The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of HS-10518 in healthy adult premenopausal females in China.

This is a double-blind, placebo-controlled, multiple-dose, single-center phase 1 study in Chinese healthy premenopausal females aged 18-45 years with a regular menstrual cycle (26-32 days). The main purpose of the study is to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of HS-10518, a gonadotropin-releasing hormone antagonist.

About 48 eligible female subjects will be enrolled. The study contains four cohorts.

In each cohort, participants will be randomly assigned to the HS-10518 arm or the placebo arm in a 3:1 ratio. HS-10518/matching placebo will be administered from Day 1 to Day 7. The study duration of each participant is up to ~10 weeks.

Inclusion Criteria:

• • Subject is a healthy premenopausal female aged 18-45 (inclusive) at Screening;

  • Subject has a body weight ≥45kg with a body mass index (BMI) of 18-28 kg/m^2 (inclusive);
  • Subject has a normal menstrual cycle for no less than 2 years (Cycle: 26-32 days, menstrual period: 2-7 days), and have a positive ovulation test in the cycle prior to drug administration;
  • Subject is willing to use highly effective, non-hormone contraceptive methods from signing the consent form until 3 months after the last dose;
  • Subject agrees to draw blood in pre-specified time points throughout the study and to attend the follow-up visit;
  • Subject is able to understand the purpose, process and potential adverse events of the study, and is willing to sign a written informed consent form.

Exclusion Criteria:

• • Subject took caffeine-rich or xanthine-rich food or drink (e.g. coffee, tea, chocolate, cola, etc.), tobacco or alcoholic products within 48 hours prior to drug administration;

  • Subject took any grapefruit, grapefruit juice or other products within 7 days prior to first dose of study drug;
  • Subject has a positive breath alcohol test or a history of alcohol abuse;
  • Subject is a heavy smoker, or smokes ≥5 cigarettes per day, or is not able to cease smoking during the study (including e-cigarette);
  • Subject has a history of drug abuse or a positive urine drug test;
  • Subject is pregnant, breastfeeding or has a positive pregnancy test at Screening