The United States Patent Office has rejected four key patents to Gilead Sciences for its antiretroviral drug tenofovir DF (found in Viread, Truvada and Atripla), according to widespread news reports. Though Gilead is appealing the ruling, the company could lose its rights to exclusively manufacture and sell the drug if their appeal is ultimately rejected.

The U.S. Patent Office issued its ruling based on a challenge to the patents filed by the Public Patent Foundation (PPF), a not-for-profit organization that seeks to limit perceived abuse of the U.S. patent system. PPF claims that specific scientific information about tenofovir DF was widely known before Gilead filed its patents and began to develop the drug for HIV.

A Morgan Stanley analyst quoted by news sources says that it could take three or four years for the appeal to be ruled on. Though the analyst and a Gilead spokesperson both stated that the chance for Gilead to lose its patents is low, PPF’s executive director, Daniel Ravicher, says that two thirds of companies who are initially ruled against by the U.S. patent office ultimately lose their appeals.

AIDS activists have expressed mixed reactions to the news. Health GAP, a nonprofit organization devoted to ensuring access to HIV medications for people in developing countries, points out that Gilead’s patent to exclusively produce tenofovir DF in India—the world’s largest producer of low-cost generic HIV drugs for poor countries—is also being challenged. They issued a press release saying, “This victory should be viewed as a victory for AIDS activists in developing nations struggling to provide affordable treatment to the millions of people who need it.”

Another prominent AIDS activist and the antiretroviral director at the Treatment Action Group in New York City, Bob Huff, disagrees, saying, “I don’t think invalidation of Gilead’s tenofovir patents should be seen as a victory for AIDS activists or for people with HIV.”

He concedes that prices may drop to some degree if Gilead loses its patents in the U.S. and India, but also argues that the situation is far more complicated than it may seem on the surface. For one thing, because of tenofovir DF’s complexity and large dose, it is unlikely that even a generic manufacturer could find a way to sell the drug at a price as low as other AIDS drugs currently being sold in the developing world.

Huff also explains that at least in the U.S. and Europe, tenofovir is rarely prescribed by itself in a single pill. Instead the most popular use of the drug is in fixed-dose combination tablets like Truvada, which contains tenofovir DF and emtricitabine, and Atripla, which contains tenofovir DF, emtricitabine and efavirenz. Such combination pills would not be affected, nor their price reduced, should Gilead lose its patents on tenofovir DF.

While Huff notes that he is not an expert patent issues, he feels that Gilead has a pretty good case for patent protection, and fears that if they lose their appeal it could have a chilling effect on research for new HIV medications. He says, “AIDS activists need to not only think about the immediate crisis or the next step, but also about the state of AIDS 10, 20, and 50 years ahead. Despite the inequities of the intellectual property system, or the abuses of the pharmaceutical industry, drugmakers know how to develop drugs—and we urgently need new and better HIV drugs.”