Treatment of Refractory Epilepsy With MEK Inhibitor in Patients With RASopathy

Trametinib as a targeted treatment in cardiac and lymphatic presentations of Noonan syndrome

Introduction

Rare pathogenic variants in the PTPN11, KRAS, SOS1 and RAF1 genes are the main molecular causes of Noonan syndrome (NS). Most are dominant gain-of-function variants that cause an overactivation of the RAS/MAPK signaling pathway leading to uncontrolled cell proliferation in many organs and systems. Albeit phenotypically heterogeneous, NS can be associated with severe cardiovascular and lymphatic anomalies, potentially lethal during infancy, neonatal and fetal periods. MEK inhibitors, a class of drugs targeting the final steps of the RAS/MAPK pathway and originally developed for cancer therapy, have been tested in preclinical studies as a targeted treatment for NS. These studies led to the occasional off-label use of MEK inhibitors in patients with RASopathies.

Methods

We report the case of a preterm infant with congenital pulmonary lymphangiectasis, chylothorax and hypoxic respiratory failure refractory to conventional management, who was treated with trametinib after identification of a NS PTPN11 class 5 variant. We performed a systematic review of the current published evidence on trametinib efficacy and safety for severe respiratory and/or cardiac manifestations in infants and children with Noonan syndrome, querying PubMed, Embase, Cochrane and Scopus databases, following the PRISMA guideline for systematic reviews, and using the Joanna Briggs Institute (JBI) Critical Appraisal tool for quality assessment of published evidence.

Results

In our patient, a five-week trametinib course, maximum dose 0.025 mg/kg/day, led to chylothorax resolution and gradual pulmonary function improvement, allowing extubation to non-invasive support, discharge home at a corrected age of 4 months, and weaning off home oxygen therapy by 10 months. No formal clinical trial of trametinib in neonatal/pediatric Noonan syndrome has been published to our knowledge. We collected 16 published cases, and added this case for reviewing trametinib regimen, efficacy and safety. A short-term improvement of symptoms was reported in all cases, with three deaths presumably unrelated to trametinib. Moderate side effects were reported in a subset of patients. Long-term follow-up data were not available.

Discussion

Trametinib is a promising drug in NS. Clinical trials are warranted to establish safety, efficacy, and standardized protocols for the use of trametinib as a rescue therapy in critically ill children and explore its potential place in the treatment of various NS comorbidities.

Systematic Review Registration

clinicaltrials.gov, identifier [NCT06555237].

Cancer in Multilineage Mosaic RASopathies due to Pathogenic Variants in HRAS or KRAS: A Systematic Review and Meta-analysis

PURPOSE

To determine the cancer risk and spectrum in patients with multilineage mosaic RASopathies with pathogenic variants (PV) in HRAS or KRAS.

EXPERIMENTAL DESIGN

We conducted a systematic literature review to identify multilineage mosaic RASopathy cases with a PV in HRAS or KRAS to create a retrospective cohort. We calculated cumulative incidence, cancer-free survival, and hazard rates for cancer and standardized incidence rates (SIR).

RESULTS

This study identified 69 patients. Of these, 17% had cancer, including rhabdomyosarcoma (RMS) located in the urogenital region (n = 7), skin cancer (n = 3), Wilms tumor (n = 1), and bladder cancer (n = 1). Cumulative cancer incidence by age 20 was 20% (95% confidence interval, 4%-37%). The annual cancer hazard rate peaked at 14% within the first 2 years of life. The highest SIR was found for RMS (SIR = 800; 95% confidence interval, 300-1648).

CONCLUSIONS

This is the first investigation of cancer risk in KRAS or HRAS PV-positive mosaic RASopathies to date. The high incidence and SIR values found highlight the need for rigorous RMS surveillance in young children and skin cancer surveillance in adults with this high-risk condition.

Noonan Syndrome: Relation of Genotype to Cardiovascular Phenotype-A Multi-Center Retrospective Study

Background: Noonan syndrome (NS) is a congenital genetic disorder with a prevalence of 1 in 1000 to 2500 live births, and is characterized by distinctive facial features, short stature, chest deformities, and congenital heart disease. This study aims to evaluate the prevalence of specific genetic mutations and their impact on cardiovascular and other outcomes in NS. Methods: We conducted a retrospective clinical study of 25 pediatric patients diagnosed with NS at two institutions: The Mother and Child Health Care Institute of Serbia and the Clinic for Children Diseases, University Clinical Center of the Republic of Srpska. Patients underwent whole-exome sequencing (WES) to identify genetic mutations. Clinical data, including cardiovascular manifestations, psychomotor development, and stature, were analyzed in relation to mutation types. Results: The cohort comprised 60% male and 40% female patients, with a median age at diagnosis of 7.2 years. Cardiovascular abnormalities were present in 88% of patients. Mutations in PTPN11 were most commonly associated with pulmonary valve stenosis (PVS), while RAF1 mutations were prevalent in patients with hypertrophic cardiomyopathy (HCM). No significant association was found between cardiac disease and delayed psychomotor development (p = 0.755), even though the likelihood ratio showed significance in that regard (p = 0.018). Short stature was observed in 48% of patients but was not significantly correlated with genetic type of disease, presence of cardiac disease, or developmental delay. Conclusions: The study confirms the high prevalence of cardiovascular manifestations in NS and highlights genotype-phenotype correlations. While cardiac abnormalities are common, their impact on psychomotor development and stature is less clear. Further research is needed to explore genetic interactions influencing these outcomes and refine clinical management strategies.

