Gabriel Morin

Thérapies ciblées innovantes dans les malformations vasculaires associées aux mutations mosaïques de RAS: Les RASopathies mosaïques sont un groupe de maladies génétiques rares et graves, responsables de malformations pouvant toucher tous les tissus de l'organisme et particulièrement les vaisseaux sanguins. Les malformations vasculaires les plus sévères sont les malformations artérioveineuses, qui sont dues à une communication directe entre une artère et une veine sans réseau capillaire intermédiaire. Les formes intracrâniennes peuvent se compliquer d'hémorragie intracérébrale ou d'épilepsie responsables d'une morbidité et d'une mortalité élevées. Les RASopathies mosaïques sont causées par des mutations somatiques d'un des gènes RAS (KRAS, NRAS ou HRAS) survenant usuellement au cours du développement embryonnaire. Ces mutations sont dites mosaïques car elles sont retrouvées dans les tissus malformés mais sont absentes du reste de l'organisme. Les gènes RAS sont les gardiens de la survie, la prolifération et la croissance cellulaires. Les mutations gain de fonction de ces gènes sont responsables d'une activation constitutive des protéines RAS favorisant le développement des malformations vasculaires. A l'heure actuelle, aucun traitement n'a été approuvé pour le traitement des RASopathies mosaïques et aucun inhibiteur spécifique de RAS n'était disponible jusqu'à l'approbation récente du sotorasib, dirigé contre la mutation KRAS G12C, pour le traitement du cancer du poumon. Différentes thérapies ciblées dirigées contre les interacteurs des protéines RAS ont récemment été développées, mais celles qui ont été rapportées efficaces dans les RASopathies mosaïques dans des études rétrospectives sont associées à des effets secondaires fréquents et invalidants. Notre objectif était donc d'identifier des thérapies innovantes efficaces dans ces pathologies tout en limitant le risque d'effets secondaires. Nous avons identifié le sotorasib comme un traitement potentiel des RASopathies mosaïques associées aux mutations de KRAS G12C. Pour les patients porteurs d'autres mutations que KRAS G12C, nous avons identifié un second inhibiteur d'un partenaire de RAS avec un profil de tolérance favorable. Nous avons identifié dans notre unité 14 patients atteints de malformations vasculaires graves, sans ressource thérapeutique ou à risque de chirurgie délabrante, associées à une mutation mosaïque des gènes RAS, dont 2 portant la mutation G12C. Nous avons développé des modèles murins exprimant les mutations G12C ou G12D du gène KRAS dans les cellules endothéliales vasculaires. Ces animaux développent des malformations vasculaires récapitulant le phénotype des patients avec une mortalité sévère. Nous avons traité nos modèles murins soit par sotorasib, soit par le second inhibiteur, et avons observé une amélioration de la survie des animaux et une diminution de l'incidence des malformations vasculaires. Devant ces résultats prometteurs, nous avons ensuite traité les 14 patients: 2 patients ont reçu un traitement par sotorasib et 12 autres le second candidat inhibiteur. Dans les 2 cas, les patients traités ont présenté une régression partielle des malformations vasculaires confirmée par IRM, une diminution des complications hémorragiques, et une réduction de la douleur. Par étude transcriptomique spatiale de biopsies cutanées réalisées avant et après traitement, nous avons identifié que le traitement s'accompagnait d'une reprogrammation transcriptionnelle endothéliale anti-proliférative et anti-inflammatoire. Nous avons enfin identifié une diminution d'un panel de cytokines pro-inflammatoires dans le sérum des patients, pouvant contribuer à la régression des lésions vasculaires. En conclusion, nous avons établi la preuve de concept de l'efficacité de 2 nouvelles thérapies ciblées jusqu'alors non décrites dans les RASopathies mosaïques chez l'homme, caractérisé les modifications fonctionnelles endothéliales et identifié une réponse anti-inflammatoire systémique associées au traitement.

Vascular malformations (VMs) are congenital disorders characterized by structurally abnormal blood and lymphatic vessels. Advances in genetics have revealed that most sporadic VMs result from post-zygotic variants in genes involved in key endothelial signaling pathways, including the phosphoinositide-3-kinase (PI3K) and the mitogen-associated proliferation kinase (MAPK) pathways. As these variants are shared with cancer, genetics now have theragnostic impact by helping predict relevant targeted therapies. mTOR and PI3Kα inhibitors such as sirolimus and alpelisib have shown promising efficacy in slow-flow VMs, while reports have suggested that MAPK inhibitors such as trametinib may improve arteriovenous malformations. Despite these advances, several challenges remain, including obtaining accurate genetic diagnosis, enhancing treatment efficacy while mitigating drug-related toxicities, and personalizing multimodal treatment strategies. Emerging approaches such as mutant-selective inhibitors, proteolysis-targeting chimeras, and gene therapy hold promises for improving treatment specificity and minimizing adverse effects. This review provides an overview of the genetic bases of VMs, recent advances in targeted therapies, and future directions in the field, highlighting the ongoing evolution of precision medicine for VMs.

