OA 12.07 LOXO-292, a Potent, Highly Selective RET Inhibitor, in MKI-Resistant RET Fusion-Positive Lung Cancer Patients with and without Brain Metastases

The genomic characteristics of RET fusion positive tumors in Chinese non-small cell lung cancer (NSCLC) patients

BACKGROUND

Approximately 1-2% of non-small cell lung cancer (NSCLC) patients harbor RET (rearranged during transfection) fusions. The oncogenic RET fusions could lead to constitutive kinase activation and oncogenesis.

METHODS

1746 Chinese NSCLC patients were analyzed in this study. Tumor tissues were collected, and were formalin fixed, paraffin-embedded (FFPE) and archived. Peripheral blood (PB) samples were also collected from each patient as control. In addition, we selected 17 of them for cfDNA NGS testing and 14 tumor samples for immunohistochemistry testing using PD-L1 rabbit monoclonal antibody, clones 28-8 (Abcam, Cambridge, UK).

RESULTS

Of the 1746 NSCLC cases, RET rearrangements were identified in 25 cases (1.43%) with locally advanced or metastatic NSCLC, of which 20 (80%) were female. We found that 14 out of 25 patients had an KIF5B-RET fusion, with KIF5B exon15-RET exon12, KIF5B exon23-RET exon12, and KIF5B exon24-RET exon11 detected in 14, 3, and 1 patients, respectively. We also identified one novel RET fusion partner PLCE1 and 4 intergenic-breakpoint fusions.

CONCLUSION

In this study, using the hybrid capture based next generation sequencing (NGS) techniques, we revealed the genomic profiling for the patients with RET fusion-positive NSCLC. To the best of our knowledge, this is the first study that exhibited the detailed breakpoints of Chinese NSCLC patients with RET rearrangement, and we found a novel new partner PLCE1. The results provided genomic information for patients with RET fusion which is significant for personalized clinical management in the era of precision medicine.

Antitarget Selectivity and Tolerability of Novel Pyrrolo[2,3-d]pyrimidine RET Inhibitors

The selective inhibition of RET kinase as a treatment for relevant cancer types including lung adenocarcinoma has garnered considerable interest in recent years and prompted a variety of efforts toward the discovery of small-molecule therapeutics. Hits uncovered via the analysis of archival kinase data ultimately led to the identification of a promising pyrrolo[2,3-d]pyrimidine scaffold. The optimization of this pyrrolo[2,3-d]pyrimidine core resulted in compound 1, which demonstrated potent in vitro RET kinase inhibition and robust in vivo efficacy in RET-driven tumor xenografts upon multiday dosing in mice. The administration of 1 was well-tolerated at established efficacious doses (10 and 30 mg/kg, po, qd), and plasma exposure levels indicated a minimal risk of KDR or hERG inhibition in vivo, as evaluated by Miles assay and free plasma concentrations, respectively.

Next-Generation Kinase Inhibitors Targeting Specific Biomarkers in Non-Small Cell Lung Cancer (NSCLC): A Recent Overview

Lung cancer causes many deaths globally. Mutations in regulatory genes, irregularities in specific signal transduction events, or alterations of signalling pathways are observed in cases of non-small cell lung cancer (NSCLC). Over the past two decades, a few kinases have been identified, validated, and studied as biomarkers for NSCLC. Among them, EGFR, ALK, ROS1, MET, RET, NTRK, and BRAF are regarded as targetable biomarkers to cure and/or control the disease. In recent years, the US Food and Drug Administration (FDA) approved more than 15 kinase inhibitors targeting these NSCLC biomarkers. The kinase inhibitors significantly improved the progression-free survival (PFS) of NSCLC patients. Challenges still remain for metastatic diseases and advanced NSCLC cases. New discoveries of potent kinase inhibitors and rapid development of modern medical technologies will help to control NSCLC cases. This article provides an overview of the discoveries of various types of kinase inhibitors against NSCLC, along with medicinal chemistry aspects and related developments in next-generation kinase inhibitors that have been reported in recent years.

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.

