Selective RET kinase inhibition for patients with RET-altered cancers

Discovery of 7-(1-methyl-1H-pyrazol-4-yl)-1,6-naphthyridine derivatives as potent inhibitors of rearranged during transfection (RET) and RET solvent-front mutants for overcoming selpercatinib resistance

Rearranged during transfection kinase (RET) inhibition has been considered a promising therapeutic approach for treatment of a variety of cancers. However, the clinical therapeutic benefits of the second-generation RET inhibitor selpercatinib are greatly compromised by acquired resistance mediated by solvent-front mutations (e.g., RETG810 R/S/C). Herein, we report a class of 7-(1-methyl-1H-pyrazol-4-yl)-1,6-naphthyridine derivatives as potent RET and RET solvent-front mutant inhibitors for overcoming selpercatinib resistance. The representative compound 20p exhibited excellent in vitro inhibitory activities against solvent-front mutations (RETG810R, RETG810S, and RETG810C) with low nanomolar range (IC50 of 5.7-8.3 nM), which was 15-29-fold more potent than selpercatinib (IC50 of 95.3-244.1 nM). Additionally, 20p exhibited acceptable pharmacokinetic properties with oral bioavailability of 30.4 %. Importantly, 20p exhibited highly impressive antitumor potency in both a Ba/F3-KIF5B-RETWT-derived xenograft mouse model and a selpercatinib-resistant Ba/F3-KIF5B-RETG810R-positive mutant xenograft mouse model. Overall, 20p represents a novel and promising drug lead for overcoming RET solvent-front mutation-based resistance to selpercatinib.

Long-term safety of selpercatinib for Rearrenged during transfection (RET)-activated advanced solid tumors in LIBRETTO-001: differing patterns of adverse events over time

BACKGROUND

Selpercatinib is a selective RET inhibitor approved for treatment of RET-activated cancers. Adverse events (AEs) are manageable with dose modifications. This post hoc analysis characterized selpercatinib's clinical safety profile after long-term follow-up in the safety population of LIBRETTO-001.

PATIENTS AND METHODS

LIBRETTO-001 is an ongoing phase I/II, single-arm, open-label trial (NCT03157128). Eligible patients were ≥18 years old with diagnosis of advanced/metastatic RET fusion-positive solid tumor, RET-mutant medullary thyroid cancer, or other RET-activated tumors. In phase I, patients received selpercatinib 20 mg QD or 20-240 mg BID; patients in phase II received 160 mg BID. The analyzed population comprised all patients who received ≥1 selpercatinib dose and were followed up until data cutoff (January 13, 2023).

RESULTS

For the 837 patients, median follow-up was 45.4 months (95% CI, 44.5-46.6); median time on treatment was 30.1 months (range 0.1-66.8). Grade ≥3 treatment-emergent AEs (TEAEs) were reported in 76.2% of patients; most common events were hypertension (19.7%), ALT increased (11.8%), and hyponatremia (9.2%). Serious TEAEs were reported in 51.4% of patients. Most frequently reported any-grade AEs at <6 months of treatment were fatigue (36.6%), dry mouth (32.8%), and ALT increased (30.5%); at ≥24 months of treatment, these were edema (63.2%), diarrhea (60.7%), and fatigue (53.0%). Selpercatinib-related TEAEs leading to reduced dosage were reported in 39.3%, those leading to treatment interruption were reported in 47.1%, and those leading to discontinuation were reported in 4.3% of patients.

CONCLUSION

Long-term treatment with selpercatinib is feasible. AEs are manageable with dose modifications, allowing most patients to continue safely on therapy.

Molecular genetics, therapeutics and RET inhibitor resistance for medullary thyroid carcinoma and future perspectives

Medullary thyroid carcinoma (MTC) is a rare type of thyroid malignancy that accounts for approximately 1-2% of all thyroid cancers (TCs). MTC include hereditary and sporadic cases, the former derived from a germline mutation of rearrangement during transfection (RET) proto-oncogene, whereas somatic RET mutations are frequently present in the latter. Surgery is the standard treatment for early stage MTC, and the 10-year survival rate of early MTC is over 80%. While for metastatic MTC, chemotherapy showing low response rate, and there was a lack of effective systemic therapies in the past. Due to the high risk (ca. 15-20%) of distant metastasis and limited systemic therapies, the 10-year survival rate of patients with advanced MTC was only 10-40% from the time of first metastasis. Over the past decade, targeted therapy for RET has developed rapidly, bringing hopes to patients with advanced and progressive MTC. Two multi-kinase inhibitors (MKIs) including Cabozantinib and Vandetanib have been shown to increase progression-free survival (PFS) for patients with metastatic MTC and have been approved as choices of first-line treatment. However, these MKIs have not prolonged overall survival (OS) and their utility is limited due to high rates of off-target toxicities. Recently, new generation TKIs, including Selpercatinib and Pralsetinib, have demonstrated highly selective efficacy against RET and more favorable side effect profiles, and gained approval as second-line treatment options. Despite the ongoing development of RET inhibitors, the management of advanced and progressive MTC remains challenging, drug resistance remains the main reason for treatment failure, and the mechanisms are still unclear. Besides, new promising therapeutic approaches, such as novel drug combinations and next generation RET inhibitors are under development. Herein, we overview the pathogenesis, molecular genetics and current management approaches of MTC, and focus on the recent advances of RET inhibitors, summarize the current situation and unmet needs of these RET inhibitors in MTC, and provide an overview of novel strategies for optimizing therapeutic effects.

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.

The evolving landscape of tissue-agnostic therapies in precision oncology

Tumor-agnostic therapies represent a paradigm shift in oncology by altering the traditional means of characterizing tumors based on their origin or location. Instead, they zero in on specific genetic anomalies responsible for fueling malignant growth. The watershed moment for tumor-agnostic therapies arrived in 2017, with the US Food and Drug Administration's historic approval of pembrolizumab, an immune checkpoint inhibitor. This milestone marked the marriage of genomics and immunology fields, as an immunotherapeutic agent gained approval based on genomic biomarkers, specifically, microsatellite instability-high or mismatch repair deficiency (dMMR). Subsequently, the approval of NTRK inhibitors, designed to combat NTRK gene fusions prevalent in various tumor types, including pediatric cancers and adult solid tumors, further underscored the potential of tumor-agnostic therapies. The US Food and Drug Administration approvals of targeted therapies (BRAF V600E, RET fusion), immunotherapies (tumor mutational burden ≥10 mutations per megabase, dMMR) and an antibody-drug conjugate (Her2-positive-immunohistochemistry 3+ expression) with pan-cancer efficacy have continued, offering newfound hope to patients grappling with advanced solid tumors that harbor particular biomarkers. In this comprehensive review, the authors delve into the expansive landscape of tissue-agnostic targets and drugs, shedding light on the rationale underpinning this approach, the hurdles it faces, presently approved therapies, voices from the patient advocacy perspective, and the tantalizing prospects on the horizon. This is a welcome advance in oncology that transcends the boundaries of histology and location to provide personalized options.

Mechanisms of resistance to tyrosine kinase inhibitor-targeted therapy and overcoming strategies

Tyrosine kinase inhibitor (TKI)-targeted therapy has revolutionized cancer treatment by selectively blocking specific signaling pathways crucial for tumor growth, offering improved outcomes with fewer side effects compared with conventional chemotherapy. However, despite their initial effectiveness, resistance to TKIs remains a significant challenge in clinical practice. Understanding the mechanisms underlying TKI resistance is paramount for improving patient outcomes and developing more effective treatment strategies. In this review, we explored various mechanisms contributing to TKI resistance, including on-target mechanisms and off-target mechanisms, as well as changes in the tumor histology and tumor microenvironment (intrinsic mechanisms). Additionally, we summarized current therapeutic approaches aiming at circumventing TKI resistance, including the development of next-generation TKIs and combination therapies. We also discussed emerging strategies such as the use of dual-targeted antibodies and PROteolysis Targeting Chimeras. Furthermore, we explored future directions in TKI-targeted therapy, including the methods for detecting and monitoring drug resistance during treatment, identification of novel targets, exploration of dual-acting kinase inhibitors, application of nanotechnologies in targeted therapy, and so on. Overall, this review provides a comprehensive overview of the challenges and opportunities in TKI-targeted therapy, aiming to advance our understanding of resistance mechanisms and guide the development of more effective therapeutic approaches in cancer treatment.

