Mumbai-based Sun Pharmaceuticals Ltd. has filed a post-grant opposition in respect to Indian Patent No. 208191 issued to Janssen Pharmaceutica N.V. against the mail-box Application No. 188/CAL/1995. The opposition was filed on January 02, 2008 with the Mumbai Patent Office, which last year in July (dated July 20, 2007) published the grant of the ‘191 patent under section 43(2) of the Patents Act, 1970. The ‘191 patent relates to sustained-release microparticle of risperidone.