The present invention provides methods of reducing nonprocessed Factor VIII or a chimeric polypeptide comprising Factor VIII comprising co-transfecting in a host cell a polynucleotide encoding Factor VIII with a polynucleotide encoding a protein convertase, where the endogenous processing enzymes of the host cell are insufficient to convert all of the Factor VIII to its processed isoform; expressing a proprotein convertase from a second polynucleotide in the host cell; and reducing the nonprocessed Factor VIII by processing with said proprotein convertase.