Blueprints of Biotech: What are the FDA-Approved GM Animals?

The alteration of plant and animal species for human benefit has long been for agricultural development. While traditional breeding relied on the slow, generational selection of traits, advances in biotechnology have revolutionized the potential for targeted genetic improvements. Technologies, such as genetic modification (GM) and gene editing, allow scientists to introduce beneficial traits more efficiently and accurately, offering promising solutions for modern agriculture.

In crop production, GM products have seen widespread global adoption since their introduction in the ‘90s. Today, major GM crops such as soybeans, corn, cotton, and canola dominate the market, with over 190 million hectares cultivated worldwide. Despite major scientific breakthroughs in biotechnology, the adoption of GM technology in livestock has been slower. The delay in adoption is deeply rooted in a complex interplay of biological, ethical, regulatory, and societal factors that present higher barriers compared to crop biotechnology.

A review, authored by Carlos Fajardo of the University of Cadiz (UCA) and partners, provides a comprehensive understanding of the state of GM animals, particularly those approved for commercialization by the U.S. Food and Drug Administration (FDA). The article outlines the specific traits targeted in approved GM animals, the purposes they serve, and the evolving regulatory frameworks governing their use.

GM Animals for Direct Human Consumption

AquAdvantage® Salmon (AAS)

The AquAdvantage Salmon (AAS), developed by AquaBounty Technologies, Inc., is an Atlantic salmon (Salmo salar) engineered to grow faster than its wild counterpart. This modification was achieved by inserting a growth hormone (GH) gene from the Chinook salmon (Oncorhynchus tshawhytscha), which enabled the salmon to grow continuously rather than seasonally. AAS grows twice as fast as regular salmon while requiring 25% less land, making it more efficient and cost-effective for land-based aquaculture systems. AAS is raised in physically secure and biologically isolated recirculating aquaculture systems (RAS) to minimize environmental risks and prevent reproduction in case of escape.

The regulatory journey of AAS took over two decades. Initiated in 1995 with the FDA, the process involved multiple stages of scientific reviews, environmental assessments, and public consultations. After a thorough study and review, the FDA concluded that AAS is safe for human consumption and the environment, and it is nutritionally comparable to conventional salmon. AAS was approved in Canada in 2016 and in the U.S. and Brazil in 2021.

Although AAS passed all safety and environmental checks, the product faced intense scrutiny from anti-GMO groups and the organic food industry, leading to mandatory labeling laws and continued public debate. The polarized public sentiment and economic uncertainties illustrate the broader challenges in bringing GM animals to market. In 2024, AquaBounty faced financial setbacks, announcing the closure of its last operational facility. Despite all this, AAS stands as the first GM animal approved for food and represents a milestone in biotechnology and food regulation.

PRLR-Slick Cattle

PRLR-Slick Cattle, developed by Acceligen, Inc., involved editing the prolactin receptor gene (PRLR) to produce cattle with short, slick hair better suited for hot climates. Using CRISPR, two founder calves were modified to carry this heritable trait, mimicking a naturally occurring mutation found in some conventional cattle. These gene-edited cattle exhibit increased heat tolerance, a beneficial trait in light of climate change.

Although the genomic assessment revealed some unexpected mutations in the gene-edited animals, these were not expected to affect protein expression or animal health. Ongoing efforts by organizations like the National Institute of Standards and Technology and the Genome Editing Consortium aim to establish standardized methods for assessing these types of genetic modifications.

The FDA concluded that PRLR-Slick Cattle pose no safety concerns to consumers, animals, or the environment. Since the trait already exists in conventional cattle, no additional labeling is required for products derived from these animals. These products are expected to reach U.S. supermarkets by 2024, with regulation of farms and production facilities following the same standards applied to traditional cattle operations.

GM Animals for Multiple Purposes (Direct Human Consumption and Xenotransplantation)

GalSafe® Pig (GSP)

GalSafe® Pig (GSP), developed by Revivicor Inc., has been approved by the U.S. FDA for human consumption and is awaiting further approval for medical uses. GSP was genetically modified to remove a sugar molecule called alpha-gal, which causes allergic reactions in people with alpha-gal syndrome (AGS) and triggers immune rejection during organ transplants. Scientists inserted rDNA into the pig’s genome to turn off GGTA1, which normally produces the enzyme that makes alpha-gal sugar. In GSPs, copies of the GGTA1 gene were disabled, completely stopping the production of alpha-gal in the pig’s body.

