Filterable duocarmycin-containing antibody-drug conjugate compositions and related methods

A method, which comprises:

• (a) combining (i) an aqueous solution or a lyophilized product of an antibody-drug conjugate of formula (I):
• Ab-(L-D)m (I),
• wherein Ab is an IgG antibody, L-D is a duocarmycin linker-drug, wherein the duocarmycin linker-drug in non-conjugated form is represented by formula (IV):
• wherein n is 0-3;
• R5 is selected from
• y is 1-16;
• and
• R6 is selected from
• m represents an average DAR of from 1 to 12, and optionally further comprising the duocarmycin linker-drug in non-conjugated form, with (ii) a dilution medium that comprises water, acetonitrile, and acid to form a filterable composition, wherein said filterable composition comprises 30% to 60% (v/v) of said acetonitrile;
• and
• (b) filtering said filterable composition across a filter having a molecular weight cutoff within the range of 3 kDa to 50 kDa to form a filtrate.