Assessing the Effectiveness of Selective RET Inhibitors in RET-Positive Cancers through Fluorodeoxyglucose Uptake Analysis

Selective RET inhibitors, such as selpercatinib and pralsetinib, have revolutionized the treatment of cancers with RET gene alterations. These inhibitors have shown remarkable clinical efficacy, particularly in RET-driven lung cancer, medullary thyroid cancer, and other solid tumors driven by RET gene fusions. The assessment of treatment response in oncology has been greatly enhanced by Fluorodeoxyglucose Positron Emission Tomography (FDG-PET), a valuable tool that measures tumor metabolism and provides early indicators of treatment effectiveness. This work explores the effectiveness of selective RET inhibitors in targeting RET-positive cancers and investigates the utility of FDG-PET in assessing treatment response. The paper includes insightful case studies that highlight the successful application of RET inhibitors in the treatment of RET-positive cancers. The findings suggest that FDG-PET has the potential to serve as a non-invasive biomarker for monitoring treatment response in patients with RET-positive cancers. However, further research is required to establish standardized criteria for interpreting FDG-PET scans in the context of selective RET inhibitors and to uncover the broader applications of FDG-PET in precision oncology.

Non-Small-Cell Lung Cancers (NSCLCs) Harboring RET Gene Fusion, from Their Discovery to the Advent of New Selective Potent RET Inhibitors: "Shadows and Fogs"

RET fusions are relatively rare in Non-Small-Cell Lung Cancers (NSCLCs), being around 1-2% of all NSCLCs. They share the same clinical features as the other fusion-driven NSCLC patients, as follows: younger age, adenocarcinoma histology, low exposure to tobacco, and high risk of spreading to the brain. Chemotherapy and immunotherapy have a low impact on the prognosis of these patients. Multitargeted RET inhibitors have shown modest activity jeopardized by high toxicity. New potent and selective RET inhibitors (RET-Is) (pralsetinib and selpercatinib) have achieved a higher efficacy minimizing the known toxicities of the multitargeted agents. This review will describe the sensitivity of immune-checkpoint inhibitors (ICIs) in RET fusion + NSCLC patients, as well their experiences with the 'old' multi-targeted RET inhibitors. This review will focus on the advent of new potent and selective RET-Is. We will describe their efficacy as well as the main mechanisms of resistance to them. We will further proceed to deal with the new drugs and strategies proposed to overcome the resistance to RET-Is. In the last section, we will also focus on the safety profile of RET-Is, dealing with the main toxicities as well as the rare but severe adverse events.

Novel therapeutic strategies targeting bypass pathways and mitochondrial dysfunction to combat resistance to RET inhibitors in NSCLC

RET fusion is an oncogenic driver in 1-2 % of patients with non-small cell lung cancer (NSCLC). Although RET-positive tumors have been treated with multikinase inhibitors such as vandetanib or RET-selective inhibitors, ultimately resistance to them develops. Here we established vandetanib resistance (VR) clones from LC-2/ad cells harboring CCDC6-RET fusion and explored the molecular mechanism of the resistance. Each VR clone had a distinct phenotype, implying they had acquired resistance via different mechanisms. Consistently, whole exome-seq and RNA-seq revealed that the VR clones had unique mutational signatures and expression profiles, and shared only a few common remarkable events. AXL and IGF-1R were activated as bypass pathway in different VR clones, and sensitive to a combination of RET and AXL inhibitors or IGF-1R inhibitors, respectively. SMARCA4 loss was also found in a particular VR clone and 55 % of post-TKI lung tumor tissues, being correlated with higher sensitivity to SMARCA4/SMARCA2 dual inhibition and shorter PFS after subsequent treatments. Finally, we detected an increased number of damaged mitochondria in one VR clone, which conferred sensitivity to mitochondrial electron transfer chain inhibitors. Increased mitochondria were also observed in post-TKI biopsy specimens in 13/20 cases of NSCLC, suggesting a potential strategy targeting mitochondria to treat resistant tumors. Our data propose new promising therapeutic options to combat resistance to RET inhibitors in NSCLC.

Association of 18F- fluorodeoxyglucose uptake with the expression of metabolism-related molecules in papillary thyroid cancer

OBJECTIVES

18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG-PET/CT) is a diagnostic imaging method that is based on the Warburg effect, which is the increased uptake of glucose through aerobic glycolysis in cancer cells. The diagnostic value of 18F-FDG-PET/CT for thyroid cancer is controversial. However, uptake of 18F-FDG and the corresponding maximum standardized uptake value (SUVmax) is expected to reflect the metabolic status of cancer cells. In the present study, we sought to determine the relationship between 18F-FDG uptake and tumor metabolism- associated factors.

METHODS

This was a single-center retrospective study. In the present study, SUVmax was compared with the expression of hexokinase 2 (HK2), glucose transporter 1 (GLUT1), vascular endothelial growth factor (VEGF), and glutaminase 1 (GLS1) in 41 patients with thyroid cancer.

RESULTS

GLS1 expression was found to be moderately correlated with SUVmax (p < 0.001, r = 0.51), whereas HK2 and VEGF expression were weakly correlated (p = 0.011, r = 0.28, p = 0.008, r = 0.29, respectively) and GLUT1 did not correlate with SUVmax (p = 0.62, r = 0.06).

CONCLUSION

Our findings suggest 18F-FDG PET/CT reflects GLS1 expression in thyroid cancer and could be used to select suitable candidates for GLS1 inhibitor treatment.

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.

Selpercatinib attenuates bleomycin-induced pulmonary fibrosis by inhibiting the TGF-β1 signaling pathway

IPF is a chronic, progressive, interstitial lung disease with high mortality. Current drugs have limited efficacy in curbing disease progression and improving quality of life. Selpercatinib, a highly selective inhibitor of receptor tyrosine kinase RET (rearranged during transfection), was approved in 2020 for the treatment of a variety of solid tumors with RET mutations. In this study, the action and mechanism of Selpercatinib in pulmonary fibrosis were evaluated in vivo and in vitro. In vivo experiments demonstrated that Selpercatinib significantly ameliorated bleomycin (BLM)-induced pulmonary fibrosis in mice. In vitro, Selpercatinib inhibited the proliferation, migration, activation and extracellular matrix deposition of fibroblasts by inhibiting TGF-β1/Smad and TGF-β1/non-Smad pathway, and suppressed epithelial-mesenchymal transition (EMT) like process of lung epithelial cells via inhibiting TGF-β1/Smad pathway. The results of in vivo pharmacological tests corroborated the results obtained from the in vitro experiments. Further studies revealed that Selpercatinib inhibited abnormal phenotypes of lung fibroblasts and epithelial cells in part by regulating its target RET. In short, Selpercatinib inhibited the activation of fibroblasts and EMT-like process of lung epithelial cells by inhibiting TGF-β1/Smad and TGF-β1/non-Smad pathways, thus alleviating BLM-induced pulmonary fibrosis in mice.

