(A) hLeptin-coil-Herceptin fusion proteins stimulate proliferation of hLeptin-dependent Ba/F3-hObR cells in a dose-dependent manner. Cells were treated with various concentrations of hLeptin, hLeptin-CDR3H-coil-Herceptin, and hLeptin-CDR3L-coil-Herceptin, and cell viability was quantified using PrestoBlue reagent; assays were performed in triplicate. (B) Body weight changes of ob/ob mice treated with hLeptin or hLeptin-coil-Herceptin fusion. Groups of mice (n = 8) were injected s.c. with vehicle, hLeptin (0.2 mg/kg or 10 nmol/kg), or hLeptin-coil-Herceptin (2 mg/kg or 10 nmol/kg) with either a single injection on day 1 or one injection per d on 2 consecutive days (day 1 and day 2) as indicated on the figure. Their body weights were monitored daily for 10 d. Arrows indicate the time points at which vehicle or proteins were injected. The body weight change compared with the initial body weight (6 d before injection) was calculated for each group. Error bars represent the standard deviation.