In 2000 Hazuda and her team published two landmark papers showing that integrase inhibitors could be made.

FORBES: Innovation

"Very senior management said I should stop working on integrase and start working on CCR5 inhibitors, " Hazuda says.

FORBES: Innovation

But she couldn't get her drug screen for integrase blockers to work with the robots Merck had at the time.

FORBES: Innovation

But she insisted the right target was integrase, part of the virus, not CCR5, which is part of the patient.

FORBES: Innovation

One is an integrase inhibitor, a new class of antivirals, for HIV.

FORBES: Gilead's Half-Empty Pipeline

The first challenge was figuring out how to measure whether or not chemicals were blocking the integrase enzyme so that hundreds of different potential medicines could be tried out.

FORBES: Innovation

Merck did fine here, with many years as the only maker of an integrase inhibitor, but it does seem the companies following in its wake may have an easier time.

FORBES: An Innovator's Dilemma For Merck AIDS Drug

GlaxoSmithKline and Merck have both attempted to develop integrase inhibitors, which inhibit the viral DNA from integrating with human DNA. But their drugs have failed in trials due to problems with toxicity and other issues.

FORBES

GlaxoSmithKline (nyse: GSK - news - people ) and Merck (nyse: MRK - news - people ) have both attempted to develop integrase inhibitors, which inhibit the viral DNA from integrating with human DNA. But their drugs have failed in trials due to problems with toxicity and other issues.

FORBES: Gilead's Half-Empty Pipeline