The rapidly changing field of predictive biomarkers of non-small cell lung cancer

Lung cancer is a leading cause of cancer-related death worldwide in both men and women, however mortality in the US and EU are recently declining in parallel with the gradual cut of smoking prevalence. Consequently, the relative frequency of adenocarcinoma increased while that of squamous and small cell carcinomas declined. During the last two decades a plethora of targeted drug therapies have appeared for the treatment of metastasizing non-small cell lung carcinomas (NSCLC). Personalized oncology aims to precisely match patients to treatments with the highest potential of success. Extensive research is done to introduce biomarkers which can predict the effectiveness of a specific targeted therapeutic approach. The EGFR signaling pathway includes several sufficient targets for the treatment of human cancers including NSCLC. Lung adenocarcinoma may harbor both activating and resistance mutations of the EGFR gene, and further, mutations of KRAS and BRAF oncogenes. Less frequent but targetable genetic alterations include ALK, ROS1, RET gene rearrangements, and various alterations of MET proto-oncogene. In addition, the importance of anti-tumor immunity and of tumor microenvironment has become evident recently. Accumulation of mutations generally trigger tumor specific immune defense, but immune protection may be upregulated as an aggressive feature. The blockade of immune checkpoints results in potential reactivation of tumor cell killing and induces significant tumor regression in various tumor types, such as lung carcinoma. Therapeutic responses to anti PD1-PD-L1 treatment may correlate with the expression of PD-L1 by tumor cells. Due to the wide range of diagnostic and predictive features in lung cancer a plenty of tests are required from a single small biopsy or cytology specimen, which is challenged by major issues of sample quantity and quality. Thus, the efficacy of biomarker testing should be warranted by standardized policy and optimal material usage. In this review we aim to discuss major targeted therapy-related biomarkers in NSCLC and testing possibilities comprehensively.

Developing Dynamic Structure-Based Pharmacophore and ML-Trained QSAR Models for the Discovery of Novel Resistance-Free RET Tyrosine Kinase Inhibitors Through Extensive MD Trajectories and NRI Analysis

Activation of RET tyrosine kinase plays a critical role in the pathogenesis of various cancers, including non-small cell lung cancer, papillary thyroid cancers, multiple endocrine neoplasia type 2A and 2B (MEN2A, MEN2B), and familial medullary thyroid cancer. Gene fusions and point mutations in the RET proto-oncogene result in constitutive activation of RET signaling pathways. Consequently, developing effective inhibitors to target RET is of utmost importance. Small molecules have shown promise as inhibitors by binding to the kinase domain of RET and blocking its enzymatic activity. However, the emergence of resistance due to single amino acid changes poses a significant challenge. In this study, a structure-based dynamic pharmacophore-driven approach using E-pharmacophore modeling from molecular dynamics trajectories is proposed to select low-energy favorable hypotheses, and ML-trained QSAR models to predict pIC50 values of compounds. For this aim, extensive small molecule libraries were screened using developed ligand-based models, and potent compounds that are capable of inhibiting RET activation were proposed.

Efficacy and safety of selpercatinib in treating RET-altered MTC: A single-arm meta-analysis

Background

Selpercatinib is effective in the treatment of RET-altered medullary thyroid carcinoma (MTC). This study aimed to evaluate the efficacy and safety of selpercatinib in the treatment of patients with RET-altered MTC.

Methods

PubMed, Embase, the Cochrane Library, and ClinicalTrials.gov were searched from their inception to April 5, 2024. Outcomes included complete response (CR), partial response (PR), stable disease (SD), objective response rate (ORR), disease control rate (DCR), and adverse events (AEs). We carried out a meta-analysis of these studies and exploratory subgroup analyses. The effect sizes for all pooled results were presented as 95% confidence intervals with upper and lower limits.

Results

The pooled CR, PR, and SD rates for all patients were 10%, 59%, and 26%, respectively. The pooled ORR in all patients was 70%, while the pooled ORR in pre-treated and non-pre-treated groups were 67% and 70%, respectively. The pooled DCR in all patients was 95%, while the pooled DCR in pre-treated and non-pre-treated groups were 96% and 95%, respectively. The most common AEs associated with selpercatinib were hypertension, alanine aminotransferase (ALT) increased and aspartate aminotransferase (AST) increased.

Conclusion

Selpercatinib offers significant benefits to patients with RET-altered MTC with assessable CR, PR, SD, ORR, and grade 3-4 AEs; however, treatment-related AEs should be considered.

Pyrazolopyridine-based kinase inhibitors for anti-cancer targeted therapy

The need for effective cancer treatments continues to be a challenge for the biomedical research community. In this case, the advent of targeted therapy has significantly improved therapeutic outcomes. Drug discovery and development efforts targeting kinases have resulted in the approval of several small-molecule anti-cancer drugs based on ATP-mimicking heterocyclic cores. Pyrazolopyridines are a group of privileged heterocyclic cores in kinase drug discovery, which are present in several inhibitors that have been developed against various cancers. Notably, selpercatinib, glumetinib, camonsertib and olverembatinib have either received approval or are in late-phase clinical studies. This review presents the success stories employing pyrazolopyridine scaffolds as hinge-binding cores to address various challenges in kinase-targeted drug discovery research.

In Silico Search for Drug Candidates Targeting the PAX8-PPARγ Fusion Protein in Thyroid Cancer

The PAX8/PPARγ rearrangement, producing the PAX8-PPARγ fusion protein (PPFP), is thought to play an essential role in the oncogenesis of thyroid follicular tumors. To identify PPFP-targeted drug candidates and establish an early standard of care for thyroid tumors, we performed ensemble-docking-based compound screening. Specifically, we investigated the pocket structure that should be adopted to search for a promising ligand compound for the PPFP; the position of the ligand-binding pocket on the PPARγ side of the PPFP is similar to that of PPARγ; however, the shape is slightly different between them due to environmental factors. We developed a method for selecting a PPFP structure with a relevant pocket and high prediction accuracy for ligand binding. This method was validated using PPARγ, whose structure and activity values are known for many compounds. Then, we performed docking calculations to the PPFP for 97 drug or drug-like compounds registered in the DrugBank database with a thiazolidine backbone, which is one of the characteristics of ligands that bind well to PPARγ. Furthermore, the binding affinities of promising ligand candidates were estimated more reliably using the molecular mechanics Poisson-Boltzmann surface area method. Thus, we propose promising drug candidates for the PPFP with a thiazolidine backbone.

Next-generation sequencing identified that RET variation associates with lymph node metastasis and the immune microenvironment in thyroid papillary carcinoma

BACKGROUND

To date, although most thyroid carcinoma (THCA) achieves an excellent prognosis, some patients experience a rapid progression episode, even with differentiated THCA. Nodal metastasis is an unfavorable predictor. Exploring the underlying mechanism may bring a deep insight into THCA.

METHODS

A total of 108 THCA from Chinese patients with next-generation sequencing (NGS) were recruited. It was used to explore the gene alteration spectrum of THCA and identify gene alterations related to nodal metastasis in papillary thyroid carcinoma (PTC). The Cancer Genome Atlas THCA cohort was further studied to elucidate the relationship between specific gene alterations and tumor microenvironment. A pathway enrichment analysis was used to explore the underlying mechanism.

RESULTS

Gene alteration was frequent in THCA. BRAF, RET, POLE, ATM, and BRCA1 were the five most common altered genes. RET variation was positively related to nodal metastasis in PTC. RET variation is associated with immune cell infiltration levels, including CD8 naïve, CD4 T and CD8 T cells, etc. Moreover, Step 3 and Step 4 of the cancer immunity cycle (CIC) were activated, whereas Step 6 was suppressed in PTC with RET variation. A pathway enrichment analysis showed that RET variation was associated with several immune-related pathways.

CONCLUSION

RET variation is positively related to nodal metastasis in Chinese PTC, and anti-tumor immune response may play a role in nodal metastasis triggered by RET variation.

Mechanisms of resistance to targeted therapy and immunotherapy in non-small cell lung cancer: promising strategies to overcoming challenges

Resistance to targeted therapy and immunotherapy in non-small cell lung cancer (NSCLC) is a significant challenge in the treatment of this disease. The mechanisms of resistance are multifactorial and include molecular target alterations and activation of alternative pathways, tumor heterogeneity and tumor microenvironment change, immune evasion, and immunosuppression. Promising strategies for overcoming resistance include the development of combination therapies, understanding the resistance mechanisms to better use novel drug targets, the identification of biomarkers, the modulation of the tumor microenvironment and so on. Ongoing research into the mechanisms of resistance and the development of new therapeutic approaches hold great promise for improving outcomes for patients with NSCLC. Here, we summarize diverse mechanisms driving resistance to targeted therapy and immunotherapy in NSCLC and the latest potential and promising strategies to overcome the resistance to help patients who suffer from NSCLC.