Alpelisib is a selective PI3Kα inhibitor approved for treating PIK3CA-related overgrowth spectrum (PROS), a group of rare malformation disorders. Given that PI3Kα is a ubiquitous protein involved in cell proliferation, understanding the long-term impact of alpelisib on fertility is of critical importance. Here, we report the favorable outcomes of three pregnancies in PROS patients after prolonged treatment with alpelisib. Although disease progression was observed in all three patients during pregnancy, vascular malformations remained sensitive to alpelisib without evidence of secondary resistance upon resuming treatment. In conclusion, we provide the first evidence that alpelisib does not appear to affect fertility in female patients with PROS.

Mutations in PIK3R1 have recently been identified in patients with overgrowth syndromes and complex vascular malformations. PIK3R1 encodes p85α which acts as the regulatory subunit of the lipid kinase PI3Kα. PIK3R1 mutations result in the excessive activation of the AKT/mTOR pathway. Currently, there are no approved treatments specifically dedicated to patients with PIK3R1 mutations, and medical care primarily focuses on managing symptoms. In this study, we identified three patients, including two children, who had mosaic somatic PIK3R1 mutations affecting the iSH2 domain, along with severe associated symptoms that were unsuccessfully treated with rapamycin. We conducted in vitro experiments to investigate the impact of these mutations, including a double PIK3R1 mutation in cis observed in one patient. Our findings revealed that p85α mutants in the iSH2 domain showed sensitivity to alpelisib, a pharmacological inhibitor of PI3Kα. Based on these findings, we received authorization to administer alpelisib to all three patients. Following drug introduction, patients rapidly demonstrated clinical improvement, pain, fatigue and inflammatory flares were attenuated. Magnetic Resonance Imaging showed a mean decrease of 22.67% in the volume of vascular malformations over twelve months of treatment with alpelisib. No drug-related adverse events were reported during the course of the study. In conclusion, this study provides support for the use of PI3Kα inhibition as a promising therapeutic approach for individuals with PIK3R1 -related anomalies.

KRAS gain-of-function mutations are frequently observed in sporadic arteriovenous malformations. The mechanisms underlying the progression of such KRAS-driven malformations are still incompletely understood, and no treatments for the condition are approved. Here, we show the effectiveness of sotorasib, a specific KRAS G12C inhibitor, in reducing the volume of vascular malformations and improving survival in two mouse models carrying a mosaic Kras G12C mutation. We then administered sotorasib to two adult patients with severe KRAS G12C-related arteriovenous malformations. Both patients had rapid reductions in symptoms and arteriovenous malformation size. Targeting KRAS G12C appears to be a promising therapeutic approach for patients with KRAS G12C-related vascular malformations. (Funded by the European Research Council and others.).

PIK3CA -related overgrowth syndrome (PROS) is a genetic disorder caused by somatic mosaic gain-of-function mutations of PIK3CA . Clinical presentation of patients is diverse and associated with endocrine disruption. Adipose tissue is frequently involved, but its role in disease development and progression has not been elucidated. Here, we created a mouse model of PIK3CA -related adipose tissue overgrowth that recapitulates patient phenotype. We demonstrate that PIK3CA mutation leads to GLUT4 membrane accumulation with a negative feedback loop on insulin secretion, a burst of liver IGFBP1 synthesis with IGF-1 sequestration, and low circulating levels. Mouse phenotype was mainly driven through AKT2. We also observed that PIK3CA mutation induces metabolic reprogramming with Warburg-like effect and protein and lipid synthesis, hallmarks of cancer cells, in vitro, in vivo, and in patients. We lastly show that alpelisib is efficient at preventing and improving PIK3CA -adipose tissue overgrowth and reversing metabolomic anomalies in both animal models and patients.

PIK3CA-related overgrowth spectrum (PROS) includes rare genetic conditions due to gain-of-function mutations in the PIK3CA gene. There is no approved medical therapy for patients with PROS, and alpelisib, an approved PIK3CA inhibitor in oncology, showed promising results in preclinical models and in patients. Here, we report for the first time the outcome of two infants with PROS having life-threatening conditions treated with alpelisib (25 mg) and monitored with pharmacokinetics. Patient 1 was an 8-mo-old girl with voluminous vascular malformation. Patient 2 was a 9-mo-old boy presenting with asymmetrical body overgrowth and right hemimegalencephaly with West syndrome. After 12 mo of follow-up, alpelisib treatment was associated with improvement in signs and symptoms, morphological lesions and vascular anomalies in the two patients. No adverse events were reported during the study. In this case series, pharmacological inhibition of PIK3CA with low-dose alpelisib was feasible and associated with clinical improvements, including a smaller size of associated complex tissue malformations and good tolerability.

Alplesib exerts therapeutic effects in a mouse model of lymphatic anomalies and in six patients with lymphatic malformations over 6 months’ treatment.