CD74/SLC34A2-ROS1 Fusion Variants Involving the Transmembrane Region Predict Poor Response to Crizotinib in NSCLC Independent of TP53 Mutations.

INTRODUCTION: Variable partners and breakpoints have been reported in patients with ROS1-rearranged NSCLC. Here, we investigated the association of fusion partners and breakpoints with crizotinib efficacy in NSCLCs with common ROS1 fusions. METHODS: DNA and RNA next-generation sequencing (NGS) and immunohistochemistry were performed to characterize ROS1 fusions. RESULTS: Using DNA NGS, we identified ROS1 fusions in 210 cases, comprising 171 common (CD74/EZR/TPM3/SDC4/SLC34A2-ROS1) and 39 uncommon (variants identified in <5%) ROS1 fusion cases. DNA NGS detected variable ROS1 genomic breakpoints in common ROS1 fusions, whereas RNA NGS found ROS1 breakpoints mainly occurring in exons 32, 34 and 35, resulting in long (exon 32) and short (exon 34 or 35) ROS1 fusions. ROS1 immunohistochemistry revealed that membranous and cytoplasmic staining was predominant in long ROS1 fusions, whereas cytoplasmic staining was predominant in short ROS1 fusions (p = 0.006). For patients who received first-line crizotinib, median progression-free survival (mPFS) was lower in patients with long ROS1 fusions than those with short ROS1 fusions (8.0 versus 24.0 mo, p = 0.006). Moreover, mPFS for patients with and without TP53 mutations was 8.0 and 19.0 months, respectively (p = 0.159); mPFS for patients with and without BIM deletion polymorphism was 5.0 and 22.0 months, respectively (p = 0.003). When analyzing together with fusion partners, patients with long CD74/SLC34A2-ROS1 fusions were found to have shorter PFS than those with other ROS1, regardless of the presence or absence of TP53 mutations (p < 0.001 and p = 0.002, respectively). CONCLUSIONS: Long CD74/SLC34A2-ROS1 fusions, which retain transmembrane regions in ROS1 and fusion partners, are associated with poor response to crizotinib independent of TP53 mutations.

Taletrectinib for the treatment of ROS-1 positive non-small cell lung cancer: a drug evaluation of phase I and II data.

INTRODUCTION: While crizotinib and entrectinib have been approved to treat ROS1 fusion-positive (ROS1+) non-small-cell lung cancer (NSCLC), unmet needs remain. These unmet needs include treatment options for patients with resistance mutations and efficacious options even in the presence of brain metastasis while simultaneously avoiding unwanted neurological side effects. AREAS COVERED: Taletrectinib was designed to: improve efficacy; overcome resistance to first-generation ROS1 inhibitors; and address central nervous system penetration while conferring fewer neurological adverse events. All of these features are demonstrated and supported by data from the phase I and the regional phase II TRUST-I clinical trial. Here, we describe the preclinical and clinical characteristics of taletrectinib and evaluate the data from phase I and II studies and review the rationale and design of TRUST-II, a global phase II study of taletrectinib, which is enrolling patients in North America, Europe, and Asia. EXPERT OPINION: Taltrectinib has the potential to improve PFS based on its greater potency against ROS1+ tumors and high CNS penetration. By selectively inhibiting ROS1 wild-type and its resistant mutations over TRKB, taltrectinib has a better safety profile with minimal CNS-related AEs compared to other ROS1+ inhibitors.

Long-Term Efficacy and Safety of Entrectinib in ROS1 Fusion-Positive NSCLC.

Introduction: Entrectinib is an approved tyrosine kinase inhibitor (TKI) for ROS1 fusion-positive NSCLC. An updated integrated analysis of entrectinib from the ALKA-372-001, STARTRK-1, and STARTRK-2 trials is presented, with substantially longer follow-up, more patients, and the first description of the median overall survival (OS). An exploratory analysis of entrectinib in ROS1 fusion-positive NSCLC with the central nervous system (CNS)-only progression post-crizotinib is reported. Methods: Adults with ROS1 fusion-positive, locally advanced or metastatic NSCLC who received at least one dose of entrectinib and had 12 months or longer of follow-up were included in the analysis. Co-primary end points were confirmed objective response rate (ORR) and duration of response (DoR) by blinded independent central review. The data cutoff was on August 31, 2020. Results: The efficacy-assessable population comprised 168 ROS1 TKI-naïve patients. The median survival follow-up was 29.1 months (interquartile range, 21.8-35.9). The ORR was 68% (95% confidence interval [CI]: 60.2-74.8); the median DoR was 20.5 months. The median progression-free survival (PFS) was 15.7 months and the median OS was 47.8 months. In the 25 patients with measurable baseline CNS metastases, the intracranial ORR was 80% (95% CI: 59.3-93.2), median intracranial DoR was 12.9 months, and median intracranial PFS was 8.8 months. Among 18 patients with CNS-only progression on previous crizotinib treatment, two achieved a partial response (11%) and four had stable disease (22%). In seven patients with measurable CNS disease from this cohort, the intracranial ORR was 14% (1 partial response). Conclusions: Entrectinib is active and achieves prolonged survival in ROS1 TKI-naïve patients with ROS1 fusion-positive NSCLC. Modest activity is seen in patients with CNS-only progression post-crizotinib.

