Alpelisib administration reduced lymphatic malformations in a mouse model and in patients

Complex lymphatic anomalies: Molecular landscape and medical management

The lymphatic system is one of the most essential and complex systems in the human body. Disorders that affect the development or function of the lymphatic system can lead to multi-system complications and life-long morbidity. The past two decades have seen remarkable progress in our knowledge of the basic biology and function of the lymphatic system, the molecular regulators of lymphatic development, and description of disorders associated with disrupted lymphangiogensis. In this chapter we will touch on the clinical features of complex lymphatic anomalies, new molecular knowledge of the drivers of these disorders, and novel developmental therapeutics for lymphatic disease.

Central conducting lymphatic anomaly: from bench to bedside

Central conducting lymphatic anomaly (CCLA) is a complex lymphatic anomaly characterized by abnormalities of the central lymphatics and may present with nonimmune fetal hydrops, chylothorax, chylous ascites, or lymphedema. CCLA has historically been difficult to diagnose and treat; however, recent advances in imaging, such as dynamic contrast magnetic resonance lymphangiography, and in genomics, such as deep sequencing and utilization of cell-free DNA, have improved diagnosis and refined both genotype and phenotype. Furthermore, in vitro and in vivo models have confirmed genetic causes of CCLA, defined the underlying pathogenesis, and facilitated personalized medicine to improve outcomes. Basic, translational, and clinical science are essential for a bedside-to-bench and back approach for CCLA.

Lymphatic malformations: mechanistic insights and evolving therapeutic frontiers

The lymphatic vascular system is gaining recognition for its multifaceted role and broad pathological significance. Once perceived as a mere conduit for interstitial fluid and immune cell transport, recent research has unveiled its active involvement in critical physiological processes and common diseases, including inflammation, autoimmune diseases, and atherosclerosis. Consequently, abnormal development or functionality of lymphatic vessels can result in serious health complications. Here, we discuss lymphatic malformations (LMs), which are localized lesions that manifest as fluid-filled cysts or extensive infiltrative lymphatic vessel overgrowth, often associated with debilitating, even life-threatening, consequences. Genetic causes of LMs have been uncovered, and several promising drug-based therapies are currently under investigation and will be discussed.

Updates in Genetic Testing for Head and Neck Vascular Anomalies

Vascular anomalies include benign or malignant tumors or benign malformations of the arteries, veins, capillaries, or lymphatic vasculature. The genetic etiology of the lesion is essential to define the lesion and can help navigate choice of therapy. . In the United States, about 1.2% of the population has a vascular anomaly, which may be underestimating the true prevalence as genetic testing for these conditions continues to evolve.

Microcystic lymphatic malformations in Turner syndrome are due to somatic mosaicism of PIK3CA

Turner syndrome (45,X) is caused by a complete or partial absence of a single X chromosome. Vascular malformations occur due to abnormal development of blood and/or lymphatic vessels. They arise from either somatic or germline pathogenic variants in the genes regulating growth and apoptosis of vascular channels. Aortic abnormalities are a common, known vascular anomaly of Turner syndrome. However, previous studies have described other vascular malformations as a rare feature of Turner syndrome and suggested that vascular abnormalities in individuals with Turner syndrome may be more generalized. In this study, we describe two individuals with co-occurrence of Turner syndrome and vascular malformations with a lymphatic component. In these individuals, genetic testing of the lesional tissue revealed a somatic pathogenic variant in PIK3CA-a known and common cause of lymphatic malformations. Based on this finding, we conclude that the vascular malformations presented here and likely those previously in the literature are not a rare part of the clinical spectrum of Turner syndrome, but rather a separate clinical entity that may or may not co-occur in individuals with Turner syndrome.

Alpelisib for treatment of patients with PIK3CA-related overgrowth spectrum (PROS)

PURPOSE

PIK3CA-related overgrowth spectrum (PROS) encompasses several rare conditions resulting from activating variants in PIK3CA. Alpelisib, a PI3Kα-selective inhibitor, targets the underlying etiology of PROS, offering a novel therapeutic approach to current management strategies. This study evaluated the safety and efficacy of alpelisib in pediatric and adult patients with PROS.

