HIT IC-mediated thrombocytopenia in vivo. HIT model mice were divided into sex- and weight-matched experimental and control groups and treated with the HIT-like antibody KKO (20 mg/kg body weight, intraperitoneally) on day 0. On days 1 through 7, experimental mice received PRT318 (30 mg/kg body weight) orally via gavage twice a day, whereas control mice received vehicle only (sterile water). Both groups received heparin (1400 U/kg, subcutaneously) once daily on days 1 to 7. Blood was collected 3 days before the antibody injections for baseline values and then on days 1 through 7 after antibody injections. Platelet counts were monitored over time to assess thrombocytopenia. (A) Time course of platelet counts expressed as percentage of baseline values. (B) Nadir platelet counts expressed as percentage of baseline values. □ represents control (vehicle only); and ■, PRT treated. n = 6 for each group. *P < .002.