Scientific and Regulatory Policy Committee Points to Consider: Nonclinical Research and Development of In Vivo Gene Therapy Products, Emphasizing Adeno-Associated Virus Vectors.

Sequencing of the human genome and numerous advances in molecular techniques have launched the era of genetic medicine. Increasingly precise technologies for genetic modification, manufacturing, and administration of pharmaceutical-grade biologics have proved the viability of in vivo gene therapy (GTx) as a therapeutic modality as shown in several thousand clinical trials and recent approval of several GTx products for treating rare diseases and cancers. In recognition of the rapidly advancing knowledge in this field, the regulatory landscape has evolved considerably to maintain appropriate monitoring of safety concerns associated with this modality. Nonetheless, GTx safety assessment remains complex and is designed on a case-by-case basis that is determined by the disease indication and product attributes. This article describes our current understanding of fundamental biological principles and possible procedures (emphasizing those related to toxicology and toxicologic pathology) needed to support research and development of in vivo GTx products. This article is not intended to provide comprehensive guidance on all GTx modalities but instead provides an overview relevant to in vivo GTx generally by utilizing recombinant adeno-associated virus-based GTx-the most common in vivo GTx platform-to exemplify the main points to be considered in nonclinical research and development of GTx products.

Use of an animal model of disease for toxicology enables identification of a juvenile no observed adverse effect level for cyclocreatine in creatine transporter deficiency.

In standard general toxicology studies in two species to support clinical development, cyclocreatine, a creatine analog for the treatment of creatine transporter deficiency, caused deaths, convulsions, and/or multi-organ pathology. The potential translatability of these findings to patients was evaluated by comparing toxicity of cyclocreatine in wild-type mice to creatine transporter-deficient mice, a model of the human disease. A biodistribution study indicated greater accumulation of cyclocreatine in the brains of wild-type mice, consistent with its ability to be transported by the creatine transporter. Subsequent toxicology studies confirmed greater sensitivity of wild-type mice to cyclocreatine-induced toxicity. Exposure at the no observed adverse effect level in creatine transporter-deficient (554 µg*hr/ml) mice exceeded exposure at the maximum tolerated dose in wild-type (248 µg*hr/ml) mice. When dosed at 300 mg/kg/day for 3 months, cyclocreatine-related mortality, convulsions, and multi-organ pathology were observed in wild-type mice whereas there were no adverse findings in creatine transporter-deficient mice. Brain vacuolation was common to both strains. Although transporter-deficient mice appeared to be more sensitive, the finding had no functional correlates in this strain. The results highlight the importance of considering models of disease for toxicology in cases where they may be relevant to assessing safety in the intended patient population.

Report of the international conference on manufacturing and testing of pluripotent stem cells.

Sessions included an overview of past cell therapy (CT) conferences sponsored by the International Alliance for Biological Standardization (IABS). The sessions highlighted challenges in the field of human pluripotent stem cells (hPSCs) and also addressed specific points on manufacturing, bioanalytics and comparability, tumorigenicity testing, storage, and shipping. Panel discussions complemented the presentations. The conference concluded that a range of new standardization groups is emerging that could help the field, but ways must be found to ensure that these efforts are coordinated. In addition, there are opportunities for regulatory convergence starting with a gap analysis of existing guidelines to determine what might be missing and what issues might be creating divergence. More specific global regulatory guidance, preferably from WHO, would be welcome. IABS and the California Institute for Regenerative Medicine (CIRM) will explore with stakeholders the development of a practical and innovative road map to support early CT product (CTP) developers.

Applying a weight of evidence approach to the evaluation of developmental toxicity of biopharmaceuticals.

Toxicity studies in pregnant animals are not always necessary for assessing the human risk of developmental toxicity of biopharmaceuticals. The growing experience and information on target biology and molecule-specific pharmacokinetics present a powerful approach to accurately anticipate effects of target engagement by biopharmaceuticals using a weight of evidence approach. The weight of evidence assessment should include all available data including target biology, pharmacokinetics, class effects, genetically modified animals, human mutations, and a thorough literature review. When assimilated, this weight of evidence evaluation may be sufficient to inform risk for specific clinical indications and patient populations. While under current guidance this approach is only applicable for drugs and biologics for oncology, the authors would like to suggest that this approach may also be appropriate for other disease indications. When there is an unacceptable level of uncertainty and a toxicity study in pregnant animals could impact human risk assessment, then such studies should be considered. Determination of appropriate nonclinical species for developmental toxicity studies to inform human risk should consider species-specific limitations, reproductive physiology, and pharmacology of the biopharmaceutical. This paper will provide considerations and examples of the weight of evidence approach to evaluating the human risk of developmental toxicity of biopharmaceuticals.

Pre-clinical Specificity and Safety of UC-961, a First-In-Class Monoclonal Antibody Targeting ROR1.

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncoembryonic antigen. Because of its expression on the cell surface of leukemia cells from patients with chronic lymphocytic leukemia (CLL), but not on normal B-cells or other postpartum tissues, ROR1 is an attractive candidate for targeted therapies. UC-961 is a first-in-class humanized monoclonal antibody that binds the extracellular domain of ROR1. In this article we outline some of the preclinical studies leading to an investigational new drug designation, enabling clinical studies in patients with CLL.

The application of ICH S6 to the preclinical safety evaluation of plasma derivative therapeutic products.

The ICH S6 guidance was developed to describe a rational science-based flexible approach to the preclinical evaluation for biotechnology-derived pharmaceutical products. It also suggested that some of the principles described may be suitable for plasma-derived therapeutics. Some of the specific concerns unique to protein-based therapeutics include complexity in structure and potential immunogenicity. S6 has been interpreted by some industry and regulatory authorities, often due to lack of experience with these types of products, as encouraging a broader or more conventional toxicology program similar to that normally conducted for small molecules. The guidance does encourage important and necessary preclinical evaluations but also recognizes the limitations of studies in non-relevant animal species because they are without pharmacological interaction with the biologic. In addition, studies of human proteins are often limited in useful chronic, reproductive and carcinogenic toxicity evaluations by the immunological response in animals. Thus the safety evaluation of biopharmaceuticals and plasma derivatives in animals has limitations that cannot be adequately addressed by the use of testing paradigms used for small molecule pharmaceuticals. S6 focuses evaluations on well-designed studies in relevant species for reasonable time periods to make the best use of available resources and enable clinical trials.

Duration of chronic toxicity studies for biotechnology-derived pharmaceuticals: is 6 months still appropriate?

For chronic use biotechnology-derived pharmaceuticals, toxicity studies of 6 months have generally been accepted for regulatory approval. This review assessed the data for 23 approved biotechnology-derived pharmaceuticals to determine whether the studies conducted were predictive of human safety and whether there is new data from approved products indicating that longer than 6 months is necessary. This assessment involved three approaches; whether new toxicities were identified at >6 months, similarity of findings between 6 months and shorter studies and predictivity of clinical adverse events. In two cases there were apparently new findings in studies >6 months. On examination however, one of these cases was a well established risk with foreign protein administration to animals (adalimumab). For insulin aspart, the 12 month study identified tumors not seen in shorter term studies, however, determination of carcinogenic potential is not a goal of chronic toxicity studies and is addressed by separate studies. In most cases the toxicology studies were predictive of common clinical adverse reactions, but were poorly predictive of rare clinical events or some serious adverse reactions. Although specific circumstances may require a longer study, this review indicates no new data is available to refute the utility of 6 month studies to support chronic clinical dosing with biotechnology-derived pharmaceuticals.