METHODS

EPIK-P1 (NCT04285723) was a non-interventional, retrospective chart review of 57 patients with PROS (≥2 years) treated with alpelisib through compassionate use. Patients had severe/life-threatening PROS-related conditions and confirmed PIK3CA pathogenic variant. The primary end point assessed patient response to treatment at Week 24 (6 months).

RESULTS

Twenty-four weeks (6 months) after treatment initiation, 12 of 32 (37.5%) patients with complete case records included in the analysis of the primary end point experienced a ≥20% reduction in target lesion(s) volume. Additional clinical benefit independent from lesion volume reduction was observed across the full study population. Adverse events (AEs) and treatment-related AEs were experienced by 82.5% (47/57) and 38.6% (22/57) of patients, respectively; the most common treatment-related AEs were hyperglycemia (12.3%) and aphthous ulcer (10.5%). No deaths occurred.

CONCLUSION

EPIK-P1 provides real-world evidence of alpelisib effectiveness and safety in patients with PROS and confirms PI3Kα as a valid therapeutic target for PROS symptom management.

Genetic mutations and phenotype characteristics in peripheral vascular malformations: A systematic review

Vascular malformations (VMs) are clinically diverse with regard to the vessel type, anatomical location, tissue involvement and size. Consequently, symptoms and disease impact differ significantly. Diverse causative mutations in more and more genes are discovered and play a major role in the development of VMs. However, the relationship between the underlying causative mutations and the highly variable phenotype of VMs is not yet fully understood. In this systematic review, we aimed to provide an overview of known causative mutations in genes in VMs and discuss associations between the causative mutations and clinical phenotypes. PubMed and EMBASE libraries were systematically searched on November 9th, 2022 for randomized controlled trials and observational studies reporting causative mutations in at least five patients with peripheral venous, lymphatic, arteriovenous and combined malformations. Study quality was assessed with the Newcastle-Ottawa Scale. Data were extracted on patient and VM characteristics, molecular sequencing method and results of molecular analysis. In total, 5667 articles were found of which 69 studies were included, reporting molecular analysis in a total of 4261 patients and 1686 (40%) patients with peripheral VMs a causative mutation was detected. In conclusion, this systematic review provides a comprehensive overview of causative germline and somatic mutations in various genes and associated phenotypes in peripheral VMs. With these findings, we attempt to better understand how the underlying causative mutations in various genes contribute to the highly variable clinical characteristics of VMs. Our study shows that some causative mutations lead to a uniform phenotype, while other causal variants lead to more varying phenotypes. By contrast, distinct causative mutations may lead to similar phenotypes and result in almost indistinguishable VMs. VMs are currently classified based on clinical and histopathology features, however, the findings of this systematic review suggest a larger role for genotype in current diagnostics and classification.

Clinical effectiveness and safety of sirolimus in pediatric patients with complex vascular anomalies: necessitating personalized and comprehensive approaches

Background

Managing complex vascular anomalies in pediatric care requires comprehensive approaches. Sirolimus, an mTOR inhibitor with immunosuppressive and anti-angiogenic properties, offers promise. We evaluated sirolimus's effectiveness and safety in pediatric patients with complex vascular anomalies at a tertiary children's hospital.

Methods

Our study included 20 patients, aged 1 month to 19 years, with diverse vascular anomalies resistant to conventional therapies or located in high-risk areas precluding surgery. The evaluation of response encompassed measuring the reduction in the size of the targeted vascular or lymphatic lesions as observed on radiologic imaging, along with considering improvements reported by the patients.

