BAL2420 (also known as BAL0302420) is being developed as an antibacterial agent for the treatment of severe infections caused by Gram-negative bacteria. In this study, the sponsor aims to investigate the safety, tolerability and pharmacokinetics (PK) of BAL2420 following administration of single ascending doses (Part A) and multiple ascending doses (Parts B and C) in healthy adult volunteers. In all parts of the study, in each cohort, a different dose of study drug is to be investigated against a matched placebo in a randomized and double-blind manner.

Inclusion Criteria:

• Body mass index: 18.0 to 30.0 kg/m2, inclusive, at screening
• Total body weight: > 50 kg at screening

Exclusion Criteria:

• Any uncontrolled or active major systemic disease,
• Active infection
• Acute illness within 5 days prior to the first study drug administration that, in the opinion of the Investigator, may impact safety assessments.
• Clinically-significant physical examination, vital signs, laboratory safety tests, or ECG abnormalities
• History of risk factors for QT prolongation or Torsades de Pointes
• QTcF (Fridericia's corrected QT interval) > 450 msec (males) and > 470 msec (females) at screening.
• Receipt of prescribed medication other than hormonal contraceptives within the 30 days prior to admission to the clinical site.
• Receipt of over-the-counter medication, vitamin preparations and other food supplements, or herbal medications (e.g., St. John's wort) within 14 days prior to admission to the clinical site.
• History of relevant drug and/or food allergies, particularly to antibiotics.
• History of tobacco use or e-cigarette within the past 6 months prior to the first study drug administration.
• History of alcohol abuse or drug addiction (including soft drugs like cannabis products) within 12 months prior to screening.
• Average intake of more than 24 units of alcohol per week: one unit of alcohol equals approximately 250 mL of beer, 100 mL of wine, or 35 mL of spirits.
• Positive screen for hepatitis B surface antigen, hepatitis B core antibodies, hepatitis C virus antibodies, human immunodeficiency virus 1 and 2 antibodies, or syphilis at screening. Note: Hepatitis B vaccination is allowed.