Detection of ROS1 gene fusions using next-generation sequencing for patients with malignancy in China.

Objective: This study aimed to identify ROS1 fusion partners in Chinese patients with solid tumors. Methods: Next-generation sequencing (NGS) analysis was used to detect ROS1 rearrangement in 45,438 Chinese patients with solid tumors between 2015 and 2020, and the clinical characteristics and genetic features of gene fusion were evaluated. H&E staining of the excised tumor tissues was conducted. Samples with a tumor cell content ≥ 20% were included for subsequent DNA extraction and sequencing analysis. Results: A total of 92 patients with ROS1 rearrangements were identified using next-generation sequencing, and the most common histological type lung cancer. From the 92 ROS1 fusion cases, 24 ROS1 fusion partners had been identified, including 14 novel partners and 10 reported partners. Of these, CD74, EZR, SDC4, and TPM3 were the four most frequently occurring partners. Fourteen novel ROS1 fusion partners were detected in 16 patients, including DCBLD1-ROS1, FRK-ROS1, and VGLL2-ROS1. In many patients, the ROS1 breakpoint was located between exons 32 and 34. Conclusion: This study describes 14 novel ROS1 fusion partners based on the largest ROS1 fusion cohort, and the ROS1 breakpoint was mostly located between exons 32 and 34. Additionally, next-generation sequencing is an optional method for identifying novel ROS1 fusions.

Clinical significance of ROS1 5' deletions in non-small cell lung cancer.

OBJECTIVES: Patients harboring rearrangements of the ROS1 gene are eligible for first-line therapy with Crizotinib, which represents the best available treatment option. Diagnostic criteria, based on break-apart fluorescence in situ hybridization, were mirrored from ALK by analogy and include tumors with 5' deletions. However, the probability of response to Crizotinib in patients with 5' deletion in ROS1 is unknown given the rarity of this condition. MATERIALS AND METHODS: We hereby describe clinical outcome of 8 NSCLC patients harboring a 5' deletion at FISH treated with Crizotinib RESULTS: Three out of 4 cases whose 5' deletion was confirmed by NGS as a ROS1/EZR fusion displayed an objective response to Crizotinib while a case with ROS1/SDC4 fusion did not. By contrast, among the 4 cases where NGS did not detect ROS1 gene fusions only 2 patients responded to crizotinib therapy with one also harboring a concomitant EML4-ALK rearrangement. CONCLUSION: 5' ROS1 deletions detected by FISH are associated with a high chance of response to Crizotinib in NSCLC, similarly to canonical ROS1 split-apart FISH rearrangements. However, the confirmation of the ROS1 gene fusion with at least another method, such as NGS, seems beneficial in order to define the ROS1 fusion partner and to avoid possible false positive results.

ALK, ROS1 and RET fusions in 1139 lung adenocarcinomas: a comprehensive study of common and fusion pattern-specific clinicopathologic, histologic and cytologic features.

BACKGROUND: To have a comprehensive investigation of the clinicopathologic, histologic and cytologic features of fusion-positive lung adenocarcinomas. METHODS: Quantitative real-time reverse transcriptase PCR (qRT-PCR) and reverse transcriptase PCR (RT-PCR) were simultaneously performed to screen ALK, ROS1 and RET fusions in resected tumor samples from 1139 Chinese lung adenocarcinoma patients, with validation of positive results using fluorescent in situ hybridization. Clinicopathologic characteristics, predominant histologic subtype and cytomorphology were assessed in fusion-positive lung adenocarcinomas and compared to those harboring EGFR, KRAS, HER2 or BRAF mutations. RESULTS: There were 58 (5.1%) ALK fusions, 11 (1.0%) ROS1 fusions and 15 (1.3%) RET fusions. Tumors with ROS1 fusions had significantly larger diameter than ROS1 fusion-negative tumors (P = 0.007), whereas all the 15 tumors harboring RET fusions were ≤ 3 cm in diameter (P = 0.001). The three fusion genes were all more prevalent in solid-predominant adenocarcinoma. Compared to fusion-negative lung adenocarcinomas, tumors harboring a fusion gene had significantly higher prevalence of extracellular mucin (P < 0.001), cribriform pattern (P < 0.001), signet ring cells (P < 0.001) and hepatoid cytology (P < 0.001). No significant difference in relapse-free survival (P = 0.147) and overall survival (P = 0.444) was observed between fusion-positive and fusion-negative patients. CONCLUSIONS: This study showed fusion-positive lung adenocarcinomas had identifiable common and fusion-pattern specific clinicopathologic, histologic and cytologic features, offering implications for fusion genes screening.