Results

Patients used sirolimus for a median of 2.1 years, ranging from 0.6-4.3 years. Results indicated that 60% of patients achieved complete or partial response (CR/PR), whereas 40% had stable disease (SD). Notably, no disease progression occurred. Lesion size assessment was complex, yet patients' self-reported improvements were considered. Three patients reinitiated sirolimus after discontinuation due to worsening lesions. Sirolimus treatment demonstrated good tolerability, with minor complications except for one case of Pneumocystis jiroveci pneumonia. Group comparisons based on response highlighted better outcomes in patients with vascular tumors (CR/PR group 58.0% vs. SD group 0.0%, P = 0.015) or localized measurable lesions (83.3% vs. 12.5%, P = 0.005).

Conclusion

Our study underscores sirolimus's potential for treating complex vascular anomalies in pediatric patients. Challenges associated with optimal treatment duration and concurrent interventions necessitate a comprehensive approach and genetic testing to optimize outcomes.

Hemifacial myohyperplasia is due to somatic muscular PIK3CA gain-of-function mutations and responds to pharmacological inhibition

Hemifacial myohyperplasia (HFMH) is a rare cause of facial asymmetry exclusively involving facial muscles. The underlying cause and the mechanism of disease progression are unknown. Here, we identified a somatic gain-of-function mutation of PIK3CA in five pediatric patients with HFMH. To understand the physiopathology of muscle hypertrophy in this context, we created a mouse model carrying specifically a PIK3CA mutation in skeletal muscles. PIK3CA gain-of-function mutation led to striated muscle cell hypertrophy, mitochondria dysfunction, and hypoglycemia with low circulating insulin levels. Alpelisib treatment, an approved PIK3CA inhibitor, was able to prevent and reduce muscle hypertrophy in the mouse model with correction of endocrine anomalies. Based on these findings, we treated the five HFMH patients. All patients demonstrated clinical, esthetical, and radiological improvement with proof of target engagement. In conclusion, we show that HFMH is due to somatic alteration of PIK3CA and is accessible to pharmacological intervention.

Facial infiltrating lipomatosis with hemimegalencephaly and lymphatic malformations caused by nonhotspot phosphatidylinositol 3-kinase catalytic subunit alpha mutation

We report an unusual case of facial infiltrating lipomatosis with hemimegalencephaly and lymphatic malformations. In addition to the clinical data and imaging findings, detection of a heterozygous PIK3CA nonhotspot known pathogenic variant C420R in a facial epidermal nevus provided novel insight into the pathogenic effect of somatic PIK3CA mutations.

Precision medicine in rare diseases: What is next?

Molecular diagnostics is a cornerstone of modern precision medicine, broadly understood as tailoring an individual's treatment, follow-up, and care based on molecular data. In rare diseases (RDs), molecular diagnoses reveal valuable information about the cause of symptoms, disease progression, familial risk, and in certain cases, unlock access to targeted therapies. Due to decreasing DNA sequencing costs, genome sequencing (GS) is emerging as the primary method for precision diagnostics in RDs. Several ongoing European initiatives for precision medicine have chosen GS as their method of choice. Recent research supports the role for GS as first-line genetic investigation in individuals with suspected RD, due to its improved diagnostic yield compared to other methods. Moreover, GS can detect a broad range of genetic aberrations including those in noncoding regions, producing comprehensive data that can be periodically reanalyzed for years to come when further evidence emerges. Indeed, targeted drug development and repurposing of medicines can be accelerated as more individuals with RDs receive a molecular diagnosis. Multidisciplinary teams in which clinical specialists collaborate with geneticists, genomics education of professionals and the public, and dialogue with patient advocacy groups are essential elements for the integration of precision medicine into clinical practice worldwide. It is also paramount that large research projects share genetic data and leverage novel technologies to fully diagnose individuals with RDs. In conclusion, GS increases diagnostic yields and is a crucial step toward precision medicine for RDs. Its clinical implementation will enable better patient management, unlock targeted therapies, and guide the development of innovative treatments.

