Researchers have initiated a phase 1 study to assess the safety and pharmacokinetics of intravenous and oral formulations of lefamulin, an antimicrobial agent used to treat patients with acute exacerbations of cystic fibrosis due to Staphylococcus aureus infection.

Exacerbations of cystic fibrosis are a constant cause of hospitalization for patients with the disease. One of the causes of acute exacerbations is microbial infections, and studies indicate that Staphylococcus aureus is one of the primary causative pathogens. 

Due to a lack of treatment guidelines, many physicians opt to use unapproved antibacterial agents. Some of the treatments suggested in medical literature can only be administered intravenously and have limited data on safety and tolerability. 

Cystic fibrosis transmembrane regulator (CFTR) modulators have improved clinical outcomes for patients with cystic fibrosis, particularly in terms of lung function, and have a significant impact on quality of life. However, there is limited data on the impact of the concomitant use of CFTR modulators and antibacterial agents. 

Read more about cystic fibrosis etiology

Nabriva Therapeutics AG is hence conducting an open-label, crossover study involving 12 participants with cystic fibrosis to investigate the safety and pharmacokinetics of lefamulin, which is marketed as Xenleta®.

The participants have been divided into 2 groups. The first group will receive a single 150 mg dose of intravenous lefamulin, followed by a single 600 mg dose of oral lefamulin. The second group will receive a single 600 mg dose of oral lefamulin, followed by a single 150 mg dose of intravenous lefamulin. 

The primary outcome measure of this trial is the plasma pharmacokinetic parameters of lefamulin, as well as that of its main metabolite, BC-8041. The study started on March 1, 2022, and patient enrollment was recently completed. Nabriva expects to release topline data in early 2023, and the study is expected to be completed on June 30, 2023. 


Study to assess the safety and PK of oral and IV Xenleta in adults with cystic fibrosis. February 7, 2022. Updated March 18, 2022. Accessed August 12, 2022.

Nabriva Therapeutics completes patient enrollment in phase 1 Trial of Xenleta® (lefamulin) in adult patients with cystic fibrosis. News release. Nabriva Therapeutics; August 15, 2022.