1982: First Recombinant Human Insulin (1982)

Since Banting and Best's 1921 discovery, insulin had been extracted from porcine and bovine
pancreata—a supply that was finite, variable in purity, and caused hypersensitivity reactions in
some patients. By the late 1970s, fears grew that demand from an increasing diabetic population
would outstrip the supply of animal-derived insulin.

The solution came from recombinant DNA technology. Genentech—co-founded by Herbert Boyer, who had
co-developed restriction enzyme cloning with Stanley Cohen—applied its gene synthesis and
bacterial expression platform to insulin. The human insulin gene was synthesised chemically,
inserted into plasmid vectors, and expressed in Escherichia coli. Genentech published successful
expression of human insulin chains in 1978. After validation by Eli Lilly—Genentech's commercial
partner—the finished product, "Humulin," was approved by the FDA on 29 October 1982.

Humulin was the first approved recombinant human protein therapeutic and the first product of the
modern biotechnology industry. Its approval demonstrated that genetically engineered microorganisms
could produce human proteins in commercial quantities with sufficient purity and safety for
clinical use—a proof-of-concept that had far-reaching implications.

The recombinant insulin success created the template for the biotechnology pharmaceutical industry:
identify a medically important human protein, clone its gene, express it in a microbial or
mammalian cell system, purify the product, and develop it as a biopharmaceutical. This approach
subsequently yielded recombinant erythropoietin (1989), recombinant growth hormone (1985),
recombinant Factor VIII (1992), and eventually the entire class of biologic drugs that now
represents the largest revenue segment of the pharmaceutical industry.