Methods for providing a homogenous solution of lyophilized mutant diptheria toxin in dimethylsulfoxide

A method for making a homogeneous solution of mutant diphtheria toxin (mDT) in anhydrous dimethyl sulfoxide (DMSO), the method comprising:

• (a) providing a dried composition of mDT;
• and
• (b) reconstituting the dried composition to a final concentration of 10 mg/mL or less in anhydrous DMSO by adding the anhydrous DMSO to the dried composition over a time period of two minutes or less and mixing for at least 10 seconds to provide a homogenous solution comprising the mDT.