A randomized, placebo-controlled study to evaluate safety and pharmacokinetics of ART-001 with a novel oral pediatric formulation in healthy subjects

ART-001 is an orally available selective PI3Kα inhibitor currently being developed for the treatment of slow-flow vascular malformations (SFVMs). ART-001 used to be developed for advanced solid tumors, but was suspended largely due to significant pharmacokinetic (PK) variability in its phase I studies. This phase I, randomized, double-blinded, placebo-controlled study evaluated safety, tolerability and PK of ART-001 with a newly developed dry syrup formulation, which was designed to optimize PK properties of ART-001 and to be compliant with the pediatric population. Single and multiple doses of ART-001 were administered to healthy male adults. ART-001 was rapidly absorbed after the single and repeated doses, and the exposure of ART-001 increased with increased dose. The dry syrup formulation substantially improved the intersubject PK variability. Food decreased area under the concentration-time curve (AUC) and maximum plasma concentration by 12% and 36%, respectively. The plasma concentration had reached a steady-state on day 5 of the repeated doses of 100 mg and AUC accumulation ratio was 1.9. There were no deaths or serious adverse events. The most frequent adverse event was hyperglycemia. All cases of hyperglycemia were mild to moderate and transient, and required no medical interventions. Serum creatinine increase was observed in 300 mg once daily dosing group leading to dose discontinuation on day 5. In conclusion, it was demonstrated that the single doses and repeated doses of the ART-001 dry syrup formulation, at up to 400 and 100 mg, respectively, were safe and tolerated with favorable PK profile, supporting further clinical development for the treatment of SFVMs.

Repurposing of antiangiogenic agents for treatment of vascular anomalies

Vascular anomalies (VA) are developmental anomalies of veins, arteries, lymphatics or capillaries thought to be caused by mutations in genes that drive angiogenesis. Treatments targeting these genes are limited. We review the literature for conventional medications and products from traditional medicine cultures that have been found to have antiangiogenic activity. Fewer than 50 drugs with credible human activity in VA were identified and include β blockers, monoclonal antibodies, microtubule inhibitors, multi-kinase inhibitors, PIK3CA- and RAS-MAPK pathway inhibitors, and thalidomides. Other drug categories of potential interest are ACE-inhibitors, antifungals, antimalarials, MMP9-inhibitors, and over-the-counter compounds used in Eastern traditional medicine. Low toxicity for some offers the possibility of combined use with known effective agents. In addition to already familiar drugs, others with antiangiogenic capabilities already in use in children or adults may deserve further attention for repurposing for VA.

Pathophysiology of Slow-Flow Vascular Malformations: Current Understanding and Unanswered Questions

Background

Slow-flow vascular malformations include venous, lymphatic, and lymphaticovenous malformations. Recent studies have linked genetic variants hyperactivating either the PI3K/AKT/mTOR and/or RAS/RAF/MAPK signaling pathways with slow-flow vascular malformation development, leading to the use of pharmacotherapies such as sirolimus and alpelisib. It is important that clinicians understand basic and translational research advances in slow-flow vascular malformations.

Methods

A literature review of basic science publications in slow-flow vascular malformations was performed on Pubmed, using search terms "venous malformation," "lymphatic malformation," "lymphaticovenous malformation," "genetic variant," "genetic mutation," "endothelial cells," and "animal model." Relevant publications were reviewed and summarized.

Results

The study of patient tissues and the use of primary pathogenic endothelial cells from vascular malformations shed light on their pathological behaviors, such as endothelial cell hyperproliferation and disruptions in vessel architecture. The use of xenograft and transgenic animal models confirmed the pathogenicity of genetic variants and allowed for preclinical testing of potential therapies. These discoveries underscore the importance of basic and translational research in understanding the pathophysiology of vascular malformations, which will allow for the development of improved biologically targeted treatments.

Conclusion

Despite basic and translation advances, a cure for slow-flow vascular malformations remains elusive. Many questions remain unanswered, including how genotype variants result in phenotypes, and genotype-phenotype heterogeneity. Continued research into venous and lymphatic malformation pathobiology is critical in understanding the mechanisms by which genetic variants contribute to vascular malformation phenotypic features.

