ERK signaling promotes resistance to TRK kinase inhibition in NTRK fusion-driven glioma mouse models.

Pediatric-type high-grade gliomas frequently harbor gene fusions involving receptor tyrosine kinase genes, including neurotrophic tyrosine kinase receptor (NTRK) fusions. Clinically, these tumors show high initial response rates to tyrosine kinase inhibition but ultimately recur due to the accumulation of additional resistance-conferring mutations. Here, we develop a series of genetically engineered mouse models of treatment-naive and -experienced NTRK1/2/3 fusion-driven gliomas. All tested NTRK fusions are oncogenic in vivo. The NTRK variant, N-terminal fusion partners, and resistance-associated point mutations all influence tumor histology and aggressiveness. Additional tumor suppressor losses greatly enhance tumor aggressiveness. Treatment with TRK kinase inhibitors significantly extends the survival of NTRK fusion-driven glioma mice, but fails to fully eradicate tumors, leading to recurrence upon treatment discontinuation. Finally, we show that ERK activation promotes resistance to TRK kinase inhibition and identify MEK inhibition as a potential combination therapy. These models will be invaluable tools to study therapy resistance of NTRK fusion tumors.

Extended 73-month survival in an elderly patient with BRAF V600E-mutated lung adenocarcinoma: A case report.

BRAF is a mediator that activates the mitogen-activated protein kinase pathway. A mutation in BRAF can cause abnormal pathway activation, leading to cell proliferation. In a Phase II study, the combination therapy of the BRAF inhibitor dabrafenib and the MEK inhibitor trametinib was found to be effective in non-small cell lung cancer (NSCLC) patients with the BRAF mutation. However, this study has limited efficacy and safety data for elderly patients. We present a case of a patient who started treatment at 87 years old and showed a good prognosis, remaining alive 73 months from the start of treatment with no significant adverse events. The patient also maintained a partial response (PR) according to RECIST 1.1 at the last follow-up. This case suggests that the dabrafenib and trametinib combination therapy is safe and effective for elderly NSCLC patients with the BRAF mutation.

A phase Ib study of the combination of naporafenib with rineterkib or trametinib in patients with advanced and metastatic KRAS- or BRAF-mutant non-small cell lung cancer.

BACKGROUND: Genetic alterations activating the MAPK pathway are common in non-small cell lung cancer (NSCLC). Patients with NSCLC may benefit from treatment with the pan-RAF inhibitor naporafenib (LXH254) plus the ERK1/2 inhibitor rineterkib (LTT462) or MEK1/2 inhibitor trametinib. METHODS: This first-in-human phase 1b dose-escalation/dose-expansion study investigated the combinations of naporafenib (50-350 mg once daily [QD] or 300-600 mg twice daily [BID]) with rineterkib (100-300 mg QD) in patients with KRAS-/BRAF-mutant NSCLC and naporafenib (200 mg BID or 400 mg BID) with trametinib (0.5 mg QD, 1 mg QD or 1 mg QD 2 weeks on/2 weeks off) in patients with KRAS-/BRAF-mutant NSCLC and NRAS-mutant melanoma. The primary objectives were to identify the recommended dose for expansion (RDE) and evaluate tolerability and safety. Secondary objectives included antitumor activity and pharmacodynamics. RESULTS: Overall, 216 patients were treated with naporafenib plus rineterkib (NSCLC: n = 101) or naporafenib plus trametinib (NSCLC: n = 79; melanoma: n = 36). In total, 10 of 62 (16%) patients experienced at least one dose-limiting toxicity. The RDEs were established as naporafenib 400 mg BID plus rineterkib 200 mg QD, naporafenib 200 mg BID plus trametinib 1 mg QD and naporafenib 400 mg BID plus trametinib 0.5 mg QD. The most frequent grade ≥ 3 treatment-related adverse event was increased lipase (8/101 [7.9%] patients) for naporafenib plus rineterkib and rash (22/115 [19.1%] patients) for naporafenib plus trametinib. Among patients with NSCLC, partial response was observed in three patients (one with KRAS-mutant, two with BRAFnon-V600-mutant NSCLC) treated with naporafenib plus rineterkib and two patients (both with KRAS-mutant NSCLC) treated with naporafenib plus trametinib. On-treatment median reductions in DUSP6 mRNA levels from baseline were 45.5% and 76.1% with naporafenib plus rineterkib or trametinib, respectively. CONCLUSIONS: Both naporafenib combinations had acceptable safety profiles. Antitumor activity was limited in patients with NSCLC, despite the observed on-target pharmacodynamic effect. CLINICALTRIALS: gov identifier: NCT02974725.

