%). Of note, ROS1 L2086F was a novel resistance mutation not previously reported in the literature, but analogous to ALK L1256F (a lorlatinib-resistant ALK mutation). Structural modeling studies showed that ROS1 L2086F causes steric interference with binding of lorlatinib, as well as crizotinib and entrectinib. In addition to ROS1 kinase domain mutations, NGS analyses also identified MET copy number gain in a lorlatinib-resistant case, validated by fluorescence in situ hybridization as high-level focal MET amplification (MET/CEP7 copy number ratio 6.3) without a concomitant ROS1 resistance mutation. Duration of therapy on lorlatinib was significantly shorter in pts with a post-lorlatinib ROS1 resistance mutation compared to those without (8.3 vs 18.1 months; p = 0.005). Conclusions: ROS1 resistance mutations are observed in over one-third of cases progressing on lorlatinib, including the solvent front mutation G2032R and a novel L2086F mutation. These findings underscore the importance of developing next-generation ROS1 TKIs with activity against ROS1 mutations, and the need to elucidate ROS1-independent resistance mechanisms.

Treatment Patterns and Clinical Outcomes Among Patients With ROS1-rearranged Non–small-cell Lung Cancer Progressing on Crizotinib

BackgroundROS1 rearrangements define a subset of non–small-cell lung cancers (NSCLCs) that are susceptible to therapeutic ROS1 kinase inhibition. Despite the fact that most patients initially respond to the first-generation ROS1 tyrosine kinase inhibitor (TKI) crizotinib, relapse invariably occurs, and therapeutic options upon disease progression are limited. Patients and MethodsWe conducted a multicenter study of patients with ROS1-rearranged NSCLC who progressed on ROS1 TKIs and examined the clinical outcomes based on the post-progression treatment approaches. ResultsAmong 29 patients with ROS1-rearrangement who received at least 1 ROS1 inhibitor, the median age was 51 years (range, 30-80 years), 70.8% of patients were female, and 68.9% were never-smokers. Upon progression to the first TKI, 11 patients (37.9%) received treatment with TKIs beyond progression. The median second progression-free survival to TKIs in patents treated beyond progression was 5.5 months (95% confidence interval [CI], 4.1-9.1 months), whereas the post-progression survival was 21.0 months (95% CI, 5.5 months-not reached [NR]). Eleven (37.9%) patients received a sequential treatment with lorlatinib ROS1 TKIs following a first generation ROS1 TKI. The overall response rate, median progression-free survival, and median overall survival (OS) to next-generation TKIs were 41.7% (95% CI, 15.2%-72.3%), 12.7 months (95% CI, 8.5 months-NR), and 17.0 months (95% CI, 15.8 months-NR), respectively. Patients treated with sequential ROS1 TKIs had a significantly longer median OS compared with those who were not (NR vs. 16.1 months; hazard ratio, 0.26; 95% CI, 0.10-0.78; P = .017). ConclusionIn this study, we reported that a subset of patients with ROS1-rearranged NSCLC may benefit from treatment with TKIs beyond progression and that sequential treatment with crizotinib followed by lorlatinib is associated with improved OS in patients with ROS1-rearranged NSCLC.

Reactive Oxygen Species (ROS)-Sensitive Prodrugs of the Tyrosine Kinase Inhibitor Crizotinib.

Tyrosine kinase inhibitors revolutionized cancer therapy but still evoke strong adverse effects that can dramatically reduce patients’ quality of life. One possibility to enhance drug safety is the exploitation of prodrug strategies to selectively activate a drug inside the tumor tissue. In this study, we designed a prodrug strategy for the approved c-MET, ALK, and ROS1 tyrosine kinase inhibitor crizotinib. Therefore, a boronic-acid trigger moiety was attached to the 2-aminopyridine group of crizotinib, which is a crucial position for target kinase binding. The influence of the modifications on the c-MET- and ALK-binding ability was investigated by docking studies, and the strongly reduced interactions could be confirmed by cell-free kinase inhibition assay. Furthermore, the newly synthesized compounds were tested for their activation behavior with H2O2 and their stability in cell culture medium and serum. Finally, the biological activity of the prodrugs was investigated in three cancer cell lines and revealed a good correlation between activity and intrinsic H2O2 levels of the cells for prodrug A. Furthermore, the activity of this prodrug was distinctly reduced in a non-malignant, c-MET expressing human lung fibroblast (HLF) cell line.

