KHENERFIN Study: A Trial to Evaluate the Efficacy and Safety of Sonlicromanol in Primary Mitochondrial Diseases

Inclusion Criteria:

• Males and females aged ≥18 years.

• A confirmed mitochondrial DNA tRNALeu(UUR) m.3243A>G mutation plus a heteroplasmypercentage ≥ 20% in white blood cells, or urine (urinary epithelial cells), orbuccal smear or skeletal muscle (results must be available prior to the subjectbeing randomized).

• Presence of chronic fatigue (not attributable to otherwise treatable or reversibleetiologies):

• Complaints of patient self-reported chronic fatigue for at least 3 months priorto the Screening Visit and recorded in the clinical patient files AND

• Presence of fatigue (raw total score >22 being a T-score >50), assessed byNeuro-QoL SFv1-F at Screening.

• Presence of mitochondrial myopathy defined as:

• 5XSST at Screening and Baseline ≥ 9.1 seconds.

• Myopathy (proximal muscle weakness), NMDAS Section III Clinical Assessment atScreening, item 5 score ≥1, which reads: "mild but clear proximal weakness inhip flexion and shoulder abduction - MRC 4/5". For the inclusion only hipflexion, but not shoulder abduction, should be taken into account.

• The patient is able and willing to provide written Informed Consent prior toscreening evaluations and to attend study appointments within the specified timewindows.

• The patient is, in the investigator's opinion, likely to comply with the protocoland able to adhere to the study requirements for the length of the study, andswallowing study medication, as well as the use of digital applications (ability tocomplete electronic patient reported outcomes (PROs).

• Clinically stable (apart from PMD symptoms) at screening as determined by medicalhistory, physical examination, vital signs measurements, 12-lead ECG, and clinicallaboratory evaluations at Screening, and as assessed by the Investigator.

• The patient has been on stable exercise regimen for at least 4 weeks prior torandomization and willing to not change their exercise regimen for the duration ofthe study treatment period.

• Left Ventricular wall thickness ≤15 mm at screening if not explained by cardiacinvolvement of mitochondrial disease (e.g., by cardiovascular magnetic resonance [CMR]).

• Women of childbearing potential must be willing to use highly effectivecontraceptive methods during the entire study. To be considered not of childbearingpotential, potential female participants must be post-menopausal for at least twoyears, or have been surgically sterilised (bilateral tubal ligation, hysterectomy orbilateral oophorectomy) for at least 6 months prior to Screening. Sonlicromanol hasbeen shown non-genotoxic judged from the Ames test, Chromosomal Aberration test andin vivo Micronucleus test. Moreover, appreciable systemic exposure from the exposureto (~2.5 mL) semen is extremely unlikely. However, until reproductive toxicologystudies have confirmed that sonlicromanol does not adversely affect normalreproduction in adult males and females, as well as causing developmental toxicityin the offspring, the following contraceptive precautions must be adhered to:

• Male subjects with female partners of childbearing potential must be willing touse condoms during the entire study.

• Female partners of childbearing potential of male subjects must be willing touse adequate contraceptive methods during the entire study, i.e., a hormonalcontraceptive method (pill, vaginal ring, patch, implant, injectable, hormonemedicated intrauterine device) or an intrauterine device.

Exclusion Criteria:

• Progressive External Ophthalmoplegia (PEO) as the single clinical manifestationassociated with m.3243A>G.

• Treatment with an IMP for PMD within 3 months (or 5 times the half-life of the IMP,whichever is longer) prior to screening or plans to use an IMP (other than the studyintervention) during the study.

• Bone deformities or motor abnormalities of PMD or other than those related tomitochondrial myopathy or significant other medical conditions that in the opinionof the PI may interfere with and confound the interpretation the participant'sperformance during the 5 times sit to stand test (5XSST).

• Surgery of gastrointestinal tract that might interfere with drug absorption. Orsevere GI dysmotility, chronic diarrhea, bouts of pseudo-obstruction which willimpair appropriate IMP absorption in the opinion of the investigator.

• Documented history of sustained ventricular tachycardia (HR >110 beats/min) at restand absence of an implanted cardioverter-defibrillator (ICD). In case ofnon-sustained ventricular tachycardia, myocardial ischemia must be excluded.

• History of ischemic heart disease with reduced left ventricular ejection fraction (<45%) and/or severe valvular heart disease.

• Symptomatic heart failure with reduced ejection-fraction with LVEF to 40% (HFrEF);in case of heart failure with preserved ejection-fraction (HFpEF) or only mildlyreduced ejection-fraction (HFmrEF) (defined as LVEF ≥40%) patients may be includedif the clinical symptoms are stable for at least 3 months as judged by theInvestigator.

• History of acute heart failure (within the last 3 months), (family) history ofunexplained syncope or congenital long and short QT syndrome or sudden death.

• Higher degree of AV-blocks (AVB II° or III°) in the absence of a pacemaker or ICD.

