NVL-520 Is a Selective, TRK-Sparing, and Brain-Penetrant Inhibitor of ROS1 Fusions and Secondary Resistance Mutations

Macrocycles and macrocyclization in anticancer drug discovery: Important pieces of the puzzle

Increasing disease-related proteins have been identified as novel therapeutic targets. Macrocycles are emerging as potential solutions, bridging the gap between conventional small molecules and biomacromolecules in drug discovery. Inspired by successful macrocyclic drugs of natural origins, macrocycles are attracting more attention for enhanced binding affinity and target selectivity. Due to the conformation constraint and structure preorganization, macrocycles can reach bioactive conformations more easily than parent acyclic compounds. Also, rational macrocyclization combined with sequent structural modification will help improve oral bioavailability and combat drug resistance. This review introduces various strategies to enhance membrane permeability in macrocyclization and subsequent modification, such as N-methylation, intramolecular hydrogen bonding modulation, isomerization, and reversible bicyclization. Several case studies highlight macrocyclic inhibitors targeting kinases, HDAC, and protein-protein interactions. Finally, some macrocyclic agents targeting tumor microenvironments are illustrated.

CRISPR/Cas9-edited ROS1 + non-small cell lung cancer cell lines highlight differential drug sensitivity in 2D vs 3D cultures while reflecting established resistance profiles

INTRODUCTION

The study of resistance-causing mutations in oncogene-driven tumors is fundamental to guide clinical decisions. Several point mutations affecting the ROS1 kinase domain have been identified in the clinical setting, but their impact requires further exploration, particularly in improved pre-clinical models. Given the scarcity of solid pre-clinical models to approach rare cancer subtypes like ROS1 + NSCLC, CRISPR/Cas9 technology allows the introduction of mutations in patient-derived cell lines for which resistant variants are difficult to obtain due to the low prevalence of cases within the clinical setting.

METHODS

In the SLC34A2-ROS1 rearranged NSCLC cell line HCC78, we knocked-in through CRISPR/Cas9 technology three ROS1 drug resistance-causing mutations: G2032R, L2026M and S1986Y. Such variants are located in different functional regions of the ROS1 kinase domain, thus conferring TKI resistance through distinct mechanisms. We then performed pharmacological assays in 2D and 3D to assess the cellular response of the mutant lines to crizotinib, entrectinib, lorlatinib, repotrectinib and ceritinib. In addition, immunoblotting assays were performed in 2D-treated cell lines to determine ROS1 phosphorylation and MAP kinase pathway activity. The area over the curve (AOC) defined by the normalized growth rate (NGR_fit) dose-response curves was the variable used to quantify the cellular response towards TKIs.

RESULTS

Spheroids derived from ROS1G2032R cells were significantly more resistant to repotrectinib (AOC fold change = - 7.33), lorlatinib (AOC fold change = - 6.17), ceritinib (AOC fold change = - 2.8) and entrectinib (AOC fold change = - 2.02) than wild type cells. The same cells cultured as a monolayer reflected the inefficacy of crizotinib (AOC fold change = - 2.35), entrectinib (AOC fold change = - 2.44) and ceritinib (AOC fold change = - 2.12) in targeting the ROS1 G2032R mutation. ROS1L2026M cells showed also remarkable resistance both in monolayer and spheroid culture compared to wild type cells, particularly against repotrectinib (spheroid AOC fold change = - 2.19) and entrectinib (spheroid AOC fold change = - 1.98). ROS1S1986Y cells were resistant only towards crizotinib in 2D (AOC fold change = - 1.86). Overall, spheroids showed an increased TKI sensitivity compared to 2D cultures, where the impact of each mutation that confers TKI resistance could be clearly distinguished. Western blotting assays qualitatively reflected the patterns of response towards TKI observed in 2D culture through the levels of phosphorylated-ROS1. However, we observed a dose-response increase of phosphorylated-Erk1/2, suggesting the involvement of the MAPK pathway in the mediation of apoptosis in HCC78 cells.

CONCLUSION

In this study we knock-in for the first time in a ROS1 + patient-derived cell line, three different known resistance-causing mutations using CRISPR/Cas9 in the endogenous translocated ROS1 alleles. Pharmacological assays performed in 2D and 3D cell culture revealed that spheroids are more sensitive to TKIs than cells cultured as a monolayer. This direct comparison between two culture systems could be done thanks to the implementation of normalized growth rates (NGR) to uniformly quantify drug response between 2D and 3D cell culture. Overall, this study presents the added value of using spheroids and positions lorlatinib and repotrectinib as the most effective TKIs against the studied ROS1 resistance point mutations.

