“The medicines we had were believed to be antiangiogenic and they were used not only for tumors but for all sorts of malformations,” Dr. Adams, a pediatric hematologist-oncologist at Children’s Hospital of Philadelphia, recalled during the annual meeting of the Society for Pediatric Dermatology. “I didn’t understand how so many different phenotypes could respond to the same medicine. Not all of them did, but some did have some response.”
She also grew frustrated by the lack of clinical trials and collaborative research groups involving patients with vascular anomalies. “I called this the chicken soup of medical management,” she said. “As we got more involved in vascular anomalies, the power of one patient or that power of a few patients led us in a direction for improved medical management. Or knowledge was gained by one patient who failed all noted medical management and led us into a direction repurposing a drug that actually wound up working.”
Propranolol, for example, became a key medicine for the treatment of vascular anomalies when it was found to improve hemangiomas in children who were given the drug for other reasons. “From this observation a key prospective study was performed and this beta-blocker became FDA approved for the treatment of complicated hemangiomas,” said Dr. Adams, who directs the hospital’s Comprehensive Vascular Anomalies Program. “That was how a bedside observation let to bench intervention, and how presently we are investigating bench interventions related to the mechanism of propranolol therapy.”
Then there is the story of the mammalian target of rapamycin (mTOR) inhibitor sirolimus. In her previous role as medical director of the Hemangioma and Vascular Malformation Center at Cincinnati Children’s Hospital, Dr. Adams and colleagues cared for an infant who presented with a Kaposiform hemangioendothelioma (KHE). “At that time, she was given our standard of practice for the treatment, but our standard of practice was not good enough,” she said.
While other options were being discussed for this patient, “we had been doing some collaborative work with pathology and nephrology on the PIKC3A pathway, because we knew that germline mutations of TEK were involved in this pathway, and we knew that 50% of patients with PTEN mutations had vascular anomalies. So, we hypothesized that this pathway was involved in vascular anomalies.”
They also had earlier success using mTOR inhibition for tuberous sclerosis patients with angiomyolipomas and patients with neurofibromatosis. “We needed a medicine that could be given orally because we did not think this patient was going to do well, so we started her on sirolimus,” Dr. Adams said. “She had a great response. This was followed by a phase 2 study, which proved efficacy and led to discovery of biomarkers.” This is where the angiopoietin-2 story started, she said, noting that this biomarker is now used “to differentiate KLA [Kaposiform lymphangiomatosis] from KHE and KLAs and KHE from other disorders.”
This bedside work helped researchers to better understand the mechanism of action in other disorders, such as observing somatic mutations in PIK3CA in patients with CLOVES syndrome. “This meant that we could now correlate the phenotype to the genotype, and it opened up targeted therapy with developmental therapeutics that were already in use for oncology,” Dr. Adams said. “We know we had mTOR inhibition with sirolimus and everolimus. We now have an AKT inhibitor, a PIK3CA inhibitor, and we now have another side of the pathway which deals with RASopathies, and some other medicines that we can use.”
Miransertib, a potent PAN-AKT inhibitor initially used for breast cancer, is currently being evaluated in open-label, phase 1 and 2 trials in patients with PIK3CA-related overgrowth spectrum (PROS) and Proteus syndrome. The dose used in a pilot study is about one-sixth of the dose used for oncology patients, Dr. Adams said.
She and her colleagues used miransertib to treat a 3-year-old with CLOVES syndrome who had lipomatous infiltration of the abdomen and retroperitoneum with failure to thrive. “He was not eating and was G-tube dependent,” she recalled. “After a month of therapy, he started eating and had improvement in his quality of life,” although despite this improvement volumetric MRI remained unchanged.
Advances in bench to bedside approaches are also under way. Hakon Hakonarson, MD, PhD, the founding director of the Center for Applied Genomics at CHOP, has discovered several genes with in vitro testing and zebra fish modeling, which has been followed by testing medicines on patients.
One such patient, according to Dr. Adams, had a severe central conducting lymphatic anomaly, with a pericardial effusion and significant dysfunction of the central conducting system. The patient was found to have an ARAF mutation, which induces ERK activation. “ERK is downstream of MEK, so the question was whether a MEK inhibitor, trametinib, could be used to treat this patient,” she said. “Trametinib was first used in tissue culture, then used in a zebra fish model and it showed some positive results. Then it was taken to the patient, who had improvement of pulmonary function, remodeling of the lymphatic system, and decrease in the size of his legs.”
Other antiangiogenic agents being used for the treatment of vascular anomalies include bevacizumab, which is being used in hereditary hemorrhagic telangiectasia, and thalidomide for HHT and arteriovenous malformations. For more information, Dr. Adams recommended a comprehensive review of vascular anomalies, related genes, and treatments that was published in Circulation Research.
The goal of future drug therapies is to support normal growth, “so we don’t need a maximum tolerated dose,” Dr. Adams said. “We need to be very careful of short-term and long-term side effects.”
Going forward, she said that she would like to see more natural history studies of vascular anomalies, improved outcome measures for clinical trials, adaptive study design, preclinical testing, animal model studies, universal availability of genomic testing, improvement of NIH funding, research collaboration nationally and internationally, and industry support.
Dr. Adams disclosed that she is a consultant to Venthera and Novartis.