The potential of GSPs goes far beyond allergy-safe meat. These pigs could be a reliable source of organs, like kidneys and hearts, for patients in need of transplants, helping address a critical shortage. In the U.S. alone, over 100,000 people are waiting for organ transplants, and around 6,000 die each year waiting for organ transplantation. Although this is still in the experimental phase, these efforts signal a big step forward in medicine and the future of organ transplantation.

In terms of safety, the FDA has evaluated the GSP for both environmental and food safety risks. The FDA concluded that raising GSPs poses no greater environmental risk than conventional swine commercial operations and that their meat is safe to eat. The FDA also found a low risk of antibiotic-resistant bacteria emerging from GSP farming. While GalSafe pigs have not yet been approved for full-scale use in transplants, they mark a historic milestone as the first GM animal approved for both food and potential medical use.

GM Animals as Bioreactors

Molecular farming, also known as pharming, is an approach where GM animals are used to produce biopharmaceutical products. Compared to traditional cell cultures, animals can serve as more efficient bioreactors due to their natural metabolic processes, consistent production, easier maintenance, and lower facility costs.

Several GM animals have received FDA approval for use in pharmaceutical production. One of these includes a line of GM rabbits engineered to produce recombinant human factor VII (rhFVII) used to treat hemophilia B or A. Similarly, GM goats were approved to produce human antithrombin (NADA 141-294), commercialized by the name ATryn®. This was the first GM animal-derived medicine approved by the FDA. Another case is the GM chickens that were modified to produce recombinant human lysosomal acid lipase (rhLAL) in their egg whites, used for treating a rare genetic disorder. These products are strictly regulated and are not allowed to enter the food or feed supply chain.

GM animals are also developed as models for human diseases. These animals help researchers study conditions such as cancer, heart disease, cystic fibrosis, and neurological disorders. Companies like Exemplar Genetics and Recombinetics have produced multiple FDA-approved GM miniature swine species designed to mimic human disease for testing new treatments and medical devices. At present, over 14 GM animal models developed by these companies are being commercially utilized in the United States.

GM Animals for Pest Control

Oxitec Mosquito

Oxitec Mosquito is a GM mosquito developed by Oxitec Ltd. to reduce populations of Aedes aegypti, a species known for transmitting diseases like dengue, Zika, yellow fever, and chikungunya. These GM mosquitoes carry a self-limiting gene that causes their offspring to die before reaching adulthood. This approach targets mosquito population control by releasing sterile males into the environment, which then mate with wild females. The resulting offspring do not survive, leading to a gradual population decline. Field trials have taken place in several countries, including Malaysia, Brazil, and the USA, showing success in significantly lowering mosquito numbers without increasing environmental risks.

The U.S. regulatory review of these GM mosquitoes was carried out by the FDA, Center for Disease Control and Prevention (CDC), and the Environmental Protection Agency (EPA). Their assessment for a Florida trial concluded there would be no significant negative impact on the environment. However, this approval was limited to specific test sites and did not allow for commercial release. More recently, the regulatory authority over mosquito-related biotechnologies was clarified: the EPA oversees products aimed at population control under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), while the FDA regulates those claiming disease prevention or treatment under the Federal Food, Drug, and Cosmetic Act (FD&C Act).

Conclusion and Future Outlook

Recent advances in biotechnology have demonstrated immense potential in addressing public concerns, such as sustainable food production, disease control, and the development of human therapeutics. While the FDA ensures the safe and effective commercialization of GM animal-derived products, the prolonged approval poses challenges for sponsors due to regulatory hurdles, technical setbacks, financial limitations, or public skepticism influenced by long-standing activist campaigns.

The global support for gene editing has encouraged increased investment in research, development, and innovation. While regulatory bodies, industry sponsors, and consumers may approach these innovations from different angles, they share a common goal of advancing technologies that improve food systems, health outcomes, and animal welfare, making a robust, science-based regulatory framework essential for continued progress.

For more information, read the review from MDPI.

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