A Study to Evaluate the Safety, Tolerability, and Pharmacokinetics (PK, the Measure of How the Human Body Processes a Substance) of ETX0282 When Administered Orally to Healthy Participants

This research project is being conducted to investigate the safety, tolerability, and pharmacokinetics (PK) of a single ascending dose (SAD) and multiple ascending doses (MAD) of oral ETX0282 when administered alone and in combination with cefpodoxime proxetil in healthy adult participants.

This Phase 1, single-center, double-blind, randomized, placebo-controlled study will be conducted to:

* Determine the safety and tolerability of oral ETX0282 when administered as a SAD and MAD to healthy participants;
* Determine the safety and tolerability of oral ETX0282 when administered as a single oral dose in combination with cefpodoxime proxetil to healthy participants;
* Characterize the PK in plasma and in urine of ETX0282 and ETX1317 following administration of single and multiple oral doses of ETX0282 in healthy participants; and
* Determine the PK profile in plasma and in urine of ETX0282 and ETX1317 and of cefpodoxime proxetil and cefpodoxime following administration of single oral doses of ETX0282 and cefpodoxime proxetil alone and when ETX0282 is co-administered with cefpodoxime proxetil at the same time as single oral doses in healthy participants.

Eligibility Criteria:
Inclusion Criteria:

* Aged 18 to 55 years (inclusive) for all participants except for those in Cohort 6 (in Part A); for Cohort 6, only participants aged ≥ 65 years will be enrolled.
* Be in general good health without clinically significant medical history
* Provide voluntary written informed consent prior to any study procedures and are willing and able to comply with the prescribed treatment protocol and evaluations
* Body mass index (BMI) ≥18.0 kilograms per meters squared (kg/m\^2) and ≤32.0 kg/m\^2
* Clinical laboratory values within the normal limits as defined by the clinical laboratory, unless the Principal Investigator decides that out-of-range values are not clinically significant
* Negative screen for drugs of abuse, alcohol, hepatitis B surface antigen, hepatitis C virus antibody, and human immunodeficiency virus at Screening; and drugs of abuse, alcohol predose on Day -1
* Female participants must be of non-childbearing potential (postmenopausal or with evidence of tubal ligation) or using a medically acceptable (highly effective method) contraceptive regimen and must have a negative pregnancy test at Screening (serum) and on Day -1 (urine) prior to study drug dosing. Male participants must be surgically sterile or using a medically acceptable contraceptive regimen. Men should not donate sperm during the study or for 90 days after the final dose of study medication.

Exclusion Criteria:

* History of any moderate or severe hypersensitivity or allergic reaction to any β-lactam antimicrobial (e.g., penicillin or cephalosporin)
* History of hypersensitivity or severe allergic reaction of any type to medications, bee stings, food, or environmental factors. A severe allergic reaction is defined as any of the following: anaphylaxis, urticaria, or angioedema.
* Use of prescription or over-the-counter medications within 7 days of investigational product administration, with the exception of contraceptive medications, paracetamol, oral non-steroidal anti-inflammatory agents, topical over-the-counter preparations, and routine vitamins (if they do not exceed an intake of 20 to 600 times the recommended daily dose), unless agreed as non-clinically relevant by the Principal Investigator and Sponsor
* Participation in an investigational drug or device study within 30 days before study drug dosing, i.e., there were at least 30 days between the last dose in a prior study and dose administration in this study
* Current smoker or difficulty abstaining from smoking for the duration of study confinement
* History of major organ dysfunction
* Infection or any serious underlying medical condition that would impair the participant from receiving study drug
* History of excessive alcohol intake (more than 4 standard drinks daily, on average) or use of recreational drugs within the last 3 months
* Standard donation of blood within 30 days of the study
* Concomitant disease or condition, including laboratory abnormality, which could interfere with the conduct of the study or which would, in the opinion of the Investigator, pose an unacceptable risk to the participant in this study
* Anticipated need for surgery or hospitalization during the study
* Surgery within 30 days before study enrolment
* Unwillingness or inability to comply with the study protocol for any other reason