A patent reflects a bargain between the inventor and the public. The inventor gains a time-limited monopoly over the making and use of a product. In return, the public gains the ability to make the product after the expiry of the monopoly. Regeneron obtained two patents with a priority date of 16 February 2001, EP(UK) 1 360 287 (“the ’287 Patent”) and EP (UK) 2 264 163 (“the ’163 Patent”, a divisional of the 287 Patent). Kymab’s challenge to validity arose in defence to an infringement action brought by Regeneron against Kymab’s commercialisation of its own transgenic mice, “Kymouse”. Martin
MacLean and Andrea Hadfield at Mathys & Squire demonstrate how transgenic mice claims have been found insufficient by the Court of Appeal.