Safety and efficacy of pralsetinib in RET fusion-positive non-small cell lung cancer including as first-line therapy: update from the ARROW trial

BACKGROUND

RET fusions are present in 1%-2% of non-small cell lung cancer (NSCLC). Pralsetinib, a highly potent, oral, central nervous system-penetrant, selective RET inhibitor, previously demonstrated clinical activity in patients with RET fusion-positive NSCLC in the phase I/II ARROW study, including among treatment-naïve patients. We report an updated analysis from the ARROW study.

PATIENTS AND METHODS

ARROW is a multi-cohort, open-label, phase I/II study. Eligible patients were ≥18 years of age with locally advanced or metastatic solid tumours and an Eastern Cooperative Oncology Group performance status 0-2 (later 0-1). Patients initiated pralsetinib at the recommended phase II dose of 400 mg once-daily (QD) until disease progression, intolerance, consent withdrawal, or investigator's decision. The co-primary endpoints (phase II) were overall response rate (ORR) by blinded independent central review and safety.

RESULTS

Between 17 March 2017 and 06 November 2020 (data cutoff), 281 patients with RET fusion-positive NSCLC were enrolled. The ORR was 72% (54/75; 95% CI, 60-82) for treatment-naïve patients and 59% (80/136; 95% CI, 50-67) for patients with prior platinum-based chemotherapy (enrolment cutoff for efficacy analysis: 22 May 2020); median duration of response was not reached for treatment-naïve patients and 22.3 months for prior platinum-based chemotherapy patients. Tumour shrinkage was observed in all treatment-naïve patients and in 97% of patients with prior platinum-based chemotherapy; median progression-free survival was 13.0 and 16.5 months, respectively. In patients with measurable intracranial metastases, the intracranial response rate was 70% (7/10; 95% CI, 35-93); all had received prior systemic treatment. In treatment-naïve patients with RET fusion-positive NSCLC who initiated pralsetinib by the data cutoff (n = 116), the most common Grade 3-4 treatment-related adverse events (TRAEs) were neutropenia (18%), hypertension (10%), increased blood creatine phosphokinase (9%), and lymphopenia (9%). Overall, 7% (20/281) discontinued due to TRAEs.

CONCLUSIONS

Pralsetinib treatment produced robust efficacy and was generally well tolerated in treatment-naïve patients with advanced RET fusion-positive NSCLC. Results from the confirmatory phase III AcceleRET Lung study (NCT04222972) of pralsetinib versus standard of care in the first-line setting are pending.

Uncommon targets in non-small cell lung cancer: Everyone wants a slice of cake

Target therapies completely changed the clinical approach in EGFR mutated and ALK rearranged non-small cell lung cancer, ensuring these patients exceptional outcomes with a better toxicity profile compared to conventional chemotherapy. In recent years, beyond EGFR and ALK alterations, new data are emerging about less common alterations, new drugs have been already approved and others agents have been recently investigated or are currently under investigation. In this review we will discuss some uncommon alterations in non-small cell lung cancer such as ROS1, BRAF, RET, HER2, NTRK, MET and other targets that are in an early evaluation phase. We will summarize the characteristics of patients harboring these alterations, the already approved or under investigation therapies and the related resistance mechanisms.

Practical Considerations Relating to Routine Clinical Biomarker Testing for Non-small Cell Lung Cancer: Focus on Testing for RET Fusions

For patients with advanced non–small cell lung cancer, genomic profiling of tumors to identify potentially targetable alterations and thereby inform treatment selection is now part of standard care. While molecular analyses are primarily focused on actionable biomarkers associated with regulatory agency-approved therapies, there are a number of emerging biomarkers linked to investigational agents in advanced stages of clinical development will become approved agents. A particularly timely example is the reported data and US Food and Drug Administration approval of highly specific small molecule inhibitors of the proto-oncogene tyrosine-protein kinase receptor RET indicate that testing for tumor RET gene fusions in patients with NSCLC has become clinically important. As the number of biomarkers to be tested in NSCLC grows, it becomes increasingly important to optimize and prioritize the use of biopsy tissue, in order to both continue to allow accurate histopathological diagnosis and also to support concurrent genomic profiling to identify perhaps relatively uncommon genetic events. In order to provide practical expert consensus guidance to optimize processes facilitating genomic testing in NSCLC and to overcome barriers to access and implementation, a multidisciplinary advisory board was held in New York, on January 30, 2019. The panel comprised physicians involved in sample procurement (interventional radiologists and a thoracic surgeon), surgical pathologists specializing in the lung, molecular pathologists, and thoracic oncologists. Particular consideration was given to the key barriers faced by these experts in establishing institutional genomic screening programs for NSCLC. Potential solutions have been devised in the form of consensus opinions that might be used to help resolve such issues.

Optimizing Mutation and Fusion Detection in NSCLC by Sequential DNA and RNA Sequencing

INTRODUCTION

Frequently, patients with locally advanced or metastatic NSCLC are screened for mutations and fusions. In most laboratories, molecular workup includes a multitude of tests: immunohistochemistry (ALK, ROS1, and programmed death-ligand 1 testing), DNA sequencing, in situ hybridization for fusion, and amplification detection. With the fast-emerging new drugs targeting specific fusions and exon-skipping events, this procedure harbors a growing risk of tissue exhaustion.

METHODS

In this study, we evaluated the benefit of anchored, multiplexed, polymerase chain reaction-based targeted RNA sequencing (RNA next-generation sequencing [NGS]) in the identification of gene fusions and exon-skipping events in patients, in which no pathogenic driver mutation was found by DNA-based targeted cancer hotspot NGS (DNA NGS). We analyzed a cohort of stage IV NSCLC cases from both in-house and referral hospitals, consisting 38.5% cytology samples and 61.5% microdissected histology samples, mostly core needle biopsies. We compared molecular findings in a parallel workup (DNA NGS and RNA NGS, cohort 1, n = 198) with a sequential workup (DNA NGS followed by RNA NGS in selected cases, cohort 2, n = 192). We hypothesized the sequential workup to be the more efficient procedure.