Successful utilization of topical trametinib for neurofibromatosis type I-associated plexiform neurofibroma.

An 11-year-old female with neurofibromatosis type 1 (NF-1) and history of optic glioma presented with a progressive cutaneous plexiform neurofibroma of the breast. The lesion was treated with topical application of a mitogen-activated protein kinase inhibitor, trametinib, resulting in stable, non-progression cutaneous plexiform neurofibroma for greater than 2 years. This case demonstrates the potential application of topical trametinib for NF1-associated superficial cutaneous plexiform neurofibroma without the toxicities associated with systemic treatment.

Efficacy and tolerability of osimertinib with dabrafenib and trametinib in BRAF V600E acquired EGFR-mutant non-small cell lung cancer: a case series.

Background: Acquired mutations within bypass pathways including BRAF V600E have been observed in post-osimertinib progression in EGFR-mutant non-small cell lung cancer (NSCLC). The combination of dabrafenib and trametinib is currently Food and Drug Administration-approved in BRAF V600E-mutant NSCLC. However, the application of osimertinib and dabrafenib and trametinib in the setting of acquired BRAF V600E mutation resistance from osimertinib therapy has not been clearly defined. In this case series, we evaluate the efficacy and tolerability of continued osimertinib in combination with dabrafenib and trametinib in BRAF V600E acquired EGFR-mutant NSCLC. Case Description: We retrospectively reviewed our clinical patient cohort at the University of California San Diego and patients from published case studies. Individuals who had metastatic EGFR-mutant lung adenocarcinoma treated with osimertinib at any line whom subsequently developed an acquired BRAF V600E mutation confirmed by next-generation sequencing were included for analysis. All patients had subsequent dabrafenib and trametinib in combination with osimertinib after detection of the novel BRAF V600E mutation post-osimertinib therapy. We identified three cases from our practice and nine cases from literature review. In our study cohort (n=12), we observed a median progression-free survival of 7 months on triplet therapy (osimertinib, dabrafenib, and trametinib) post progression on osimertinib, median overall survival of 46.2 months, and 60% partial response on first scan after treatment initiation. Dose reductions were required in 5/12 patients due to adverse events and treatment discontinuation in 2/12 patients. The most common adverse events were pyrexia and rash, and two cases of pneumonitis were observed (grade 1 & unreported grade). Conclusions: We concluded that the addition of combination dabrafenib and trametinib can be tolerable and effective in patients with acquired BRAF V600E mutation post progression on osimertinib. This study supports molecular profiling at osimertinib progression and provides additional information on the appropriate sequencing of targeted therapies in the EGFR tyrosine kinase inhibitor resistance setting.

Letter to Editor, "The effects of dabrafenib and/or trametinib treatment in Braf V600mutant glioma: a systematic review and metaanalysis".

This systematic review and meta-analysis evaluates the effects of dabrafenib and/or trametinib in treating BRAF V600-mutant gliomas. The study analyzed eight trials involving both high-grade and low-grade glioma patients, assessing outcomes such as progression-free survival (PFS), overall survival (OS), adverse events (AEs), and disease response. The pooled results showed a median PFS of 6.10 months and OS of 22.73 months, with notable improvement in disease response rates when using combination therapy. However, the high incidence of AEs (50%) and death events (43%) necessitates caution in interpreting these results. The study's limitations include a lack of randomized controlled trials and high heterogeneity in AE data. Future research should focus on larger, controlled studies, standardized AE assessments, and exploration of neurocognitive outcomes to better understand and optimize treatment strategies for BRAF V600-mutant gliomas.

A Case Report and Literature Review of Vogt-Koyanagi-Harada-Like Uveitis Secondary to Dabrafenib and Trametinib: 4-Year Follow-Up Using Retinal Multimodal Imaging.

