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In a bid to prevent the patent system from being abused, the U.S. Patent and Trademark Office has proposed a new rule designed to stem the use of so-called patent thickets, which are wielded by pharmaceutical companies to delay the arrival of lower-cost generic medicines in the marketplace.

Essentially, thickets are collections of numerous patents that add only incremental changes to a drug and, therefore, produce little to no additional benefit to patients. Yet they extend precious monopolies for brand-name drugmakers and, consequently, are blamed for contributing to ongoing high drug costs for countless Americans.


To assemble a thicket, drug companies rely on a critical tool with a wonky name — a terminal disclaimer — which is the subject of the proposed rule. In short, a terminal disclaimer is a stipulation made by a drug company to the PTO that a continuation or follow-on patent — essentially, a minor patent that makes few substantive changes to a medicine — will expire at the same time as the original patent.

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