A Study to Learn About the Study Medicine Called CTB+AVP in Healthy Adult People.

The purpose of this clinical trial is to learn about the pharmacokinetics, safety and tolerability of various single- and multiple-doses of CTB+AVP in healthy adult participants. CTB+AVP is a study medicine that is being developed to treat people with complicated urinary tract infections.

This study is seeking healthy adult male and female participants, 18-60 years of age, with a body weight \> 50 kg and a BMI of 17.5 to 30.5 kg/m2.

Participants in Part-1 of the study will receive increasing single doses of CTB and/or AVP. Participants in Part-2 will receive increasing multiple doses of CTB+AVP three times a day for 7 days. The study team will monitor how each participant is doing with the study treatments via close monitoring in an in-patient setting. Experiences of people receiving CTB+AVP will be compared to those of people who do not. This will help determine if CTB+AVP is safe and well-tolerated at each dose of the study medicine.

Participants will take part in this study for a maximum of 12 weeks for Part-1 (up to 4 weeks for screening, up to 3 weeks of taking study medicine and up to 5 weeks for safety follow-up visit) and for a maximum of 10 weeks for Part-2 (up to 4 weeks for screening, up to 1 week of taking study medicine and up to 5 weeks for safety follow-up visit). During the duration of the study, blood samples for study medicine levels, and various measures for monitoring safety such as blood samples for clinical laboratory measurements, electrocardiograms and vital sign measurements will be taken.

This is a 2-part study in healthy male and female adult participants.

Part-1 is to evaluate safety, tolerability and pharmacokinetics (PK) of 3 planned and 2 optional doses in 8 participants, in a 5-period sequential single dose design.

Part-2 is to evaluate safety, tolerability and PK of 1 planned and 2 optional cohorts in 8 participants each, in a multiple dose sequential design, with 7 days of repeated every 8 hours (q8h) dosing in each cohort. In addition, 2 optional cohorts in 6 participants each of Japanese descent and Chinese descent will also receive multiple doses of CTB+AVP repeated every 8 hours (q8h) for 7 days.

Eligibility Criteria:
Inclusion Criteria:

1. BMI of 17.5 to 30.5 kg/m2; and a total body weight \>50 kg (110 lb)
2. For optional Japanese cohort only: Japanese participants who have 4 Japanese biologic grandparents who were born in Japan
3. For optional Chinese cohort only: Chinese participants who were born in mainland China, and both parents are of Chinese descent.

Exclusion Criteria:

1. Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurological, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at the time of dosing)
2. Known allergy to the cephalosporin group of antibiotics
3. History of HIV infection, hepatitis B, or hepatitis C; positive testing for HIV, HBsAg, or HCVAb. Hepatitis B vaccination is allowed
4. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality \[or other conditions or situations related to COVID-19 pandemic (eg, Contact with positive case, residence, or travel to an area with high incidence)\] that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study
5. A positive urine drug test
6. Positive test result for SARS-CoV-2 infection at the time of screening or Day -1