definiens: means any and all maytansinoid compounds and any and all derivatives of any such maytansinoid compounds, to theextent, in any case, Controlled by [COMPANY], including without limitation, ( a ) N2′-deacetyl - N2′-(c - 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 )