Discovery of liver-targeted inhibitors of stearoyl-CoA desaturase (SCD1).

Inhibitors based on a benzo-fused spirocyclic oxazepine scaffold were discovered for stearoyl-coenzyme A (CoA) desaturase 1 (SCD1) and subsequently optimized to potent compounds with favorable pharmacokinetic profiles and in vivo efficacy in reducing the desaturation index in a mouse model. Initial optimization revealed potency preferences for the oxazepine core and benzylic positions, while substituents on the piperidine portions were more tolerant and allowed for tuning of potency and PK properties. After preparation and testing of a range of functional groups on the piperidine nitrogen, three classes of analogs were identified with single digit nanomolar potency: glycine amides, heterocycle-linked amides, and thiazoles. Responding to concerns about target localization and potential mechanism-based side effects, an initial effort was also made to improve liver concentration in an available rat PK model. An advanced compound 17m with a 5-carboxy-2-thiazole substructure appended to the spirocyclic piperidine scaffold was developed which satisfied the in vitro and in vivo requirements for more detailed studies.

Danicopan, an Oral Complement Factor D Inhibitor, Exhibits High and Sustained Exposure in Ocular Tissues in Preclinical Studies.

Purpose: Complement alternative pathway (AP) dysregulation has been implicated in geographic atrophy, an advanced form of age-related macular degeneration. Danicopan is an investigational, first-in-class inhibitor of factor D, an essential AP activation enzyme. We assessed danicopan distribution to the posterior segment of the eye after oral dosing. Methods: Tissue distribution of drug-derived radioactivity was evaluated using whole-body autoradiography following oral administration of [14C]-danicopan to pigmented and albino rats. Pharmacokinetics and ocular tissue distribution were studied in pigmented and albino rabbits following single and multiple oral dosing of danicopan. The melanin binding property was characterized in vitro. Results: Radioactivity was distributed widely in rats and became nonquantifiable in most tissues 24 hours postdose except in the pigmented rat uvea (quantifiable 672 hours postdose). Danicopan binding to melanin was established in vitro. After single dosing, the maximum concentration (Cmax) and area under the curve (AUC) in neural retina and plasma were similar in both rabbit types. After multiple dosing, AUC in neural retina was 3.4-fold higher versus plasma in pigmented rabbits. Drug levels in choroid/Bruch's membrane (BrM)/retinal pigment epithelium (RPE) were similar to plasma in albino rabbits but higher in pigmented rabbits: Cmax and AUC were 2.9- and 23.8-fold higher versus plasma after single dosing and 5.8- and 62.7-fold higher after multiple dosing. In pigmented rabbits, ocular tissue exposures slowly declined over time but remained quantifiable 240 hours postdose. Conclusions: The results demonstrate that danicopan crosses the blood-retina barrier and binds melanin reversibly, leading to a higher and more sustained exposure in melanin-containing ocular tissues (choroid/BrM/RPE) and in the neural retina as compared to in plasma after repeated oral dosing in pigmented animals. Translational Relevance: These findings suggest that oral danicopan possesses potential for treating geographic atrophy because AP dysregulation in the posterior segment of the eye is reported to be involved in the disease pathogenesis.

Phospholipidosis in neurons caused by posaconazole, without evidence for functional neurologic effects.

The azole antifungal drug posaconazole caused phospholipidosis in neurons of the central nervous system, dorsal root ganglia of the spinal cord, and myenteric plexus in chronic toxicity studies in dogs. The time of onset, light and electron microscopic features, neurologic and electrophysiologic effects on the central and peripheral nervous systems, and potential for regression were investigated in a series of studies with a duration of up to one year. Nuclei of the medulla oblongata were the prominently affected areas of the brain. Neurons contained cytoplasmic vacuoles with concentrically whorled plasma membrane-like material (i.e., multilamellar bodies) morphologically identical to that commonly caused in other tissues by cationic amphiphilic drugs. Some axons in the brain and spinal cord were swollen and contained granular eosinophilic, electron-dense lysosomes. There were no features suggesting degeneration or necrosis of neurons or any associated elements of nervous tissue. The earliest and most consistent onset was in neurons of dorsal root ganglia. The observed neural phospholipidosis did not result in any alteration in the amplitude or latency of the auditory, visual, or somatosensory evoked potentials. The histopathologic changes did not progress or regress within the three-month postdose period. The results indicate that phospholipidosis can be induced in central and peripheral neurons of dogs by administration of posaconazole, but this change is not associated with functional effects in the systems evaluated.

