This study is a phase 1 single dose escalation study of SHR-1905 in healthy subjects and subjects with mild asthma. The purpose of the study is to evaluate the safety, tolerability and pharmacokinetics of SHR-1905 in healthy subjects and subjects with mild asthma.

Inclusion Criteria:

1. Ability to understand the trial procedures and possible adverse events, volunteers to participate in the trial, and provides written informed consent, be able to comply with all the requirements and able to complete the study.
2. Male or female aged between 18 years and 55 years (inclusive) at the date of signed consent form.
3. Total body weight ≥ 45 kg, body mass index (BMI) between 18 and 28 kg/m2 at screening.
4. For healthy subjects, no clinically significant abnormalities in medical history, general physical examination, vital signs, laboratory tests (hematology, urinalysis, blood chemistry, coagulation function and thyroid function) and ECG at the investigator's discretion during screening and baseline.

Exclusion Criteria:

1. Known medical history of severe disease in cardiovascular, liver, kidney, digestive tract, mental, nerve, hematology, metabolic disorders, etc.
2. Severe injuries or major surgeries within 6 months before screening or plan to do surgeries during the trial.
3. Positive hepatitis B virus (HBsAg), hepatitis C virus (HCV-Ab), human immunodeficiency virus (HIV-Ab) at screening.
4. Hyper/Hypotension which define as Systolic blood pressure (SBP) >140mmHg or <90mmHg, or Diastolic blood pressure (DBP)>90mmHg or <40mmHg at screening and at check in.
5. Clinically significant abnormalities in 12-Lead ECG (e.g., For male QTcF > 450msec, for female QTcF > 470msec) at screening and at check in
6. Positive alcohol breath test during baseline visit.
7. Positive nicotine test during screening.
8. Positive urine drug screen during screening.
9. Participation in clinical trials of other investigational drugs or medical devices within 3 months prior to screening or within 5 half-lives of any drugs during screening visit, or in the follow-up period of a clinical study whichever is longer (according to the date of signed consent form) which is defined as have consented and used other investigational drugs (including placebo) or trial medical devices
10. Any other circumstances that, in the investigator's judgment, may increase the risk to the subject, or associated with the subject's participation in and completion of the study or could preclude the evaluation of the subject's response