This is a single-centre, open-label, non-randomized, single dose study in healthy male subjects designed to assess mass balance recovery, metabolite profile and metabolite identification of radio-labeled BC-3781 administered via the intravenous or oral routes.

This is a single-centre, open-label, non-randomised, single dose study to assess the pharmacokinetics, mass balance recovery, and metabolite profiling and identification following administration of iv or oral 14C-BC-3781 to healthy male subjects It is planned to enrol 2 cohorts of 5 subjects or 10 subjects in total. The active substance being investigated in this study is radiolabeled lefamulin ([14C] BC 3781), present in the investigational medicinal products (IMPs) as the acetate salt ([14C]-BC-3781.Ac).

Subjects assigned to Cohort A will receive a single IV administration of 14C-BC-3781 containing 150 mg BC-3781 and not more than (NMT) 4.3 MBq (117 µCi) 14C, administered as an infusion over 60 min after a light breakfast.

Subjects assigned to Cohort B will receive a single oral administration of 14C-BC-3781 containing 600 mg BC-3781 and NMT 4.1 MBq (112 µCi) 14C, in the fasted state

Inclusion Criteria:

• Healthy males
• Aged 30 to 65 years
• Body mass index of 18.0 to 35.0 kg/m2, inclusive
• Must have regular bowel movements
• Must provide written informed consent
• Must agree to use an adequate method of contraception

Exclusion Criteria:

• Subjects who have received any IMP in a clinical research study within the previous 3 months
• History of any drug or alcohol abuse in the past 2 years
• Regular alcohol consumption in males >21 units per week and females >14 units per week
• Radiation exposure, including that from the present study, excluding background radiation but including diagnostic x-rays and other medical exposures, exceeding 5 mSv in the last 12 months or 10 mSv in the last 5 years. No occupationally exposed worker, as defined in the Ionising Radiation Regulations 1999, shall participate in the study
• Subjects who do not have suitable veins for multiple venepunctures/cannulation as assessed by the investigator at screening
• Subjects who have been dosed in an ADME study in the last 12 months
• Clinically significant abnormal biochemistry, haematology or urinalysis as judged by the investigator
• Positive drugs of abuse test result at screening and admission
• Positive hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (HCV Ab) or human immunodeficiency virus (HIV) results
• Evidence of renal impairment at screening, as indicated by an estimated creatinine clearance (CLcr) of <90 mL/min using the Cockcroft-Gault equation
• Significant history of cardiovascular, renal, hepatic, chronic respiratory or gastrointestinal disease, or psychiatric disorders as judged by the investigator
• A familial history or presence of Long QT syndrome
• Subjects with QT interval corrected according to Fridericia's formula (QTcF) >480 ms
• A serum potassium level of less than 3.5 mmol/L at screening
• Serious adverse reaction or serious hypersensitivity to any drug or the formulation excipients
• Presence or history of clinically significant allergy requiring treatment, as judged by the investigator.
• Donation or loss of greater than 400 mL of blood within the previous 3 months
• Have taken medications known to be strong P-gp inhibitors, or strong CYP3A4 inducers or inhibitors, within 28 days before IMP administration
• Subjects who are taking, or have taken, any prescribed or over-the-counter drug (other than 4 g per day paracetamol or herbal remedies) in the 14 days before IMP administration

open label