PF-4523655

Network medicine is a molecular-bioinformatic approach analyzing gene-gene interactions that can perturb the human interactome. This review focuses on epigenetic changes involved in several ocular diseases, such as DNA methylation, histone and nonhistone post-translational modifications, and noncoding RNA regulators. Although changes in aberrant DNA methylation play a major role in the pathogenesis of most ocular diseases, histone modifications are seldom investigated. Hypermethylation in TGM-2 and hypomethylation in MMP-2/CD24 promoter genes may play a crucial role in pterygium development; hypermethylation in regulatory regions of GSTP1 and OGG1 genes appear to be diagnostic biomarkers of cataract; hypomethylation of TGF-β1 promoter may trigger glaucoma onset; hypermethylation of the LOXL1 gene might be associated with pseudoexfoliation syndrome. A large panel of upregulated micro-RNAs (miRNAs), including hsa-hsa-miR-494, hsa-let-7e, hsa-miR-513-1, hsa-miR-513-2, hsa-miR-518c, hsa-miR-129-1, hsa-miR-129-2, hsa-miR-198, hsa-miR-492, hsa-miR-498, hsa-miR-320, hsa-miR-503, and hsa-miR-373,∗ may have a putative role in the development of retinoblastoma. Hypermethylation of H3K4 and hypomethylation of H3K27 at the TGFBIp locus are putative pathogenic mechanisms involved in corneal dystrophies. Determining how, where, and when specific epigenetic changes trigger ocular diseases may provide useful clinical biomarkers for their prevention, diagnosis, and management, as well as innovative drug targets. PF-04523655, a 19-nucleotide methylated double-stranded siRNA targeting the RTP80 gene, showed a dose-related improvement in best-corrected visual acuity (BCVA) in patients affected by diabetic macular edema. The observed results support a clinical network-based research program aimed to clarify the role of epigenetic regulators in the development of ocular diseases and personalized therapy.

The intraocular pharmacodynamics of PF-04523655, a small-interfering RNA (siRNA) directed against RTP801, was characterized using rat models of retinopathy.

Rat models of streptozotocin-induced diabetes and wet AMD were used to determine the onset, extent, and duration of siRNA inhibition of retinal RTP801 expression by PF-04523655, and this inhibition was characterized by pharmacokinetic/pharmacodynamic (PK/PD) modeling. A rat model of wet AMD was also used to examine PF-04523655 dose-dependent effects on the incidence of clinical grade 3 or 4 choroidal neovascularization lesions. Whole homogenate versus laser-capture microdissected (LCM) retinal samples were analyzed by quantitative PCR for RTP801 expression.

RTP801 expression in RPE/choroid (RPE/C) increased in diabetic rats by up to 70% above nondiabetic rat levels. Inhibition of retinal RTP801 expression by PF-04523655 began 1 day after intravitreous injection and was observed through day 7 in the neurosensory retina and through day 14 or longer in RPE/C. PF-04523655 inhibition of RTP801 expression was maintained well after clearance of PF-04523655 from the eye and was best characterized by an effect compartment PK/PD model. Moreover, PF-04523655 administration decreased the incidence of clinical grade 3 or 4 lesions by approximately 60% (P = 0.053), and dose-dependently inhibited retinal RTP801 expression (P < 0.01). RTP801 expression was enriched in the outer nuclear layer in LCM samples.

In rodent retinopathy models, administration of the siRNA, PF-04523655, reduced RTP801 expression in the retina, consistent with the RNA-induced silencing complex (RISC) mechanism of action. The pharmacodynamic profile from the animal models could be useful to elucidate dose and exposure dependency of RTP801 expression inhibition by siRNA.