definiens: shall mean any and all maytansinoid compounds and any and all derivatives ofany such maytansinoid compounds, to the extent, in any case, Controlled by [COMPANY], including without limitation,(a ) N2’-deacetyl - N2’-(3 - mercapto-1 - oxopropyl)-maytansine ( CAS No . 139504 - 50 - 0 ) ( commonly referred to as DM1 ) ; ( b)N2’-deacetyl - N2-(4 - mercapto-1 - oxopentyl)-maytansine ( commonly referred as DM3 ) ; and ( c ) N2’-deacetyl - N2-(4 - mercapto-4 - methyl-1 - oxopentyl)-maytansine ( commonly referred as DM4 )