Emily Anthes, Frankenstein'

 This passage is adapted from Emily Anthes, Frankenstein's

Cat. ©2013 by Emily Anthes.

When scientists first learned how to edit the

genomes of animals, they began to imagine all the

ways they could use this new power. Creating

brightly colored novelty pets was not a high priority.

Instead, most researchers envisioned far more

consequential applications, hoping to create

genetically engineered animals that saved human

lives. One enterprise is now delivering on this dream.

Welcome to the world of “pharming,” in which

simple genetic tweaks turn animals into living

pharmaceutical factories.

Many of the proteins that our cells crank out

naturally make for good medicine. Our bodies’ own

enzymes, hormones, clotting factors, and antibodies

are commonly used to treat cancer, diabetes,

autoimmune diseases, and more. The trouble is that

it’s difficult and expensive to make these compounds

on an industrial scale, and as a result, patients can

face shortages of the medicines they need. Dairy

animals, on the other hand, are expert protein

producers, their udders swollen with milk. So the

creation of the first transgenic animals—first mice,

then other species—in the 1980s gave scientists an

idea: What if they put the gene for a human antibody

or enzyme into a cow, goat, or sheep? If they put the

gene in just the right place, under the control of the

right molecular switch, maybe they could engineer

animals that produced healing human proteins in

their milk. Then doctors could collect medicine by

the bucketful.

Throughout the 1980s and ’90s, studies provided

proof of principle, as scientists created transgenic

mice, sheep, goats, pigs, cattle, and rabbits that did in

fact make therapeutic compounds in their milk.

At first, this work was merely gee-whiz, scientific

geekery, lab-bound thought experiments come true.

That all changed with ATryn, a drug produced by the

Massachusetts firm GTC Biotherapeutics. ATryn is

antithrombin, an anticoagulant that can be used to

prevent life-threatening blood clots. The compound,

made by our liver cells, plays a key role in keeping

our bodies clot-free. It acts as a molecular bouncer,

sidling up to clot-forming compounds and escorting

them out of the bloodstream. But as many as 1 in

2,000 Americans are born with a genetic mutation

that prevents them from making antithrombin.

These patients are prone to clots, especially in their

legs and lungs, and they are at elevated risk of

suffering from fatal complications during surgery

and childbirth. Supplemental antithrombin can

reduce this risk, and GTC decided to try to

manufacture the compound using genetically

engineered goats.

To create its special herd of goats, GTC used

microinjection, the same technique that produced

GloFish and AquAdvantage salmon. The company’s

scientists took the gene for human antithrombin and

injected it directly into fertilized goat eggs. Then they

implanted the eggs in the wombs of female goats.

When the kids were born, some of them proved to be

transgenic, the human gene nestled safely in their

cells. The researchers paired the antithrombin gene

with a promoter (which is a sequence of DNA that

controls gene activity) that is normally active in the

goat’s mammary glands during milk production.

When the transgenic females lactated, the promoter

turned the transgene on and the goats’ udders filled

with milk containing antithrombin. All that was left

to do was to collect the milk, and extract and purify

the protein. Et voilà—human medicine! And, for

GTC, liquid gold. ATryn hit the market in 2006,

becoming the world’s first transgenic animal drug.

Over the course of a year, the “milking parlors” on

GTC’s 300-acre farm in Massachusetts can collect

more than a kilogram of medicine from a single

animal.

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