Intravenous (JEB) caused by nonsense variants.
The newly generated structural protein persisted during the 3-month randomized clinical trial and was associated with significant wound closure – with no signs of ototoxic effects, nephrotoxic effects, or anti–laminin 332 autoantibody induction, investigators recently reported in JAMA Dermatology.
JEB is a rare, autosomal recessive disorder caused mainly by nonsense variants (i.e., mutations) in the LAMA3, LAMB3, or LAMC2 genes that encode laminin, resulting in widespread blisters and erosions of the skin. Current treatment is limited to supportive management and palliative care, and children with its severe subtype are likely to die within the first year of life.
“With data indicating a robust response to short-term gentamicin treatment and the marked stability of laminin 332, we envision that gentamicin could be delivered as a short-term pulse therapy every 2-3 months for patients with JEB caused by nonsense variants,” the researchers wrote.
Of the five patients, ages 3 months to 10 years, three received 7.5 mg/kg IV gentamicin daily for 14 days, and two received 10 mg/kg daily for 24 days at the University of Southern California, Los Angeles.
All had confirmed nonsense variants in LAMA3 or LAMB3 in one or two alleles, and all had minimal laminin 332 expression at baseline as determined by immunofluorescence. After treatment, each of the children had increased, sustained expression of laminin 332.
The researchers monitored three open wounds in each patient. By 1 month, seven of nine wounds in those receiving the lower-dose therapy and all of the wounds in those receiving the higher-dose therapy showed at least 50% closure. By 3 months, eight of nine wounds in the lower-dose group, and all wounds in the higher-dose group showed greater than 85% closure.
In an interview, senior investigators Mei Chen, PhD, professor of dermatology, and David T. Woodley, MD, professor and chair of dermatology, both at USC, emphasized laminin’s long half-life.“Once these skin structural proteins are generated at the dermal-epidermal junction, they are long-lasting structures, which means the therapy can be pulsed rather than continuously delivered, which can obviate some of the known side effects of the medication,” Dr. Woodley said.
Gentamicin, an aminoglycoside, works as a “read-through therapy,” inducing ribosomal read-through of premature termination codons (PTCs) caused by nonsense mutations. The read-through allows translation to proceed and full-length proteins to be generated.
Gentamicin read-through therapy is also being investigated for recessive dystrophic epidermolysis bullosa (RDEB) attributable to nonsense mutations. The culprit mutations in this form of EB occur in a gene that encodes collagen type VII alpha 1, which, like laminin, is responsible for dermal-epidermal adherence. A clinical trial of intravenous gentamicin for RDEB is ongoing at USC, Dr. Chen said.
EBS-MD case report
It may also have a role in treating epidermolysis bullosa simplex with muscular dystrophy (EBS-MD), according to investigators in Madrid. Their case report, published in JAMA Dermatology, details how two 14-day courses of infused gentamicin therapy were followed by re-expression of plectin in the skin for 4-5 months and mild improvement in symptoms in one patient, a woman in her 30s, with a homozygous nonsense variant in PLEC1.
In an editorial accompanying the two reports, Anna L. Bruckner, MD, MSCS, professor of dermatology, University of Colorado at Denver, Aurora, and colleagues expressed cautious optimism and said that additional research on the feasibility, possible cumulative toxic effects, risk of microbial resistance, and overall clinical relevance is needed.
Still, the “investigators should be applauded for taking advantage of a readily available systemic treatment to target cutaneous and extracutaneous symptoms of patients who have very limited treatment options at this time,” they wrote. While all forms of EB are considered orphan disorders, JEB and EBS-MD have received less research attention than RDEB.
The JEB study evaluated patients with clinical assessments/quality of life surveys and with a validated clinical score that considers skin and mucosae – the Epidermolysis Bullosa Disease Activity and Scarring Index (EBDASI). There were small positive changes in EBDASI scores, but data were incomplete and therefore difficult to interpret.
A “noteworthy” finding, the authors wrote, were improvements in emotions and functioning in two of the children who were eligible given their older ages for assessment with the Skindex-16 quality-of-life survey. The improvements suggest “potential psychosocial benefits” of the gentamicin therapy.
The JEB study was supported in part by grants from the EB Research Partnership and EB Medical Research Foundation and an award from the Congressionally Directed Medical Research Program. In addition to the grants, Dr. Woodley and Dr. Chen reported receiving personal fees from Phoenix Tissue Repair outside of the submitted work. For the EBS-MD case report, the authors reported no disclosures. Dr. Bruckner, corresponding author of the editorial, reported grants from several companies outside the submitted work.