NCT07514338

Open Label Extension to Assess Long Term Safety and Efficacy of KL1333 in Patients With Primary Mitochondrial Disease

An Open-label, Single-arm Extension Study to Evaluate the Long-term Safety, Tolerability, and Efficacy of KL1333 (Napazimone) in Patients With Primary Mitochondrial Disease

• Status: Not Yet Recruiting
• Phase: Phase 2
• Study type: Interventional
• Enrollment: 140 (estimated)
• Sponsor: Pharming Technologies B.V. · Industry
• Sex: All
• Age: 18 Years
• Healthy volunteers: Not accepted

Summary

The purpose of this study is to investigate if the study medicine, KL1333, is safe, well-tolerated and effective long-term in improving the symptoms of fatigue and impacts on daily living and functional capacity (physical abilities) in people with PMD.

Detailed description

This is a 12-month open-label extension (OLE) study to evaluate the safety, tolerability, and efficacy of KL1333 in subjects previously treated with KL1333 or placebo in Study KL1333-2020-104A (hereafter referred to as FALCON). Subjects can be enrolled in this extension study either directly at the FALCON study completion visit (FALCON Week 48) or the safety follow-up visit (FALCON Week 53) or later in time. Subjects who previously received KL1333 in FALCON will receive retreatment whereas subjects previously treated with placebo will be treatment naïve to KL1333. The study consists of a screening visit (if the subject rolls over directly from the FALCON study completion visit \[FALCON Week 48\] or the safety follow up visit \[FALCON Week 53\], the screening visit is coincident with the visit), a 48-week treatment course with KL1333 up to 100 mg/day, a completion visit (end of treatment; EoT) and approximately 5 weeks of follow up, including the end of study (EoS) visit. The treatment period may extend beyond 48 weeks until the study drug is commercially or otherwise available, in which case the EoT visit will occur later than Week 48. Periodic safety monitoring visits (phone visits every 4 weeks after Week 48 and clinic visits every 24 weeks after Week 48) will continue for subjects who receive KL1333 in the optional extended treatment period until the study drug is commercially or otherwise available.

Conditions

• Mitochondrial Diseases

Interventions

Type	Name	Description
DRUG	Napazimone	Product: KL1333 (international nonproprietary name: napazimone) Dose: Each subject will be up-titrated to his/her maximum well tolerated dose. The starting dose will be 25 mg KL1333 twice daily (BID; total daily dose of 50 mg). If KL1333 is considered to be well tolerated after 4 weeks of treatment, the dose will be increased to 50 mg KL1333 BID (total daily dose of 100 mg). The dose may be lowered from 50 mg BID to 25 mg BID at the investigator's discretion throughout the study in case of tolerability issues. Frequency: Twice daily Route: Oral

Timeline

• Start date: 2026-06-09
• Primary completion: 2029-03-31
• Completion: 2029-03-31
• First posted: 2026-04-07
• Last updated: 2026-04-07

Regulatory

• FDA-regulated drug study