PURPOSE: To report a case of Vogt-Koyanagi-Harada (VKH)-like uveitis under treatment with Dabrafenib and Trametinib for metastatic malignant melanoma, representing the longest follow-up (49 months) with retinal multimodal imaging. METHODS: Retrospective case report. RESULTS: A 49-year-old female with metastatic relapsing cutaneous malignant melanoma presented with blurry vision in both eyes for 1 week. She had been treated with Dabrafenib and Trametinib for 2 months. Fundus examination detected serous retinal detachments (SRDs) and hyperemic optic disks. Spectral-domain optical coherence tomography (SD-OCT) revealed SRDs, retinal pigment epithelium undulations, choroidal thickening, and loss of normal choroidal vascular architecture. The patient was diagnosed with VKH-like uveitis secondary to targeted agents since systemic investigations were unremarkable. Dabrafenib and Trametinib were discontinued, and pulse steroid treatment was started. Following the improvement of retinal and choroidal signs, the same targeted agents were restarted 6 weeks later. No recurrence of uveitis occurred during 49 months of follow-up; however, the convalescent phase findings of VKH were observed in the fundus examination. The systemic status of the patient, who is still using Dabrafenib and Trametinib, is stable. CONCLUSION: Although the mechanism is still unknown, the development of VKH-like uveitis secondary to targeted therapy may indicate successful tumor control in patients with metastatic melanoma. Providing effective immunosuppression with corticosteroids and making necessary dose modifications with a multidisciplinary approach may extend the survival of patients.

Microsecond Molecular Dynamics Simulation to Gain Insight Into the Binding of MRTX1133 and Trametinib With KRASG12D Mutant Protein for Drug Repurposing.

The Kirsten Rat Sarcoma (KRAS) G12D mutant protein is a primary driver of pancreatic ductal adenocarcinoma, necessitating the identification of targeted drug molecules. Repurposing of drugs quickly finds new uses, speeding treatment development. This study employs microsecond molecular dynamics simulations to unveil the binding mechanisms of the FDA-approved MEK inhibitor trametinib with KRASG12D, providing insights for potential drug repurposing. The binding of trametinib was compared with clinical trial drug MRTX1133, which demonstrates exceptional activity against KRASG12D, for better understanding of interaction mechanism of trametinib with KRASG12D. The resulting stable MRTX1133-KRASG12D complex reduces root mean square deviation (RMSD) values, in Switch I and II domains, highlighting its potential for inhibiting KRASG12D. MRTX1133's robust interaction with Tyr64 and disruption of Tyr96-Tyr71-Arg68 network showcase its ability to mitigate the effects of the G12D mutation. In contrast, trametinib employs a distinctive binding mechanism involving P-loop, Switch I and II residues. Extended simulations to 1 µs reveal sustained network interactions with Tyr32, Thr58, and GDP, suggesting a role of trametinib in maintaining KRASG12D in an inactive state and impede the further cell signaling. The decomposition binding free energy values illustrate amino acids' contributions to binding energy, elucidating ligand-protein interactions and molecular stability. The machine learning approach reveals that van der Waals interactions among the residues play vital role in complex stability and the potential amino acids involved in drug-receptor interactions of each complex. These details provide a molecular-level understanding of drug binding mechanisms, offering essential knowledge for further drug repurposing and potential drug discovery.

MEK inhibitor trametinib combined with PI3K/mTOR inhibitor BEZ-235 as an effective strategy against NSCLC through impairment of glucose metabolism.

The MAPK and PI3K/AKT/mTOR pathways are aberrantly activated in non-small cell lung cancer (NSCLC) patients, but therapeutic efficacy of NSCLC using trametinib (MEK inhibitor) or BEZ-235 (dual PI3K/mTOR inhibitor) alone is still unsatisfactory. Therefore, in this study, we aimed to determine whether the combination of trametinib with BEZ-235 exerted synergistic effects against NSCLC in both in vitro and in vivo models, and we preliminarily explored the effect of this combination therapy on glucose metabolism. Our results showed that trametinib combined with BEZ-235 could better inhibit cell proliferation and colony formation, induce G0/G1 phase arrest and apoptosis, and suppress cell invasion and migration compared with the single agent. The combination index demonstrated that trametinib and BEZ-235 exerted strong synergistic effects. Additionally, trametinib and BEZ-235 exhibited synergistic antitumor effects in vivo. Furthermore, trametinib and BEZ-235 synergistically downregulated the expression of related proteins in the MAPK and PI3K/AKT/mTOR pathways, and decreased glucose consumption and lactic acid production through suppressing the expressions of glucose transporter 1 (GLUT1) and lactate dehydrogenase A (LDHA). These data imply that simultaneous inhibition of the MAPK and PI3K/AKT/mTOR pathways using trametinib combined with BEZ-235 could synergistically impair glucose metabolism, resulting in an obvious synergistic therapeutic effect against NSCLC.

