David Kappos will leave his post as USPTO director early next year, calling an end to an impressive three-and-a-half year tenure.

"I believe we have made great progress in reducing the patent backlog, increasing operational efficiency and exerting leadership in IP policy domestically and internationally," Kappos wrote in an email circulated to colleagues.

According to The Hill, the technical acumen Kappos acquired in his time as head of intellectual property at IBM served him well in his latest role. Under his administration, the agency's patent backlog fell from approximately 750,000 to its current total of 605,000.

This ethic of efficiency should far outlast Kappos' tenure, as it was at the heart of landmark legislation passed in 2011. Although the America Invents Act still has several implementation stages left to clear, provisions such as first to file and the establishment of the agency's first domestic satellite offices will remain as his legacy.

The first to file transition could be among the most important marks on Kappos' record, according to the Wall Street Journal, as it brought the American patent system into closer alignment with those used by Asian and European nations.