Species selection for nonclinical safety assessment of drug candidates: Examples of current industry practice.

In drug development, nonclinical safety assessment is pivotal for human risk assessment and support of clinical development. Selecting the relevant/appropriate animal species for toxicity testing increases the likelihood of detecting potential effects in humans, and although recent regulatory guidelines state the need to justify or dis-qualify animal species for toxicity testing, individual companies have developed decision-processes most appropriate for their molecules, experience and 3Rs policies. These generally revolve around similarity of metabolic profiles between toxicology species/humans and relevant pharmacological activity in at least one species for New Chemical Entities (NCEs), whilst for large molecules (biologics) the key aspect is similarity/presence of the intended human target epitope. To explore current industry practice, a questionnaire was developed to capture relevant information around process, documentation and tools/factors used for species selection. Collated results from 14 companies (Contract Research Organisations and pharmaceutical companies) are presented, along with some case-examples or over-riding principles from individual companies. As the process and justification of species selection is expected to be a topic for continued emphasis, this information could be adapted towards a harmonized approach or best practice for industry consideration.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Minipig.

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions) Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the minipig used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Toxicologic Pathology Forum: Opinion on Obligatory Microscopic Examination of Intermediate-Dose Groups in Toxicity Studies With Biotherapeutics in Cynomolgus Monkeys.

In nonrodent toxicity studies that are usually conducted in cynomolgus monkeys or beagle dogs, the added value of examining all tissues from all dose groups (current practice) versus all tissues in only control and high-dose groups and target tissues in intermediate-dose groups by default, is a subject of debate. A previous retrospective review of 325 nonrodent toxicity studies that included a limited number of biotherapeutics suggested that the evaluation of all tissues from all groups was not justified as a routine practice and recommended the examination of all tissues in control and high-dose groups and only target tissues in intermediate-dose groups. In contrast, the present retrospective review which examined 213 nonrodent studies (212 in cynomolgus monkeys and 1 in dog) from 4 multinational pharmaceutical companies (Bristol-Myers Squibb, Novartis, Pfizer Inc, and Roche) conducted only with biotherapeutics showed that restricting the microscopic examination in intermediate-dose groups to target tissues has the potential to miss findings in 6.6% of studies, possibly impacting the overall study interpretation and conclusion. In conclusion and in the opinion of the authors, all tissues from all dose groups should be examined in toxicity studies with biotherapeutics conducted in nonrodent species.

Angiomatous hyperplasia in the heart of a young rat.

This case report describes angiomatous hyperplasia in the heart which is an unusual location in a young male Sprague-Dawley rat in a short-term toxicity study. Histologically, the lesion was characterized by blood-filled vascular channels of variable diameter lined by a thin wall and surrounded by a thin fibrous stroma and minimal lympho-plasmacytic and neutrophilic infiltrate in the apex of the heart. Immunohistopathology using CD31 confirmed the blood vessel origin, and using Ki67 confirmed low cell-proliferative activity in the vascular endothelial cells. To the authors' knowledge, this is the first report of spontaneous angiomatous hyperplasia in the heart of a young rat.

Spontaneous and Drug-induced Arteritis/Polyarteritis in the Göttingen Minipig-Review.

Arteritis/polyarteritis occurs spontaneously in many species used in preclinical toxicology studies. In Göttingen minipigs, arteritis/polyarteritis is an occasionally observed background change. In the minipig, this finding differs in frequency and nature from age-related polyarteritis nodosa in rats or monkeys, and Beagle pain syndrome in dogs. In minipigs, it can be present in a single small- or medium-sized artery of an organ or a few organs and is most commonly recorded in the cardiac and extracardiac blood vessels, vagina, oviduct, rectum, epididymis, spinal cord, pancreas, urinary bladder, kidneys, and stomach. The etiology is unknown although it has been considered in minipigs as well as in rats, dogs, and monkeys to be possibly immune mediated. This background change is important with respect to its nature and distribution in the minipig in order to distinguish it from drug-induced vascular changes, which might occur in similar locations and have similar morphologic features. This review summarizes the morphology, incidence, and predilection sites of arteritis as a spontaneously occurring background change and as a drug-induced vasculopathy in the minipig, and also describes the main aspects to consider when evaluating vascular changes in Göttingen minipig toxicity studies and their human relevance.

