Glucagon-like peptide-1 (GLP-1) mimetics are widely used for treating type 2 diabetes (T2D) with pleiotropic effects on heart and kidneys. The safety/tolerability and pharmacokinetics/pharmacodynamics ((PK/PD) of CJC-1134-PC (a long-acting GLP-1) were investigated in Chinese.Two randomized, double-blind, placebo-controlled phase I studies were conducted. Study A: 30 healthy subjects received (subcutaneously injected) a single dose (2 mg) or titrate doses (2 + 3 and 2 + 3 + 4 mg at weekly intervals) of CJC-1134-PC. Study B: 49 T2D subjects received 10 weekly doses (1, 2, 3, and 4 mg).CJC-1134-PC was well tolerated with gastrointestinal (GI) side effects. Higher doses increased the adverse events risk. CJC-1134-PC was steadily absorbed, with maximum plasma concentrations(Cmax) occurring at 36-72 h and 48 h after administration in healthy and T2D subjects, respectively. The steady-state exposures in T2D subjects increased more than the dose-proportionality(1-3 mg). The mean t1/2 ranged from 111.6 to 127.6 h. After four- five weeks of targeting doses, steady state was reached in T2D subjects with apparent accumulation effect. At week 11 for T2D subjects, HbA1c mean baseline change was significantly different than that of the placebo, and the fasting plasma glucose (FPG) was not significantly altered.The safety and PK/PD profiles of weekly CJC-1134-PC doses support Phase II studies with guidance on optimal-dose selection. Clinical trial registration: ChiCTR-IPC-15007190.