Deterministic reprogramming and signaling activation following targeted therapy in non-small cell lung cancer driven by mutations or oncogenic fusions

INTRODUCTION

Targeted therapy is used to treat lung adenocarcinoma caused by epidermal growth factor receptor (EGFR) mutations in the tyrosine kinase domain and rare subtypes (<5%) of non-small cell lung cancer. These subtypes include fusion oncoproteins like anaplastic lymphoma kinase (ALK), ROS1, rearranged during transfection (RET), and other receptor tyrosine kinases (RTKs). The use of diverse selective oral inhibitors, including those targeting rat sarcoma viral oncogene homolog (KRAS) mutations, has significantly improved clinical responses, extending progression-free and overall survival.

AREAS COVERED

Resistance remains a critical issue in lung adenocarcinoma, notably in EGFR mutant, echinoderm microtubule associated protein-like 4 (EML4)-ALK fusion, and KRAS mutant tumors, often associated with epithelial-to-mesenchymal transition (EMT).

EXPERT OPINION

Despite advancements in next generation EGFR inhibitors and EML4-ALK therapies with enhanced brain penetrance and identifying resistance mutations, overcoming resistance has not been abated. Various strategies are being explored to overcome this issue to achieve prolonged cancer remission and delay resistance. Targeting yes-associated protein (YAP) and the mechanisms associated with YAP activation through Hippo-dependent or independent pathways, is desirable. Additionally, the exploration of liquid-liquid phase separation in fusion oncoproteins forming condensates in the cytoplasm for oncogenic signaling is a promising field for the development of new treatments.

TKI Type Switching Overcomes ROS1 L2086F in ROS1 Fusion-Positive Cancers

Purpose

Despite the robust efficacy of ROS1 tyrosine kinase inhibitors (TKIs) in ROS1-positive non-small cell lung cancer, TKI resistance continues to hamper durability of the therapeutic response. The resistance liabilities of next-generation ROS1 TKI are sparsely characterized.

Design

We compared the activity of type I TKIs (crizotinib, entrectinib, taletrectinib, lorlatinib, and repotrectinib) to the type II TKIs (cabozantinib and merestinib), and to the type I FLT3 inhibitor, gilteritinib, in CD74-ROS1 wildtype and F2004C, L2026M, G2032R, or L2086 mutant Ba/F3 cells. The findings from the Ba/F3 cell model were confirmed using NIH3T3 colony formation assays and in vivo tumor growth. CRISPR/Cas9 gene editing was used to generate isogenic wildtype and L2086F mutant TPM3-ROS1 expressing patient-derived cell lines. These lines were used to further evaluate TKI activity using cell viability and immunoblotting methods. Molecular modeling studies enabled the characterization of structural determinants of TKI sensitivity in wildtype and mutant ROS1 kinase domains. We also report clinical cases of ROS1 TKI resistance that were treated with cabozantinib.

Results

ROS1 L2086F mutant kinase is resistant to type I TKI including crizotinib, entrectinib, lorlatinib, repotrectinib, taletrectinib, while the type II TKI cabozantinib and merestinib retain activity. Additionally, we found that gilteritinib, a type I FLT3 inhibitor, inhibited wildtype and L2086F mutant ROS1, however ROS1 G2032R solvent front mutation imposed resistance. The specific binding poses adopted by cabozantinib in the DFG-out kinase conformation and gilteritinib in the DFG-in kinase, provide rationale for their activity in the ROS1 mutants. Clinical cases demonstrated response to cabozantinib in tumors developing TKI resistance due to the ROS1 L2086F mutation.

Conclusion

Cabozantinib and gilteritinib effectively inhibit ROS1 L2086F. Clinical activity of cabozantinib is confirmed in patients with TKI-resistant, ROS1 L2086F mutant NSCLC. Gilteritinib may offer an alternative with distinct off-target toxicities, however further studies are required. Since cabozantinib and gilteritinib are multi-kinase inhibitors, there is a persistent unmet need for more selective and better-tolerated TKI to overcome ROS1 L2086F kinase-intrinsic resistance.

Translational relevance

ROS1 L2086F is an emerging recurrent resistance mutation to type I ROS1 TKIs, including later generation TKIs. Here, we show corroborating preclinical and clinical evidence for the activity of the quinolone-based type II TKI, cabozantinib, in ROS1 L2086F resistance setting. In addition, we show activity of the pyrazine carboxamide-based type I TKI, gilteritinib, in ROS1 L2086F resistance, suggesting that gilteritinib could be another option for ROS1 L2086F TKI-resistant patients. This study represents the first comprehensive report of ROS1 L2086F in the context of later-generation TKIs, including the macrocyclic inhibitors.

