Evaluation of photopoint photosensitizer MV6401, indium chloride methyl pyropheophorbide, as a photodynamic therapy agent in primate choriocapillaris and laser-induced choroidal neovascularization

Purpose: To assess the potential of a new photosensitizer, indium chloride methyl pyropheophorbide (PhotoPoint MV6401), for ocular photodynamic therapy (PDT) in normal choriocapillaris vessels and experimentally induced choroidal neovascularization in New-World monkeys (Saimiri sciureus). Methods: PhotoPoint MV6401 (Miravant Pharmaceuticals, Inc., Santa Barbara, CA) was activated at 664 nm using a DD3-0665 (Miravant Systems, Inc., Santa Barbara, CA) 0.5 W diode laser. The efficacy of MV6401 was evaluated by indirect ophthalmoscopy, fundus photography, fluorescein angiography, and histology. The drug and light doses were 0.10 mumoles/kg to 0.3 mumoles/kg and 10 J/cm(2) to 40 J/cm(2), respectively, and post-injection activation times ranged from +10 minutes to +120 minutes. Results: Best closure of normal choriocapillaris was achieved at a dosage level of 0.15 mumoles/kg in primates. Histology demonstrated that increased post-injection activation times (+60 minutes to +90 minutes) and low laser light doses (10 J/cm(2) to 20 J/cm(2)) in the primate model resulted in selective closure of the choriocapillaris and medium sized choroidal vessels with minimal effect to the retina. Histology from neovascular lesions PDT-treated with MV6401 revealed significant diminution of vascularity, correlating with diminution of leakage observed on angiography. Conclusion: PhotoPoint MV6401, indium chloride methyl pyropheophorbide, is a potent photosensitizer that demonstrates both efficacy and selectivity in primate choriocapillaris and laser-induced choroidal neovascularization occlusion. Maximum selectivity was achieved using a post infusion interval of +60 to +90 minutes.