Teva initially claimed the patent was invalid due to obviousness, but eventually changed its defense to inequitable conduct.

FORBES: Teva Agrees To End IP Suit Over Aricept Patent

These NPEs must uncover evidence of infringement, rule out prior art and inequitable conduct, and interact at length with the patent office.

FORBES: Not So Scary, After All: In Defense Of Patent Trolls

Essentially, the PTO assumed every instance in which inequitable conduct might be charged will necessarily result in a supplemental examination request being submitted.

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The PTO multiplied the total number of all patent applications filed by the rate at which all issued patents might potentially be subject to a charge of inequitable conduct historically.

FORBES: New Patent Regs May Inspire More Litigation, Not Less