RET kinase inhibitors for the treatment of RET-altered thyroid cancers: Current knowledge and future directions

RET gain-of-function mutations are the most common drivers in medullary thyroid carcinoma, while RET fusions are identified in 5-10% of papillary thyroid carcinomas. Thus, RET plays a major role in the tumorigenesis of thyroid neoplasia, making it a valuable therapeutic target. Over a decade ago, multikinase inhibitors (MKIs) were first shown to have variable degrees of anti-RET activity. Despite some clinical efficacy in RET-altered thyroid cancers, significant off-target activity of MKIs led to marked toxicities limiting their use. More recently, two potent, highly selective RET inhibitors, selpercatinib and pralsetinib, were shown to have notable efficacy in RET-altered cancers, associated with more tolerable side effect profiles than those of MKIs. However, these treatments are non-curative, and emerging evidence suggests that patients who progress on therapy acquire mutations conferring drug resistance. Thus, the quest for a more definitive treatment for advanced, RET-altered thyroid cancers continues. This year we celebrate the 30th anniversary of the association of germline mutations of the RET proto-oncogene with the multiple endocrine neoplasia (MEN) type 2 syndromes. In this timely review, we summarize the current state-of-the-art treatment strategies for RET-altered thyroid cancers, their limitations, as well as future therapeutic avenues.

Targeting RET alterations in non-small cell lung cancer

Rearranged during transfection (RET) alterations, which lead to aberrant activation of the RET proto-oncogene, have been identified in various cancers. In non-small cell lung cancer (NSCLC), RET mutations often manifest as RET fusion genes and are observed in 1-2 % of patients with NSCLC. In recent years, selective RET inhibitors such as selpercatinib and pralsetinib, approved by the Food and Drug Administration (FDA) in 2020, have been part of the revolutionary changes in the treatment landscape for non-small cell lung cancer. While first-generation RET inhibitors have become part of the standard of care for RET-fusion positive NSCLC, a new challenge has emerged: acquired resistance to RET inhibitors. RET resistance is a complex phenomenon that can manifest as either on-target or off-target resistance. Numerous studies have been conducted to identify the mechanisms behind this resistance. This review provides an overview of the biology of RET in NSCLC, methods of RET testing, and a comprehensive analysis of the clinical outcomes associated with multikinase and selective RET inhibitors for NSCLC. Additionally, we will explore future perspectives for RET fusion-positive NSCLC, including ongoing trials and the challenges involved in overcoming resistance to RET inhibitors.

Tumor-agnostic baskets to N-of-1 platform trials and real-world data: Transforming precision oncology clinical trial design

Choosing the right drug(s) for the right patient via advanced genomic sequencing and multi-omic interrogation is the sine qua non of precision cancer medicine. Traditional cancer clinical trial designs follow well-defined protocols to evaluate the efficacy of new therapies in patient groups, usually identified by their histology/tissue of origin of their malignancy. In contrast, precision medicine seeks to optimize benefit in individual patients, i.e., to define who benefits rather than determine whether the overall group benefits. Since cancer is a disease driven by molecular alterations, innovative trial designs, including biomarker-defined tumor-agnostic basket trials, are driving ground-breaking regulatory approvals and deployment of gene- and immune-targeted drugs. Molecular interrogation further reveals the disruptive reality that advanced cancers are extraordinarily complex and individually distinct. Therefore, optimized treatment often requires drug combinations and N-of-1 customization, addressed by a new generation of N-of-1 trials. Real-world data and structured master registry trials are also providing massive datasets that are further fueling a transformation in oncology. Finally, machine learning is facilitating rapid discovery, and it is plausible that high-throughput computing, in silico modeling, and 3-dimensional printing may be exploitable in the near future to discover and design customized drugs in real time.

Tissue-Agnostic Cancer Therapy Approvals

Tumor-agnostic, or histology-agnostic, cancer therapy marks a groundbreaking evolution in the realm of precision oncology. In stark contrast to conventional cancer treatments that categorize malignancies based on their tissue of origin (eg, breast, lung, renal cell, etc), tumor-agnostic therapies transcend histologic boundaries, honing in on the genetic and molecular attributes of tumors, regardless of their location. This article offers a comprehensive review of the current landscape of tissue-agnostic cancer therapies and provides clinical insights to empower surgical oncologists with a deeper understanding of these innovative therapeutic approaches.

State of the Art in 3D Culture Models Applied to Thyroid Cancer

Thyroid cancer (TC) is the prevalent endocrine tumor with a rising incidence, particularly in higher-income countries, leading to an increased interest in its management and treatment. While overall, survival rates for TC are usually favorable, advanced cases, especially with metastasis and specific histotypes, pose challenges with poorer outcomes, advocating the need of systemic treatments. Targeted therapies have shown efficacy in both preclinical models and clinical trials but face issues of resistance, since they usually induce partial and transient response. These resistance phenomena are currently only partially addressed by traditional preclinical models. This review explores the limitations of traditional preclinical models and emphasizes the potential of three-dimensional (3D) models, such as transwell assays, spheroids, organoids, and organ-on-chip technology in providing a more comprehensive understanding of TC pathogenesis and treatment responses. We reviewed their use in the TC field, highlighting how they can produce new interesting insights. Finally, the advent of organ-on-chip technology is currently revolutionizing preclinical research, offering dynamic, multi-cellular systems that replicate the complexity of human organs and cancer-host interactions.

A Highly Sensitive XNA-Based RT-qPCR Assay for the Identification of ALK, RET, and ROS1 Fusions in Lung Cancer

Lung cancer is often triggered by genetic alterations that result in the expression of oncogenic tyrosine kinases. Specifically, ALK, RET, and ROS1 chimeric receptor tyrosine kinases are observed in approximately 5-7%, 1-2%, and 1-2% of NSCLC patients, respectively. The presence of these fusion genes determines the response to tyrosine kinase inhibitors. Thus, accurate detection of these gene fusions is essential in cancer research and precision oncology. To address this need, we have developed a multiplexed RT-qPCR assay using xeno nucleic acid (XNA) molecular clamping technology to detect lung cancer fusions. This assay can quantitatively detect thirteen ALK, seven ROS1, and seven RET gene fusions in FFPE samples. The sensitivity of the assay was established at a limit of detection of 50 copies of the synthetic template. Our assay has successfully identified all fusion transcripts using 50 ng of RNA from both reference FFPE samples and cell lines. After validation, a total of 77 lung cancer patient FFPE samples were tested, demonstrating the effectiveness of the XNA-based fusion gene assay with clinical samples. Importantly, this assay is adaptable to highly degraded RNA samples with low input amounts. Future steps involve expanding the testing to include a broader range of clinical samples as well as cell-free RNAs to further validate its applicability and reliability.

Kinase inhibitor macrocycles: a perspective on limiting conformational flexibility when targeting the kinome with small molecules

Methods utilized for drug discovery and development within the kinome have rapidly evolved since the approval of imatinib, the first small molecule kinase inhibitor. Macrocycles have received increasing interest as a technique to improve kinase inhibitor drug properties evident by the FDA approvals of lorlatinib, pacritinib, and repotrectinib. Compared to their acyclic counterparts, macrocycles can possess improved pharmacodynamic and pharmacokinetic properties. This review highlights clinical success stories when implementing macrocycles in kinase-based drug discovery and showcases that macrocyclization is a clinically validated drug discovery strategy when targeting the kinome.

