Large Animal Model Efficacy Testing Is Needed Prior to Launch of a Stem Cell Clinical Trial: An Evidence-Lacking Conclusion Based on Conjecture.

Stem cell therapeutics, as other therapeutic strategies, must surmount multiple requirements before reaching the phase of clinical trials. These requirements can be onerous in terms of time and funding and could, thereby, lead to abandonment of many promising therapeutics. One of these requirements is the perceived necessity of conducting large animal efficacy studies—especially pig studies—prior to initiating a clinical trial. The value of such a strategy, despite acceptance by experts, has never been demonstrated scientifically, raising the question of whether bias rather than evidence hampers the development of new therapeutic strategies. Of the questions facing investigators involved in developing new treatment strategies, one is common across disease disciplines and therapeutic approaches: What animal models should be used to determine whether the likelihood a therapeutic will be clinically successful is high enough to justify spending years of effort and tens, or even hundreds, of millions of dollars in clinical trials? A particularly vexing extension of this question is whether it is necessary to test efficacy in a large animal model prior to clinical trial launch. The purpose of this Viewpoint is to challenge the prevailing view, epitomized by the following quote: “Translational studies in large animal models (usually pigs) are rare because they are expensive, complex, time-consuming, technically demanding, slow, and usually not suitable for mechanistic investigations; nevertheless, because they are conducted in settings closer to the human situation than those found in rodent models, these studies are essential to justify the risks and costs of clinical trials.”1 This quote reflects current unofficial dogma that once efficacy of an intervention is established in mouse or other rodent models, efficacy needs confirmation in a large animal model—the most popular one being the pig.1–3 This is not a trivial conclusion because adequately powered pig studies are expensive from both …