This case relates to Patent 97126347.7 entitled “a method for preparing a pharmaceutical composition for treating or preventing hypertension”, which was filed on February 21, 1992 by Daiichi Sankyo Company Limited and granted on September 24, 2003.

Claim 1 as granted of the subject patent can be read as:

A method for preparing a pharmaceutical composition for treating or preventing hypertension, comprising mixing an antihypertensive agent with a pharmaceutically acceptable carrier or diluent, wherein the antihypertensive agent is at least one compound as represented by Formula (I) or a pharmaceutically acceptable salt or ester thereof,

wherein:

R¹ represents alkyl having 1-6 carbons;

R² and R³ are identical or different and each represent alkyl having 1-6 carbons;

R⁴ represents:

hydrogen; or
      alkyl having 1-6 carbons;

R⁵ represents carboxyl, COOR^5a or –CONR⁸R⁹, wherein R⁸ and R⁹ are identical or different and each represent:

       Hydrogen;
       unsubstituted alkyl comprising 1-6 carbons;
       alkyl comprising 1-6 carbons and substituted with carboxyl or carbalkoxy having 1-6 carbons in its alkyl moiety; or

R⁸ and R⁹ together represent alkylene having 2-6 carbons and substituted with one carbalkoxy having 1-6 carbons in its alkyl moiety;

and wherein R^5a represents:

       alkyl having 1-6 carbons;
      alkylacyloxyalkyl, wherein its alkylacyl moiety and alkyl moiety each comprise 1-6 carbons;
      carbalkoxyoxyalkyl, wherein its alkoxy moiety and alkyl moiety each comprise 1-6 carbons;
      (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl; or
      2-benzo[c]furanonyl;

R⁶ represents hydrogen; and
R⁷ represents carboxyl or tetrazol-5-yl.

Beijing Winsunny Harmony filed a request for invalidation against this patent before the Patent Reexamination Board on April 23, 2010, alleging that, among others, claim 1 does not possess inventiveness.

In reply to the request for invalidation, the patentee amended claim 1 by, among others, deleting “alkyl having 1-6 carbons” from the definition of R⁴, and other options except carboxyl and COOR^5a wherein R^5a represents (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl from the definition of R⁵.