RET-rearranged non-small-cell lung cancer and therapeutic implications

First-line tyrosine kinase inhibitors are standard of care for non-small-cell lung cancers (NSCLC) harbouring an epidermal growth factor receptor mutation, anaplastic lymphoma kinase fusion or c-ros oncogene 1 rearrangement. Other targetable oncogenic drivers have been identified but testing for these is neither funded nor commonly performed in Australia. Using a case example, we discuss the importance of considering several other genomic aberrations in our population, such as rearrangements in the RET proto-oncogene, which occur in 1-2% of lung adenocarcinoma. New oncogenic drivers and corresponding targeted agents are constantly being discovered; these will continue to refine the treatment of non-small-cell lung cancer in the era of precision medicine.

Efficacy and Tolerability of Pyrazolo[1,5-a]pyrimidine RET Kinase Inhibitors for the Treatment of Lung Adenocarcinoma

RET (REarranged during Transfection) kinase gain-of-function aberrancies have been identified as potential oncogenic drivers in lung adenocarcinoma, along with several other cancer types, prompting the discovery and assessment of selective inhibitors. Internal mining and analysis of relevant kinase data informed the decision to investigate a pyrazolo[1,5-a]pyrimidine scaffold, where subsequent optimization led to the identification of compound WF-47-JS03 (1), a potent RET kinase inhibitor with >500-fold selectivity against KDR (Kinase insert Domain Receptor) in cellular assays. In subsequent mouse in vivo studies, compound 1 demonstrated effective brain penetration and was found to induce strong regression of RET-driven tumor xenografts at a well-tolerated dose (10 mg/kg, po, qd). Higher doses of 1, however, were poorly tolerated in mice, similar to other pyrazolo[1,5-a]pyrimidine compounds at or near the efficacious dose, and indicative of the narrow therapeutic windows seen with this scaffold.

Targeting Molecular Pathways in Intracranial Metastatic Disease

The discovery and clinical application of agents targeting pivotal molecular pathways in malignancies such as lung, breast, renal cell carcinoma, and melanoma have led to impressive improvements in clinical outcomes. Mutations in epidermal growth factor receptor (EGFR), and rearrangements of anaplastic lymphoma kinase (ALK) are targetable in lung cancer, while BRAF mutations have been successfully targeted in metastatic melanoma. Targeting estrogen receptors, cyclin dependent kinases, and HER2 (Human Epidermal Receptor) have resulted in improvement in survival in breast cancer. Major strides have been made in the management of metastatic renal cell carcinoma by targeting the vascular endothelial growth factor (VEGF) pathway. However, intracranial metastases remain a major hurdle in the setting of targeted therapies. Traditional treatment options for brain metastases include surgery, whole brain radiation therapy (WBRT), and stereotactic radiosurgery (SRS). Surgery is effective in symptomatic patients with dominant lesions or solitary intracranial metastases, however, recovery time can be prolonged, often requiring an interruption in systemic treatment. WBRT and SRS provide symptomatic relief and local control but data on improving overall survival is limited. Most targeted therapies which provide extracranial control have limited penetration through the blood brain barrier. Given the limited therapeutic options and increasing prevalence of brain metastases, finding new strategies for the management of intracranial metastatic disease is critical. Genomic analysis of brain metastases has led to a better understanding of variations in the driver mutations compared to the primary malignancy. Furthermore, newer generations of targeted agents have shown promising intracranial activity. In this review, we will discuss the major molecular alterations in brain metastases from melanoma, lung, breast, and renal cell carcinoma. We will provide an in-depth review of the completed and ongoing clinical trials of drugs targeting the molecular pathways enriched in brain metastases.

Frequency of Brain Metastases and Multikinase Inhibitor Outcomes in Patients With RET-Rearranged Lung Cancers

INTRODUCTION

In ret proto-oncogene (RET)-rearranged lung cancers, data on the frequency of brain metastases and, in particular, the outcomes of multikinase inhibitor therapy in patients with intracranial disease are not well characterized.

METHODS

A global, multi-institutional registry (cohort A, n = 114) and a bi-institutional data set (cohort B, n = 71) of RET-rearranged lung cancer patients were analyzed. Patients were eligible if they had stage IV lung cancers harboring a RET rearrangement by local testing. The incidence of brain metastases and outcomes with multikinase inhibitor therapy were determined.