Selpercatinib combination with the mitochondria-targeted antioxidant MitoQ effectively suppresses RET-mutant thyroid cancer

Genetic alternation of REarranged during Transfection (RET) that leads to constitutive RET activation is a crucial etiological factor for thyroid cancer. RET is known to regulate mitochondrial processes, although the underlying molecular mechanisms remain unclear. We previously showed that the multi-kinase inhibitors vandetanib and cabozantinib increase the mitochondrial membrane potential (Δψm) in RET-mutated thyroid tumor cells and that this effect can be exploited to increase mitochondrial enrichment of Δψm-sensitive agents in the tumor cells. In this study, we hypothesized that the RET-selective inhibitor, selpercatinib, can increase Δψm and, subsequently, tumor cell uptake of the mitochondria-targeted ubiquinone (MitoQ) to the level to break the mitochondrial homeostasis and induce lethal responses in RET-mutated thyroid tumor cells. We show that selpercatinib significantly increased Δψm, and its combination with MitoQ synergistically suppressed RET-mutated human thyroid tumor cells, which we validated using RET-targeted genetic approaches. Selpercatinib and MitoQ, in combination, also suppressed CCDC6-RET fusion cell line xenografts in mice and prolonged animal survival more effectively than single treatments of each agent. Moreover, we treated two patients with CCDC6-RET or RETM918T thyroid cancer, who could not take selpercatinib at regular doses due to adverse effects, with a dose-reduced selpercatinib and MitoQ combination. In response to this combination therapy, both patients showed tumor reduction. The quality of life of one patient significantly improved over a year until the tumor relapsed. This combination of selpercatinib with MitoQ may have therapeutic potential for patients with RET-mutated tumors and intolerant to regular selpercatinib doses.

Oncogenic alterations in advanced NSCLC: a molecular super-highway

Lung cancer ranks among the most common cancers world-wide and is the first cancer-related cause of death. The classification of lung cancer has evolved tremendously over the past two decades. Today, non-small cell lung cancer (NSCLC), particularly lung adenocarcinoma, comprises a multitude of molecular oncogenic subsets that change both the prognosis and management of disease.Since the first targeted oncogenic alteration identified in 2004, with the epidermal growth factor receptor (EGFR), there has been unprecedented progress in identifying and targeting new molecular alterations. Almost two decades of experience have allowed scientists to elucidate the biological function of oncogenic drivers and understand and often overcome the molecular basis of acquired resistance mechanisms. Today, targetable molecular alterations are identified in approximately 60% of lung adenocarcinoma patients in Western populations and 80% among Asian populations. Oncogenic drivers are largely enriched among non-smokers, east Asians, and younger patients, though each alteration has its own patient phenotype.The current landscape of druggable molecular targets includes EGFR, anaplastic lymphoma kinase (ALK), v-raf murine sarcoma viral oncogene homolog B (BRAF), ROS proto-oncogene 1 (ROS1), Kirstin rat sarcoma virus (KRAS), human epidermal receptor 2 (HER2), c-MET proto-oncogene (MET), neurotrophic receptor tyrosine kinase (NTRK), rearranged during transfection (RET), neuregulin 1 (NRG1). In addition to these known targets, others including Phosphoinositide 3-kinases (PI3K) and fibroblast growth factor receptor (FGFR) have garnered significant attention and are the subject of numerous ongoing trials.In this era of personalized, precision medicine, it is of paramount importance to identify known or potential oncogenic drivers in each patient. The development of targeted therapy is mirrored by diagnostic progress. Next generation sequencing offers high-throughput, speed and breadth to identify molecular alterations in entire genomes or targeted regions of DNA or RNA. It is the basis for the identification of the majority of current druggable alterations and offers a unique window into novel alterations, and de novo and acquired resistance mechanisms.In this review, we discuss the diagnostic approach in advanced NSCLC, focusing on current oncogenic driver alterations, through their pathophysiology, management, and future perspectives. We also explore the shortcomings and hurdles encountered in this rapidly evolving field.

Case report: First evidence of impressive efficacy of modulated dose selpercatinib in a young Caucasian with ANK3-RET fusion-positive NSCLC

Over the past decade, molecular characterization has led to change the management of advanced non-small cell lung cancer (NSCLC) harboring driver mutations. Rearranged during transfection (RET) gene fusions, occurring in 1% to 2% of NSCLC, have emerged as an oncogenic druggable target. Systemic targeted therapies with highly selective RET inhibitors (RETi), selpercatinib and pralsetinib, represent a recent clinical breakthrough. While the development of RETi has improved survival, with their increasing use, it is crucial to be aware of the risks of rare but serious adverse events (AEs). A particular challenge for clinicians in applying targeted therapies is not only diagnosing but also interpreting rare mutations. Herein, we report a case of a 43-year-old Caucasian advanced NSCLC patient diagnosed with a rare RET gene fusion, ANK3::RET, identified with Next Generation Sequencing (NGS). Selpercatinib has been initiated at the recommended initial dose after one incomplete chemotherapy cycle due to a severe infusion reaction, but it subsequently required a dose adjustment following grade 3 (G3) AEs. During treatment, we used a particular selpercatinib dosage (160 mg in the morning and 80 mg in the evening) with good tolerance and without compromising effectiveness. Our finding broadens the range of RET fusion types in not-Asian NSCLC. To the best of our knowledge, our case demonstrates, for the first time, a clinical and radiological response to frontline highly selective RETi selpercatinib, expanding the spectrum of potential oncogenic RET fusion partners in newly diagnosed NSCLC patients. Furthermore, to our knowledge, this is the first case describing a RET fusion-positive (RET+) NSCLC patient treated with a modified selpercatinib dosage outside the drug data sheet and demonstrating a safe and effective use.

Path Less Traveled: Targeting Rare Driver Oncogenes in Non-Small-Cell Lung Cancer

Over the past decade, tremendous efforts have been made in the development of targeted agents in non-small-cell lung cancer (NSCLC) with nonsquamous histology. Pivotal studies have used next-generation sequencing to select the patient population harboring oncogenic driver alterations that are targetable with targeted therapies. As treatment paradigm rapidly evolves for patients with rare oncogene-driven NSCLC, updated comprehensive overview of diagnostic approach and treatment options is paramount in clinical settings. In this review article, we discuss the epidemiology, molecular testing, and landmark clinical trials addressing the targeted agents for ROS1 rearrangement, METex14 skipping mutation, EGFR exon 20 insertion, KRAS G12C mutation, HER2 mutation, RET fusion, NTRK fusion, and BRAF mutations.

Revolutionizing cancer drug development: Harnessing the potential of basket trials

The landscape of cancer therapy has been transformed by advances in clinical next-generation sequencing, genomically targeted therapies, and immunotherapies. Well designed clinical trials and efficient clinical trial conduct are crucial for advancing our understanding of cancer, improving patient outcomes, and identifying personalized treatments. Basket trials have emerged as one of the efficient modern clinical trial designs that evaluate the efficacy of these therapies across multiple cancer types based on specific molecular alterations or biomarkers, irrespective of histology or anatomic location. This review delves into the evolution of basket trials in cancer drug development, highlighting their potential prospects and current obstacles. The design of basket trials involves screening patients for specific molecular alterations or biomarkers and enrolling them in the trial to receive the targeted therapy under investigation. Statistical considerations play a crucial role in the design, analysis, and interpretation of basket trials. Several notable examples of basket trials that have led to US Food and Drug Administration approval for uncommon molecular alterations (e.g., NTRK fusions, BRAF mutations, RET and FGFR1 alterations) are discussed, including LOXO-TRK (ClinicalTrials.gov identifier NCT02122913)/SCOUT (ClinicalTrials.gov identifier NCT02637687)/NAVIGATE (ClinicalTrials.gov identifier NCT02576431)/STARTRK (ClinicalTrials.gov identifiers NT02097810, NT02568267), VE-BASKET (ClinicalTrials.gov identifier NCT01524978), ROAR Basket (ClinicalTrials.gov identifier NCT02034110), LIBRETTO-001 (ClinicalTrials.gov identifier NCT03157128), ARROW (ClinicalTrials.gov identifier NCT03037385), FIGHT-203 (ClinicalTrials.gov identifier NCT03011372), and the National Cancer Institute-Molecular Analysis for Therapy Choice trial (ClinicalTrials.gov identifier NCT02465060). Basket trials have the potential to revolutionize cancer treatment by identifying effective therapies for patients based on specific molecular alterations or biomarkers rather than traditional histology-based approaches. PLAIN LANGUAGE SUMMARY: To gain more knowledge about cancer, improve patient outcomes, and discover personalized treatments, it is crucial to conduct clinical trials efficiently. One effective type of clinical trial is called a basket trial. In basket trials, new treatments are tested on various types of cancer, regardless of their location in the body; instead, researchers focus on specific abnormalities in the cancer cells. Basket trials offer hope that we can find personalized treatments that are more effective for each individual battling cancer.

