(FORTUNE Magazine) – Patients who want the rheumatoid arthritis-fighting drug Enbrel have to show a special card to their pharmacist, who then verifies that the patient is enrolled in the Enbrel program before dispensing the drug. These tight checks aren't performed because the drug is dangerous, but because its creator, Immunex, can't make enough.

This supply problem will only get worse. There isn't enough manufacturing capacity to meet the explosion in protein drugs now being developed. These drugs, which include monoclonal antibodies ("mabs," in biotech-speak), are based on human proteins and have fewer side effects than traditional therapies.

Interest in mabs helped fuel biotech's boom in the late '80s. But a better understanding of the genome has set off a new race in drug creation. As many as 200 mabs and protein drugs are under development for a host of diseases, including cancer, cardiovascular disease, and cataracts.

But mabs are tricky to make. Currently they are created chiefly from the cells of Chinese hamster ovaries or E. coli bacteria, which are cultured in stainless-steel vats. Manufacturing facilities can take five years to build, and they don't come cheap. Immunex is spending $400 million to gut an existing facility in Rhode Island that will double its production of Enbrel in mid-2002.

That may help Immunex but doesn't do much for the big picture. "[This] is only going to get worse as new products move through clinical development and commercialization," says David Molowa, an analyst at JPMorgan H&Q. He says only one company, Biogen, will have some excess manufacturing capacity when it completes its new facility this year.

Other companies are betting the farm--literally--on an alternative manufacturing method called transgenics. Genzyme Transgenics, Viragen, and CropTech are transferring human genes into goats, chickens, and tobacco plants, respectively, to produce protein drugs. The companies say they can produce the drugs in greater quantities at cheaper prices. "We don't need to build a $400 million facility," says Gerald Smith, CEO of Viragen, which is breeding a flock of transgenic chickens in Scotland. "We have unlimited facilities. All we need is land and chickens."

Still, it will be a long time before chicken eggs cure cancer. Even if drugs made through transgenic means pass clinical tests, they will still face tough regulatory scrutiny. "There's obviously a lot of issues right now with animal-derived products," notes Sylvie Gregoire, vice president of manufacturing for Biogen. "It's likely we'll have to build another [traditional] facility before these new transgenic manufacturing methods can be used." In other words, get your Enbrel connection now.