A Novel Selective Soluble Guanylate Cyclase Activator, MGV354, Lowers Intraocular Pressure in Preclinical Models, Following Topical Ocular Dosing.

Purpose: The nitric oxide/soluble guanylate cyclase/protein kinase G (NO/sGC/PKG) is known to be involved in the regulation of intraocular pressure (IOP) and may be dysregulated in glaucoma. The purpose is to demonstrate that the sGC activator MGV354 lowers IOP in a monkey model of glaucoma and could be considered as a possible new clinical drug candidate. Methods: Changes to cGMP were assessed in primary human trabecular meshwork (hNTM) cells and binding studies were conducted using human sGC full-length protein. Ocular safety tolerability, exposure, and efficacy studies were conducted in rabbit and monkey models following topical ocular dosing of MGV354. Results: sGC was highly expressed in the human and cynomolgus monkey outflow pathways. MGV354 had a 7-fold greater Bmax to oxidized sGC compared to that of reduced sGC and generated an 8- to 10-fold greater cGMP compared to that of a reduced condition in hTM cells. A single topical ocular dose with MGV354 caused a significant dose-dependent reduction of 20% to 40% (versus vehicle), lasting up to 6 hours in pigmented rabbits and 24 hours postdose in a cynomolgus monkey model of glaucoma. The MGV354-induced IOP lowering was sustained up to 7 days following once-daily dosing in a monkey model of glaucoma and was greater in magnitude compared to Travatan (travoprost)-induced IOP reduction. Mild to moderate ocular hyperemia was the main adverse effect noted. Conclusions: MGV354 represents a novel class of sGC activators that can lower IOP in preclinical models of glaucoma. The potential for sGC activators to be used as effective IOP-lowering drugs in glaucoma patients could be further determined in clinical studies.

Inflammation and immunogenicity limit the utility of the rabbit as a nonclinical species for ocular biologic therapeutics.

The nonclinical safety evaluation of therapeutic drug candidates is commonly conducted in two species (rodent and non-rodent) in keeping with international health authority guidance. Biologic drugs typically have restricted species cross-reactivity, necessitating the evaluation of safety in non-human primates and thus limiting the utility of lower order species. Safety studies of cross-reactive ocular biologic drug candidates have been conducted in rabbits as a second toxicology species, despite the fact that rabbits are not a rodent species. Such studies are often confounded by the development of anti-drug antibodies and severe ocular inflammation, the latter requiring studies to be terminated prematurely for animal welfare reasons. Notably, these confounding factors preclude the interpretation of safety. Nonclinical toxicology programs should be designed with consideration of ethical animal use and 3Rs principles (Replacement, Reduction and Refinement). The experience of several pharmaceutical sponsors, demonstrating that toxicology studies of ocular (intravitreal and topical ocular) biologic drug candidates in the rabbit are of limited interpretive value, calls into question the utility of such studies in this species and indicates that such studies should not be conducted.

Peroxidase and catalase activities are involved in direct adventitious shoot formation induced by thidiazuron in eastern white pine (Pinus strobus L.) zygotic embryos.

We reported establishment of an efficient plant regeneration procedure through direct adventitious shoot (DAS) formation from cotyledons and hypocotyls of eastern white pine (Pinus strobus L.) mature embryos in this investigation. Multiple DASs were initiated from cotyledons of embryos on PS medium containing N6-benzyladenine (BA), thidiazuron (TDZ), or kinetin (KIN). Among different concentrations of casein enzymatic hydrosylate (CH) and glutamine used in this study, 500 mg l(-1) CH or 600 mg l(-1) glutamine induced the highest frequency of DAS formation. Rooting of regenerated shoots was obtained on PS medium supplemented with 0.01-0.1 microM indole-3-acetic acid (IAA) with the highest frequency on medium containing 0.01 muM IAA. No DASs were obtained on medium without TDZ. Measurement of peroxidase (POD) and catalase (CAT) activity during direct shoot induction and differentiation demonstrated that the lowest POD activity appeared in the 5-6th week of culture and lowest CAT activity occurred in the 7-8th week of culture on medium with TDZ. No such a change in POD and CAT activities was observed on medium without TDZ. These results demonstrated that POD and CAT activities were involved in DAS formation induced by TDZ in eastern white pine.

Administration of a PPARalpha agonist increases serum apolipoprotein A-V levels and the apolipoprotein A-V/apolipoprotein C-III ratio.

Apolipoprotein A-V (apoA-V) first gained attention as a regulator of triglycerides through transgenic mouse studies. Furthermore, peroxisome proliferator-activated receptor alpha (PPARalpha) agonists such as fenofibrate increase apoA-V mRNA expression. Our group recently developed the first assay to quantitate serum apoA-V levels. Therefore, we sought to determine whether administration of a PPARalpha agonist would increase circulating apoA-V. Cynomolgus monkeys were dosed for 14 days with 0.3 mg/kg/day LY570977 L-lysine, a potent and selective PPARalpha agonist. Blood samples were drawn throughout the treatment period and after a 2 week washout. Administration of the PPARalpha agonist caused a 50% decrease in triglycerides that reversed at washout. Serum apoA-V concentrations increased 2-fold, correlated inversely with triglycerides, and were reversible at washout. The apoA-V/apoC-III ratio increased >2-fold, with this increase also reversible at washout. These data demonstrate for the first time that a PPARalpha agonist increases circulating apoA-V protein levels and the apoA-V/apoC-III ratio.