Rapid Development of Glaucoma Via ITV Nonselective ANGPT 1/2 Antibody: A Potential Role for ANGPT/TIE2 Signaling in Primate Aqueous Humor Outflow.

Purpose: Investigate a significant, dose-related increase in IOP, leading to glaucomatous damage to the neuroretina and optic nerve following intravitreal (ITV) administration of a bispecific F(ab')2 [anti-VEGF/Angiopoietins [ANGPT]F(ab')2] molecule in adult monkeys. Methods: ITV ocular tolerability and investigation of anti-VEGF/ANGPT F(ab')2 (blocking both ANGPT1 and ANGPT2) was done in monkeys; mechanistic studies were done in neonatal mice. Results: Following the second ITV dose of anti-VEGF/ANGPT F(ab')2, all 1.5- and 4-mg/eye treated monkeys developed elevated IOP, which eventually was associated with optic disc cupping and thinning of the neuroretinal rim. Histopathologic examination showed nonreversible axonal degeneration in the optic nerves of animals administered 1.5 mg/eye and higher that was considered secondary to high IOP. Anti-ANGPT Fab also caused elevated IOP in monkeys, but anti-VEGF Fab did not contribute to the IOP increase. In addition, an anti-ANGPT2-selective antibody did not change IOP. In mice simultaneous blockade of ANGPT1 and ANGPT2 impaired the expansion and formation of Schlemm's canal (SC) vessels, similar to genetic ablation of Angpt1/Angpt2 and their receptor TIE2. As previously reported, blocking ANGPT2 alone did not affect SC formation in mice. Conclusions: Dual inhibition of ANGPT1/ANGPT2, but not ANGPT2 alone, leads to increased IOP and glaucomatous damage in monkeys. This confirms a role for TIE2/ANGPT signaling in the control of IOP in adults, a finding initially identified in transgenic mice. Dual pharmacologic inhibition of ANGPT1/ANGPT2 may affect aqueous drainage and homeostasis in adult monkeys and may be useful in developing novel models of glaucoma.

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.

Intravitreal administration of known phototoxicants in the rabbit fails to produce phototoxicity: implications for phototoxicity testing of intravitreally administered small molecule therapeutics.

CONTEXT: Intravitreal (ITV) dosing has become a clinically important route of administration for the treatment of uveitis, endophthalmitis, retinal vein occlusion, diabetic macular edema and age-related macular degeneration. Despite this, there are no validated non-clinical models of phototoxicity for ITV products. OBJECTIVE: The objective of this study was to develop an ITV rabbit model of phototoxicity for use in assessing the photosafety of small molecules therapeutics. MATERIALS AND METHODS: Dutch Belted rabbits were intravitreally injected bilaterally with four known phototoxicants: 8-methoxypsoralen, lomefloxacin, doxycycline and stannsoporfrin. Triescence(®), a non-phototoxic triamcinolone acetonide steroid formulation designed for ITV administration, was used as a negative control. One eye was then irradiated with solar-simulated ultraviolet radiation for 30 min, 1 h after dosing, while the other eye was occluded, serving as a non-irradiated control. RESULTS: Despite the direct administration of known phototoxicants into the vitreous, no evidence of ocular phototoxicity was observed in any dose group. Direct (non-phototoxic) retinal toxicity was observed in the doxycycline dose group only. CONCLUSION: These data suggest that the posterior segment of the rabbit eye is protected against phototoxicity by anatomical and/or physiological mechanisms, and is not a useful model for the assessment of phototoxicity of intravitreally administered molecules.

Vehicle selection for nonclinical oral safety studies.

INTRODUCTION: The development of poorly soluble or permeable new chemical entities within the pharmaceutical industry often requires the use of nonstandard enabling nonclinical oral formulations. Despite this, the toxicity profile of many commonly used nonclinical vehicles is poorly understood. This lack of data can lead to unexpected formulation-related effects being observed in critical oral safety studies. AREAS COVERED: This article summarizes the key considerations for formulation selection for oral nonclinical safety studies, and provides a strategy for appropriate development-phase formulation selection. The industry's use of oral nonclinical vehicles is reviewed, based on data from the FDA's Orange Book. Finally, a summary of the repeat dose oral toxicity of commonly used vehicles is presented. EXPERT OPINION: The rapid identification of a suitable nonclinical oral formulation is a critical step in small-molecule drug development. In order to maintain flexibility and address the needs of a diverse set of new chemical entities (NCEs) with widely varying physiochemical properties, a "tool belt" of multiple oral formulations is recommended. The appropriate formulation is identified based on the goals of the study, as well as exposure required, species, duration and therapeutic indication of the NCE.