Radioiodine-refractory differentiated thyroid cancer: Molecular mechanisms and therapeutic strategies for radioiodine resistance

Radioiodine-refractory differentiated thyroid cancer (RAIR-DTC) is difficult to treat with radioactive iodine because of the absence of the sodium iodide transporter in the basement membrane of thyroid follicular cells for iodine uptake. This is usually due to the mutation or rearrangement of genes and the aberrant activation of signal pathways, which result in abnormal expression of thyroid-specific genes, leading to resistance of differentiated thyroid cancer cells to radioiodine therapy. Therefore, inhibiting the proliferation and growth of RAIR-DTC with multikinase inhibitors and other drugs or restoring its differentiation and then carrying out radioiodine therapy have become the first-line treatment strategies and main research directions. The drugs that regulate these kinases or signaling pathways have been studied in clinical and preclinical settings. In this review, we summarized the major gene mutations, gene rearrangements and abnormal activation of signaling pathways that led to radioiodine resistance of RAIR-DTC, as well as the medicine that have been tested in clinical and preclinical trials.

Integrated budget impact model to estimate the impact of introducing selpercatinib as a tumor-agnostic treatment option for patients with RET-altered solid tumors in the US

OBJECTIVE

To estimate the potential budget impact on US third party payers (commercial or Medicare) associated with addition of selpercatinib as a tumor-agnostic treatment for patients with Rearranged during Transfection (RET)-altered solid tumors.

METHODS

An integrated budget impact model (iBIM) with 3-year (Y) time horizon was developed for 19 RET-altered tumors. It is referred to as an integrated model because it is a single model that integrated results across multiple tumor types (as opposed to tumor-specific models developed traditionally). The model estimated eligible patient populations and included tumor-specific comparator treatments for each tumor type. Estimated annual total costs (2022USD, $) included costs of drug, administration, supportive care, and toxicity. For a one-million-member plan, the number of patients with RET-altered tumors eligible for treatment, incremental total costs, and incremental per-member per-month (PMPM) costs associated with introduction of selpercatinib treatment were estimated. Uncertainty associated with model parameters was assessed using various sensitivity analyses.

RESULTS

Commercial perspective estimated 11.68 patients/million with RET-altered tumors as treatment-eligible annually, of which 7.59 (Y1), 8.17 (Y2), and 8.76 (Y3) patients would be selpercatinib-treated (based on forecasted market share). The associated incremental total and PMPM costs (commercial) were estimated to be: $873,099 and $0.073 (Y1), $2,160,525 and $0.180 (Y2), and $2,561,281 and $0.213 (Y3), respectively. The Medicare perspective estimated 55.82 patients/million with RET-altered tumors as treatment-eligible annually, of which 36.29 (Y1), 39.08 (Y2), and 41.87 (Y3) patients would be selpercatinib-treated. The associated incremental total and PMPM costs (Medicare) were estimated to be: $4,447,832 and $0.371 (Y1), $11,076,422 and $0.923 (Y2), and $12,637,458 and $1.053 (Y3), respectively. One-way sensitivity analyses across both perspectives identified drug costs, selpercatinib market share, incidence of RET, and treatment duration as significant drivers of incremental costs.

CONCLUSIONS

Three-year incremental PMPM cost estimates suggest a modest impact on payer-budgets associated with introduction of tumor-agnostic selpercatinib treatment.

Management of Advanced Medullary Thyroid Carcinoma: Current Systemic Therapy Options

The current rapid development of more selective and effective drugs for the treatment of thyroid cancer has open a new era in the treatment of patients with this condition, in the past limited to the possibility of only radioactive iodine for well differentiated tumor and surgery for medullary thyroid carcinoma (MTC). The treatment of advanced medullary thyroid carcinoma has evolved in the last few years and options for patients with advanced disease are now available. Multikinase inhibitors (MKIs) with nonselective RET inhibition like Vandetanib and Cabozantinib were approved for the treatment of MTC, although the efficacy is limited due to the lack of specificity resulting in a higher rate of drug-related adverse events, leading to subsequent dose reductions, or discontinuation, and the development of a resistance mechanism like seen on the RET Val804 gatekeeper mutations. MTC is associated with mutations in the RET protooncogene, and new highly selective RET inhibitors have been developed including Selpercatinib and Pralsetinib, drugs that have demonstrate excellent results in clinical trials, and efficacy even in the presence of gatekeeper mutations. However, despite their efficacy and great tolerability, mechanisms of resistance have been described, such as the RET solvent front mutations. Due to this, the need of constant evolution and drug research is necessary to overcome the emergence of resistance mechanisms.

Comparative Effectiveness of First-Line Selpercatinib versus Standard Therapies in Patients with RET-Activated Cancers: An Exploratory Interpatient Analysis of LIBRETTO-001

Selpercatinib is indicated for locally advanced/metastatic RET-activated solid tumors after progression or following prior systemic therapies. Until the recently published data from LIBRETTO-431 and LIBRETTO-531, there were limited effectiveness data comparing selpercatinib with other first-line treatments in RET-activated non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC), and thyroid cancer (TC). This study analyzed patient data from LIBRETTO-001 and compared the outcomes (time to treatment discontinuation {TTD}, time to next treatment or death {TTNT-D}, time to progression {TTP}, and the objective response rate {ORR}) of first-line selpercatinib (selpercatinib arm) use with the outcomes of first-line standard therapies in patients who then received selpercatinib in later lines of treatment (comparator arm). Overall, the first-line selpercatinib arm had a longer TTD, TTNT-D, and TTP versus the first-line comparator arm. The hazard ratios (HRs) for TTD were 0.29 (NSCLC), 0.15 (MTC), 0.08 (TC); for TTNT-D, the HRs were 0.48 (NSCLC), 0.11 (MTC), 0.09 (TC); and for TTP, the HRs were 0.54 (NSCLC), 0.15 (MTC), and 0.12 (TC). The ORR was higher for first-line selpercatinib versus the first-line comparator (NSCLC: 85.3% vs. 39.7%; MTC: 82.6% vs. 15.2%; and TC: 81.8% vs. 31.8%). First-line selpercatinib use is associated with improved outcomes compared to first-line comparator therapies for patients with advanced/metastatic RET-activated cancers.

The Establishment and Verification of a Nomogram Model for Predicting the Overall Survival of Medullary Thyroid Carcinoma: An Analysis Based on the SEER Database

(1) Background: This study aimed to establish a nomogram model for predicting the overall survival (OS) of medullary thyroid carcinoma (MTC) patients based on the Surveillance, Epidemiology, and End Results (SEER) database. (2) Methods: Patients with MTC in the SEER database from 2004 to 2015 were included and divided into a modeling group and an internal validation group. We also selected MTC patients from our center from 2007 to 2019 to establish an external validation group. Univariate and multivariate Cox regression analyses were used to screen for significant independent variables and to establish a nomogram model. Kaplan-Meier (K-M) curves were plotted to evaluate the influence of the predictors. The C-indexes, areas under the curves (AUCs), and calibration curves were plotted to validate the predictive effect of the model. (3) Results: A total of 1981 MTC patients from the SEER database and 85 MTC patients from our center were included. The univariate and multivariate Cox regression analyses showed that age, tumor size, N stage, and M stage were significant factors, and a nomogram model was established. The C-index of the modeling group was 0.792, and the AUCs were 0.811, 0.825, and 0.824. The C-index of the internal validation group was 0.793, and the AUCs were 0.847, 0.846, and 0.796. The C-index of the external validation group was 0.871, and the AUCs were 0.911 and 0.827. The calibration curves indicated that the prediction ability was reliable. (4) Conclusions: A nomogram model based on age, tumor size, N stage, and M stage was able to predict the OS of MTC patients.

