Clofazimine (CFZ) is a promising drug for the treatment of NTM diseases. CFZ is highly active in vitro against M. abscessus and M. avium, the most common NTM pathogens, and shows synergy with macrolides and amikacin. The results from limited clinical studies with CFZ-based treatment regimens are promising. CFZ is currently considered an alternative drug for patients with M. avium complex infections, who are intolerant of first-line drugs. CFZ is a first-line oral drug for treatment of M. abscessus infections.

CFZ might prove to be a cornerstone in NTM treatment, but its optimal dosage is not known. The current dose for adults is 100 mg oncedaily. However, due to the complex pharmacokinetics (PK) of CFZ - it is highly protein bound, extremely lipophilic and accumulates in fatty tissues resulting in a long elimination half-life of ~30 days - it takes several months before steady state, and presumably effective, concentrations are achieved. With the use of a loading dose regimen concentrations similar to those at steady state could be reached faster, possibly leading to improved early treatment efficacy.

The overarching aim of this study is to contribute to dose optimization of CFZ in the treatment of NTM diseases. It will be an explorative, single-center, one-arm, open label, pharmacokinetic study. A number of 10 patients with pulmonary or extrapulmonary NTM disease will be included. Patients will receive a loading dose regimen of 300 mg once daily for 4 weeks and will then continue with a standard dose of 100 mg once daily until a total 4 months of treatment with CFZ.

The primary objective of this study is to describe the PK of CFZ, after 4 weeks of treatment with a loading dose regimen of 300 mg once daily, in adult patients with pulmonary or extrapulmonary NTM disease

Inclusion Criteria:

• The participant is diagnosed with pulmonary or extrapulmonary NTM disease and is eligible for treatment with CFZ
• The participant is at least 18 years of age
• The participant has a body weight (in light clothing and with no shoes) of at least 45 kg
• The participant is able and willing to provide written, informed consent

Exclusion Criteria:

• The participant is in poor general condition where participation in the study cannot be accepted per discretion of the Investigator
• There is evidence showing the participant has clinically significant metabolic, gastrointestinal, or other abnormalities that could possibly alter the PK of CFZ
• The participant is diagnosed with cystic fibrosis
• The participant has a prolongation of the QTc interval, > 450 milliseconds for males and > 460 milliseconds for females, on the screening ECG
• The participant has abnormal alanine aminotransferase (ALT) and/or aspartate transferase (AST) levels of > 3 times the upper limit of the laboratory reference range at screening
• The participant is pregnant or is using inadequate contraceptive measures (if applicable)
• The participant is breastfeeding (if applicable)
• The participant has a known or suspected, current drug or alcohol abuse, that is, in the opinion of the Investigator, sufficient to compromise the safety or cooperation of the patient
• The participant has as history of allergy/hypersensitivity to CFZ
• The participant has received clofazimine in the past 3 months before inclusion with the exception of short-term use of no more than 7 days in the period of 1 to 3 months before inclusion