Pathophysiological Consequences of a Break in S1P1-Dependent Homeostasis of Vascular Permeability Revealed by S1P1 Competitive Antagonism.

RATIONAL: Homeostasis of vascular barriers depends upon sphingosine 1-phosphate (S1P) signaling via the S1P1 receptor. Accordingly, S1P1 competitive antagonism is known to reduce vascular barrier integrity with still unclear pathophysiological consequences. This was explored in the present study using NIBR-0213, a potent and selective S1P1 competitive antagonist. RESULTS: NIBR-0213 was tolerated at the efficacious oral dose of 30 mg/kg BID in the rat adjuvant-induced arthritis (AiA) model, with no sign of labored breathing. However, it induced dose-dependent acute vascular pulmonary leakage and pleural effusion that fully resolved within 3-4 days, as evidenced by MRI monitoring. At the supra-maximal oral dose of 300 mg/kg QD, NIBR-0213 impaired lung function (with increased breathing rate and reduced tidal volume) within the first 24 hrs. Two weeks of NIBR-0213 oral dosing at 30, 100 and 300 mg/kg QD induced moderate pulmonary changes, characterized by alveolar wall thickening, macrophage accumulation, fibrosis, micro-hemorrhage, edema and necrosis. In addition to this picture of chronic inflammation, perivascular edema and myofiber degeneration observed in the heart were also indicative of vascular leakage and its consequences. CONCLUSIONS: Overall, these observations suggest that, in the rat, the lung is the main target organ for the S1P1 competitive antagonism-induced acute vascular leakage, which appears first as transient and asymptomatic but could lead, upon chronic dosing, to lung remodeling with functional impairments. Hence, this not only raises the question of organ specificity in the homeostasis of vascular barriers, but also provides insight into the pre-clinical evaluation of a potential safety window for S1P1 competitive antagonists as drug candidates.

The Potential of Minipigs in the Development of Anticancer Therapeutics: Species Comparison and Examples of Special Applications.

Minipigs are increasingly being used as an alternative to dog or monkey in nonclinical safety testing of pharmaceuticals since they share similar anatomical and physiological characteristics to humans. Integrative assessment of pharmacodynamic and pharmacokinetic data sets of drug candidates fromin silico,in vitro, andin vivoinvestigations form the basis for selecting the most relevant nonrodent species for toxicology studies. Developing anticancer therapeutics represents a special challenge for species selection due to their effects on multiple organ systems. The toxicological profile of anticancer drugs can be associated with steep dose-response curves, especially due to dose-limiting toxicity on the alimentary, hematopoietic, and immune systems. Selection of an appropriate species for toxicology studies is of importance to avoid an inappropriately low (without benefit for the late-stage cancer patient) or high clinical starting dose (with a risk of unexpected adverse reactions). Although the minipig has been the preferred species to develop drugs applied topically, it is only rarely used in anticancer drug development compared to dog and monkey. In this context, we discuss the potential of minipigs in anticancer drug development with examples of programs for oral and dermal administration, intravascular application in drug-eluting stents, and local chemotherapy (chemoembolization).

Preclinical safety assessment of a DNA vaccine using particle-mediated epidermal delivery in domestic pig, minipig and mouse.

DNA vaccination involves the direct injection of genes coding for specific antigenic proteins. One technique known as particle-mediated epidermal delivery (PMED) is a practical approach for epidermal delivery and provides a strong immune response. An important aspect of the preclinical safety assessment of DNA vaccines is the selection of a pharmacologically relevant animal model for the assessment of antigen expression, optimization of delivery and formulation of the plasmid. This paper describes a comparative study of domestic pig, minipig and mouse in regard to local tolerance and antigen expression of HIV immunotherapeutic using PMED. Pig/minipig is considered a good model for the safety assessment of DNA vaccines due to the similarity to human skin. Local reactions were evaluated at 10 min, 4, 24 and 48 h. Histology of administration sites revealed epidermal necrosis with associated dermal inflammation at 10 min and 4h, and subsequent regeneration with repair at 24 and 48 h. The degree and extent of these changes varied according to species. Domestic pig and minipig showed superficial epidermal necrosis and complete repair, while the mouse showed full-thickness epidermal necrosis and partial repair. Expression of HIV antigen was confirmed using immunohistochemistry in all three species at 4, 24 and 48 h. The results showed that PMED is an effective system for DNA vaccine delivery as demonstrated by the antigen expression seen as early as 4 h.