(264c) Targeted, Systemic Dendrimer-Drug Therapies for Age Related Macular Degeneration

Introduction: Age related macular degeneration (AMD) is a complex, multifactorial progressive disease often implicated with key pathological events such as oxidative stress, inflammation and neovascularization (CNV) in retina and choroid. Current treatments involve frequent, localized intravitreal injections of anti-VEGF agents for CNV suppression that doesn’t work in 1/3 of the patients and there is no viable therapy for early AMD. These treatments only focus on addressing neovascularization and often associated with side-effects such as choriocapillaries atrophy, RPE loss and intraocular toxicity. Hence, targeting and delivering drugs to the key cells involved in disease progression will highly beneficial for both early and late stages, improve compliance and reduce costs. Increasing evidence suggests inflammation (activated microglia/macrophages (mi/ma)) may play a critical role in the development and the progression of AMD. We showed that hydroxyl terminated PAMAM dendrimer can target and localize in activated retinal microglia/macrophages (mi/ma) and RPE upon intravenous injections (IV) [1]. In this study, we utilize the intrinsic targeting ability of dendrimers to deliver drugs to the key cells and evaluate is efficacy for early and late AMD in subretinal lipid injected rat AMD model

Methods: Dendrimer-Triamcinolone acetonide (D-TA) and Dendrimer-N-Acetyl cysteine (D-NAC) were designed and synthesized to release drugs intracellularly. Cy5-labelled D-TA and D-NAC were used to evaluate the biodistribution and cellular localization using fluorescence spectroscopy and confocal microscopy. For early AMD, D-NAC monotherapy was administered intravenously on day 3, 5 and 7 post subretinal lipid and evaluated on day 10. For late AMD, a combination of D-NAC + D-TA were administered intravenously on day 11, 13 and 15 and evaluated on day 20. CNV suppression and regression were evaluated by accessing the CNV area and volumes using flat-mount imaging. Attenuation of inflammation were evaluated using macrophage counts and RT-qPCR was employed to evaluate inflammatory cytokines and oxidative stress markers.

Results: Subretinal lipid injection produced blebs that stimulated migration of mi/ma and formation of CNV. Both D-TA and D-NAC were stable in plasma and released drugs under intracellular conditions in a sustained manner. Intravenously administered D-NAC and D-TA were found localized in activated mi/ma and hypertrophic RPE in retina and choroid and were retained for more than 30 days but cleared intact from systemic circulation intact within 24 hrs [2]. D-NAC monotherapy suppressed CNV growth (~78%), reduction in mi/ma accumulation (~63%) and attenuated inflammation by suppressing cytokine production. D-NAC+D-TA combination therapy treatment promotes CNV regression (~72%), reduced CNV volume, enhanced adhesion molecules expression and reduced leakage in late stages of AMD than compared to controls. Dendrimer-drug therapy did not lead to ocular or systemic toxicity.

Conclusions: Targeting and selectively co-localization of dendrimers, in activated mi/ma and RPE, makes them excellent carriers for systemic drug delivery to specific affected cells in the choroid/retina. The efficacy of D-NAC and D-TA in CNV suppression/regression, attenuation of retinal/choroidal inflammation may offer an effective treatment option for early and late stages of AMD and other ocular diseases such as diabetic retinopathy (DR), glaucoma, retinitis pigmentosa (RP) and etc. where inflammation is involved.

Acknowledgements: This study was supported by the funds from NIH-NEIRO1EY025304 (RMK) and Altsheler Durell foundation.

References:

1. Kambhampati, SP., Clunies-Ross, A.J., Bhutto, I., Mishra, MK., Edwards, M., McLeod, D.S., Kannan, RM., Lutty, GA. Systemic and Intravitreal Delivery of Dendrimers to Activated Microglia/Macrophage in Ischemia/Reperfusion Mouse. IOVS. 2015, 56(8), 4413-4424.
2. Kannan, RM., Lutty, G., Kambhampati, SP., Mishra, Mk., Bhutto. I.A. "Dendrimer compositions and their use in treatment of diseases of the eye." U.S. Patent Application 15/307,284, filed February 16, 2017.