The primary purpose of this phase 3 study is to evaluate the safety and the efficacy of HS-10506 (change versus placebo) on latency to persistent sleep (LPS) and wakefulness after sleep onset (WASO) measured by polysomnography (PSG) in Chinese adult participants with insomnia disorder.

The study will comprise 4 periods : a Screening Period, a Run-in Period, a Treatment Period during which participants will be treated for 84 nights (3 month) and a minimum 3-day Follow-up Period before an End of Study (EOS) Visit. The total study duration for each participant on this study is 105-113 days.

Inclusion Criteria:

1. participants must be 18 to 65 years of age (inclusive 18, not inclusive 65);
2. participants are required to voluntarily sign the informed consent form;
3. Body mass index (BMI): BMI (weight/height2 [kg/m2]) must be in the range of 18 to 35 kg/m2 (inclusive);
4. Participants must meet Diagnostic and Statistical Manual of Mental Disorders (5th edition) (DSM-5) criteria for insomnia disorder;
5. Participants must have Insomnia Severity Index (ISI) scores ≥ 15 at screening and run-in period;
6. Subjective sleep assessment: Participants must have an sSOL≥30 minutes, sWASO≥30 minutes, and sTST < 6.5 hours for at least three nights every week within one month prior to screening; and sSOL ≥ 30 minutes, sWASO≥30 minutes, and sTST < 6.5 hours for at least 3 nights from sleep diary in the last 7 consecutive days before V2 visit and V3 visit respectively;
7. PSG: Participants must demonstrate a 2-night mean LPS ≥ 30 minutes with neither night < 20 minutes, a 2-night mean WASO ≥ 30 minutes with neither nigh < 20 minutes, and a 2-night mean TST < 7 hours.

Exclusion Criteria:

1. Has history of/current sleep-wake disorders or sleep-related breathing disorders other than insomnia disorder, such as restless legs syndrome, periodic limb movement disorder, circadian rhythm disorder, narcolepsy, rapid eye movement sleep phase (REM) behavioral disorders, and obstructive sleep apnea;
2. Has a Apnea-Hypopnea Index (AHI) ≥ 10 times/hour or periodic leg movement with arousal index (PLMAI) ≥ 10 times/hour monitored by PSG at V2 visit;
3. Has history of/current neurodevelopmental retardation, cognitive impairment, epilepsy, schizophrenia, bipolar disorder, hyperthyroidism, cancer, severe cardio-cerebrovascular diseases or respiratory diseases; or current chronic pain that affects sleep, nocturia resulting in frequent need to get out of bed to use the bathroom during the night; or clinically significant and/or unstable neurological, psychiatric, respiratory, cardiovascular, digestive, immunologic, urologic, endocrine diseases within the past 3 months prior to screening; or other systemic diseases that are inappropriate for the study;
4. Has a Hamilton Anxiety Scale (HAM-A) score ≥ 14 or Hamilton Depression Scale (HAM-D-17) score ≥ 18;
5. Has used any medication that may affect the pharmacokinetics of HS-10506 or GLP-1R-related single/multi-target drugs within the past 2 weeks or 5 half-lives of the medication;
6. Has used any medication that may affect sleep-wake function, or any other prohibited central nervous system active medications within 1 week or 5 half-lives of the medication;
7. Has received systemic hypnotherapy, cognitive behavioral therapy (CBT), or other non-pharmacological treatments for insomnia in last 4 weeks or have plans during the study;
8. Has been working across 3 or more time zones or shift work within 2 weeks prior to screening;
9. Has taken more than 3 naps per week for > 1 hour each time within the past 2 weeks prior to screening;
10. Has a risk of suicide according to the Columbia Suicide Severity Rating Scale (C-SSRS), or has a high risk of suicide at the discretion of the investigator;
11. Has a history of drug dependency or abuse within the past 1 year or showed positive in urine drug test at screening;
12. Has a history of alcohol abuse within the past 1 year or can't obey the rules of alcohol restriction;
13. Has a history of smoking ≥ 10 cigars daily within the past 3 months or can't obey the rules of cigar restriction;
14. Has a history of caffeine consumption ≥ 600 mg per day or can't obey the rules of caffeine restriction;
15. Previously participated in any clinical trial of HS-10506;
16. Has any circumstances or conditions, which, in the opinion of the investigator, may affect the participant's full participation in the study or compliance with the protocol.