A class of drugs originally approved for stopping tumor growth in adult cancers including melanoma and small cell lung cancer may be the key to treating plexiform neurofibromas in neurofibromatosis type 1 (NF1), too. If effective, doctors will finally have a treatment to offer for children with complicated plexiform neurofibromas that can’t be removed via surgery.
These drugs, including selumentinib, work by inhibiting the activity of the mitogen-activated protein kinase enzymes MEK1 and MEK2. The enzymes have a direct impact on the activity of the cellular signaling pathway MAPK/ERK, which can be overactive some cancers.
Ongoing pre-clinical studies made possible by national and international neurofibromatosis research collaborations demonstrated that this same pathway is overactive in children with NF1 who have plexiform neurofibromas. The compelling findings from these studies set the stage for clinical trials to test the safety and efficacy of selumetinib and other MEK inhibitors as a therapy for pediatric NF1 patients with inoperable plexiform neurofibromas.
At Children’s National, these studies are run by clinicians such as Miriam Bornhorst, M.D., clinical director of the Gilbert Family Neurofibromatosis Institute and Aerang Kim, M.D., Ph.D. Children’s is one of only four sites in the United States to participate in a National Institutes of Health-led clinical trial to study the use of selumetinib in NF1. Dr. Kim is the site principal investigator and Dr. Bornhorst serves as co-principal investigator on phase 2 of the trial.
“Any time we find a medication that works with NF1, we’re excited, especially because for so many years, we didn’t have any of these options for these families,” Dr. Bornhorst says. “We’re offering something these families have never had before – a treatment that may stop growth and maybe even keep these tumors from returning. It means we’re doing more than managing symptoms – we’re really treating them.”
NF1 affects a relatively small number of people, particularly children. However, researchers and clinicians who are dedicated to the condition have banded together via collaborations and consortia to fuel research and development of new therapies across multiple institutions in the U.S. and abroad.
“Patients come to see me who’ve been at our clinic for years and I’ll talk about MEK inhibitors, and they are just shocked to hear there may be a new option,” Dr. Bornhorst says.
The NIH trial continues to collect data at four U.S. centers, with the ultimate goal of submitting the results for FDA review. Additional data is also collected from patients who didn’t qualify for the trial but who received the drug for compassionate use, an effort led by Dr. Bornhorst. The information collected from that compassionate use trial also helps investigators make the case to broaden the eligibility criteria for future trials.
“The medications are showing that they work,” Dr. Bornhorst notes. “Now we need to determine how to identify the patients who we know will need these therapies.”
To meet that need, other studies, led by both Dr. Bornhorst and Dr. Kim, seek radiographic and blood biomarkers that will identify children with NF1 who are more likely to develop plexiform neurofibromas, and whose plexiforms may progress to something malignant.