Pathological angiogenesis: mechanisms and therapeutic strategies

In multicellular organisms, angiogenesis, the formation of new blood vessels from pre-existing ones, is an essential process for growth and development. Different mechanisms such as vasculogenesis, sprouting, intussusceptive, and coalescent angiogenesis, as well as vessel co-option, vasculogenic mimicry and lymphangiogenesis, underlie the formation of new vasculature. In many pathological conditions, such as cancer, atherosclerosis, arthritis, psoriasis, endometriosis, obesity and SARS-CoV-2(COVID-19), developmental angiogenic processes are recapitulated, but are often done so without the normal feedback mechanisms that regulate the ordinary spatial and temporal patterns of blood vessel formation. Thus, pathological angiogenesis presents new challenges yet new opportunities for the design of vascular-directed therapies. Here, we provide an overview of recent insights into blood vessel development and highlight novel therapeutic strategies that promote or inhibit the process of angiogenesis to stabilize, reverse, or even halt disease progression. In our review, we will also explore several additional aspects (the angiogenic switch, hypoxia, angiocrine signals, endothelial plasticity, vessel normalization, and endothelial cell anergy) that operate in parallel to canonical angiogenesis mechanisms and speculate how these processes may also be targeted with anti-angiogenic or vascular-directed therapies.

Targeted treatment of severe vascular malformations harboring PIK3CA and TEK mutations with alpelisib is highly effective with limited toxicity

This was a prospective cohort study of eighteen patients with large and debilitating vascular malformations with one or more major systemic complications. In all patients, we discovered activating alterations in either TEK or PIK3CA. Based on these findings, targeted treatment using the PI3K inhibitor alpelisib was started with regular check-ups, therapy duration varied from 6 to 31 months. In all patients, marked improvement in quality of life was observed. We observed radiological improvement in fourteen patients (two of them being on combination with either propranolol or sirolimus), stable disease in 2 patients. For 2 patients, an MRI scan was not available as they were shortly on treatment, however, a clinically visible response in size reduction or structure regression, together with pain relief was observed. In patients with elevated D-dimer levels before alpelisib administration, a major improvement was noted, suggesting its biomarker role. We observed overall very good tolerance of the treatment, documenting a single patient with grade 3 hyperglycemia. Patients with size reduction were offered local therapies wherever possible. Our report presents a promising approach for the treatment of VMs harboring different targetable TEK and PIK3CA gene mutations with a low toxicity profile and high efficacy.

Microphysiological model of PIK3CA-driven vascular malformations reveals a role of dysregulated Rac1 and mTORC1/2 in lesion formation

Somatic activating mutations of PIK3CA are associated with development of vascular malformations (VMs). Here, we describe a microfluidic model of PIK3CA-driven VMs consisting of human umbilical vein endothelial cells expressing PIK3CA activating mutations embedded in three-dimensional hydrogels. We observed enlarged, irregular vessel phenotypes and the formation of cyst-like structures consistent with clinical signatures and not previously observed in cell culture models. Pathologic morphologies occurred concomitant with up-regulation of Rac1/p21-activated kinase (PAK), mitogen-activated protein kinase cascades (MEK/ERK), and mammalian target of rapamycin (mTORC1/2) signaling networks. We observed differential effects between alpelisib, a PIK3CA inhibitor, and rapamycin, an mTORC1 inhibitor, in mitigating matrix degradation and network topology. While both were effective in preventing vessel enlargement, rapamycin failed to reduce MEK/ERK and mTORC2 activity and resulted in hyperbranching, while inhibiting PAK, MEK1/2, and mTORC1/2 mitigates abnormal growth and vascular dilation. Collectively, these findings demonstrate an in vitro platform for VMs and establish a role of dysregulated Rac1/PAK and mTORC1/2 signaling in PIK3CA-driven VMs.

