Post Grant Review, or PGR, impacts patents filed on or after March 16, 2013. A PGR challenge can be made on any ground covered by § 282(b)(2) or (3). This is a relatively new proceeding with not many challenges yet because the patent must have an effective filing date later than March 15, 2013 and also have issued as a patent. Pendency time of patent applications thus far have limited the number of patents having that criteria.
The final rules for PGR are linked below: