FDA OKs genomic alteration of pigs for human food, possible medical uses

Scott P. Commings, MD, PhD

I am incredibly excited about this FDA approval. The typical treatment for those with alpha-gal allergy is avoidance and carrying an epinephrine auto-injector. Therefore, the FDA’s approval of IGA is a massive breakthrough for the estimated 34,000 people in the United States — most of them in the Southeastern and Eastern states — with alpha-gal allergy. Not only has the allergy recently been identified in the Midwest and Great Lakes areas, but there are also people with the condition in Australia, Europe, Scandinavia, South Africa and Asia who have the same allergy and will likely benefit from this approval.

Revivicor, the company that received the FDA approval, has been doing work in this scientific space for some time. Its pigs were initially bred about 12 to 15 years ago to be a potential safe source for xenotransplantation. Now that the company has received FDA approval, we can expect food challenges to begin shortly. Over the long term, we expect to see alpha-gal-free medications (such as the common blood thinner heparin) and tissues (such as heart valves) derived from these animals that will provide safer options for patients with alpha-gal allergy.

It is hard to say if IGA will become a standard treatment for patients with any type of food allergy. Whereas patients with peanut allergy may be allergic to three or six of the various proteins in peanut, making it harder to engineer a peanut that is completely allergen-free, patients with alpha-gal allergy are specifically allergic to the alpha-1,3 arrangement of galactose sugar molecules in pigs, cows, sheep and other nonhuman mammals. Therefore, patients with alpha-gal allergy present an ideal scenario for IGA.

Jay Lieberman, MD

Alpha-gal syndrome is becoming more common in certain regions of the United States. For example, individuals in the southeast part of the country are more likely to get it than those in the northwest. This is assumed to be due to exposure to ticks, as tick bites are thought to initiate the immune response that leads to alpha-gal allergy. You can detect the allergic antibody to alpha-gal very frequently in patients with history of tick bites. For example, the authors of a German study found that the allergic antibody to alpha-gal was present in about one-third of forest workers. However, only 8% were truly allergic. This shows how hard it is to get true estimates of prevalence, because you really must challenge the patients to prove the allergy, which few people do.

Alpha-gal is somewhat a unique food allergy for a few reasons. First, the symptoms do not occur until hours after the meat that is the source of the allergen is consumed. Second, alpha-gal, besides mammalian meat, can also be found in milk, gelatin, medications and artificial heart valves (usually those derived from a pig). Third, the symptoms do not always occur every time a patient is exposed to alpha-gal, since higher fatty meats (eg, pork ribs) typically illicit symptoms more reproducibly vs. lean meats. In addition, most patients tolerate things such as milk/dairy and gelatin, but not others. All these conditions make it challenging for patients and health care providers to diagnose alpha-gal allergy.

Until the recent FDA announcement involving IGA, avoidance of the food causing the allergic reaction was the only treatment. Patients were also encouraged to have auto-injectable epinephrine available as well. This will not really change much. Rather, the FDA announcement is the first step to help ease the burden of alpha-gal syndrome. If IGA is successful, patients with the allergy could eat pork from modified animals, but this is not going to happen with this one announcement. More importantly, patients who use artificial heart valves would not have to worry about health-related products that come from these animals. This is probably where I see this announcement being more beneficial. However, perhaps it paves the way for further research into modifications like this for patients with food allergy.

Reference:

Fischer J, et al. Allergy. 2017;doi:10.1111/all.13156.