Discovery of novel 3-(1H-pyrazol-4-yl)-1H-indazole derivatives as potent type II TRK inhibitors against acquired resistance

Tropomyosin receptor kinase (TRK) is a promising target for treating NTRK fusion cancers. The solvent front and xDFG mutations induced by larotrectinib and entrectinib result in acquired resistance in advanced-stage patients. In this study, we report a highly potent and selective type II TRK inhibitor, 40l, developed using a structure-based design strategy. Compound 40l significantly suppressed Km-12, Ba/F3-TRKAG595R, and Ba/F3-TRKAG667C cell proliferation. In biochemical and cellular assays, 40l showed better inhibitory activity against TRKAG667C than that by the positive control, selitrectinib. Additionally, it induced apoptosis of Ba/F3-TRKAG595R and Ba/F3-TRKAG667C cells in a dose-dependent manner. Furthermore, 40l showed good selectivity for a panel of 41 kinases. In vitro assays indicated that 40l possessed outstanding plasma stability and moderate liver microsomal stability. Based on the above results, compound 40l could be further optimized to overcome the solvent front and xDFG TRK mutations.

Repotrectinib in ROS1 Fusion-Positive Non-Small-Cell Lung Cancer

BACKGROUND

The early-generation ROS1 tyrosine kinase inhibitors (TKIs) that are approved for the treatment of ROS1 fusion-positive non-small-cell lung cancer (NSCLC) have antitumor activity, but resistance develops in tumors, and intracranial activity is suboptimal. Repotrectinib is a next-generation ROS1 TKI with preclinical activity against ROS1 fusion-positive cancers, including those with resistance mutations such as ROS1 G2032R.

METHODS

In this registrational phase 1-2 trial, we assessed the efficacy and safety of repotrectinib in patients with advanced solid tumors, including ROS1 fusion-positive NSCLC. The primary efficacy end point in the phase 2 trial was confirmed objective response; efficacy analyses included patients from phase 1 and phase 2. Duration of response, progression-free survival, and safety were secondary end points in phase 2.

RESULTS

On the basis of results from the phase 1 trial, the recommended phase 2 dose of repotrectinib was 160 mg daily for 14 days, followed by 160 mg twice daily. Response occurred in 56 of the 71 patients (79%; 95% confidence interval [CI], 68 to 88) with ROS1 fusion-positive NSCLC who had not previously received a ROS1 TKI; the median duration of response was 34.1 months (95% CI, 25.6 to could not be estimated), and median progression-free survival was 35.7 months (95% CI, 27.4 to could not be estimated). Response occurred in 21 of the 56 patients (38%; 95% CI, 25 to 52) with ROS1 fusion-positive NSCLC who had previously received one ROS1 TKI and had never received chemotherapy; the median duration of response was 14.8 months (95% CI, 7.6 to could not be estimated), and median progression-free survival was 9.0 months (95% CI, 6.8 to 19.6). Ten of the 17 patients (59%; 95% CI, 33 to 82) with the ROS1 G2032R mutation had a response. A total of 426 patients received the phase 2 dose; the most common treatment-related adverse events were dizziness (in 58% of the patients), dysgeusia (in 50%), and paresthesia (in 30%), and 3% discontinued repotrectinib owing to treatment-related adverse events.

CONCLUSIONS

Repotrectinib had durable clinical activity in patients with ROS1 fusion-positive NSCLC, regardless of whether they had previously received a ROS1 TKI. Adverse events were mainly of low grade and compatible with long-term administration. (Funded by Turning Point Therapeutics, a wholly owned subsidiary of Bristol Myers Squibb; TRIDENT-1 ClinicalTrials.gov number, NCT03093116.).

Comprehensive Review of ROS1 Tyrosine Kinase Inhibitors-Classified by Structural Designs and Mutation Spectrum (Solvent Front Mutation [G2032R] and Central β-Sheet 6 [Cβ6] Mutation [L2086F])

Despite ROS1 fusion-positive NSCLC accounting for approximately 1% to 2% of NSCLC, there is a long list of ROS1 tyrosine kinase inhibitors (TKIs) being developed in addition to three approved ROS1 TKIs, crizotinib, entrectinib and repotrectinib. Here, we categorized ROS1 TKIs by their structures (cyclic versus noncyclic) and inhibitory abilities (active against solvent front mutation G2032R or central β-sheet #6 [Cβ6] mutation L2086F) and summarized their reported clinical activity in order to provide a dashboard on how to use these ROS1 TKIs in various clinical situations. In addition, the less known Cβ6 mutation ROS1 L2086F confer resistances to next-generation ROS1 TKIs (repotrectinib, taletrectinib, and potentially NVL-520) that can be overcome by cabozantinib as documented in published patient reports and potentially by certain L-shaped type I ROS1 TKIs including ceritinib and gilteritinib, which is approved as a FLT3 inhibitor for relapsed refractory FLT3+ acute myeloid leukemia but have published preclinical activites against ROS1 (and ALK). Future clinical trials should investigate cabozantinib and gilteritinib to repurpose them as ROS1 TKIs that can target ROS1 L2086F Cβ6 mutation.

