A Phase 2 interventional study of Napazimone in Mitochondrial Diseases, sponsored by Pharming Technologies B.V.. Recruiting at 23 sites in 9 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-16.
Sponsored by Pharming Technologies B.V. (part of Pharming Group N.V.) · Phase 2, Interventional, and Treatment
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.
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.
189 studies on the registry are indexed under Mitochondrial Diseases; 60 are open to participants now.
This study's planned enrollment of 140 is above the median of 35 across 114 interventional studies indexed under Mitochondrial Diseases.
Browse Mitochondrial Diseases studies →Pharming Technologies B.V. is the lead sponsor of 22 studies on the registry; 3 are open to participants now.
Of its 5 completed or terminated interventional studies of FDA-regulated products, 3 (60%) have results posted.
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Exclusion Criteria:
Subjects not enrolling directly at the FALCON study completion visit (FALCON Week 48) or the safety follow-up visit (FALCON Week 53) study will be required to fulfill the additional exclusion criteria below during the screening visit:
Subjects will receive medication twice a day for 48 weeks minimum
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
Also known as: KL1333
Adverse events
Number of adverse events will be monitored throughout the study for all subjects
Time frame: Through study at least for 48 weeks
Physical examination
The following parameters and body systems will be examined and any abnormalities described: height and weight; general appearance; skin; head, ears, eyes, nose, and throat; lungs; heart; lower extremity examination; abdomen; neurologic and lymph nodes. Any clinically significant changes from baseline should be recorded as AEs.
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Vital signs
Body temperature, systolic and diastolic cuff blood pressure, pulse rate and pulse oximetry will be measured and any clinically significant changes from baseline should be recorded as AEs.
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Electrocardiogram
Changes from baseline of ECG parameters will be evaluated.
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Safety laboratory - blood chemistry
Monitoring of the clinically significant laboratory results for sodium, potassium, chloride, bicarbonate/carbon dioxide;, blood urea nitrogen, serum creatinine, glucose, albumin, total protein, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, total bilirubin, direct bilirubin, indirect bilirubin, calcium, gamma-glutamyl transferase, creatine kinase
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Safety laboratory - urinalysis
Monitoring of the clinically significant laboratory results for specific gravity, pH, semi-quantitative "dipstick" evaluation of glucose, protein, bilirubin, ketones, leukocytes, blood microscopy and/or culture to be performed if clinically indicated or if urinalysis results positive.
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Safety laboratory - hematology
Monitoring of the clinically significant laboratory results for Hemoglobin, hematocrit, white blood cell with differentials (monocytes, eosinophils, basophils, neutrophils, lymphocytes) as an absolute value, red blood cell count, platelet count, C-reactive protein
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Occurence of metabolic decompensation and lactic acidosis or image-verified stroke-like episodes consequent to GI AE and AESIs
These events will be monitored throughout the study.
Time frame: Through study at least for 48 weeks
Columbia Suicide Severity Rating Scale (C-SSRS)
C-SSRS assesses suicidal ideation and behavior risk through a series of questions to assess for suicidal ideation and behavior, the severity and immediacy of the risk, and the level of support the subject may need. C-SSRS Severity of Ideation scores of 4 or 5 are considered SAEs.
Time frame: At Baseline Week 0
Patient-reported mitochondrial fatigue
Patient-Reported Outcomes Measurement Information System® Fatigue PMD short form. The PROMIS® Fatigue PMD short form consists of 9 items. Each item has numerical rating scale (NRS) response options consisting of never (1), rarely (2), sometimes (3), often (4), and always (5).
Time frame: Through study at least for 48 weeks
Functional outcome
30 seconds sit-to-stand test
Time frame: At Baseline Week 0, Week 4, Week 24 and Week 48
Patient-reported lower extremity function
Neuro-QOL Lower Extremity Function (Mobility) - short form. It is a reliable and validated brief 8-item survey of one's ability to carry out various activities involving the lower limb/trunk region and increasing degrees of bodily movement. Each item has numeric rating scale (NRS) response options consisting of Without any difficulty (5), With a little difficulty (4), With some difficulty (3), With much difficulty (2), and unable to do (1).
Time frame: At Baseline Week 0, Week 4, Week 12, Week 24, Week 36 and Week 48
Other patient-reported outcome - Patient Global Impression (multiple)
The Patient Global Impression of Severity is rated on a 4-point NRS, assessed on a scale ranging from 1 (none) to 4 (severe) for severity. The Patient Global Impression of Change is rated on a 5-point numeric rating scale (NRS), with the change from baseline assessed on a scale ranging from 2 (much better) to -2 (much worse), with 0 indicating no change from baseline.
Time frame: At Baseline Week 0, Week 4, Week 12, Week 24, Week 36 and Week 48
Other patient-reported outcomes - 5-level EuroQol-5 Dimension
The EQ-5D-5L includes items addressing mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. The scale yields a single score on a 0 to 100 scale.
Time frame: At Baseline Week 0, Week 4, Week 12, Week 24, Week 36 and Week 48
Global impression of severity of PMD disease expression
Clinician Global Impression of PMD - severity and change
Time frame: At Baseline Week 0, Week 24 and Week 48
Assessments of mitochondrial disease progression
Newcastle Mitochondrial Disease Adult Scale, Subscales I-III
Time frame: At Baseline Week 0, Week 24 and Week 48
Mitochondrial diabetes, subgroup analysis
Glycated hemoglobin (HbA1c, in subjects with diabetes)
Time frame: At Baseline Week 0, Week 24 and Week 48
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Studies of the drug tested here: Napazimone