In the NAPA-2 clinical trial, the primary endpoint of 30-day open vascular surgery avoidance was achieved in 34.9% of patients receiving alfimeprase, 37.2% of patients receiving intra-thrombus (IT) placebo, and 18.4% of patients receiving peri-thrombus (PT) placebo. An interim analysis of the NAPA-3 study shows that 30-day open vascular surgery avoidance was achieved in 29.4% of patients receiving alfimeprase and 17.6% of patients receiving IT placebo. However, serious adverse events (SAE), major hemorrhage, cardiac events and infections were higher in subjects receiving alfimeprase in NAPA-2, but were higher in subject receiving IT placebo in NAPA-3.
Efficacy data from subjects with longer clots or smaller drops in alpha-2 macroglobulin, which rapidly and irreversibly inactivates alfimeprase, suggest improved retention of alfimeprase at the site of the clot might improve lysis.