Nonclinical development of biopharmaceuticals

By Scott E. Boley, PhD, DABT Senior Director of General Toxicology and Infusion Toxicology MPI Research

The only thing certain is change. This axiom holds true for many aspects of today’s world but it is a central tenet for drug development. Fifteen years ago, small molecules
(chemically synthesized molecules designed to interact with a specific cellular receptor) represented the majority of pharmaceuticals under development. During the past 10
years, however, the number of therapies being developed that fall into the category of biopharmaceuticals has exploded, with predictions that the majority of therapies
developed in the next 10 years will fall into this class.

For purposes of this article, the term biopharmaceutical is used interchangeably with the
terms biotechnology-derived pharmaceutical, large molecule, biologic, or biotherapeutic. In the most general sense, the term biopharmaceutical can be used to refer to anything that was produced by a living cell (bacterial, yeast, mammalian, insect, or plant) and may include antibodies, peptides, intact proteins, oligonucleotides, vaccines, and stem cells. The nonclinical safety program used to support development of a biopharmaceutical can differ significantly from that used to support development of traditional small molecules.  This article will discuss some of those differences, with the understanding there are exceptions to every rule and in drug development there is typically more than one exception.
 
While the nonclinical development of small molecules is not straightforward, the nonclinical development of biopharmaceuticals is more complicated. For a small molecule, companies would follow an approach consisting of general toxicology studies, reproductive toxicology studies, safety pharmacology studies, and genetic toxicology studies. In many cases the rodent and nonrodent species are selected based on the in vitro metabolism profile of the small molecule in a variety of species (including humans). The selected species would be those that best represent the profile expected for humans. For biopharmaceuticals, regulatory bodies allow the animal studies needed to support the clinical trials to be conducted in a single species if the biopharmaceutical is pharmacologically active in only a single species. If the biopharmaceutical is active in both rodent and nonrodent species, both are used during development. Many biopharmaceuticals show pharmacological activity only in nonhuman primates (NHP, typically cynomolgus or rhesus monkeys). If the species specificity is not known, it is best to conduct literature searches to investigate the level of homology for various
species, followed up by cell-based assays with pharmacodynamic endpoints to provide preliminary data for the compound. 
 
Another common characteristic of biopharmaceuticals is their propensity to elicit an immune response in the test system. Small molecules do not typically elicit such responses due to their small size, whereas biopharmaceuticals are much larger and can be recognized by the immune system as a potentially foreign substance. Levels of anti-drug antibodies (ADAs) formed against biopharmaceuticals are often measured as a means of assessing the immune response against the test article.  ADAs may have no effect on the activity of the test article or they can cause inactivation of the test article, with a functional assay needed to determine this point.  
 
In the case of small molecules, a standard battery of separate safety pharmacology studies
is conducted, where the potential for the test article to affect the major physiological systems (e.g., central nervous, cardiovascular, and respiratory systems) is examined. For biopharmaceuticals these studies are not typically conducted as stand-alone studies, rather safety pharmacology endpoints are included in the design of the general toxicology studies. If a particular class of biopharmaceuticals is known to have potential risks for any of the major systems, stand-alone safety pharmacology studies would still be warranted.
 
For small molecules, the standard approach is to conduct reproductive toxicity testing in two species. As with the general toxicology studies, if the pharmacological activity of the biopharmaceutical is limited to NHP, reproductive toxicology studies can be conducted solely in NHP with the rationale being that if there is no pharmacological activity of the test article in a particular species, conducting reproductive toxicology studies in that species would not provide meaningful data. However, the size and duration of these studies are significant, because the average female gives birth to a single offspring, and the typical gestation period is approximately 180 days. To complicate matters further, the success rate of mating can be as low as 40%, adding more time to the front end of the study. If the biopharmaceutical is active in rodents, a standard reproductive toxicology plan can be followed for that test article.
 
The preparation of dosing solutions used for nonclinical safety studies with biopharmaceuticals also differs from those used for small molecules. For example, biopharmaceuticals are more prone to “adhesion” than are small molecules and may, therefore, require specific materials during their formulation (for example glass instead of plastic, etc.). In addition, vigorous homogenization procedures that are used during preparation of small molecules are seldom consistent with the preparation of biopharmaceuticals because of the propensity to create bubbles that can denature a protein. In addition, small molecules are generally analyzed by LC-MS/MS, for biopharmaceuticals, however, analysis of the dosing formulation is not as straightforward. Some can be analyzed using procedures identical to those used for small
molecules, while others may require more sophisticated approaches (for example, ELISAs for monoclonal antibodies). It is critical that laboratories conducting studies with biopharmaceuticals have sufficient knowledge of and experience with the handling and analysis of biopharmaceuticals to prevent issues that may affect the integrity of formulations being used to dose the animals.
 
The delivery of biopharmaceuticals presents its own challenges. Biopharmaceuticals cannot be administered orally, because they would be broken down in the acidic environment of the stomach before they had an opportunity to become systemically available. Therefore, the common routes of administration are parenteral (subcutaneous, intravenous, intraperitoneal, intramuscular). 
 
As indicated above, the nonclinical studies involved in development of biopharmaceuticals demonstrate a number of differences compared to those needed for small molecules. For many companies, the required expertise may not be available in house, requiring that this work be outsourced to a contract research organization (CRO). It is critical that the CRO selected have the experience, expertise, and equipment needed to provide a complete study that will be accepted by a regulatory agency. 

Biography

Scott E. Boley, PhD, DABT, is Senior Director of General Toxicology and Infusion Toxicology at MPI Research. He received his PhD in biochemistry and environmental toxicology from Michigan State University and did postdoctoral work at CIIT Centers for Health Research. Contact Dr. Boley at Scott.Boley@mpiresearch.com or +1- 269-668-3336, extension 1887.