Vascular malformations: An overview of their molecular pathways, detection of mutational profiles and subsequent targets for drug therapy

Vascular malformations are anomalies in vascular development that portend a significant risk of hemorrhage, morbidity and mortality. Conventional treatments with surgery, radiosurgery and/or endovascular approaches are often insufficient for cure, thereby presenting an ongoing challenge for physicians and their patients. In the last two decades, we have learned that each type of vascular malformation harbors inherited germline and somatic mutations in two well-known cellular pathways that are also implicated in cancer biology: the PI3K/AKT/mTOR and RAS/RAF/MEK pathways. This knowledge has led to recent efforts in: (1) identifying reliable mechanisms to detect a patient's mutational burden in a minimally-invasive manner, and then (2) understand how cancer drugs that target these mutations can be repurposed for vascular malformation care. The idea of precision medicine for vascular pathologies is growing in potential and will be critical in expanding the clinician's therapeutic armamentarium.

Drug repurposing: From the discovery of a useful pharmacological effect to making the treatment available to the patient

The repurposing of a medicine already on the market to a new indication could be an opportunity to respond rapidly to a therapeutic need not yet covered, particularly in the context of rare and neglected diseases, or health emergencies. However, at each stage, difficulties may arise that will prevent the repurposed drug from being provided to patients. Beyond fortuity or a systematic strategy to detect a useful pharmacological effect, the implementation of the preclinical and clinical stages is sometimes complicated by the difficulty of accessing the molecule and its pharmaceutical data. Furthermore, relevant clinical results will not always be sufficient to ensure that a marketing authorisation is obtained or that patients receive satisfactory care. In addition to describing these various obstacles, the round table provided an opportunity to put forward recommendations for overcoming them, in particular the creation of a public-private partnership structure with sufficient funding to be able to offer individualised support for projects up to and including the marketing application.

PIK3CA gain-of-function mutation in adipose tissue induces metabolic reprogramming with Warburg-like effect and severe endocrine disruption

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.

Alpelisib for the treatment of PIK3CA-related head and neck lymphatic malformations and overgrowth

PURPOSE

PIK3CA-related overgrowth spectrum (PROS) conditions of the head and neck are treatment challenges. Traditionally, these conditions require multiple invasive interventions, with incomplete malformation removal, disfigurement, and possible dysfunction. Use of the PI3K inhibitor alpelisib, previously shown to be effective in PROS, has not been reported in PIK3CA-associated head and neck lymphatic malformations (HNLMs) or facial infiltrating lipomatosis (FIL). We describe prospective treatment of 5 children with PIK3CA-associated HNLMs or head and neck FIL with alpelisib monotherapy.

METHODS

A total of 5 children with PIK3CA-associated HNLMs (n = 4) or FIL (n = 1) received alpelisib monotherapy (aged 2-12 years). Treatment response was determined by parental report, clinical evaluation, diary/questionnaire, and standardized clinical photography, measuring facial volume through 3-dimensional photos and magnetic resonance imaging.

RESULTS

All participants had reduction in the size of lesion, and all had improvement or resolution of malformation inflammation/pain/bleeding. Common invasive therapy was avoided (ie, tracheotomy). After 6 or more months of alpelisib therapy, facial volume was reduced (range 1%-20%) and magnetic resonance imaging anomaly volume (range 0%-23%) were reduced, and there was improvement in swallowing, upper airway patency, and speech clarity.

CONCLUSION

Individuals with head and neck PROS treated with alpelisib had decreased malformation size and locoregional overgrowth, improved function and symptoms, and fewer invasive procedures.

