Timelines: 1994
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Thrombopoietin
Technical breakthrough, no medical payoff
Researchers at Zymogenetics, Inc., of Seattle, and Molecumetics, Inc., of Bellvue, Washington, work together to clone the platelet-replenishing cytokine, thrombopoietin. Scientists at Genentech and three other groups soon report that they have duplicated the feat independently. Thrombopoietin (TPO) had proven an elusive target for cloners. So difficult was the purification of the protein from plasma that some researchers doubted its existence.
Once the gene for the protein is cloned, a race ensues, with Zymogenetics and Genentech leading the field, to develop a pharmaceutical product that will help patients recover platelet counts after rounds of chemotherapy that suppress bone marrow function.
None of the horses ever finds a finish line. Perversely, clinical trials show that recombinant TPO frequently inhibits platelet production. Patients often develop antibodies against the drug that cross-react with natural TPO. This worsens rather than improves their conditions. Despite the scientific and technological accomplishments of finding and manipulating the protein, the experts concede defeat to the complexities of biology – the battle is lost and the research programs abandoned.