A Real-World Pharmacovigilance Study of the FDA Adverse Event Reporting System Events for Trametinib.

OBJECTIVE: This research investigates adverse drug events (ADEs) linked to trametinib, utilizing data from the FDA Adverse Event Reporting System (FAERS) database, covering the period from Q2 2013 to Q4 2023. METHODS: We gathered data on ADEs associated with trametinib from the second quarter of 2013 to the fourth quarter of 2023. After standardizing the data, we applied various analytical methods to quantify signals, including the reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian Confidence Propagation for Neural Networks (BCPNN), and multi-item gamma Poisson shrinker (MGPS). RESULTS: In our examination of 2200 ADE reports with trametinib cited as the primary suspect, we identified 191 adverse reaction terms across 23 system organ classifications. The most frequently reported classifications were general disorders and administration site conditions, with 1254 cases (ROR 0.83, PRR 0.85, IC -0.23, EBGM 0.85), followed by neoplasms (benign, malignant, and unspecified, including cysts and polyps) with 802 cases (ROR 3.59, PRR 3.32, IC 1.73, EBGM 3.32), and investigations with 794 cases (ROR 1.74, PRR 1.66, IC 0.73, EBGM 1.66). Notably, this study also uncovered previously unlabeled adverse reactions such as cheilitis, lobular panniculitis, ulcerative keratitis, and stridor. CONCLUSION: While trametinib provides therapeutic advantages, it is associated with several potential adverse reactions. It is crucial for healthcare providers to closely monitor patients for symptoms such as cheilitis, lobular panniculitis, ulcerative keratitis, stridor, and other adverse events (AEs) during treatment.

Letter to editor: The efects of dabrafenib and/or trametinib treatment in Braf V600­mutant glioma: a systematic review and meta-analysis.

The systematic review and meta-analysis titled "The Effects of Dabrafenib and/or Trametinib Treatment in BRAF V600-Mutant Glioma" provides a critical evaluation of these targeted therapies for a challenging subset of gliomas. This review is notable for its comprehensive data integration, offering a robust assessment of the efficacy and safety of dabrafenib and trametinib. By focusing on BRAF V600 mutations, it contributes valuable insights into personalized treatment strategies. However, limitations include study heterogeneity and a lack of long-term follow-up data, which hinder the generalizability and complete understanding of treatment effects. Additionally, while the review emphasizes therapeutic potential, it requires a thorough evaluation of adverse effects. Future research should address these limitations by providing more consistent data, longer follow-up, and a balanced view of treatment risks and benefits.

Successful treatment of MAP2K1 mutant stage IV-M1d melanoma with trametinib plus low-dose dabrafenib: a case report.

Clonal MAPK-pathway activating mutations in the MAP2K1 (MEK1) gene are present in approximately 9% of cutaneous melanomas. These mutations are divided into three classes: RAF-dependent, RAF-regulated, RAF-independent. Cell lines with class-2 or RAF-regulated MAP2K1-mutations are most responsive to MEK-inhibitors. We present a patient with a class-2 MAP2K1-mutant stage IV-M1d melanoma who experienced extra- and intracranial progressive disease following treatment with immune-checkpoint inhibitors. The patient was treated with the MEK-inhibitor trametinib (2 mg OD) to which a low-dose of dabrafenib (50 mg BID) was added to mitigate skin-toxicity. Following documentation of a partial response (PR), she developed one new, and increase in volume of two pre-existing brain metastases that were treated with stereotactic radiosurgery (SRS) while continuing trametinib and dabrafenib. Thereafter, a deep partial radiologic and metabolic response both extra-and intra-cranially was achieved and is ongoing 88 weeks after initiating trametinib. She experienced no grade > 2 adverse events. Focal post-radiation necrosis at site of an irradiated brain metastasis developed 9 months after SRS and is successfully being treated with low-dose bevacizumab. This is the first published case of a durable intracranial disease control with the MEK-inhibitor trametinib of a stage IV-M1d class-2 MAP2K1-mutant melanoma. This illustrates the utility of NGS profiles that include class-1/2 MAP2K1-mutations in patients with melanoma and other malignancies to provide valuable information on a potentially active individualized treatment option. A prospective clinical trial that further evaluates the efficacy of MEK-inhibitor therapies in MAP2K1-mutated tumors is justified.