Progressing preclinical drug candidates: strategies on preclinical safety studies and the quest for adequate exposure.

Drug discovery lead optimization teams face many diverse challenges in the search for drug development candidates. This includes understanding the toxicology profile of a candidate, and some strategies call for in vivo preclinical safety studies to be moved increasingly earlier in the discovery phase to increase the likelihood of success in development. One of the final hurdles in these pursuits is achieving adequate exposure to support safety margins for human clinical trials. In this article, we describe several strategies on early toxicology studies along with various enabling formulation methods that can be employed to achieve optimal oral absorption. These two elements of research together can significantly increase the speed preclinical drug candidates can move through development, and the overall probability of success in identifying viable new drugs.

Exploratory drug safety: a discovery strategy to reduce attrition in development.

Identification of novel new molecules which hold the greatest promise of safe and effective therapies remains a continuous challenge to the pharmaceutical industry. This has led the industry to implement strategies for identification of the most promising candidates during the discovery phase and for their safe and expeditious advancement through development. Testing for potential liable properties in the discovery phase has included the evaluation of major areas of pharmaceutics that have led to failure such as its physical and pharmaceutical properties, drug metabolism and pharmacokinetic characteristics, various safety endpoints including pre-development safety pharmacology, general toxicology and genetic toxicology and interrogation of counter-screen data to identify off-target affinities (i.e., receptors, ion channels, transporters, kinases, etc.) that pose a concern. Amongst the many important areas of concern is the potential for toxicities of the major organ systems. To mitigate this concern, a strategy pursued is to identify the prominent toxicological properties of the candidate prior to its recommendation for development. The results of these studies in discovery allow exclusion of the candidate before the expenditure of resources and time typical of development. In addition, the discovery phase toxicology studies serve to address key questions that may have arisen from the study of another molecule, the phenotypic profile from pre-clinical models where the therapeutic target has been genetically modified or concerns that have been raised as a result of other investigations. Importantly, the results of the exploratory drug safety studies will be used by the sponsor to judge the potential risks associated with continued pursuit of a potential development candidate. In many ways, pre-clinical toxicological investigations in discovery serve the important objective of identifying the most promising candidates to progress into development and onto registration.

SCH 412499: biodistribution and safety of an adenovirus containing P21(WAF-1/CIP-1) following subconjunctival injection in Cynomolgus monkeys.

Monkey studies were conducted for the preclinical safety assessment of SCH 412499, an adenovirus encoding p21, administered by subconjunctival injection prior to trabeculectomy for postoperative maintenance of the surgical opening. Biodistribution of SCH 412499 was minimal and there was no systemic toxicity. Findings included swollen, partially closed or shut eye(s) and transient congestion in the conjunctiva. A mononuclear cell infiltrate was present in the conjunctiva, choroid and other ocular tissues, but completely or partially resolved over time. Electroretinograms and visual evoked potentials revealed no adverse findings. Thus, the findings are not expected to preclude the clinical investigation of SCH 412499.

Incidental mononuclear cell infiltrate in the uvea of cynomolgus monkeys.

Mononuclear cell infiltrate (MCI) in the uvea was observed in naïve, untreated (control group) cynomolgus monkeys in approximately 25% of drug safety evaluation studies. The total incidence of MCI in the choroid and the ciliary body was 29% of 342 males and 25% of 306 female monkeys. In the studies in which MCI was present in the ciliary body or choroid, the incidence was as high as 75%. There were no other ocular histopathologic findings in these monkeys. All monkeys were clinically healthy and the eyes were not remarkable when examined ophthalmoscopically.