Selective RET Inhibitors (SRIs) in Cancer: A Journey from Multi-Kinase Inhibitors to the Next Generation of SRIs

RET is a receptor tyrosine kinase that plays an important role in the development of neurons and kidneys. The gene encoding the rearranged-during-transfection (RET) receptor tyrosine kinase was first discovered in the 1980s. Activating RET mutations and rearrangements have since been identified as actionable drivers of oncogenesis in numerous cancer types and are most prevalent in thyroid and non-small-cell lung cancer. Following the modest success of repurposed RET-active multikinase inhibitors, the first selective RET inhibitors (SRIs), selpercatinib and pralsetinib, received regulatory approval in 2020. Now, thousands of patients with RET-altered cancers have benefited from first-generation SRIs, with impressive deep and durable responses. However, following prolonged treatment with these SRIs, a number of acquired on-target resistance mutations have been identified together with other non-RET-dependent resistance mechanisms. Today, the focus is on how we can further evolve and improve the treatment of RET-altered tumors with next-generation SRIs, and a number of candidate drugs are in development. The ideal next-generation SRIs will be active against on-target acquired resistance alterations, including those that emerge in the CNS, and will have improved safety and tolerability relative to first-generation SRIs. In this review, we will provide an update on these candidates and their potential to meet the unmet clinical need for patients who progress on first-generation SRIs.

Targeted radionuclide therapy in endocrine-related cancers: advances in the last decade

Targeted radionuclide therapy plays an increasingly important role in managing endocrine-related tumors and significantly advances the therapeutic landscape for patients with these diseases. With increasing FDA-approved therapies and advances in the field, come an increased knowledge of the potential for long-term toxicities associated with these therapies and the field must develop new strategies to increase potency and efficacy while individualizing the selection of patients to those most likely to respond to treatment. Novel agents and modalities of therapy are also being explored. This review will discuss the current landscape and describe the avenues for growth in the field currently being explored.

Phase 3 Trial of Selpercatinib in Advanced RET-Mutant Medullary Thyroid Cancer

BACKGROUND

Selpercatinib, a highly selective, potent RET inhibitor, has shown efficacy in advanced RET-mutant medullary thyroid cancer in a phase 1-2 trial, but its efficacy as compared with approved multikinase inhibitors is unclear.

METHODS

We conducted a phase 3, randomized trial comparing selpercatinib as first-line therapy with the physician's choice of cabozantinib or vandetanib (control group). Eligible patients had progressive disease documented within 14 months before enrollment. The primary end point in the protocol-specified interim efficacy analysis was progression-free survival, assessed by blinded independent central review. Crossover to selpercatinib was permitted among patients in the control group after disease progression. Treatment failure-free survival, assessed by blinded independent central review, was a secondary, alpha-controlled end point that was to be tested only if progression-free survival was significant. Among the other secondary end points were overall response and safety.

RESULTS

A total of 291 patients underwent randomization. At a median follow-up of 12 months, median progression-free survival as assessed by blinded independent central review was not reached in the selpercatinib group and was 16.8 months (95% confidence interval [CI], 12.2 to 25.1) in the control group (hazard ratio for disease progression or death, 0.28; 95% CI, 0.16 to 0.48; P<0.001). Progression-free survival at 12 months was 86.8% (95% CI, 79.8 to 91.6) in the selpercatinib group and 65.7% (95% CI, 51.9 to 76.4) in the control group. Median treatment failure-free survival as assessed by blinded independent central review was not reached in the selpercatinib group and was 13.9 months in the control group (hazard ratio for disease progression, discontinuation due to treatment-related adverse events, or death, 0.25; 95% CI, 0.15 to 0.42; P<0.001). Treatment failure-free survival at 12 months was 86.2% (95% CI, 79.1 to 91.0) in the selpercatinib group and 62.1% (95% CI, 48.9 to 72.8) in the control group. The overall response was 69.4% (95% CI, 62.4 to 75.8) in the selpercatinib group and 38.8% (95% CI, 29.1 to 49.2) in the control group. Adverse events led to a dose reduction in 38.9% of the patients in the selpercatinib group, as compared with 77.3% in the control group, and to treatment discontinuation in 4.7% and 26.8%, respectively.

CONCLUSIONS

Selpercatinib treatment resulted in superior progression-free survival and treatment failure-free survival as compared with cabozantinib or vandetanib in patients with RET-mutant medullary thyroid cancer. (Funded by Loxo Oncology, a subsidiary of Eli Lilly; LIBRETTO-531 ClinicalTrials.gov number, NCT04211337.).

Expert consensus on the diagnosis and treatment of RET gene fusion non-small cell lung cancer in China

The rearranged during transfection (RET) gene is one of the receptor tyrosine kinases and cell-surface molecules responsible for transmitting signals that regulate cell growth and differentiation. In non-small cell lung cancer (NSCLC), RET fusion is a rare driver gene alteration associated with a poor prognosis. Fortunately, two selective RET inhibitors (sRETi), namely pralsetinib and selpercatinib, have been approved for treating RET fusion NSCLC due to their remarkable efficacy and safety profiles. These inhibitors have shown the ability to overcome resistance to multikinase inhibitors (MKIs). Furthermore, ongoing clinical trials are investigating several second-generation sRETis that are specifically designed to target solvent front mutations, which pose a challenge for first-generation sRETis. The effective screening of patients is the first crucial step in the clinical application of RET-targeted therapy. Currently, four methods are widely used for detecting gene rearrangements: next-generation sequencing (NGS), reverse transcription-polymerase chain reaction (RT-PCR), fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC). Each of these methods has its advantages and limitations. To streamline the clinical workflow and improve diagnostic and treatment strategies for RET fusion NSCLC, our expert group has reached a consensus. Our objective is to maximize the clinical benefit for patients and promote standardized approaches to RET fusion screening and therapy.

Tailoring Therapeutic Strategies in Non-Small-Cell Lung Cancer: The Role of Genetic Mutations and Programmed Death Ligand-1 Expression in Survival Outcomes

BACKGROUND

This study aims to assess the real-world impact of advancements in first-line systemic therapies for non-small-cell lung cancer (NSCLC), focusing on the role of driver gene mutations and programmed death-ligand 1 (PD-L1) expression levels.

METHODS

Conducted across eight medical facilities in Japan, this multicenter, retrospective observational research included 863 patients diagnosed with NSCLC and treated between January 2015 and December 2022. The patients were categorized based on the type of systemic therapy received: cytotoxic agents, molecular targeting agents, immune checkpoint inhibitors, and combination therapies. Comprehensive molecular and immunohistochemical analyses were conducted, and statistical evaluations were performed.

RESULTS

The median overall survival (OS) shows significant variations among treatment groups, with targeted therapies demonstrating the longest OS. This study also revealed that high PD-L1 expression was common in the group treated with immune checkpoint inhibitors. Multivariate analysis was used to identify the type of anticancer drug and the expression of PD-L1 at diagnosis as the impactful variables affecting 5-year OS.

CONCLUSIONS

This study underscores the efficacy of targeted therapies and the critical role of comprehensive molecular diagnostics and PD-L1 expression in affecting OS in NSCLC patients, advocating for their integration into routine clinical practice.

Design and synthesis of indol-2-one derivatives as potential RET inhibitors

We synthesized and assessed five series of indol-2-one derivatives for their potential as RET kinase inhibitors. Notably, compounds B3, B6, D1, D2, D3, and D5 demonstrated significant inhibitory activity. Among these, D5 exhibited the best activity of inhibiting RET kinase, which provided reference for the subsequent development of RET kinase inhibitors as anti-thyroid cancer chemical.

New Generations of Tyrosine Kinase Inhibitors in Treating NSCLC with Oncogene Addiction: Strengths and Limitations

Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of patients with advanced or metastatic non-small cell lung cancer (NSCLC) harboring most driver gene alterations. Starting from the first generation, research rapidly moved to the development of newer, more selective generations of TKIs, obtaining improved results in terms of disease control and survival. However, the use of novel generations of TKIs is not without limitations. We reviewed the main results obtained, as well as the ongoing clinical trials with TKIs in oncogene-addicted NSCLC, together with the biology underlying their potential strengths and limitations. Across driver gene alterations, novel generations of TKIs allowed delayed resistance, prolonged survival, and improved brain penetration compared to previous generations, although with different toxicity profiles, that generally moved their use from further lines to the front-line treatment. However, the anticipated positioning of novel generation TKIs leads to abolishing the possibility of TKI treatment sequencing and any role of previous generations. In addition, under the selective pressure of such more potent drugs, resistant clones emerge harboring more complex and hard-to-target resistance mechanisms. Deeper knowledge of tumor biology and drug properties will help identify new strategies, including combinatorial treatments, to continue improving results in patients with oncogene-addicted NSCLC.

