A health advocacy group today announced that it has challenged a set of United States patents for a hepatitis C medicine. The group says drug maker Gilead Sciences has obtained unmerited patents for sofosbuvir, blocking millions of US patients from affordable treatment.

The Initiative for Medicines, Access & Knowledge (I-MAK) filed the first-ever set of US patent challenges against sofosbuvir with the US Patent Trial and Appeal Board. The group challenged six patents, arguing that sofosbuvir’s patents do not meet patentability criteria such as novelty and non-obviousness, according to a press release.

The group also issued a new white paper “America’s Overspend: How the Pharmaceutical Patent Problem is Fueling High Drug Prices.”

The white paper finds that unmerited patents and other strategies allegedly used by the pharmaceutical industry to delay competition on three major cancer and hepatitis C treatments will cause more than $55 billion in excess costs to payers and taxpayers. The paper examines three of America’s most expensive and widely prescribed drugs for cancer and hepatitis C: Revlimid, Sovaldi and Gleevec.

According to the press release, the market for medicines is not working, and removing unmerited patents will allow more affordable generic drugs to be introduced much sooner. The release states that pharmaceutical drugs patents fail too often to meet the standards of US law.

“Pharmaceutical corporations are over-patenting drugs even when there is no new science that justifies their exclusivity and are stacking up as many unmerited patents as possible to prolong their monopolies and block cheaper generics from entering the market,” it says.