The primary purpose of this phase Ⅰb/Ⅱ study is to investigate the safety, tolerability, pharmacokinetics (the study of the way a drug enters and leaves the blood and tissues over time) after multiple dose administration and the efficacy of HS-10506 (change versus placebo) on latency to persistent sleep (LPS) measured by polysomnography (PSG) in Chinese adult participants with insomnia disorder.

This study consists of two stages: phase Ib and phase II. Primary objective of phase Ib Study is to assess the safety, tolerability of HS-10506 in subjects with insomnia disorder. .

Primary objective of phase II Study is to assess the efficacy of HS-10506 in subjects with insomnia disorder.

Inclusion Criteria:

1. Subjects must be 18 to 64 years of age, inclusive
2. Subjects are required to voluntarily sign the informed consent form;
3. Body mass index (BMI): for phase Ib, males must weigh at least 50 kilogram (kg), females at least 45 kg, and BMI (weight/height2 [kg/m2]) must be in the range of 18 to 30 kg/m2 (inclusive) for both gender; for phase II, BMI must be in the range of 18 to 35 kg/m2 (inclusive);
4. Participant 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 baseline;
6. Subjective sleep assessment: for phase Ib, subjects must have a self-reported sleep latency (sSOL) >= 30 minutes, a subjective sleep awakening time (sWASO) >= 30 minutes, and a subjective total sleep time (sTST) =< 6.5 hours using the sleep diary for at least three nights every week in the last 1 month prior to screening; For phase II, subjects 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 days;
7. PSG: for phase Ib, participants must demonstrate an LPS >= 20 minutes, TST < 420 minutes, and WASO >= 30 minutes at screening; for phase II, participants must demonstrate a 2-night mean LPS >= 30 minutes with neither night < 20 minutes, a 2-night mean TST =< 6.5 hours with neither night > 7 hours and a 2-night mean WASO >= 30 minutes with neither nigh < 20 minutes.

Exclusion Criteria:

1. Has history of or 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 hypopnea index (AHI) >10 times/hour or periodic leg movement index (PLMI) >10 times/hour monitored by PSG at screening or run-in period;
3. Has history of or current neurodevelopmental retardation, cognitive impairment, epilepsy, schizophrenia, bipolar disorder, hyperthyroidism, cancer, severe cardio-cerebrovascular diseases or respiratory diseases; 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. (For phase II only) Has a Hamilton Anxiety Scale (HAMA) score >= 14 or Hamilton Depression Scale (HAMD-17) score >= 18;
5. Use of any medication that may affect the pharmacokinetics of HS-10506 within the past 2 weeks or 5 half-lives of the medication;
6. Use of 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. Working across 3 or more time zones or shift work within 2 weeks prior to screening;
9. Regularly naps 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. Any circumstances or conditions, which, in the opinion of the investigator, may affect the subject's full participation in the study or compliance with the protocol.