The complexity of non-clinical safety studies has been increasing in recent years as researchers seek to obtain as much information as possible about the safety and pharmacology of their therapeutics prior to commencing clinical studies. The toxicological testing of pharmaceuticals has been an important part of regulatory drug development for more than half a century, and there is now an extensive library of regulations and guidance that researchers must consider when developing new products or new formulations of existing products.
As each therapeutic is different, there is deliberate flexibility in much of the guidance to ensure that product-specific considerations are investigated. Navigating this guidance effectively forms a major part of the successful partnership between contract research organizations (CROs) and their customers.
Non-clinical therapeutic product development is not as straightforward as following a prescriptive list of investigations to satisfy regulators. Studies often contain product specific measurements, loosely termed “biomarkers,” to assess both off-target effects on normal tissue, as well as on-target effects based on the mechanism of the product being developed. Both these on- and off-target effects can have dose-limiting implications on the effective use of a chosen therapeutic.
It should be noted that the objectives of preclinical pharmaceutical development are essentially the same whether you are developing small or large molecule therapeutics. The goal is to understand the potential efficacy, bioavailability and safety of your product in a series of in silico, in vitro and in vivo studies before entering the clinic. However, there are some critical differences regarding how the non-clinical safety testing of biologics has developed.
The term “biologics” refers to newer classes of products that include a wide range of different therapeutic modalities such as monoclonal antibodies, recombinant proteins, peptides, DNA and RNA oligonucleotides, cell and gene therapies, as well as vaccines. Vaccines have, of course, been successfully used clinically for many years, and new approaches to vaccination are continually being developed — along with the need to demonstrate both safety and clinically relevant pharmacology in non-clinical safety studies.
The molecules that make up most, but not all, biologics are amino and nucleic acids. The catabolism of proteins, peptides, DNA and RNA by enzymatic cleavage and subsequent clearance and recycling is well understood, so the possibility of producing bioactive or toxic metabolites is limited. Hence the general focus of safety studies for biologics is on “on-target” effects, and more occasionally on non-target tissue effects (pharmacology). The emphasis is different in small molecule safety assessment wherein xenobiotics introduced into the body are cleared by many different mechanisms, all of which can contribute to the toxicity of the product.
It is important to consider whether the exaggerated pharmacological effects of a biopharmaceutical can be dose limiting. As a consequence, those studying these effects need to assess the pharmacological response within well-designed and executed safety studies. Researchers are therefore required to perform safety studies in pharmacologically relevant species; that is, those non-clinical species in which the therapeutic has a comparable mode of action with that expected in the clinical setting. This means that species selection is essential, and that a series of in silico, in vitro and in vivo investigations are done to understand the drug pharmacology in a range of laboratory animals and thus identify the most relevant species.
Small molecule safety programmes typically use a rodent and non-rodent species; however, there is more flexibility in a biologics safety programme. The default position is still to identify a rodent and non-rodent species in which the therapeutic is active; but, if this is not possible and only one species exists, then a one-species safety programme can be conducted.
There are also examples of when there is no relevant species because the therapeutic is only active in humans. In this instance, several other options may be explored, such as using a transgenic animal that expresses the human target, or developing a surrogate molecule (usually a murine version of the human therapeutic) to generate safety data.
With appropriate scientific justification some standalone studies that are relevant for small molecule drugs may be combined with other studies when developing biologics, and some studies may be excluded altogether. The essential safety data is still collected, but usually in conjunction with other investigations rather than in separate studies. This has the added benefit of meeting our 3Rs goals by reducing the total number of animals used in such investigations, but has the knock-on effect of making these studies far more complex.
As with all generalities, there are exceptions. Not all biologics are made up of “naturally occurring” molecules; some have been extensively chemically modified. This can mean that hybrid NCE/biologics approaches are undertaken to assess the safety profile of those modified components. These challenges, including the need to demonstrate clinically relevant pharmacology, mean that the designs of biologics safety programmes require a great deal of understanding of the therapeutics’ mode of action.
So, whereas some differences exist in the approach taken to assess the non-clinical safety of small and large molecule therapeutics, there are increasingly greater similarities. As discussed earlier, there are potential off target toxicities that need to be investigated for xenobiotics where the selection of a relevant species is just as critical. For example, some drugs produce specific metabolites that are relevant in the clinical setting but are not reproduced in all non-clinical species. In these instances, the toxicity of the therapeutic may need to be evaluated in species that produce a similar metabolic profile to that in human.
If the metabolite is human-specific, it may be also necessary to test the safety of that human metabolite in a relevant safety testing species. Equally, the importance of dose-limiting pharmacology can be a critical investigation, and this may be explored in non-clinical safety studies.
In practice, this means that many product-specific biomarkers of drug intervention are now included in safety studies to measure the pharmacology of the drug, as well as traditional safety endpoints. Also, specific safety markers may be included to assist in the selection of safe clinical doses. In all cases, a sound understanding of the expected biology of the therapeutic is required to design product-specific packages that stand up to regulatory scrutiny and predict clinical safety.
With an increasing focus on the use of biomarkers to measure all manner of potential toxicities, as well as pharmacodynamics in studies, one of the biggest barriers to being able to support non-clinical product development is the bioanalytical support required. Many of the complex biological responses we measure are focused on specific therapeutic areas and preclinical CROs are increasing their knowledge and experience across a wide range of therapeutic areas. This knowledge base is becoming integrated into all aspects of the projects that the CROs support and being made available to drug developers.
Drug developers recognize the added value of full service non-clinical CROs that take a very translational approach to study design and execution. Those that can bring their experience, scientific and technical expertise to bear in developing and optimizing the best possible programme for their customer’s molecules have an advantage in the marketplace. From early programme design and the identification of relevant biomarkers, through to problem solving as they review the findings from these complex biological systems, this is where CROs can really create value for their customers. CROs that are equipped with the knowledge base and infrastructure to support development in this way play an essential role in product development partnerships.
About the Author
Lee Coney is the Chief Scientific Officer of Huntingdon Life Sciences’ biologics business; he has been with the company for 10 years after working in a number of UK biotech organizations. His experience to date has been spent developing therapies including vaccines, recombinant proteins, monoclonal antibodies, viral and non-viral gene delivery systems, and cell-based therapies. He has a well-rounded knowledge of the regulatory environment for biologics and particular expertise in the development of immunomodulatory therapeutics.