Lorlatinib and capmatinib in a ROS1-rearranged NSCLC with MET-driven resistance: tumor response and evolution

Acquired drug resistance remains a major problem across oncogene-addicted cancers. Elucidation of mechanisms of resistance can inform rational treatment strategies for patients relapsing on targeted therapies while offering insights into tumor evolution. Here, we report acquired MET amplification as a resistance driver in a ROS1-rearranged lung adenocarcinoma after sequential treatment with ROS1 inhibitors. Subsequent combination therapy with lorlatinib plus capmatinib, a MET-selective inhibitor, induced intracranial and extracranial tumor response. At relapse, sequencing of the resistant tumor revealed a MET D1246N mutation and loss of MET amplification. We performed integrated molecular analyses of serial tumor and plasma samples, unveiling dynamic alterations in the ROS1 fusion driver and MET bypass axis at genomic and protein levels and the emergence of polyclonal resistance. This case illustrates the complexity of longitudinal tumor evolution with sequential targeted therapies, highlighting challenges embedded in the current precision oncology paradigm and the importance of developing approaches that prevent resistance.

Discovery of oncogenic ROS1 missense mutations with sensitivity to tyrosine kinase inhibitors

ROS1 is the largest receptor tyrosine kinase in the human genome. Rearrangements of the ROS1 gene result in oncogenic ROS1 kinase fusion proteins that are currently the only validated biomarkers for targeted therapy with ROS1 TKIs in patients. While numerous somatic missense mutations in ROS1 exist in the cancer genome, their impact on catalytic activity and pathogenic potential is unknown. We interrogated the AACR Genie database and identified 34 missense mutations in the ROS1 tyrosine kinase domain for further analysis. Our experiments revealed that these mutations have varying effects on ROS1 kinase function, ranging from complete loss to significantly increased catalytic activity. Notably, Asn and Gly substitutions at Asp2113 in the ROS1 kinase domain were found to be TKI-sensitive oncogenic variants in cell-based model systems. In vivo experiments showed that ROS1 D2113N induced tumor formation that was sensitive to crizotinib and lorlatinib, FDA-approved ROS1-TKIs. Collectively, these findings highlight the tumorigenic potential of specific point mutations within the ROS1 kinase domain and their potential as therapeutic targets with FDA-approved ROS1-TKIs.

Type I inhibitors of tropomyosin receptor kinase (Trk): a 2020-2022 patent update

INTRODUCTION

Trk inhibitors are significant in the realm of personalized medicine as they target specific genetic alterations, such as NTRK gene fusions, leading to improved treatment outcomes for cancer patients. By tailoring the treatment to the genetic characteristics of the tumor rather than the tumor type, Trk inhibitors offer the potential for more effective and precise therapies, resulting in enhanced response rates and prolonged survival for patients with NTRK fusion-positive cancers.

AREAS COVERED

Patents covering type I inhibitors targeting the Trk family are discussed, building upon our prior review series on Trk inhibitors. Relevant patents were identified through the Web of Science database, Google, and Google Patents.

EXPERT OPINION

The field of Trk inhibitors has evolved significantly, as reflected in the current patent literature, which emphasizes the selective structural refinement of clinical champions. Efforts now concentrate on enhancing efficacy against on-target resistance mechanisms, with modifications made to improve potency, reduce toxicity, and enhance pharmacokinetics. Combination therapies show potential to address off-target resistance mechanisms and improve treatment outcomes. Challenges remain in accurately diagnosing NTRK gene alterations and integrating screening into routine clinical practice. Trk inhibitors have surpassed their conventional role of inhibition and are now seeing new applications in radiopharmaceutical development and as molecular targeting agents.

Fluorescence In Situ Hybridization (FISH) for the Characterization and Monitoring of Primary Cultures from Human Tumors

Genetic and drug sensitivity assays on primary cultures are not only of basic but also of translational interest and could eventually aid oncologists in the selection of treatments. However, cancer cells need to be identified and differentiated from the non-tumor cells always present in primary cultures. Also, successive passages can change the proportions of these two subpopulations. In this study, we propose fluorescence in situ hybridization (FISH) analysis on cell smears to determine the presence of tumor cells in primary cultures obtained from patients carrying translocations or copy number gains. FISH proved to be an easy, fast, economic, and reliable method of characterizing cell populations, which could be used repeatedly at different passages to monitor variations and to confirm the maintenance of translocations and copy number gains throughout the culture process.