The invention provides methods for obtaining compositions having antibody drug conjugates (ADCs) with specified drug to antibody ratios (DARs). Included in the invention is a method for purifying an ADC mixture having ADCs with a drug loaded species of 6 or more by contacting the mixture with a hydrophobic resin such that a composition comprising less than 15% of the 6 or more drug loaded species is obtained. The invention also provides a composition wherein 70% or more of the ADCs present have a drug loaded species of 4 or less, wherein the ADC comprises an anti-EGFR antibody and an auristatin.
