definiens: means, with respect to a particular compound : ( a ) prodrugs and active metabolites thereof ( provided in the case of active metabolites that such metabolites arethemselves MEK Modulators ) ; ( b ) all stereoisomers and diastereoisomers thereof and of the compounds described in Sections ( a ), ( c ), ( d ), ( e ) and ( f ) ; ( c ) all tautomers, including purified tautomers, the corresponding tautomeric mixtures and any combination oftautomers in any degree of tautomeric purity thereof and of the compounds described in Sections ( a ), ( b ), ( d ), ( e ), and(f ) ; ( d ) all salt forms and esters thereof and of the compounds described in Sections ( a ), ( c ), ( e ), and ( f ) ; ( e ) all crystal and amorphous forms thereof and of the compounds described in Sections ( a ), ( d ) and ( f ) ; and ( f ) all derivatives of such compound or the compounds described in Sections ( a ), ( b ) and ( c ) consisting of one or moreatoms substituted with a radio isotope of the same element ( including derivatives containing deuterium substitutedfor hydrogen )