Implications of retinal effects observed in chronic toxicity studies on the clinical development of a CNS-active drug candidate

Discovery of Novel Pyrimidine-Based Derivatives as Nav1.2 Inhibitors with Efficacy in Mouse Models of Epilepsy

Dysfunction of voltage-gated sodium channel Nav1.2 causes various epileptic disorders, and inhibition of the channel has emerged as an attractive therapeutic strategy. However, currently available Nav1.2 inhibitors exhibit low potency and limited structural diversity. In this study, a novel series of pyrimidine-based derivatives with Nav1.2 inhibitory activity were designed, synthesized, and evaluated. Compounds 14 and 35 exhibited potent activity against Nav1.2, boasting IC50 values of 120 and 65 nM, respectively. Compound 14 displayed favorable pharmacokinetics (F = 43%) following intraperitoneal injection and excellent brain penetration potency (B/P = 3.6). Compounds 14 and 35 exhibited robust antiepileptic activities in the maximal electroshock test, with ED50 values of 3.2 and 11.1 mg/kg, respectively. Compound 35 also demonstrated potent antiepileptic activity in a 6 Hz (32 mA) model, with an ED50 value of 18.5 mg/kg. Overall, compounds 14 and 35 are promising leads for the development of new small-molecule therapeutics for epilepsy.

Electrochemical oxidative cyclization of N-allylamides for the synthesis of CF3-containing benzoxazines and oxazolines

The introduction of trifluoromethyl (-CF3) groups into compounds is a common synthetic strategy in organic chemistry. Commonly used methods for introducing trifluoromethyl groups are limited by harsh reaction conditions, low regioselectivity, or the need for excess reagents. In this study, a facile electrochemical oxidative and radical cascade cyclization of N-(2-vinylphenyl)amides for the synthesis of CF3-containing benzoxazines and oxazolines was obtained. This sustainable protocol features inexpensive and durable electrodes, a wide range of substrates, diverse functional group compatibility under transition-metal-free, external-oxidant-free, and additive-free conditions, and can be applied in an open environment.

Ocular bioanalysis: challenges and advancements in recent years for these rare matrices

There are many ocular diseases still presenting unmet medical needs. Therefore, new ophthalmologic drugs are being developed. Bioanalysis of eye compartments (along with plasma and other tissues) is important to determine exposure of the target organ to the drug and to help interpret local pharmacological or toxic effects. This review article identifies several challenges that occur within ocular bioanalysis. They include sample collection and preparation, analytical issues, sourcing control matrix, data interpretation and regulatory requirements. It summarizes how these challenges have been recently addressed, how research has advanced and which questions remain unanswered. Recommendations are made based on the literature and our practical experience within ocular bioanalysis and future perspectives are discussed.

Spontaneously occurring fundus findings observed using confocal scanning laser ophthalmoscopy in wild type Sprague Dawley rats

PURPOSE

Non-invasive in vivo imaging is an increasingly used component of pre-clinical research. However, to reliably interpret data, it may be necessary to identify and document pre-existent findings prior to initiating long-term or intensive protocols, particularly where toxicity or efficacy is under investigation. Here we report here spontaneously occurring findings from the Sprague Dawley (SD) rat eye using multi-modal confocal scanning laser ophthalmoscopy (cSLO).

METHODS

As part of ongoing studies, with the goal of excluding animals with abnormalities from further investigation, a total of 165 wild type SD rats (312 eyes) were assessed using cSLO imaging at baseline prior to initiating experiments to detect, describe, and determine the prevalence of spontaneous fundus findings.

RESULTS

Using fundus autofluorescence (FAF) as the primary screening modality, over 30% of analyzed eyes possessed some fundus finding that differed from the normal composite reference image. Unexpectedly, 100% of eyes demonstrated a diffuse hyperfluorescent region in the posterior pole that was ultimately considered normal, and formed part of the reference. Evaluated by three independent reviewers, five groups of FAF abnormalities were defined, based primarily on shape and size of the lesion. Of these, the most extensive lesions were further analyzed using infrared reflectance (IR) and red free (RF) imaging. White light and autofluorescent microscopy of excised tissue confirmed that the extensive lesions were derived from abnormalities in both the isolated retina and posterior eyecups.

CONCLUSIONS

Given the newly described hyperfluorescent glow that appears in all eyes, and the high basal rate of spontaneous lesions in the outbred SD rat, we suggest that investigators be aware of the variants of normal, and that baseline in vivo screening be considered prior to initiating intensive or expensive investigation.

The effects of taurine on vigabatrin, high light intensity and mydriasis induced retinal toxicity in the pigmented rat

The overall purpose of this study was to establish a model that may be used for examining the effect of Vigabatrin-induced retinal toxicity in pigmented rats, and subsequently examine the possible effects of taurine on the retinal toxicity. In the first part of the study, pigmented Long Evans rats were subjected to combinations of induced mydriasis, low/high light intensities (40/2000 lx) and oral administration of near-MTD (Maximum Tolerated Dose) doses (200 mg/kg/day) of Vigabatrin for up to 6 weeks. The combination of mydriasis and high light intensity applied to Long Evans rats resulted in retinal damage that was increased by the administration of Vigabatrin. In the second part of the study Long Evans rats were subjected to combinations of induced mydriasis and high/low light intensity (40/2000 lx) while being orally administered low (30 mg/kg/day) or high (200 mg/kg/day) doses of Vigabatrin for up to 6 weeks. In addition, selected groups of animals were administered taurine via the drinking water (20 mg/ml), resulting in systemic taurine concentrations of approximately threefold the endogenous concentration. The combined results of the studies demonstrate that retinal damage can be induced in pigmented animals when combining mydriasis and high light intensity. Retinal damage was functionally evaluated by electroretinography (ERG), then confirmed by histopathology. While depending on mydriasis and high light intensity, administration of Vigabatrin increased the retinal toxicity and resulted in the formation of rosette-like structures in the retina in a dose-related manner. Administration of taurine did not alleviate the Vigabatrin-induced retinal toxicity, as demonstrated either functionally by ERG or morphologically, although systemic concentrations of 3-fold the endogenous levels were reached, and it was thus not possible to demonstrate a protective effect of taurine in these pigmented animals.