The effects of dabrafenib and/or trametinib treatment in Braf V600-mutant glioma: a systematic review and meta-analysis.

This study aimed to evaluate the effects of dabrafenib and/or trametinib therapy in BRAF v600-mutant glioma treatment. PubMed, the Cochrane Library, EMBASE and Web of Science were searched from inception to Sep 2023. Inclusion criteria were designed based on the PICO principle to select relevant articles. Search keywords included 'dabrafenib', 'trametinib', 'glioma' and other related keywords. Outcomes included overall survival (OS), progression-free survival (PFS), adverse events (AEs), and death events. Methodological index for non-randomized studies (MINORS) was used to assess the methodological quality. Stata 14.0 was selected to perform the Cochrane Q and I2 statistics to test the heterogeneity among all studies. As for publication bias assessment and sensitivity analysis, the funnel plot, Egger regression test, Begg test, and trim and fill method were selected. Including 8 studies for meta-analysis. The pooled results of the single-arm trials showed that the median PFS and median OS after treatment were 6.10 months and 22.73 months, respectively. Notably, this study found a high incidence of AEs and death events of 50% and 43% after treatment. All the above findings were statistically significant. Also, this study statistically supported the advantage of disease response improvement after the combination therapy in BRAF v600-mutant glioma patients, which were shown as a pooled rate of PR (30%), a pooled rate of CR (18%), and a pooled rate of ORR (39%). And the AE rate was lower in the monotherapy group (AE: 25%) than in the combination treatment group (AE: 60%). Sensitivity analysis indicated that all the results were robust. Based on current literature outcomes, dabrafenib and/or trametinib may lead to the median PFS of 6.10 months and median OS as 22.73 months for BRAF v600-mutant glioma patients, and the safety of monotherapy is better than that of combination therapy. This conclusion needs to be treated with caution and further verified.

Current Trial Report: A Multicenter Phase I/Ib study of Capmatinib Plus Trametinib in Patients With Metastatic Nonsmall Cell Lung Center Harboring MET Exon 14 Skipping Mutations and Other MET-Alterations.

INTRODUCTION: MET tyrosine kinase inhibitor (TKI) therapy is associated with improved outcomes in patients with nonsmall cell lung cancer (NSCLC) harboring a MET alteration, including MET exon 14 (METex14) skipping mutation, MET amplification, or MET fusion. However, primary or acquired resistance to TKI therapy ultimately develops. In preclinical models, hyperactivation of MAPK signaling was shown to promote resistance to MET TKI; resistance was overcome by co-treatment with a MET inhibitor and a MEK inhibitor. This phase I/Ib study offers a potential combination strategy simultaneously targeting MET (with capmatinib) and MEK signaling (with trametinib) to overcome resistance to MET inhibitor monotherapy in METex14 NSCLC. METHODS: In the dose escalation phase, a minimum of 6 and maximum of 18 patients will be enrolled using a conventional 3+3 design with the primary endpoint of identifying a recommended phase 2 dose (RP2D) of capmatinib in combination with trametinib. Once the RP2D is identified, patients will continue to enroll in a dose expansion phase to a total of 15 patients. The primary endpoint of the dose expansion phase is to further characterize the safety profile of the combination. CONCLUSION: This phase I/Ib clinical trial will assess the safety and efficacy of combination capmatinib and trametinib in NSCLC patients whose tumors harbor METex14 skipping mutations, MET amplification, or MET fusion and had developed progressive disease on single agent MET inhibitor therapy.