Repurposing alpelisib, an anti-cancer drug, for the treatment of severe TIE2-mutated venous malformations: Preliminary pharmacokinetics and pharmacodynamic data

Extensive venous malformations involving limbs severely impact quality of life, mostly due to chronic pain and functional limitations. But patients can also display coagulopathy with associated risks of life-threatening thromboembolism and bleeding. Available pharmacological treatments (e.g., sirolimus) are not universally effective. Novel therapies are urgently needed for patients with treatment-resistant venous malformations. We report three patients with TIE-2 receptor mutations treated with alpelisib for 6 months (daily dosing: 50 mg for children weighing <50 kg and 100 mg for those >50 kg). Pain was controlled, gait improved, size of the abnormal venous network decreased, and coagulopathy dramatically improved. Drug exposure was highly variable, suggesting that alpelisib dosing should be individualized to patient's characteristics and guided by therapeutic drug monitoring.

Genomic landscape of lymphatic malformations: a case series and response to the PI3Kα inhibitor alpelisib in an N-of-1 clinical trial

Background

Lymphatic malformations (LMs) often pose treatment challenges due to a large size or a critical location that could lead to disfigurement, and there are no standardized treatment approaches for either refractory or unresectable cases.

Methods

We examined the genomic landscape of a patient cohort of LMs (n = 30 cases) that underwent comprehensive genomic profiling using a large-panel next-generation sequencing assay. Immunohistochemical analyses were completed in parallel.

Results

These LMs had low mutational burden with hotspot PIK3CA mutations (n = 20) and NRAS (n = 5) mutations being most frequent, and mutually exclusive. All LM cases with Kaposi sarcoma-like (kaposiform) histology had NRAS mutations. One index patient presented with subacute abdominal pain and was diagnosed with a large retroperitoneal LM harboring a somatic PIK3CA gain-of-function mutation (H1047R). The patient achieved a rapid and durable radiologic complete response, as defined in RECIST1.1, to the PI3Kα inhibitor alpelisib within the context of a personalized N-of-1 clinical trial (NCT03941782). In translational correlative studies, canonical PI3Kα pathway activation was confirmed by immunohistochemistry and human LM-derived lymphatic endothelial cells carrying an allele with an activating mutation at the same locus were sensitive to alpelisib treatment in vitro, which was demonstrated by a concentration-dependent drop in measurable impedance, an assessment of cell status.

Conclusions

Our findings establish that LM patients with conventional or kaposiform histology have distinct, yet targetable, driver mutations.

Funding

R.P. and W.A. are supported by awards from the Levy-Longenbaugh Fund. S.G. is supported by awards from the Hugs for Brady Foundation. This work has been funded in part by the NCI Cancer Center Support Grants (CCSG; P30) to the University of Arizona Cancer Center (CA023074), the University of New Mexico Comprehensive Cancer Center (CA118100), and the Rutgers Cancer Institute of New Jersey (CA072720). B.K.M. was supported by National Science Foundation via Graduate Research Fellowship DGE-1143953.

Clinical trial number

NCT03941782.

Medical management of vascular anomalies of the head and neck

Depending on impairment, treatment of vascular anomalies is decided on a case-by-case basis in pluridisciplinary consultations. Interventional treatments, especially surgery and sclerotherapy, are usually partially efficient and management of patients with vascular anomalies increasingly involves the use of medical drugs. The most common vascular tumor is infantile hemangioma where first-line medical treatment, when necessary, is propranolol. Kasabach-Merritt phenomenon is now largely treated with sirolimus whereas first-line treatment of coagulation disorders associated with venous malformations is based on low molecular weight heparins or direct anticoagulants. Sirolimus is the standard treatment for painful inflammatory manifestations of low-flow vascular malformations such capillary, venous, and lymphatic malformations that can occur singly or in combination but PIK3CA inhibitors, originally developed in oncology, have shown promising results in patients with PIK3CA-related overgrowth spectrum. Currently, medical treatments are poorly developed for high-flow malformations such as arteriovenous malformations. However, new research aimed at delineating the different arteriovenous malformations based on molecular findings has given new hope for future development of targeted therapies.

