Microplasmin for Children trial: Results awaited

Rochester, MI-The use of microplasmin (ocriplasmin; Jetrea, ThromboGenics), which was approved for use by the FDA in October 2012 for treatment of vitreomacular adhesions, was evaluated in the Microplasmin for Children (MIC) trial for use in pediatric patients. The results are forthcoming.

 “Pharmacologic vitreolysis is a very interesting prospect for manipulating the vitreous and retina as a surgical adjunct or alone,” said Kimberly Dresner, MD, PhD, in commenting on this technology.

“The vitreous has characteristics that make it an ideal matrix for manipulation with enzymes in that it facilitates rapid diffusion of drugs, is mostly water, has relatively few molecular components, and is mostly acellular,” said Dr. Dresner, director, Ophthalmology Research Laboratory, Oakland University, William Beaumont School of Medicine, Rochester, MI. “In the vitreoretinal interface, adhesion between the posterior vitreous cortex and the internal limiting membrane is mediated by a ‘molecular glue.’ ”

The advent of recombinant plasmin proteins has facilitated ease of use of a product that does not have to be developed from a blood product in a laboratory and prepared specifically for each case. The structure of microplasmin is advantageous, in contrast to plasmin, in that it lacks the inactive kringle domains, is recombinant, and is a direct-acting thrombolytic; its smaller molecule allows better retinal penetration. Importantly, it can induce a posterior vitreous detachment (PVD) with one 62- or 125-µg injection.

However, she emphasized that children’s eyes are substantially different from those of adults. Retinal surgeries fail in children because of the persistent attachment of the hyaloid to the retina.

The MIC trial, a phase II, randomized, placebo-controlled clinical study, evaluated the safety and efficacy of one injection (175-µg dose) of intravitreal microplasmin in infants and children (age 16 years and younger) with conditions such as tractional retinal detachment, rhegmatogenous retinal detachment, and congenital x-linked retinoschisis. A total of 24 children received either the study drug (n = 16) or a placebo injection (n = 8). All patients had attached vitreous in the posterior pole. Patients with early- or late-stage retinopathy of prematurity and those with unclear media were excluded. The surgeons assessed the efficacy of microplasmin at the time of surgery; the two main criteria were the level of the PVD and the degree of vitreous liquefaction.

The MIC enrollment has been completed and the data are being analyzed.

Dr. Dresner did not indicate any financial interest in this topic. This article is based on her presentation during Retina Subspecialty Day at the 2012 American Academy of Ophthalmology annual meeting.

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