This Phase 1a Study Will Evaluate the Safety, Tolerability, Pharmacokinetics (PK), and Relative Bioavailability of Single-dose DMI019 Nasal Spray in Healthy Participants.

Inclusion Criteria: 1. Participants who fully understand the study, voluntarily agree to participate, and provide written informed consent before any study-related procedures are performed. 2. Chinese male or female participants aged 18 to 45 years, inclusive. 3. Male participants with a body weight of at least 50.0 kg and female participants with a body weight of at least 45.0 kg, with a body mass index (BMI) of 18.5 to 28.0 kg/m², inclusive. 4. From the time of signing the informed consent form until 3 months after the last administration of the study intervention, the participant and the participant's partner must have no plans for pregnancy, sperm donation, or egg donation. Participants must agree to use at least one non-pharmacological method of contraception from the time of signing informed consent until the last pharmacokinetic blood sample is collected and to use an effective method of contraception for 3 months after the last administration of the study intervention. 5. Participants who are able to communicate effectively with the investigator, correctly use the nasal spray device after training, and understand and comply with all study requirements. Exclusion Criteria: 1. Known hypersensitivity to the study intervention or any of its components, or a history of severe allergic constitution, defined as known allergy to three or more drugs or foods. 2. Inability to comply with the standardized dietary requirements of the study. 3. Inability to tolerate venipuncture or a history of fainting associated with needles or blood. 4. A history or current presence of a clinically significant disease of the cardiovascular, endocrine, neurological, gastrointestinal, respiratory, urinary, ophthalmological, hematological, immunological, psychiatric, or metabolic system, including hypokalemia, atopic allergic disease, psychiatric disorders, or disorders of brain function, that in the investigator's judgment makes the participant unsuitable for the study. 5. A history of hypertension or hypotension, including orthostatic hypotension. 6. A clinically significant nasal medical history, disease, or abnormality that, in the investigator's judgment, may affect administration or absorption of the study intervention, including: 1. A history of persistent nasal congestion, rhinorrhea, epistaxis, or similar symptoms; 2. A history of nasal surgery, nasal trauma, severe rhinitis, or severe sinusitis that may affect drug absorption; 3. Any other structural abnormality of the nasal cavity or abnormality of the nasal mucosa that may affect drug absorption. 7. Major surgery within 6 months before screening or planned surgery during the study, except for appendectomy or hernia repair. 8. Clinically significant abnormalities identified at screening through physical examination, vital signs, 12-lead electrocardiogram, posteroanterior chest X-ray, or laboratory testing, including hematology, urinalysis, serum chemistry, coagulation tests, or testing for transfusion-transmitted infections. This includes alanine aminotransferase, aspartate aminotransferase, or gamma-glutamyl transferase above the upper limit of normal; total bilirubin greater than 1.2 times the upper limit of normal; or serum creatinine greater than 1.2 times the upper limit of normal. 9. Uncontrolled ventricular arrhythmia at screening; corrected QT interval using Fridericia's formula (QTcF) of at least 450 milliseconds in male participants or at least 460 milliseconds in female participants; a history of long QT syndrome; or any concomitant condition that may prolong the QT interval. 10. Consumption of more than 5 cups per day of tea, coffee, or other caffeine-containing beverages within 3 months before screening, with each cup defined as approximately 200 mL. 11. Consumption within 48 hours before the first administration of the study intervention of a special diet or products that may affect drug absorption, distribution, metabolism, or excretion, including grapefruit or grapefruit-containing products, chocolate, caffeine-containing products, or foods rich in xanthines such as animal liver; strenuous exercise during this period; or any other factor that may affect drug pharmacokinetics. 12. Use within 30 days before the first administration of the study intervention of any drug known to induce or inhibit hepatic drug metabolism. Examples include inducers such as barbiturates, carbamazepine, phenytoin, glucocorticoids, and omeprazole, and inhibitors such as selective serotonin reuptake inhibitors, cimetidine, diltiazem, macrolides, nitroimidazoles, sedative-hypnotics, verapamil, fluoroquinolones, and antihistamines. 13. Pregnant or breastfeeding women. 14. Use of any prescription drug, over-the-counter drug, traditional Chinese medicine, herbal product, dietary supplement, or health product within 14 days before the first administration of the study intervention. 15. Habitual smoking, smoking at least 5 cigarettes per day within 3 months before screening, a positive nicotine test at screening, or inability to abstain from smoking throughout the study. 16. Consumption of more than 14 standard units of alcohol per week within 6 months before screening, where one standard unit contains 14 g of alcohol and is approximately equivalent to 360 mL of beer, 45 mL of 40% spirits, or 150 mL of wine; a positive alcohol breath test before the first administration of the study intervention; or inability to abstain from alcohol throughout the study. 17. A history of drug abuse within 1 year before screening, including abuse of cannabis, benzodiazepines, ketamine, morphine, cocaine, methamphetamine, barbiturates, or tricyclic antidepressants, or a positive urine drug screen. 18. Participation in another clinical study involving administration of an investigational drug or use of an investigational device within 3 months before screening. 19. Donation or loss of at least 400 mL of blood within 3 months before screening; planned donation of blood or blood components during the study or within 3 months after study completion; receipt of a live attenuated vaccine within 28 days before the first administration of the study intervention; receipt of an inactivated vaccine within 14 days before the first administration; or planned vaccination during the study. 20. Any other medical or psychological condition that, in the investigator's judgment, may expose the participant to excessive risk, interfere with compliance with the protocol, or affect the participant's ability to complete the study.