P1.14-12 A Novel Activating MAP2K1 In-Frame Deletion Mediates Acquired Resistance to ROS1 TKIs in a Patient with ROS1 Fusion-Positive NSCLC

ROS1 tyrosine kinase inhibitors (TKIs) such as crizotinib, entrectinib and lorlatinib provide significant benefit in non-small cell lung cancer (NSCLC) patients with ROS1 fusions. As observed with all targeted therapies however, resistance arises. With the widespread adoption of large panel next generation sequencing (NGS) at the time of acquired resistance (AR), our appreciation of novel off-target mechanisms continues to grow. Detecting additional mechanisms of acquired resistance (AR) is crucial to find novel therapies and improve patient outcomes. We reviewed targeted large-panel sequencing data (using the MSK-IMPACT assay) of paired pre-treatment and post-progression samples from patients treated with ROS1 TKIs. Genetic alterations hypothesized to confer AR were modeled in a patient-derived cell line (LUAD-0003, expressing EZR/ROS1) as well as isogenic human (HBEC) and murine (NIH-3T3) cell lines. ROS1 fusions were expressed in these cells either by cDNA overexpression (CD74/ROS1, SLC34A2/ROS1) or CRISPR-Cas9-mediated genomic engineering (EZR/ROS1). Using these cell line models, alterations in drug sensitivity and downstream signal pathways were examined. We also explored possible therapeutic strategies to overcome the drug resistance caused by the novel AR mechanisms examined in this study. We identified a patient with NSCLC harboring a MAP2K1 (MEK1) variant encoding an in-frame deletion of amino acids E41-L54 (MEK1del) in a sample taken at the time of resistance to lorlatinib (after 9 months’ treatment). This mutation was not detected in the pre-TKI sample. Induction of ROS1 fusions in HBEC and NIH-3T3 cells increased the sensitivity of these cells to ROS1 TKIs and stimulated activation of MEK/ERK signaling in comparison with AKT signaling, suggesting the importance of the RAS-MAPK pathway in driving ROS1 fusion-positive cancers. Underscoring the importance of the RAS-MAPK pathway in ROS1-mediated tumorigenesis, we identified three patients (pancreatic, salivary, and breast cancer) with a ROS1 fusion and NF1 loss-of-function mutation concurrently, in TKI-naïve samples. Expression of MEK1del in HBEC and NIH-3T3 cells harboring ROS1 fusions, and knockdown of NF1 in LUAD-0003, activated ERK signaling and conferred resistance to ROS1 TKIs. Combined targeting of ROS1 (crizotinib, lorlatinib) and MEK (selumetinib, trametinib) inhibited growth of cells expressing both ROS1 fusion and MEK1del. Our results suggest that the activation of the RAS-MAPK pathway plays a critical role in tumorigenesis mediated by ROS1 fusions, and that activating mutations in this pathway can drive AR to ROS1 TKIs. Combined inhibition of ROS1 and MEK is a potential therapeutic strategy that should be explored clinically.

Concurrent TP53 mutation adversely impact the efficacy of crizotinib in ROS1-rearranged lung cancer patients.

e20535 Background: ROS1 tyrosine kinase inhibitors (TKIs) are now standard of care for patients with advanced ROS1-rearranged NSCLC. But factors that may affect the efficacy of ROS1 TKIs remain to be explored. Methods: We conducted a retrospective multicenter study of lung cancer patients with ROS1 rearrangements. Treatment and survival follow-up was done and clinical records were reviewed. PFS distribution was analyzed by Kaplan-Meier method with log-rank test. Results: In total, we included 94 lung cancer patients with ROS1 fusion genes profiled by next-generation sequencing from May 2016 to September 2018. Fifty of them were female. The median diagnosis age was 54 (25-83). The most common histologic type was adenocarcinoma, which was confirmed in 75 of 78 patients with available pathological results. The most common fusion partners were CD74, EZR, SDC4 and SLC34A2 identified in 42, 19, 12 and 8 patients respectively. Concurrent actionable mutations were uncommon for ROS1 fusion-positive patients. The most frequent concomitant mutated gene was TP53, which was detected in 33% of all the patients. After excluding 29 patients who were lost to follow-up at the very start, the median follow-up time was 8.5 (0-28) months from the moment when mutation profiling was performed. Thirty-nine patients received treatment with crizotinib, among whom 27 were treatment-naïve patients. The median PFS of the 39 patients with crizotinib was not reached yet. Patients with baseline CNS metastasis tend to have shorter PFS compared to patients without (median, 12 vs NR, p = 0.0073). Besides, concurrent TP53 mutations were correlated with worse PFS (median, both NR, p = 0.0417). Mutation profiles of 10 patients were derived from ctDNA testing. No difference was found in PFS between these 10 patients with others whose genomic profiles were based on fresh tissue or FFPE specimens, suggesting that plasma ctDNA serves as good specimen source for mutation profiling to monitor clinical treatment. Conclusions: Concurrent TP53 mutation and presence of CNS metastasis are associated with decreased PFS of ROS1-positive patients treated with crizotinib.

