Considering these uncertainties and drawbacks, not to mention the extremely high rate at which final IPR decisions are finding challenged claims unpatentable, it is more important than ever for patent owners to critically evaluate the strength of their claims before asserting a patent in district court – which is likely to invite an IPR challenge at the PTO. Through voluntary ex parte reexamination, a patent owner can present additional claim limitations, as well as more specific fallback claims, to more clearly define over any additional prior art, thus creating stronger claims that stand a better chance of surviving a post-grant patentability challenge at the PTO. Similarly, a reissue application can be filed to present more narrow claims or additional fallback claims. The Federal Circuit has recognized this “fallback claim” approach as a proper use of reissue applications in its 2011 Tanaka decision. Although not always practical for larger patent portfolios, maintaining a continuing application pending at the PTO for particularly important cases can provide flexibility to adapt claim scope as new prior art challenges arise. Finally, the AIA established “supplemental examination,” allowing patent owners to request PTO review of additional prior art deemed material to patentability of previously issued claims.