Enzyme therapy could replace surgical vitrectomy

ThromboGenics' experimental enzyme therapy, microplasmin, has been shown to induce a posterior vitreous detachment (PVD) in over 30% of patients in the high dose group, without the need for surgical intervention, according to the results of the Phase IIb MIVI III (Microplasmin for Vitreous Injection) trial. The results were presented by Dr George Williams of Beaumont Hospital, Michigan, US, at this year's World Ophthalmology Congress in Hong Kong.

Microplasmin is an enzyme that cleaves certain protein molecules that link the vitreous to the retina. It therefore facilitates vitrectomy by inducing PVD and could actually replace vitrectomy in some patients, thus eliminating the inherent risks of surgery.

The Phase IIb randomized, double-masked, placebo-controlled, dose-ranging trial evaluated three doses of the enzyme therapy (25, 75 and 125 µg) in 125 patients who were scheduled to undergo vitrectomy for a number of conditions. Microplasmin was administered by intravitreal injection seven days prior to the planned surgery, in 19 centres across the US.

The study showed that microplasmin was well tolerated, with the 125 µg proving to be more efficacious; 10 of the 32 patients (31%) in this dose group experienced complete resolution of their underlying disease, hence these patients did not require surgical intervention.

Five of the 33 patients (15%) in the 75 µg microplasmin group did not need a vitrectomy and, overall, the therapy facilitated the achievement of a PVD in those patients who still required surgery.

ThromboGenics will now proceed its microplasmin therapy into Phase III trials, which are expected to begin in late 2008/early 2009.