RESULTS

The frequency of brain metastases at the time of diagnosis of stage IV disease was 25% (95% confidence interval [CI]: 18%-32%) in all patients from both cohorts. The lifetime prevalence of brain metastasis in stage IV disease was 46% (95% CI: 34%-58%) in patients for whom longitudinal data was available. The cumulative incidence of brain metastases was significantly different (p = 0.0039) between RET-, ROS1-, and ALK receptor tyrosine kinase (ALK)-rearranged lung cancers, with RET intermediate between the other two groups. Although intracranial response data was not available in cohort A, the median progression-free survival of multikinase inhibitor therapy (cabozantinib, vandetanib, or sunitinib) in patients with brain metastases was 2.1 months (95% CI: 1.3-2.9 months, n = 10). In cohort B, an intracranial response was observed in 2 of 11 patients (18%) treated with cabozantinib, vandetanib (± everolimus), ponatinib, or alectinib; the median overall progression-free survival (intracranial and extracranial) was 3.9 months (95% CI: 2.0-4.9 months).

CONCLUSIONS

Brain metastases occur frequently in RET-rearranged lung cancers, and outcomes with multikinase inhibitor therapy in general are suboptimal. Novel RET-directed targeted therapy strategies are needed.

Brain Metastases in Oncogene-Addicted Non-Small Cell Lung Cancer Patients: Incidence and Treatment

Brain metastases (BM) are common in non-small cell lung cancer patients including in molecularly selected populations, such as EGFR-mutant and ALK-rearranged tumors. They are associated with a reduced quality of life, and are commonly the first site of progression for patients receiving tyrosine kinase inhibitors (TKIs). In this review, we summarize incidence of BM and intracranial efficacy with TKI agents according to oncogene driver mutations, focusing on important clinical issues, notably optimal first-line treatment in oncogene-addicted lung tumors with upfront BM (local therapies followed by TKI vs. TKI monotherapy). We also discuss the potential role of newly emerging late-generation TKIs as new standard treatment in oncogene-addicted lung cancer tumors compared with sequential strategies.

Progress in the Management of Advanced Thoracic Malignancies in 2017

The treatment paradigm of NSCLC underwent a major revolution during the course of 2017. Immune checkpoint inhibitors (ICIs) brought remarkable improvements in response and overall survival both in unselected pretreated patients and in untreated patients with programmed death ligand 1 expression of 50% or more. Furthermore, compelling preliminary results were reported for new combinations of anti-programmed cell death 1/programmed death ligand 1 agents with chemotherapy or anti-cytotoxic T-lymphocyte associated protein 4 inhibitors. The success of the ICIs appeared to extend to patients with SCLC, mesothelioma, or thymic tumors. Furthermore, in SCLC, encouraging activity was reported for an experimental target therapy (rovalpituzumab teserine) and a new chemotherapeutic agent (lurbinectedin). For oncogene-addicted NSCLC, next-generation tyrosine kinase inhibitors (TKIs) (such as osimertinib or alectinib) have demonstrated increased response rates and progression-free survival compared with first-generation TKIs in patients with both EGFR-mutated and ALK receptor tyrosine kinase gene (ALK)-rearranged NSCLC. However, because of the lack of mature overall survival data and considering the high efficacy of these drugs in patients with NSCLC previously exposed to first- or second-generation TKIs, definitive conclusions concerning the best treatment sequence cannot yet be drawn. In addition, new oncogenes such as mutant BRAF, tyrosine-protein kinase met gene (MET) and erb-b2 receptor tyrosine kinase 2 gene (HER2), and ret proto-oncogene (RET) rearrangements have joined the list of potential targetable drivers. In conclusion, the field of thoracic oncology is on the verge of a breakthrough that will open up many promising new therapeutic options for physicians and patients. The characterization of biomarkers predictive of sensitivity or resistance to immunotherapy and the identification of the optimal therapeutic combinations (for ICIs) and treatment sequence (for oncogene-addicted NSCLC) represent the toughest upcoming challenges in the domain of thoracic oncology.