• In case QTcFridericia is >450ms (male) and >470ms (female) and a simultaneousbundle-branch-block (LBBB or RBBB) is not present at screening then QTcF will becalculated using regular QT interval (three cycles averaged). In case LBBB or RBBBis present, the modified QT interval (QTm) should be calculated by subtracting 50%of the length of the BBB-QRS from the measured QT interval (QTm = QTBBB - 50%QRSBBB). Subsequently, a rate-correction formula should be applied as usual. ForQTcF = QTm / (RR_Interval/1000)1/3.

• Novel and/or dynamic ECG abnormalities (including ST-segment elevation or depressionof >1 mm in at least two contiguous leads and/or T-wave inversions) within the last 3 months suggestive of myocardial ischemia. In this case the presence of myocardialischemia must be excluded to include the patient to this study.

• Recent history of unstable disease, inadequately controlled neurologicalmanifestations or not recovered from stroke-like episodes including but not limitedto stroke-like episodes within the last 6 months, hospitalized for statusepilepticus within the last 6 months.

• Blood pressure >160/90 mmHg at screening or baseline confirmed by re-testing (3x;supine position; first measure after 20 minutes of rest).

• ≥1 clinical laboratory test value outside the reference range, based on the bloodand urine samples taken at the screening visit, that are of potential risk to thepatient's safety, or the patient has, at the screening visit:

• Estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2.

• Serum potassium >5.0 mEq/L or <3.5 mEq/L).

• AST, ALT or total bilirubin (TBL) >3 x ULN at Screening. Patients who have aslightly elevated TBL and/or ALT and/or AST and are suitable candidates for thestudy, can be enrolled in the study if the Investigator can rule out anyunderlying liver dysfunction by running additional tests and after discussingthe case with the medical monitor.

• Medical history of drug abuse (illegal drugs such as cannabinoids, amphetamines,cocaine, opiates, or problematic use of prescription drugs such as benzodiazepines,opiates).

• Within 4 weeks prior to screening, the use of:

• (multi)vitamins, co-enzyme Q10, Vitamin E, riboflavin, amino acids, andantioxidant supplements (including, but not limited to idebenone/EPI-743, mitoQor alternative names for similar products); unless stable for at least onemonth before screening and willing to remain stable throughout the study.

• any medication negatively influencing mitochondrial functioning (including butnot limited to valproic acid, glitazones, statins, anti-virals, amiodarone, andnon-steroidal anti-inflammatory drugs (NSAIDs)), unless the dose has beenstable for at least one month before screening and the dose is to remain stablethroughout the study (1).

• any strong Cytochrome P450 (CYP)3A4 inhibitors (all 'conazoles-anti-fungals',HIV antivirals, grapefruit).

• strong CYP3A4 inducers (including HIV antivirals, carbamazepine, phenobarbital,phenytoin, rifampicin, St. John's wort, pioglitazone, troglitazone).

• any medication metabolized by CYP3A4 with a narrow therapeutic index.

• medication known to be substrate of Organic Cation Transporter 1 (OCT1) andorganic cation transporter 2 (OCT2) with a narrow therapeutic index.

• strong P-glycoprotein inhibitors (including amiodarone, azithromycin,captopril, clarithromycin, cyclosporine, piperine, quercetin, quinidine,quinine, reserpine, ritonavir, tariquidar, and verapamil).

• any medication known to affect cardiac repolarisation unless QTcF interval atscreening is normal during stable treatment for a period of two weeks, or 5half lives of the medication and its major metabolite(s), whichever period isthe shortest (all anti-psychotics, several anti-depressants, e.g.nor-/amitriptyline, fluoxetine, anti-emetics: domperidone, granisetron,ondansetron). For a complete list see https://crediblemeds.org.

• Patient has psychiatric conditions such as schizophrenia, bipolar disorder or majordepressive disorder that has not been under control within 3 months prior toscreening.

• Patient has severe behavioral or cognitive problems that preclude participation inthe study.

• Patient has undergone an inpatient hospitalization that precludes participation inthe study, within the 30 days prior to the randomization.

• Patient has a planned hospitalization or a surgical procedure during the study,which may affect the study assessments.

• Patient has clinically significant and unstable respiratory disease and/or cardiacdisease (medical history or current clinical findings), or prior interventionalcardiac procedure (e.g., cardiac catheterization, angioplasty/percutaneous coronaryintervention, balloon valvuloplasty, etc.) within 3 months prior to randomization.

• Patient requires any ventilator support, including CPAP or BiPAP at night.

• Patient has severe vision impairment that may interfere with their ability tocomplete all study requirements.

• Patient has an active malignancy or any other cancer from which the Patient has beendisease-free for <5 years, except for curative treated localized non-melanoma skincancer (e.g., basal cell or squamous cell carcinoma).

• Patient has a solid organ transplant and/or is currently receiving treatment withtherapy for immunosuppression.

• Patient has a history of active human immunodeficiency virus (HIV), hepatitis B orhepatitis C infection.

• The patient has an immediate family member (defined as family members residing atthe same address) who participates in the study or the continuation protocol (toavoid potential mix up / switch of medications during participation).

• Patient has BMI below 18.5 kg/m2 or above 35 kg/m2 at screening.

• Patient has any active viral or bacterial infection at the time of randomization.

• Patient is pregnant or breast feeding.