18F-FDG PET/CT Evaluation of Crizotinib and Lorlatinib Therapy in Metastatic ROS-1–Positive Non–Small Cell Lung Cancer

ROS-1-positive non-small cell lung cancers (NSCLCs) are rare (approximately 1% of all NSCLCs) and require a first-line treatment by crizotinib. Crizotinib resistance is frequent within the first 12 months of treatment. Lorlatinib is a novel tyrosine kinase inhibitor of ROS-1 recently indicated for metastatic or locally advanced crizotinib-resistant NSCLC. We report the use of lorlatinib as second-line with a complete tumoral response after only 3 months of treatment. This case shows the major role of F-FDG PET/CT in treatment evaluation and monitoring targeted therapy in metastatic NSCLC.

Combined effect of cabozantinib and gefitinib in crizotinib-resistant lung tumors harboring ROS1 fusions.

The ROS1 tyrosine kinase inhibitor (TKI) crizotinib has shown dramatic effects in patients with non‐small cell lung cancer (NSCLC) harboring ROS1 fusion genes. However, patients inevitably develop resistance to this agent. Therefore, a new treatment strategy is required for lung tumors with ROS1 fusion genes. In the present study, lung cancer cell lines, HCC78 harboring SLC34A2‐ROS1 and ABC‐20 harboring CD74‐ROS1, were used as cell line‐based resistance models. Crizotinib‐resistant HCC78R cells were established from HCC78. We comprehensively screened the resistant cells using a phosphor‐receptor tyrosine kinase array and RNA sequence analysis by next‐generation sequencing. HCC78R cells showed upregulation of HB‐EGF and activation of epidermal growth factor receptor (EGFR) phosphorylation and the EGFR signaling pathway. Recombinant HB‐EGF or EGF rendered HCC78 cells or ABC‐20 cells resistant to crizotinib. RNA sequence analysis by next‐generation sequencing revealed the upregulation of AXL in HCC78R cells. HCC78R cells showed marked sensitivity to EGFR‐TKI or anti‐EGFR antibody treatment in vitro. Combinations of an AXL inhibitor, cabozantinib or gilteritinib, and an EGFR‐TKI were more effective against HCC78R cells than monotherapy with an EGFR‐TKI or AXL inhibitor. The combination of cabozantinib and gefitinib effectively inhibited the growth of HCC78R tumors in an in vivo xenograft model of NOG mice. The results of this study indicated that HB‐EGF/EGFR and AXL play roles in crizotinib resistance in lung cancers harboring ROS1 fusions. The combination of cabozantinib and EGFR‐TKI may represent a useful alternative treatment strategy for patients with advanced NSCLC harboring ROS1 fusion genes.

P3.02-054 Prognostic Implications of ROS1 Positivity in Non-Small Cell Lung Cancer (NSCLC): A Systematic Review of Published Literature

Oncogenic ROS1 mutations are found to occur in 1-2% of NSCLCs, and efficacy of single-agent Crizotinib (a ROS1 tyrosine-kinase inhibitor) has been demonstrated in ROS1-positive NSCLC. However, our knowledge on the natural disease course in ROS1-positive compared to ROS1-wild type (WT) NSCLC is currently limited. Furthermore, since no randomized prospective trials are likely to be planned to assess treatment outcomes in ROS-1 positive patients, the question whether ROS1-positivity is a favorable or an unfavorable prognostic factor in advanced NSCLC, may remain unanswered. To address this important question, we undertook a systematic review of published literature on the natural history of ROS1-positive NSCLC.

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.

Clinicopathological characteristics of ROS1- and RET-rearranged NSCLC in caucasian patients: Data from a cohort of 713 non-squamous NSCLC lacking KRAS/EGFR/HER2/BRAF/PIK3CA/ALK alterations.

