RTP801 gene expression is differentially upregulated in retinopathy and is silenced by PF-04523655, a 19-Mer siRNA directed against RTP801

Invest Ophthalmol Vis Sci. 2014 Mar 4;55(3):1232-40. doi: 10.1167/iovs.13-13449.

Abstract

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

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: gene expression, PK/PD, hypoxia, retinal pigment epithelium, retinal ischemia.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Diabetic Retinopathy / drug therapy
  • Diabetic Retinopathy / genetics*
  • Diabetic Retinopathy / metabolism
  • Disease Models, Animal
  • Polymerase Chain Reaction
  • RNA, Messenger / genetics*
  • RNA, Small Interfering / pharmacokinetics
  • RNA, Small Interfering / pharmacology*
  • Rats
  • Rats, Long-Evans
  • Repressor Proteins / biosynthesis
  • Repressor Proteins / drug effects
  • Repressor Proteins / genetics*
  • Retinal Pigment Epithelium / drug effects
  • Retinal Pigment Epithelium / metabolism
  • Retinal Pigment Epithelium / pathology
  • Up-Regulation / drug effects*

Substances

  • Ddit4 protein, rat
  • PF-04523655
  • RNA, Messenger
  • RNA, Small Interfering
  • Repressor Proteins