Genetically engineered animals are in the spotlight yet again as the US government recently approved transgenic drug-producing chickens.
These chickens are only the second transgenic animal approved by the Food and Drug Administration (FDA) to produce a biologic – a therapeutic product, like medicine, made from organic materials or living organisms. In 2009, the FDA approved the genetically engineered (GE) goats that produced an anticoagulant
(ATryn) in their milk to treat patients with hereditary antithrombin deficiency. Now, seven years later, the chickens were approved to produce a recombinant enzyme called sebelipase alfa
(Kanuma) to treat lysosomal acid lipase (LAL) deficiency.
Also known as Wolman disease and cholesteryl ester storage disease, LAL deficiency is rare but can be dangerous and even life-threatening, especially for infants. Patients with this condition have a faulty enzyme that cannot break down fatty molecules in certain cells, causing liver and cardiovascular problems.
Kanuma is made from chickens modified to produce the recombinant human LAL protein (rhLAL) in their egg whites. Scientists then refine the whites to extract and purify rhLAL as a medicine that’s administered intravenously. The hens essentially become bioreactors for producing the Kanuma drug, marketed by Alexion Pharmaceuticals
In its review, the FDA considered the efficacy and safety of Kanuma for treatment of LAL. Clinical trials with this drug increased survival rate for infants and improved disease-related symptoms in adults. The FDA also evaluated the safety of the recombinant DNA construct to the animal and to successive generations. Though “no adverse outcomes were noted in the chickens,” the agency requires the modified hens to be raised in “highly secured indoor facilities.”
“We reviewed all of the data to ensure that the hens do produce rhLAL in their egg whites, without suffering any adverse health effects from the introduced rDNA construct. The company has taken rigorous steps to ensure that neither the chickens nor the eggs will enter the food supply, and we have confirmed their containment systems by inspecting the manufacturing facilities.” – CVM Director Bernadette Dunham, D.V.M., Ph.D.
This means that, like the AquAdvantage salmon
that was approved in November 2015, these GE animals are contained and should not impact the environment. However, unlike the salmon, you will not see these GE chickens or eggs for consumption in your local grocery store.
Based on the rarity of the LAL disease and the efficacy of Kanuma, the FDA granted the drug a high priority review, orphan drug status, and a breakthrough therapy designation. Undoubtedly all three highly prized designations contributed to the impressively speedy review and approval of Kanuma in the transgenic chickens.
“Using this technology, these patients for the first time ever have access to a treatment that may improve their lives and chances of survival.” – CDER Director Janet Woodcock, M.D.
With this approval, Kanuma joins the ranks with ATryn as bona-fide ‘farmaceuticals.’ And many see it as a signal of more to come. “[This] shows that the ATryn goats weren’t just a one-off. The process can function for more than just one particular unique case,” says Jay Cormier, a lawyer at Hyman, Phelps and McNamara in Washington DC and a former scientific reviewer for the FDA.
Watch the video to learn more about the process of producing biologics!
Additional sources: Nature