The USPTO confirmed on Monday that Kappos, who was appointed in 2009, will leave his position at the end of January 2013.
High-profile figures in the patent community described Kappos as one of the most successful directors in recent USPTO history.
In particular, he will be remembered for overseeing the implementation of the America Invents Act (AIA) and substantially reducing the patent backlog. Over the past two years, the number of patent examiners has increased by 30% to over 8,000.
Reactions from the patent community
Judge Paul Michel, retired chief judge of the Federal Circuit, described Kappos as "the strongest USPTO leader we have had in at least a generation". "David Kappos rescued the patent office from the declining performance and growing dysfunction of several previous administrations," he said.
"He took the job out of patriotism and generosity at an enormous salary cut and he worked 18 hours a day for three and a half years, so everyone who cares about innovation and the patent system has to salute him for that."
Michel suggested that the director's decision may have been prompted by the taxing schedule, a desire to spend more time with family and attainment of his key goals.
But he also credited Kappos with putting in place a "highly talented" leadership team which will be able to continue to handle critical tasks after his departure, provided that Congress does not cut the organisation's funding.
Philip Johnson, a member of the industry lobbying body the Coalition for 21st Century Patent Reform, said Kappos has built "a stellar reputation" in the patent community.
"A public service job of that kind and the energy that he put into it might be something that might be difficult to sustain for a long period of time," he said.
"I would commend him because the office was given a massive job in rewriting regulations in a very short period of time."
Former USPTO director Q Todd Dickinson, who is now the executive director of the American Intellectual Property Law Association (AIPLA), told Managing IP: "We're very saddened to see Director Kappos resign, but understand that there is a time for these things and individuals need to do what's right for them."
He said Kappos's tenure was "marked by great successes", such as improving efficiency, beginning the implementation of the AIA, restarting harmonisation discussions and helping to restore the USPTO's relationship with the patent community.
Possible replacements for Kappos
Deputy director Teresa Stanek Rea will take over as acting director when Kappos leaves. No official announcement has been made about who will replace him permanently, but Rea is one of several potential candidates. Rea lacks Kappos's extensive corporate management experience as the former vice president and assistant general counsel of IP for IBM. But sources describe her as "a very able lawyer and a very good deputy" who "deserves to be considered" for the role.
A spokesperson for the USPTO said that the next two months would be "business as usual" for the USPTO, and that "no projects or plans are being adjusted as a result of his announcement".
Sources have also recommended Robert Armitage, who recently retired as senior vice president and general counsel at Eli Lilly, as a good candidate for the job.
Armitage "has led almost every major IP organisation" around and "has been a great friend to the patent office", they said.
When contacted by Managing IP for a reaction to the news of Kappos's resignation, Armitage said: "The global IP community should take the opportunity of Dave's announcement to stand back, admire, and then consciously celebrate his many accomplishments over the past four years. Their collective importance, domestically and internationally, stands unequalled by Dave's predecessors.
"While his accomplishments obviously speak for themselves, the manner in which the Dave has achieved them - with an openness, inclusiveness and candour - merit special accolades. They represent a government agency working with its diverse constituencies at its very best."
