Purpose: The purpose of this study was to assess whether alemtuzamab, a large antibody of 150 kDa, would be able to penetrate through the full-thickness retina of Dutch-belted rabbits. Methods: Four Dutch-belted rabbits had intravitreal injections of alemtuzumab (1.5 mg in 0.05 mL). One rabbit each was killed at Day 1, Day 8, Day 15, and Day 29. The eyes were examined under frozen section and graded by immunostaining techniques for the degree of penetration of alemtuzumab into the retina. The degree of retinal staining was graded from 0 (no stain) to 4+ (marked stain). Results: All study eyes showed antibody staining of the full-thickness retina as follows: 4+ at Day 1, 4+ at Day 8, 3+ at Day 15, and 2+ at Day 29. Conclusion: A 1.5-mg intravitreal dose of alemtuzumab was able to penetrate full-thickness retina throughout the full 29-day course of the study. Retinal toxicity studies are required before clinical use.