Central Nervous System Disease in Patients With RET Fusion-Positive NSCLC Treated With Selpercatinib

CNS Protective Effect of Selpercatinib in First-Line RET Fusion-Positive Advanced Non-Small Cell Lung Cancer

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Although the CNS activity of selpercatinib in patients with RET fusion-positive non-small cell lung cancer (NSCLC) has been previously described, the ability of potent RET inhibition to prevent new CNS metastases from developing has been challenging to measure without randomized data. Serial CNS scans were studied from LIBRETTO-431, a randomized phase III trial of selpercatinib versus platinum/pemetrexed ± pembrolizumab whose primary results have been previously disclosed. Intracranial outcomes were assessed by neuroradiologic blinded independent central review in patients with baseline and ≥1 postbaseline CNS scans. Of the 192 patients within the intention-to-treat pembrolizumab population with baseline CNS scans, 150 patients were without baseline CNS metastases. The cumulative incidence of CNS progression in these patients was reduced with selpercatinib versus chemotherapy + pembrolizumab (cause-specific hazard ratio [HR], 0.17 [95% CI, 0.04 to 0.69]). The HR for intracranial progression-free survival (PFS) was 0.46 (95% CI, 0.18 to 1.18). Among the 42 patients with baseline CNS metastases, similar trends were observed in the cumulative incidence of CNS progression (cause-specific HR, 0.61 [95% CI, 0.19 to 1.92]) and intracranial PFS (HR, 0.74 [95% CI, 0.28 to 1.97]). These data demonstrate that selpercatinib effectively treats existing CNS disease and prevents or delays the formation of new CNS metastases. These results reinforce the importance of identifying RET fusions in first-line patients with NSCLC and treating with selpercatinib.

RET Inhibitors in RET Fusion-Positive Lung Cancers: Past, Present, and Future

While activating RET fusions are identified in various cancers, lung cancer represents the most common RET fusion-positive tumor. The clinical drug development of RET inhibitors in RET fusion-positive lung cancers naturally began after RET fusions were first identified in patient tumor samples in 2011, and thereafter paralleled drug development in RET fusion-positive thyroid cancers. Multikinase inhibitors were initially tested with limited efficacy and substantial toxicity. RET inhibitors were then designed with improved selectivity, central nervous system penetrance, and activity against RET fusions and most RET mutations, including resistance mutations. Owing their success to these rationally designed features, the first-generation selective RET tyrosine kinase inhibitors (TKIs) had higher response rates, more durable disease control, and an improved safety profile compared to the multikinase inhibitors. This led to lung and thyroid cancer, and later tumor-agnostic regulatory approvals. While next-generation RET TKIs were designed to abrogate uncommon on-target (e.g., solvent front mutation) resistance to selpercatinib and pralsetinib, many of these drugs lacked the selectivity of the first-generation TKIs, raising the question of what the future holds for drug development in RET-dependent cancers.

Prevention of Brain Metastases: A New Frontier

This review discusses the topic of prevention of brain metastases from the most frequent solid tumor types, i.e., lung cancer, breast cancer and melanoma. Within each tumor type, the risk of brain metastasis is related to disease status and molecular subtype (i.e., EGFR-mutant non-small cell lung cancer, HER2-positive and triple-negative breast cancer, BRAF and NRAF-mutant melanoma). Prophylactic cranial irradiation is the standard of care in patients in small cell lung cancer responsive to chemotherapy but at the price of late neurocognitive decline. More recently, several molecular agents with the capability to target molecular alterations driving tumor growth have proven as effective in the prevention of secondary relapse into the brain in clinical trials. This is the case for EGFR-mutant or ALK-rearranged non-small cell lung cancer inhibitors, tucatinib and trastuzumab-deruxtecan for HER2-positive breast cancer and BRAF inhibitors for melanoma. The need for screening with an MRI in asymptomatic patients at risk of brain metastases is emphasized.

Brain metastases and next-generation anticancer therapies: a survival guide for clinicians

Historically, patients with brain metastases (BMs) have been characterized by few systemic treatment options and poor prognosis. The recent introduction of next-generation anticancer therapies such as molecular targeted agents and immunotherapy have revolutionized the clinical decision-making process of this sub-population, posing new challenges to physicians. In this review, current evidence for the use of checkpoint inhibitors and targeted therapies in patients with BMs are discussed, with a focus on lung cancer, breast cancer, melanoma and renal cell carcinoma, providing suggestions and potential workflows for daily clinical practice. Several other on-going and future challenges, such as clinical trials design, ways to improve CNS penetration of novel drugs and unique molecular characteristics of BMs, are also discussed. The aim is producing an updated and easy-to-read guide for physicians, to improve decision-making in clinical practice.

Emerging therapeutics and evolving assessment criteria for intracranial metastases in patients with oncogene-driven non-small-cell lung cancer

The improved survival outcomes of patients with non-small-cell lung cancer (NSCLC), largely owing to the improved control of systemic disease provided by immune-checkpoint inhibitors and novel targeted therapies, have highlighted the challenges posed by central nervous system (CNS) metastases as a devastating yet common complication, with up to 50% of patients developing such lesions during the course of the disease. Early-generation tyrosine-kinase inhibitors (TKIs) often provide robust systemic disease control in patients with oncogene-driven NSCLCs, although these agents are usually unable to accumulate to therapeutically relevant concentrations in the CNS owing to an inability to cross the blood-brain barrier. However, the past few years have seen a paradigm shift with the emergence of several novel or later-generation TKIs with improved CNS penetrance. Such agents have promising levels of activity against brain metastases, as demonstrated by data from preclinical and clinical studies. In this Review, we describe current preclinical and clinical evidence of the intracranial activity of TKIs targeting various oncogenic drivers in patients with NSCLC, with a focus on newer agents with enhanced CNS penetration, leptomeningeal disease and the need for intrathecal treatment options. We also discuss evolving assessment criteria and regulatory considerations for future clinical investigations.

RET-Altered Cancers-A Tumor-Agnostic Review of Biology, Diagnosis and Targeted Therapy Activity

RET alterations, such as fusions or mutations, drive the growth of multiple tumor types. These alterations are found in canonical (lung and thyroid) and non-canonical (e.g., gastrointestinal, breast, gynecological, genitourinary, histiocytic) cancers. RET alterations are best identified via comprehensive next-generation sequencing, preferably with DNA and RNA interrogation for fusions. Targeted therapies for RET-dependent cancers have evolved from older multikinase inhibitors to selective inhibitors of RET such as selpercatinib and pralsetinib. Prospective basket trials and retrospective reports have demonstrated the activity of these drugs in a wide variety of RET-altered cancers, notably those with RET fusions. This paved the way for the first tumor-agnostic selective RET inhibitor US FDA approval in 2022. Acquired resistance to RET kinase inhibitors can take the form of acquired resistance mutations (e.g., RET G810X) or bypass alterations.