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KL1333

Phase 2

Primary Mitochondrial Disease | Small molecule | Other |Pharming Group N.V.|Last Updated: Jun 26, 2026

Success Probability

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials1
Total Enrollment180

FDA Designations

No designations recorded

Clinical trial landscape

KL1333 · 3 trials · 6 indications

Phase 2 1Phase 1 2
NCT05650229Efficacy of KL1333 in Adult Patients With Primary Mitochondrial DiseasePrimary Mitochondrial Disease
RECRUITING180 Analytics
PHASE2RECRUITING
Efficacy of KL1333 in Adult Patients With Primary Mitochondrial Disease
Primary Mitochondrial DiseaseUnlock trial analytics

Study Endpoints

Primary Endpoints

Change in-patient-reported fatigue symptoms and impacts on daily living measured by Patient-Reported Outcomes Measurement Information System (PROMIS®) Fatigue PMD Short Form
Baseline and 48 Weeks

Change in t-score. Higher scores indicate greater fatigue severity.

Change in 30 Second Site-to-Stand Test.
Baseline and 48 Weeks

Change in number of stands

Determination of the effect of KL1333 on the PK of repaglinide, caffeine, omeprazole, midazolam, bupropion, dextromethorphan, and flurbiprofen in healthy subjects.
day 14

Area under the curve AUC

Safety: incidence and severity of AEs
Day 15
Safety: incidence of laboratory abnormalities, based on haematology, clinical chemistry, and urinalysis test results
Day 15
Safety: 12 lead ECG parameters
Day 15
Safety: Number of participants with clinically significant abnormal vital signs measurements
Day 15
Safety: Number of participants with clinically significant abnormal physical examinations
Day 15

Secondary Endpoints

Change in Quality of Life in Neurological Disorders (Neuro-QoL) Lower Extremity Function (Mobility) Short Form
Baseline and 48 weeks
Change in Individual Activity Assessments - Interference
Baseline and 48 Weeks
Individual Activity Assessment - Change
48 weeks
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
KL1333EXPERIMENTALTwice daily
Matching PlaceboPLACEBO_COMPARATORTwice daily
ActiveEXPERIMENTALDaily treatment

Interventions

NameTypeDescription
KL1333DRUGTwice daily
PlaceboDRUGTwice daily
FlurbiprofenDRUGTablet
DextromethorphanDRUGSyrap
BupropionDRUGTablet
Midazolam injectionDRUGsolution for injection
OmeprazoleDRUGCapsule
CaffeineDRUGTablet or capsule
RepaglinideDRUGTablet
Placebo Oral TabletDRUG25 and 100 mg placebo encapsulated tablets
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites55

Inclusion Criteria: * Age 18 years or older. * A confirmed PMD diagnosis caused by a known pathogenic gene mutation or deletion of the mitochondrial genome (category 6 of the International Classification of Inborn Metabolic Disorders \[ICIMD\])12 according to American College of Medical Genetics (A...

Countries:United StatesAustraliaBelgiumCzechiaDenmarkFranceGermanyItalyNetherlandsSpainUnited Kingdom
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Recent Changes (Last 90 Days)

LOWJun 26, 2026NCT05650229lastUpdatePostDate: changed
LOWJun 26, 2026NCT05650229lastUpdatePostDate: changed

Frequently asked questions about KL1333

What is KL1333 used for?

KL1333 is an investigational small molecule being developed for the treatment of primary mitochondrial disease, a group of disorders caused by mitochondrial dysfunction. It is also being studied in related conditions such as MELAS syndrome and mitochondrial myopathies. The drug is currently in clinical development and has not been approved by regulatory authorities.

Who is developing KL1333?

KL1333 is being developed by Pharming Group N.V., a biopharmaceutical company listed on the stock exchange under the ticker PHAR. The company is conducting clinical trials to evaluate the safety and efficacy of KL1333 in patients with mitochondrial disease.

What phase is KL1333 in?

KL1333 is currently in Phase 2 clinical development. It has completed Phase 1 trials in healthy subjects and patients with primary mitochondrial disease, and a Phase 2 efficacy study is now recruiting participants. The drug is investigational and has not received FDA approval.

What clinical trials is KL1333 in?

KL1333 has been studied in several clinical trials. NCT03888716 was a Phase 1 single and multiple ascending dose study in healthy subjects and patients with primary mitochondrial disease. NCT04643249 was a drug-drug interaction study in healthy subjects. NCT05650229 is an ongoing Phase 2 efficacy trial in adult patients with primary mitochondrial disease.

Is KL1333 the same as other mitochondrial disease treatments?

KL1333 is a distinct investigational small molecule developed by Pharming Group N.V. for primary mitochondrial disease. It is not known to be the same as any other approved or investigational treatment for this condition. Its mechanism of action is not publicly detailed in the available clinical trial information.