An allegation was made of infringement of a patent on ambicillin. The ‘pith and marrow’ approach resulted in the marketing of hetacillin, which was a reproduction of the substance ampicillin, albeit temporarily masked, constituting an infringement of the ampicillin patent. Infringement was established. iI was obvious to a person skilled in the art that the temporary masking of the ampicillin was an immaterial variant which did not result in the variant falling outside the claims. Thus, the variant, hetacillin, did not have a material effect upon the way the invention worked (the first Improver question) and that would have been obvious at the relevant time to the reader skilled in the art (the second Improver question). Accordingly, the variant was not intended to fall outside the claim (the outcome of the third Improver question).
Lord Diplock rejected a submission that the increasing particularity with which claims were drafted had made the doctrine of pith and marrow obsolete, and said that the doctrine ‘still remains a part of patent law’.
Lord Diplock, Lord Simon
 RPC 153,  FSR 215
England and Wales
Cited – Eli Lilly v Actavis UK Ltd and Others SC 12-Jul-2017
The issue raised on this appeal and cross-appeal is whether three products manufactured by Actavis would infringe a patent whose proprietor is Lilly, namely European Patent (UK) No 1 313 508, and its corresponding designations in France, Italy and . .
These lists may be incomplete.
Updated: 23 February 2021; Ref: scu.631410