More than a decade ago, researchers at Gilead Sciences thought they had a breakthrough: a new version of the company's key HIV medicine that was less toxic to kidneys and bones. Clinical trials ... seemed to support their optimism. Patients needed just a fraction of the dose, creating the chance of far fewer dangerous side effects. But in 2004 ... Gilead executives stopped the research. The results of the early patient studies would go unpublished for years as the original medication - tenofovir - became one of the world's most-prescribed drugs for HIV, with $11 billion in annual sales. In 2010, Gilead restarted those trials. A year of treatment with Gilead's HIV medicines costs about $30,000. Earlier this year, the Los Angeles-based AIDS Healthcare Foundation, which operates clinics and pharmacies for AIDS patients, sued Gilead, contending that it delayed the less toxic form of tenofovir to manipulate the patent system and keep prices artificially high. Animal studies showed that [tenofovir] could cause damage to the kidneys and bones. When the drug was approved in 2001, the FDA required Gilead to study whether the medicine would harm humans in the same way. [By] 2003, the company had received so many reports of patients experiencing kidney failure and other ... problems that it placed a warning on the drug's label. Several times, U.S. regulators formally warned Gilead that it was downplaying the drug's risks.