Topic: Clinical Translation of Findings from Rare Disease Animal Models to Veterinary Patients: Practical Reality or Elusive Dream

Animal models have been used since antiquity to define pathogenetic mechanisms, treatments, and potential risks of therapies for rare human diseases. These studies have ranged from drug safety testing to preclinical trials of complex gene and cell-based treatments. Research has been done in dogs, cats, and, to a lesser extent, other companion animal species to extend initial rodent experiments. These “large animals” are generally considered more physiologically like humans than rodents, increasing the likelihood that findings would translate into clinical trials. With advancements in genetics and the sequencing of the canine and feline genomes, inherited diseases in dogs and cats that share features with human conditions have increasingly been identified. This has led to the advent of truly homologous genetic models in these species and the application of sophisticated clinical outcome parameters routinely used in veterinary practice to preclinical studies. Additionally, acquired diseases – including cancerous, infectious, and developmental conditions - have been recognized in companion animals, offering valuable models for studying their human counterparts. The use of companion animals in preclinical studies has understandably raised ethical concerns, prompting a search for alternatives. 

One justification for using canine and feline models in research is the potential to eventually translate findings into treatments for veterinary patients. However, challenges like those encountered in analogous rare human diseases have provided substantial disincentives. For instance, the potential animal patient population is limited, and the cost of genetic and cell-based therapies can be prohibitive. Taken together, this makes it difficult for the pharmaceutical industry to financially justify developing therapies, especially without subsidization by third-party payers such as insurance companies. 

Considering the hurdles to developing treatments for rare diseases, the Food and Drug Administration (FDA) administers two programs, one for humans and the other for animals. The first and better-known of the two was established by the Orphan Drug Act of 1983 to expedite drug development for rare human diseases. More recently, the Minor Use and Minor Species Animal Health Act of 2004 (MUMS) established similar policies to encourage drug development for affected animals.

Despite the inherent challenges, there have been recent examples in which gene or cell therapies, advanced surgical techniques, and drugs originally developed for rare human diseases and tested for safety in dogs and cats have been applied to client-owned animals with similar or identical conditions. As awareness grows among veterinarians and pet owners, barriers to making these treatments more broadly available must be overcome. 

 
This Special Issue of RDODJ, “Clinical Translation of Findings from Rare Disease Companion Animal Models to Veterinary Patients: Practical Reality or Elusive Dream”, highlights instances when treatments, including drug safety studies, for rare human diseases were initially tested in companion animal models and later applied to veterinary patients with the same conditions, as well as the remaining challenges for their broader application. 
 
We welcome original research articles, reviews, commentaries, case reports, editorials, and other manuscripts as described here.

Topics may include, but are not limited to, the following subjects: 
1. Rare genetic diseases in companion animals for which treatments were first tested in these species and then extended to veterinary patients, or for which clinical translation is feasible in the relatively near future. 
2. Rare acquired diseases (e.g., cancerous, infectious, or other diseases) in companion animals that have been treated with drugs originally developed for humans and tested for toxicity in these animal species. 
3. Surgical techniques developed for rare human diseases that were at least partially devised in companion animals and then applied to veterinary patients with analogous conditions. 
4. Scientific and ethical considerations related to conducting research in companion animals.  
5. Challenges to translating treatments for rare companion animal diseases, including regulatory requirements, the absence of financial incentives for the pharmaceutical industry, and/or a lack of third-party payer support.