Modified SERPINs are antithrombotic in vivo. Mice (n = 7 per group) were anesthetized, after which the carotid artery was exposed. Mice were pretreated with SERPINs via IV injection (8 mg/kg α1AT variant or 16 mg/kg rC1INH [to correct for SERPIN molecular weights]), after which thrombus formation was initiated by a topical application of FeCl₃ (5% wt/vol). Vascular occlusion was monitored by a Doppler flow probe up until 40 minutes. The number of mice with patent carotid arteries after 40 minutes is indicated above the groups. rC1INH, recombinant C1INH. Data are represented as scatterplots with medians. *P < .05, compared with vehicle by Mann-Whitney Student t test.