RESULTS

In both cohorts, a maximum of one oncogenic driver mutation was found per case. This is in concordance with large, whole-genome databases and suggests that it is safe to omit RNA NGS when a clear oncogenic driver is identified in DNA NGS. In addition, this reduced the number of necessary RNA NGS to only 53% of all cases. The tumors of never smokers, however, were enriched for fusions and exon-skipping events (32% versus 4% in former and current smokers, p = 0.00), and therefore benefited more often from the shorter median turnaround time of the parallel approach (15 d versus only 9 d in the parallel workup).

CONCLUSIONS

We conclude that sequentially combining DNA NGS and RNA NGS is the most efficient strategy for mutation and fusion detection in smoking-associated NSCLC, whereas for never smokers we recommend a parallel approach. This approach was shown to be feasible on small tissue samples including for cytology tests, can drastically reduce the complexity and cost of molecular workup, and also provides flexibility in the constantly evolving landscape of actionable targets in NSCLC.

When to Consider Immune Checkpoint Inhibitors in Oncogene-Driven Non-Small Cell Lung Cancer?

OPINION STATEMENT

Targeted therapies and more recently immune checkpoint inhibitors (ICI) have transformed the treatment landscape of advanced NSCLC. Clinical trials investigating immune checkpoint inhibitors (ICI) have usually excluded patients with oncogenic drivers, so that the outcome of these agents in this population is poorly known. In patients with oncogenic addiction, targeted therapy remains clearly the best option, and the place of immunotherapy in this population has not been clearly defined yet.Based on available data, we suggest that (i) immunotherapy single agent should be proposed only after exhaustion of more validated treatments, (ii) combinations of immunotherapy with targeted therapies are of interest provided that we can manage toxicity and find the best sequence, (iii) a combination of immunotherapy with chemotherapy may be appealing in patients pretreated with targeted agents. The best way to opt in for the best strategy will depend upon the identification of adequate biomarkers. New basic and clinical research is awaited in this field.

Rearranged During Transfection Fusions in Non-Small Cell Lung Cancer

Identifying and targeting specific oncogenic drivers has become standard of care in the routine management of patients with lung cancer. Research is ongoing to expand the number of drug targets that can offer clinically meaningful outcomes. Rearranged during transfection (RET) fusions are the latest oncogenic driver alterations that show potential as a drug target. RET fusions occur in 1-2% of non-small cell lung cancer (NSCLC) cases. They are more commonly associated with younger age, female gender, non-smokers and Asian ethnicity. The RET kinase is abnormally activated through fusion with a partner protein such as KIF5B, CCDC6 or NCOA4. This leads to downstream intracellular signalling and enhancement of gene transcription and cell proliferation. The effectiveness of multi-kinase inhibitors in RET positive NSCLC has been explored in early phase and retrospective studies. From these studies, the most effective agents identified include cabozantanib and vandetanib. Overall response rates (ORR) vary from 18-47% across studies. In general, these agents have a manageable toxicity profile, although there are a number of off-target toxicities. Similar to the increased activity in ALK rearranged disease, pemetrexed has demonstrated superior response rates in this patient group and should be considered. Selective RET inhibitors, including LOXO-292 and BLU-667, are progressing in clinical trials. LOXO-292 has demonstrated an impressive ORR of 77% in RET positive solid tumours. It is anticipated this agent will be an effective targeted therapeutic option for patients with RET positive lung cancer.

GDNF and the RET Receptor in Cancer: New Insights and Therapeutic Potential

The Glial cell line-derived neurotrophic Family Ligands (GFL) are soluble neurotrophic factors that are required for development of multiple human tissues, but which are also important contributors to human cancers. GFL signaling occurs through the transmembrane RET receptor tyrosine kinase, a well-characterized oncogene. GFL-independent RET activation, through rearrangement or point mutations occurs in thyroid and lung cancers. However, GFL-mediated activation of wildtype RET is an increasingly recognized mechanism promoting tumor growth and dissemination of a much broader group of cancers. RET and GFL expression have been implicated in metastasis or invasion in diverse human cancers including breast, pancreatic, and prostate tumors, where they are linked to poorer patient prognosis. In addition to directly inducing tumor growth in these diseases, GFL-RET signaling promotes changes in the tumor microenvironment that alter the surrounding stroma and cellular composition to enhance tumor invasion and metastasis. As such, GFL RET signaling is an important target for novel therapeutic approaches to limit tumor growth and spread and improve disease outcomes.

Immunotherapy for oncogenic-driven advanced non-small cell lung cancers: Is the time ripe for a change?

Immune checkpoint inhibitors (ICIs) have been incorporated in the treatment strategy of advanced non-small cell lung cancer (NSCLC) in first- and second-line setting improving the prognosis of these patients. However, the treatment landscape has been also drastically overturned with the advent of targeted therapies in oncogenic-addicted advanced NSCLC patients. Despite ICIs represent an active and new treatment option for a wide range of advanced NSCLC patients, the efficacy and the optimal place of ICI in the treatment strategy algorithm of oncogenic-addicted tumors remains still controversial, as only a minority of trials with ICI enrol oncogenic-addicted NSCLC patients previously treated with standard therapy. Therefore, there are still several open questions about ICI in oncogenic-driven NSCLC, such as the efficacy and toxicities, which need to be addressed before considering treatment with ICI as a standard approach in this population. It is in this framework, we provide a thorough overview on this currently controversial topic.