Targeted therapies have substantially changed the management of non-small cell lung cancer (NSCLC) patients with driver oncogenes. Given the high frequency, EGFR and ALK aberrations were the first to be detected and paved the way for tyrosine kinase inhibitor (TKI) treatments. Other kinases such as ROS1 and more recently RET have emerged as promising targets, and ROS1 and RET TKIs are already available for precision medicine.We screened a large cohort of 713 Caucasian non-squamous NSCLC patients lacking EGFR/KRAS/BRAF/HER2/PI3KCA/ALK aberrations for ROS1 and RET rearrangements using fluorescence in situ hybridization to determine the frequency and clinicopathological characteristics of ROS1- and RET-positive patients.Frequencies of ROS1 and RET rearrangements were 2.1% and 2.52%, respectively. Contrary to common belief, both ROS1 and RET rearrangements were detected in patients with a history of smoking, and the RET-positive patients were not younger than the negative patients. Moreover, RET but not ROS1 rearrangement was associated with the female gender. Nearly half of the ROS1-rearranged patients were successfully treated with ROS1 TKIs. In contrast, only 5/18 RET-positive patients received off-label RET TKIs. Two patients had stable disease, and three experienced disease progression. In addition to the 18 RET-positive cases, 10 showed isolated 5′ signals. The clinical relevance is unknown but if the frequency is confirmed by other groups, the question whether these patients are eligible to TKIs will arise. More potent RET TKIs are under development and may improve the response rate in RET-positive patients. Therefore, we recommend the routine implementation of RET testing in non-squamous NSCLC patients, including those with a history of smoking.

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.

87 - Preclinical characterization and antitumor efficacy of DS-6051b, a novel, orally available small molecule tyrosine kinase inhibitor of ROS1 and NTRKs

87 - Preclinical characterization and antitumor efficacy of DS-6051b, a novel, orally available small molecule tyrosine kinase inhibitor of ROS1 and NTRKs

Structural insight into selectivity and resistance profiles of ROS1 tyrosine kinase inhibitors

Oncogenic ROS1 fusion proteins are molecular drivers in multiple malignancies, including a subset of non-small cell lung cancer (NSCLC). The phylogenetic proximity of the ROS1 and anaplastic lymphoma kinase (ALK) catalytic domains led to the clinical repurposing of the Food and Drug Administration (FDA)-approved ALK inhibitor crizotinib as a ROS1 inhibitor. Despite the antitumor activity of crizotinib observed in both ROS1- and ALK-rearranged NSCLC patients, resistance due to acquisition of ROS1 or ALK kinase domain mutations has been observed clinically, spurring the development of second-generation inhibitors. Here, we profile the sensitivity and selectivity of seven ROS1 and/or ALK inhibitors at various levels of clinical development. In contrast to crizotinib's dual ROS1/ALK activity, cabozantinib (XL-184) and its structural analog foretinib (XL-880) demonstrate a striking selectivity for ROS1 over ALK. Molecular dynamics simulation studies reveal structural features that distinguish the ROS1 and ALK kinase domains and contribute to differences in binding site and kinase selectivity of the inhibitors tested. Cell-based resistance profiling studies demonstrate that the ROS1-selective inhibitors retain efficacy against the recently reported CD74-ROS1(G2032R) mutant whereas the dual ROS1/ALK inhibitors are ineffective. Taken together, inhibitor profiling and stringent characterization of the structure-function differences between the ROS1 and ALK kinase domains will facilitate future rational drug design for ROS1- and ALK-driven NSCLC and other malignancies.

Optimization of Bipyridinyl Pyrazole Scaffolds via Design, Synthesis and Screening of a New Series of ROS1 Kinase‐modulating Compounds

A series of rationally designed ROS1 tyrosine kinase inhibitors 6a–9b with bipyridinyl pyrazole scaffold was synthesized and screened. The scaffold itself has showed an exclusive selectivity profile over ROS1 closely related kinases, ALK and c‐Met. The aim of this study was to further explore the structure–activity relationships (SAR) of the bipyridinyl pyrazole core structure, and to improve its ROS1 inhibitory potency. The rational of this study was to explore the nature of the proposed binding site for the pyrazole NH substituents. Careful selections of pyrazole NH substituent groups along with their regioisomers were considered. The compounds exhibited high degree of potency, IC50 values of 21–159 nM. A detailed SAR of bipyridinyl pyrazole scaffold has been finally well established and the virtual screening strategy, through molecular docking, has been performed for this type of ROS1 kinase inhibitors and the docked poses along with the activity data have gone in consistent with SAR specifications.