A First in Human Study of the Safety, Tolerability, and the Physiologically Based Pharmacokinetics of XFB19 in Healthy Adult Volunteers.

Inclusion Criteria:

1. Must have given written informed consent before any study-related activities arecarried out and must be able to understand the full nature and purpose of the study,including possible risks and adverse effects.

2. Adult males and females, 18 to 55 years of age (inclusive) at screening.

3. Body mass index ≥ 18.0 and ≤ 35.0 kg/m2 with a body weight ≥ 45 kg at screening.

4. Be non-smokers (including tobacco, e-cigarettes, and marijuana) for at least 1 monthprior to first investigational drug administration.

5. Medically healthy without clinically significant abnormalities (in the opinion ofthe Investigator) at the Screening Visit and prior to dosing including:

6. Physical examination without any clinically significant findings

7. Systolic blood pressure in the range of 90 to 160 mmHg (inclusive) anddiastolic blood pressure in the range of 50 to 95 mmHg (inclusive) after 5minutes rest in supine position

8. Heart rate (HR) in the range of 40 to 100 bpm (inclusive) after 5 minutes restin supine position

9. Body temperature (tympanic or oral) in the range of 35.5°C to 37.7°C (inclusive)

10. No clinically significant findings in serum chemistry, hematology, coagulation,and urinalysis tests

11. Triplicate 12-lead ECGs (taken after the volunteer has been supine for at least 5 minutes) with QT intervals corrected using Fridericia's method (QTcF) ≤ 450msec for males and ≤ 470 msec for females and no clinically significantabnormalities

12. Female volunteers must:

13. Be of nonchildbearing potential, i.e., surgically sterilised (hysterectomy,bilateral salpingectomy, bilateral tubal ligation, bilateral oophorectomy atleast 6 weeks before screening) or postmenopausal (defined as no menses for 12months without an alternative medical cause and a follicle-stimulating hormone [FSH] level > 40 IU/L at the Screening Visit) OR

14. If of childbearing potential, must agree not to donate ova, not to attempt tobecome pregnant, and, if engaging in sexual intercourse with a male partner,must agree to use an acceptable method of contraception from the time ofsigning the participant informed consent form (PICF) until at least 30 daysafter the last dose of the study drug

15. Male volunteers must agree not to donate sperm, and, if engaging in sexualintercourse with a female partner who could become pregnant, must agree to use anacceptable method of contraception from the time of signing the consent form untilat least 30 days after the last dose of study drug.

16. Have suitable venous access for blood sampling.

17. Be willing and able to comply with all study assessments and adhere to the protocolschedule and restrictions.

Exclusion Criteria:

1. History or presence of any clinically significant (as determined by the PI)cardiovascular, pulmonary, hepatic, renal, hematological, gastrointestinal,endocrine, immunologic, dermatologic, or neurological disease, including any acuteillness or major surgery, within the past 3 months.

2. Current infection that requires systemically absorbed antibiotic, antifungal,antiparasitic, or antiviral medications.

3. Any history of malignant disease in the last 5 years (excluding surgically resectedskin squamous cell or basal cell carcinoma).

4. Presence of clinically relevant immunosuppression from, but not limited to,immunodeficiency conditions such as common variable hypogammaglobulinemia.

5. Use of or plans to use systemic immunosuppressive (e.g., corticosteroids,methotrexate, azathioprine, cyclosporine) or immunomodulating medications (e.g.,interferon) during the study or within 3 months prior to the first study drugadministration.

6. History of risk factors for torsade de pointes (including a family history of longQT syndrome or sudden cardiac death) or a known arrythmia.

7. Liver function test (LFT) results > 1.5 times the upper limit of normal (ULN) forgamma glutamyl transferase (GGT), bilirubin (total, conjugated, and unconjugated),alkaline phosphatase (ALP), aspartate aminotransferase (AST), or alanineaminotransferase (ALT). Volunteers with bilirubin, ALP and/or ALT/AST above thelimits specified may be included, at the discretion of the Investigator, if thelevels are unaccompanied by clinical signs.

8. Positive test results for human immunodeficiency virus (HIV-1 or HIV-2) antibodies,hepatitis C virus (HCV) antibodies, or hepatitis B surface antigen (HBsAg) at theScreening Visit. Patients with HCV antibodies, or HBsAg could be included if theviral load for HCV or hepatitis B are negative.

9. Positive test result for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via polymerase chain reaction or commercially validated antigen test,per site's standard clinical procedure.

10. Presence of sequelae of gastrointestinal, liver, kidney, or other conditions knownto interfere with the absorption, distribution, metabolism, or excretion of drugs.

11. Estimated creatinine clearance (CrCl) < 60 mL/min using the Cockcroft-Gault formulaor serum creatinine more than 1.5 x ULN.

12. History of substance abuse or alcohol abuse (defined as more than 10 standard drinksper week or regularly consuming more than 4 standard drinks per day where 1 standarddrink is 10 g of pure alcohol and equivalent to 285 mL beer [4.9% Alc./Vol], 100 mLwine [12% Alc./Vol], or 30 mL spirit [40% Alc./Vol]) within 12 months prior to theScreening Visit.

13. Positive drugs of abuse or alcohol breath test results at the Screening Visit or atCRU check in (Day -1) (repeat tests allowed if false positive suspected).Non-habitual use and agreement to refrain from using any THC/CBD products during thestudy is allowed.

14. Use of any prescription or over the counter (OTC) medication (including herbalproducts, diet aids, and hormone supplements) within 10 days or 5 half-lives of themedication (whichever is longer) prior to the first study drug administration,excepting use of contraceptives and occasional use of acetaminophen (up to 1 g every 8 hours or 3 g per day maximum).

15. Demonstrated clinically significant (required intervention, e.g., emergency roomvisit, epinephrine administration) allergic reactions (e.g., food, drug, or atopicreactions, asthmatic episodes) which, in the opinion of the Investigator, wouldinterfere with the volunteer's ability to participate in the study.

16. Known hypersensitivity to any of the study drug ingredients.

17. Use of any vaccinations within 10 days prior to first study drug administration.

18. For women of childbearing potential, a positive serum pregnancy test at theScreening Visit or a positive urine pregnancy test (with confirmatory positive serumpregnancy test) at CRU check-in (Day -1).

19. Currently breastfeeding.

20. Donation of blood or plasma or loss of whole blood of more than 500 mL within 30days prior to first study drug administration or receipt of a blood transfusionwithin 2 months prior to first study drug administration.

21. Participation in another clinical study of an investigational drug within 30 days or 5 half-lives of the investigational agent (whichever is longer) prior to the firststudy drug administration.

22. Any other condition or prior therapy that in the opinion of the Investigator wouldmake the volunteer unsuitable for this study, including inability to cooperate fullywith the requirements of the study protocol or likelihood of noncompliance with anystudy requirements.