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A “drug,” in bare conceptual terms, is any substance that can produce an effect on the physiology of an animal. Drugs can be simple molecules; water and salt, under appropriate circumstances, can function as potent pharmacological agents. Or drugs can be complex, multifaceted chemicals— molecules derived from nature, such as penicillin, or chemicals synthesized artificially, such as aminopterin. Among the most complex drugs in medicine are proteins, molecules synthesized by cells that can exert diverse effects on human physiology. Insulin, made by pancreas cells, is a protein that regulates blood sugar and can be used to control diabetes. Growth hormone, made by the pituitary cells, augments growth by increasing the metabolism of muscle and bone cells.

Before Genentech, protein drugs, although recognizably potent, had been notoriously difficult to produce. Insulin, for instance, was produced by grinding up cow and pig innards into a soup and then extracting the protein from the mix—one pound of insulin from every eight thousand pounds of pancreas. Growth hormone, used to treat a form of dwarfism, was extracted from pituitary glands dissected out of thousands of human cadavers. Clotting drugs to treat bleeding disorders came from liters of human blood.

Recombinant DNA technology allowed Genentech to synthesize human proteins de novo: rather than extracting proteins from animal and human organs, Genentech could “engineer” a human gene into a bacterium, say, and use the bacterial cell as a bioreactor to produce vast quantities of that protein. The technology was transformative. In 1982, Genentech unveiled the first “recombinant” human insulin; in 1984, it produced a clotting factor used to control bleeding in patients with hemophilia; in 1985, it created a recombinant version of human growth hormone—all created by engineering the production of human proteins in bacterial or animal cells.

Excerpted from pages 413-414 of ‘The Emperor of All Maladies: A biography of Cancer’ by Siddharth Mukherjee