Secondary patenting of branded pharmaceuticals: a case study of how patents on two HIV drugs could be extended for decades

Abstract

Pharmaceutical manufacturers rely on patents to protect their intellectual property and often seek to extend market exclusivity for their products to maximize their return on investment. One method is by obtaining patents on features other than the original active drug ingredient, including secondary patents on alternate formulations of the drug or on methods of administration. This article examines how secondary patents can extend market exclusivity and thus delay generic competition, using as an example two key antiretroviral drugs for the management of HIV: ritonavir (Norvir) and lopinavir/ritonavir (Kaletra). We identified 108 patents, which together could delay generic competition until at least 2028--twelve years after the expiration of the patents on the drugs' base compounds and thirty-nine years after the first patents on ritonavir were filed. Some of the secondary patents that were reviewed were found to be of questionable inventiveness. We argue that increased transparency for existing patents, stricter patentability standards, and increased opportunities to challenge patent applications and patents could reduce inappropriate market exclusivity extensions on brand-name drugs and open the door to lower-cost generics.