Inhibition of posterior capsule opacification with an immunotoxin specific for lens epithelial cells: 24 month clinical results

Purpose: To assess the safety and effectiveness of an immunotoxin, MDX-RA, designed to inhibit posterior capsule opacification (PCO). Setting: Eleven private practices in the United States. Methods: This study comprised 63 eyes of 63 patients having extracapsular cataract extraction by phacoemulsification; these patients were enrolled in a Phase I/II clinical investigation of the immunotoxin MDX-RA. At the close of surgery, 21 patients were treated with placebo, 23 patients with 50 units of the immunotoxin, and 19 patients with 175 units of the immunotoxin as an aqueous solution. The patients were monitored for 24 months after primary cataract surgery using external eye and slitlamp examinations, visual acuity assessment, ophthalmoscopy, pachymetry, tonometry, endothelial cell counts, and lens capsule photography. Posterior capsule opacification, recorded on lens capsule photographs, was graded independently by a committee of 3 cataract surgeons. The incidence of neodymium:YAG (Nd:YAG) capsulotomy was projected from the opacification results. Results: The immunotoxin, at the 50 unit dose, was well tolerated and effective in inhibiting PCO. At the 175 unit dose, there was a trend toward increased postoperative inflammation that was transient with no residua. From 6 to 24 months postoperatively, the 50 unit dose significantly inhibited PCO compared with the placebo (P <.05). This significant reduction in PCO translated into a significantly lower projected need for Nd:YAG capsulotomy in the 50 unit than the placebo group (P <.004). About 60% in the placebo group and 4% in the 50 unit group were projected to need an Nd:YAG capsulotomy by 3 years postoperatively. Conclusion: The immunotoxin was well tolerated and was effective in reducing PCO for up to 24 months after cataract surgery. Although these preliminary results are encouraging, a larger study is underway to determine whether the reduction in PCO by the immunotoxin decreases the need for Nd:YAG capsulotomy.