The utility of cerebrospinal fluid-derived cell-free DNA in molecular diagnostics for the PIK3CA-related megalencephaly-capillary malformation (MCAP) syndrome: a case report

The megalencephaly-capillary malformation (MCAP) syndrome is an overgrowth disorder caused by mosaic gain-of-function variants in PIK3CA It is characterized by megalencephaly or hemimegalencephaly, vascular malformations, somatic overgrowth, among other features. Epilepsy is commonly associated with MCAP, and a subset of individuals have cortical malformations requiring resective epilepsy surgery. Like other mosaic disorders, establishing a molecular diagnosis is largely achieved by screening lesional tissues (such as brain or skin), with a low diagnostic yield from peripheral tissues (such as blood). Therefore, in individuals with MCAP in whom lesional tissues are scarce or unavailable or those ineligible for epilepsy surgery, establishing a molecular diagnosis can be challenging. Here we report on the utility of cerebrospinal fluid (CSF)-derived cfDNA for the molecular diagnosis of an individual with MCAP syndrome harboring a mosaic PIK3CA variant (c.3139C > T, p.His1047Tyr). The proband presented with asymmetric megalencephaly without significant dysgyria. He did not have refractory epilepsy and was therefore not a candidate for epilepsy surgery. However, he developed diffuse large B-cell lymphoma (DLBCL) in late childhood, with four CSF samples obtained via lumbar puncture for cancer staging during which one sample was collected for cfDNA extraction and sequencing. PIK3CA variant allele fractions in CSF cell-free DNA (cfDNA), skin fibroblasts, and peripheral blood were 3.08%, 37.31%, and 2.04%, respectively. This report illustrates the utility of CSF-derived cfDNA in MCAP syndrome. Minimally invasive-based molecular diagnostic approaches utilizing cfDNA not only facilitate accurate genetic diagnosis but also have important therapeutic implications for individuals with refractory epilepsy as repurposed PI3K-AKT-MTOR pathway-inhibitors become more widely available.

Treatment of two infants with PIK3CA-related overgrowth spectrum by alpelisib

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.

Alpelisib to treat CLOVES syndrome, a member of the PIK3CA-related overgrowth syndrome spectrum

CLOVES syndrome is a rare congenital overgrowth disorder caused by mutations in the phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) gene. It is part of the PIK3CA-related overgrowth syndrome (PROS) spectrum and its treatment is challenging. PROS malformations have traditionally been treated by surgery, but research into pharmacological treatments capable of blocking the PIK/AKT/mTOR pathway has increased over the past decade. The results have been promising and suggest that compassionate use of these treatments in patients with PROS disorders could have clinical benefits. Another promising drug is alpelisib (BYL719), which is a selective inhibitor that competitively binds to the p110a subunit of PIK3 in the intracellular PI3K/AKT signalling pathway. Compassionate use of low-dose alpelisib had striking effects in an uncontrolled case series of 19 PROS patients, several with life-threatening complications. Moreover, there were few adverse effects and the treatment did not impair linear growth, despite the young age of many of the patients. We present the case of a patient with CLOVES syndrome who was started on compassionate treatment with alpelisib after surgical debulking of a cystic lymphangioma and treatment with sirolimus. This promising drug significantly reduced the size of the lymphangioma and prevented progression of the tissue overgrowth in the gluteal region. This case suggests that low-dose PI3K inhibition may provide collateral benefits that extend beyond mitigation of disease-specific features of PROS.

Genetic and Molecular Determinants of Lymphatic Malformations: Potential Targets for Therapy

Lymphatic malformations are fluid-filled congenital defects of lymphatic channels occurring in 1 in 6000 to 16,000 patients. There are various types, and they often exist in conjunction with other congenital anomalies and vascular malformations. Great strides have been made in understanding these malformations in recent years. This review summarize known molecular and embryological precursors for lymphangiogenesis. Gene mutations and dysregulations implicated in pathogenesis of lymphatic malformations are discussed. Finally, we touch on current and developing therapies with special attention on targeted biotherapeutics.