Synergistic drug interactions of the histone deacetylase inhibitor givinostat (ITF2357) in CRLF2-rearranged pediatric B-cell precursor acute lymphoblastic leukemia identified by high-throughput drug screening.

Combining multiple drugs broadens the window of therapeutic opportunities and is crucial for diseases that are currently lacking fully curative treatments. A powerful emerging tool for selecting effective drugs and combinations is the high-throughput drug screening (HTP). The histone deacetylase inhibitor (HDACi) givinostat (ITF2357) has been shown to act effectively against CRLF2-rearranged pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL), a subtype characterized by poor outcome and enriched in children with Down Syndrome, very fragile patients with a high susceptibility to treatment-related toxicity. The aim of this study is to investigate possible synergies with givinostat for these difficult-to-treat patients by performing HTP screening with a library of 174 drugs, either approved or in preclinical studies. By applying this approach to the CRLF2-r MHH-CALL-4 cell line, we identified 19 compounds with higher sensitivity in combination with givinostat compared to the single treatments. Next, the synergy between givinostat and the promising candidates was further validated in CRLF2r cell lines with a broad matrix of concentrations. The combinations with trametinib (MEKi) or venetoclax (BCL2i) were found to be the most effective and with the greatest synergy across three metrics (ZIP, HAS, Bliss). Their efficacy was confirmed in primary blasts treated ex vivo at concentration ranges with a safe profile on healthy cells. Finally, we described givinostat-induced modifications in gene expression of MAPK and BCL-2 family members, supporting the observed synergistic interactions. Overall, our study represents a model of drug repurposing strategy using HTP screening for identifying synergistic, efficient, and safe drug combinations.

Clinical Pharmacy Initiatives Contribute to the Excellent Efficacy of the Dabrafenib/Trametinib Combination for Iodine-Refractory Thyroid Carcinoma: A Case Report.

A 76-year-old female patient presented with an iodine-refractory papillary thyroid carcinoma (PTC), diagnosed eight years earlier, with several lymph node recurrences requiring successive surgeries. Fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) imaging revealed a new unresectable loco-regional recurrence. The patient was diagnosed with a somatic BRAF V600E mutation. Therefore, dabrafenib and trametinib combination therapy was introduced and closely monitored by a dedicated multidisciplinary team, involving pharmaceutical consultations. As early as six weeks after treatment initiation, the patient reported multiple adverse events (AEs) to the clinical pharmacy team, who provided advice on resolving AEs or improving tolerance. Close interprofessional collaboration among healthcare workers involved in the care pathway allowed for the identification of the most opportune times for temporary suspension of treatment (four suspensions over seven months) or dose reduction (two reductions over 3.5 months). This resulted in a total treatment duration (one year) longer than the average times reported in the literature. The patient showed a rapid and excellent response to treatment immediately after initiation, culminating in a complete metabolic response assessed by [18F]FDG PET/CT imaging at nine months. Twenty-five months after treatment discontinuation, the disease remained controlled. Overall, dabrafenib and trametinib combination could offer excellent outcomes in selected patients with refractory BRAF-mutated PTC, with additional clinical pharmacy initiatives allowing for the optimized management of AEs and prolonged treatment periods.

Target-Driven Tissue-Agnostic Drug Approvals-A New Path of Drug Development.

The regulatory approvals of tumor-agnostic therapies have led to the re-evaluation of the drug development process. The conventional models of drug development are histology-based. On the other hand, the tumor-agnostic drug development of a new drug (or combination) focuses on targeting a common genomic biomarker in multiple cancers, regardless of histology. The basket-like clinical trials with multiple cohorts allow clinicians to evaluate pan-cancer efficacy and toxicity. There are currently eight tumor agnostic approvals granted by the Food and Drug Administration (FDA). This includes two immune checkpoint inhibitors, and five targeted therapy agents. Pembrolizumab is an anti-programmed cell death protein-1 (PD-1) antibody that was the first FDA-approved tumor-agnostic treatment for unresectable or metastatic microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) solid tumors in 2017. It was later approved for tumor mutational burden-high (TMB-H) solid tumors, although the TMB cut-off used is still debated. Subsequently, in 2021, another anti-PD-1 antibody, dostarlimab, was also approved for dMMR solid tumors in the refractory setting. Patients with fusion-positive cancers are typically difficult to treat due to their rare prevalence and distribution. Gene rearrangements or fusions are present in a variety of tumors. Neurotrophic tyrosine kinase (NTRK) fusions are present in a range of pediatric and adult solid tumors in varying frequency. Larotrectinib and entrectinib were approved for neurotrophic tyrosine kinase (NTRK) fusion-positive cancers. Similarly, selpercatinib was approved for rearranged during transfection (RET) fusion-positive solid tumors. The FDA approved the first combination therapy of dabrafenib, a B-Raf proto-oncogene serine/threonine kinase (BRAF) inhibitor, plus trametinib, a mitogen-activated protein kinase (MEK) inhibitor for patients 6 months or older with unresectable or metastatic tumors (except colorectal cancer) carrying a BRAFV600E mutation. The most recent FDA tumor-agnostic approval is of fam-trastuzumab deruxtecan-nxki (T-Dxd) for HER2-positive solid tumors. It is important to identify and expeditiously develop drugs that have the potential to provide clinical benefit across tumor types.