Exploring New Drug Repurposing Opportunities for MEK Inhibitors in RASopathies: A Comprehensive Review of Safety, Efficacy, and Future Perspectives of Trametinib and Selumetinib

The RASopathies are a group of syndromes caused by genetic variants that affect the RAS-MAPK signaling pathway, which is essential for cell response to diverse stimuli. These variants functionally converge towards the overactivation of the pathway, leading to various constitutional and mosaic conditions. These syndromes show overlapping though distinct clinical presentations and share congenital heart defects, hypertrophic cardiomyopathy (HCM), and lymphatic dysplasia as major clinical features, with highly variable prevalence and severity. Available treatments have mainly been directed to target the symptoms. However, repurposing MEK inhibitors (MEKis), which were originally developed for cancer treatment, to target evolutive aspects occurring in these disorders is a promising option. Animal models have shown encouraging results in treating various RASopathy manifestations, including HCM and lymphatic abnormalities. Clinical reports have also provided first evidence supporting the effectiveness of MEKi, especially trametinib, in treating life-threatening conditions associated with these disorders. Nevertheless, despite notable improvements, there are adverse events that occur, necessitating careful monitoring. Moreover, there is evidence indicating that multiple pathways can contribute to these disorders, indicating a current need to more accurate understand of the underlying mechanism of the disease to apply an effective targeted therapy. In conclusion, while MEKi holds promise in managing life-threatening complications of RASopathies, dedicated clinical trials are required to establish standardized treatment protocols tailored to take into account the individual needs of each patient and favor a personalized treatment.

MEK Inhibition for RASopathy-Associated Hypertrophic Cardiomyopathy: Clinical Application of a Basic Concept

The term "RASopathies" designates a group of developmental syndromes that are caused by activating variants of the rat sarcoma virus protein (RAS)/mitogen-activated protein kinase (MAPK) cascade. The most prevalent clinical diagnosis is Noonan syndrome, and other, less prevalent conditions include Noonan syndrome with multiple lentigines, Costello syndrome, cardiofaciocutaneous syndrome, and others. Hypertrophic cardiomyopathy occurs in 10% of these patients and can be severe and life-threating. Recently, repurposing of medications inhibiting the RAS/MAPK on a compassionate use basis has emerged as a promising concept to improve the outcome of these patients. Herein, we specifically review the role of the RAS/MAPK pathway in RASopathy-associated cardiomyopathy, and discuss the role of small-molecule inhibition in the treatment of this condition. We describe how drug repurposing of trametinib (mitogen-activated protein/extracellular signal-regulated kinase inhibition) and sirolimus/everolimus (mammalian target of rapamycin inhibition) was performed, how genotype-specific therapies are chosen and followed, as well as initial outcomes from early case series. Finally, we lay out the challenges and opportunities for trials that aim to quantify the benefits of this approach.

Epilepsy in cardiofaciocutaneous syndrome: Clinical burden and response to anti-seizure medication

Treatment-resistant epilepsy is among the most serious complications of cardiofaciocutaneous syndrome (CFCS), a rare disorder caused by germline variants in the RAS-MAPK signaling pathway. This study analyzed the clinical characteristics of epilepsy and response to anti-seizure medications (ASMs) in a multinational CFCS cohort. A caregiver survey provided data regarding seizure history, use of ASMs and other treatment approaches, adverse effects, caregiver perception of treatment response, and neurological disease burden impact among individuals with CFCS. Results from 138 survey responses were quantitatively analyzed in conjunction with molecular genetic results and neurological records. The disease burden impact of CFCS was higher among individuals with epilepsy (n = 74/138), especially those with more severe seizure presentation. Oxcarbazepine, a sodium-channel blocker, had the best seizure control profile with relatively infrequent adverse effects. The most commonly prescribed ASM, levetiracetam, demonstrated comparatively poor seizure control. ASM efficacy was generally similar for individuals with BRAF and MAP2K1 gene variants. The high proportion of patients with CFCS who experienced poor seizure control despite use of multiple ASMs highlights a substantial unmet treatment need. Prospective study of ASM efficacy and clinical trials of therapies to attenuate RAS-MAPK signaling may improve avenues for clinical management.