Moderate or Severe Submental Fullness

The main purpose of this study is to evaluate the safety of HY-2003 in subjects with moderate to severe submental fat accumulation at different doses and dosing frequencies in comparison with the positive control and placebo. The secondary objectives include: Evaluating the pharmacokinetic characteristics of HY-2003 after a single administration in humans and obtaining preliminary pharmacokinetic parameters; Evaluating the efficacy of HY-2003 under different doses and dosing frequencies, compared with the positive control and placebo, in the treatment of subjects with moderate to severe submental fat accumulation.