Successful treatment of pediatric patients with high-grade gliomas featuring leptomeningeal metastases by targeting BRAF V600E mutations with dabrafenib plus trametinib: two illustrative cases.

A combination of BRAF and MEK inhibitors is reported to be effective for gliomas with the BRAF V600E mutation; however, its efficacy in gliomas with leptomeningeal metastases (LMM) is still unknown. In this report, we describe two pediatric patients with high-grade glioma featuring the BRAF V600E mutation who were treated with dabrafenib and trametinib for LMM. Both 2 cases underwent craniotomy for primary intracranial lesions and were diagnosed as a high-grade glioma with BRAF V600E mutation; one case was consistent with anaplastic pleomorphic xanthoastorocytoma, the other was epithelioid glioblastoma. They received standard treatment for the lesions but subsequently were found to have new lesions including multiple spinal dissemination. We started administering dabrafenib and trametinib. Within a few days of starting treatment, the symptoms improved dramatically and MRI performed one month after the prescription of the two drugs demonstrated remission of both brain and spinal lesions. This report shows that dabrafenib and trametinib are effective not only for recurrent lesions but also for LMM in pediatric patients.

Response to trametinib, hydroxychloroquine, and bevacizumab in a young woman with NRAS-mutated metastatic intrahepatic cholangiocarcinoma: a case report.

Systemic chemotherapy is the main treatment option for patients with advanced intrahepatic cholangiocarcinoma (iCCA), however, its efficacy is limited. Herein, we report a young patient with NRAS-mutated chemoresistant metastatic iCCA, who received second-line therapy with a combination of trametinib (MEK1/2 inhibitor), hydroxychloroquine (autophagy inhibitor), and bevacizumab (angiogenesis inhibitor). A significant response was achieved during therapy, resulting in a 25% decrease in the size of tumor lesions after 2 months of treatment and an improvement in the patient's condition. The duration of this response was 4 months, but the patient died 10 months after the initiation of this triple therapy. This case report and the analysis of other available studies warrant further investigations on combined MEK and autophagy inhibition in RAS-mutated tumors.

Somatic RIT1 delins in arteriovenous malformations hyperactivate RAS-MAPK signaling amenable to MEK inhibition.

Arteriovenous malformations (AVM) are benign vascular anomalies prone to pain, bleeding, and progressive growth. AVM are mainly caused by mosaic pathogenic variants of the RAS-MAPK pathway. However, a causative variant is not identified in all patients. Using ultra-deep sequencing, we identified novel somatic RIT1 delins variants in lesional tissue of three AVM patients. RIT1 encodes a RAS-like protein that can modulate RAS-MAPK signaling. We expressed RIT1 variants in HEK293T cells, which led to a strong increase in ERK1/2 phosphorylation. Endothelial-specific mosaic overexpression of RIT1 delins in zebrafish embryos induced AVM formation, highlighting their functional importance in vascular development. Both ERK1/2 hyperactivation in vitro and AVM formation in vivo could be suppressed by pharmacological MEK inhibition. Treatment with the MEK inhibitor trametinib led to a significant decrease in bleeding episodes and AVM size in one patient. Our findings implicate RIT1 in AVM formation and provide a rationale for clinical trials with targeted treatments.