Molecular Basis and Natural History of Medullary Thyroid Cancer: It is (Almost) All in the RET

Medullary thyroid cancer (MTC) is a rare disease, which can be either sporadic (roughly 75% of cases) or genetically determined (multiple endocrine neoplasia type 2, due to REarranged during Transfection RET germline mutations, 25% of cases). Interestingly, RET pathogenic variants (mainly M918T) have also been reported in aggressive forms of sporadic MTC, suggesting the importance of RET signalling pathways in the pathogenesis of MTC. The initial theory of RET codon-related MTC aggressiveness has been recently questioned by studies suggesting that this would only define the age at disease onset rather than the aggressiveness of MTC. Other factors might however impact the natural history of the disease, such as RET polymorphisms, epigenetic factors, environmental factors, MET (mesenchymal-epithelial transition) alterations, or even other genetic alterations such as RAS family (HRAS, KRAS, NRAS) genetic alterations. This review will detail the molecular bases of MTC, focusing on RET pathways, and the potential mechanisms that explain the phenotypic intra- and interfamilial heterogeneity.

Targeting the RET tyrosine kinase in neuroblastoma: A review and application of a novel selective drug design strategy

The RET (REarranged during Transfection) gene, which encodes for a transmembrane receptor tyrosine kinase, is an established oncogene associated with the etiology and progression of multiple types of cancer. Oncogenic RET mutations and rearrangements resulting in gene fusions have been identified in many adult cancers, including medullary and papillary thyroid cancers, lung adenocarcinomas, colon and breast cancers, and many others. While genetic RET aberrations are much less common in pediatric solid tumors, increased RET expression has been shown to be associated with poor prognosis in children with solid tumors such as neuroblastoma, prompting an interest in RET inhibition as a form of therapy for these children. A number of kinase inhibitors currently in use for patients with cancer have RET inhibitory activity, but these inhibitors also display activity against other kinases, resulting in unwanted side effects and limiting their safety and efficacy. Recent efforts have been focused on developing more specific RET inhibitors, but due to high levels of conservation between kinase binding pockets, specificity remains a drug design challenge. Here, we review the background of RET as a potential therapeutic target in neuroblastoma tumors and the results of recent preclinical studies and clinical trials evaluating the safety and efficacy of RET inhibition in adults and children. We also present a novel approach to drug discovery leveraging the chemical phenomenon of atropisomerism to develop specific RET inhibitors and present preliminary data demonstrating the efficacy of a novel RET inhibitor against neuroblastoma tumor cells.

The efficacy and safety of selective RET inhibitors in RET fusion-positive non-small cell lung cancer: a meta-analysis

BACKGROUND

Rearranged during transfection (RET) fusion-positive occurs in approximately 2% of non-small cell lung cancer (NSCLC). This mutation often predicts metastasis risk and poor prognosis, and current mainstream therapies provide limited patient benefit. Selective RET inhibitors Pralsetinib and Selpercatinib are targeted drugs approved by the US Food and Drug Administration for treating RET-mutated tumors. The phase I/II clinical trial results of their treatment of NSCLC have been published. However, the clinical effect of selective RET inhibitors on RET fusion-positive NSCLC remains controversial. Purpose Meta-analysis was performed to investigate the efficacy and safety of selective RET inhibitors in treating RET fusion-positive NSCLC. Methods Qualified literature was searched in Pubmed, Cochrane Library, Embase, and Web of Science. Outcomes included objective response rate (ORR), median progression-free survival (mPFS), disease control rate (DCR), intracranial ORR, and adverse events. Stata 15.1 software was used to analyze the data. Results A total of 8 studies were included in this meta-analysis. The combined results showed that the ORR of patients treated with selective RET inhibitors was 67% (95% confidence interval:0.64 to 0.70, P < 0.01), DCR was 92% (95%CI: 0.91-0.94, P < 0.01), the mPFS was 16.09 months (95%CI: 11.66-20.52, P < 0.01). In treated patients with RET mutation, the intracranial ORR was 86% (95%CI:0.74 ~ 0.96, P < 0.01). ORR in untreated patients was more effective than untreated patients [HR = 0.44 (95%CI: 0.35-0.56, P < 0.01)]. The major adverse events (grade 3-4) are neutropenia (13%) and anaemia (13%). Conclusions Selective RET inhibitors Pralsetinib and Selpercatinib have shown a good effect on RET fusion-positive NSCLC, with a low incidence of adverse events.

Combination of Genomic Landsscape and 3D Culture Functional Assays Bridges Sarcoma Phenotype to Target and Immunotherapy

Genomic-based precision medicine has not only improved tumour therapy but has also shown its weaknesses. Genomic profiling and mutation analysis have identified alterations that play a major role in sarcoma pathogenesis and evolution. However, they have not been sufficient in predicting tumour vulnerability and advancing treatment. The relative rarity of sarcomas and the genetic heterogeneity between subtypes also stand in the way of gaining statistically significant results from clinical trials. Personalized three-dimensional tumour models that reflect the specific histologic subtype are emerging as functional assays to test anticancer drugs, complementing genomic screening. Here, we provide an overview of current target therapy for sarcomas and discuss functional assays based on 3D models that, by recapitulating the molecular pathways and tumour microenvironment, may predict patient response to treatments. This approach opens new avenues to improve precision medicine when genomic and pathway alterations are not sufficient to guide the choice of the most promising treatment. Furthermore, we discuss the aspects of the 3D culture assays that need to be improved, such as the standardisation of growth conditions and the definition of in vitro responses that can be used as a cut-off for clinical implementation.

Efficacy and Safety of RET-Specific Kinase Inhibitors in RET-Altered Cancers: A Systematic Review

RET proto-oncogene encodes receptor tyrosine kinase. Selpercatinib and pralsetinib are the only RET-specific tyrosine kinase inhibitors approved by FDA in RET-altered tumors. We searched PubMed, Embase, Cochrane, WOS, and Clinicaltrials.gov. Objective-response, complete-response, and partial-response were 60-89%, 0-11%, and 55-89%, respectively, with the use of RET-specific drugs. ≥Grade 3 adverse events were seen in 28-53% of the patients, with hypertension, change in ALT, QT prolongation, neutropenia, and pneumonitis among the common side effects. Hence, selpercatinib and pralsetinib were effective and well tolerated by most of the patients with RET-altered tumors.

PLM-101 is a novel and potent FLT3/RET inhibitor with less adverse effects in the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a prevalent form of leukemia in adults. As its survival rate is low, there is an urgent need for new therapeutic options. In AML, FMS-like tyrosine kinase 3 (FLT3) mutations are common and have negative outcomes. However, current FLT3-targeting agents, Midostaurin and Gilteritinib, face two significant issues, specifically the emergence of acquired resistance and drug-related adverse events leading to treatment failure. Rearranged during transfection (RET), meanwhile, is a proto-oncogene linked to various types of cancer, but its role in AML has been limited. A previous study showed that activation of RET kinase enhances FLT3 protein stability, leading to the promotion of AML cell proliferation. However, no drugs are currently available that target both FLT3 and RET. This study introduces PLM-101, a new therapeutic option derived from the traditional Chinese medicine indigo naturalis with potent in vitro and in vivo anti-leukemic activities. PLM-101 potently inhibits FLT3 kinase and induces its autophagic degradation via RET inhibition, providing a superior mechanism to that of FLT3 single-targeting agents. Single- and repeated-dose toxicity tests conducted in the present study showed no significant drug-related adverse effects. This study is the first to present a new FLT3/RET dual-targeting inhibitor, PLM-101, that shows potent anti-leukemic activity and fewer adverse effects. PLM-101, therefore, should be considered for use as a potential therapeutic agent for AML.