Muscle velocity recovery cycles as a biomarker for drugs targeting
muscle excitability

Part A
1. Signed informed consent prior to any study-mandated procedure
2. Healthy male subjects, 18 to 45 years of age, inclusive at screening.
3. Body mass index (BMI) between 18 and 30 kg/m2, inclusive at screening, and with a minimum weight of 50 kg.
4. All subjects must practice effective contraception during the study and be willing and able to continue
contraception for at least 90 days after their last dose of study treatment.
5. Has the ability to communicate well with the Investigator in the Dutch language and willing to comply with the
study restrictions.

Part B
1. Signed informed consent prior to any study-mandated procedure
2. Male and female subjects, above 18 years of age, inclusive at screening.
3. Diagnosis of generalized myasthenia gravis, MGFA class II-IV, based on characteristic muscle weakness and
with a positive AChR antibody test.
4. Has the ability to communicate well with the Investigator in the Dutch language and willing to comply with the
study restrictions.
5. Must be able to cease the use of pyridostigmine as per study requirements, if applicable.

Part A
1. Evidence of any active or chronic disease or condition that could interfere with, or for which the treatment of might interfere with, the conduct of the study, or that would pose an unacceptable risk to the subject in the opinion
of the investigator (following a detailed medical history, physical examination, vital signs (systolic and diastolic
blood pressure, pulse rate, body temperature) and 12-lead electrocardiogram (ECG)). Minor deviations from the
normal range may be accepted, if judged by the Investigator to have no clinical relevance.
2. Clinically significant abnormalities, as judged by the investigator, in laboratory test results (including hepatic and
renal panels, complete blood count, chemistry panel and urinalysis). Subjects with pre-dose findings of clinically
significant changes in electrolytes should be excluded. In the case of uncertain or questionable results, tests
performed during screening may be repeated before randomization to confirm eligibility or judged to be clinically
irrelevant for healthy subjects.
3. Positive Hepatitis B surface antigen (HBsAg), Hepatitis C antibody (HCV Ab), or human immunodeficiency virus
antibody (HIV Ab) at screening.
4. Systolic blood pressure (SBP) greater than 140 or less than 90 mm Hg, and diastolic blood pressure (DBP)
greater than 90 or less than 50 mm Hg at screening.
5. Abnormal findings in the resting ECG at screening or baseline defined as:
a. QTcF> 450 or < 300 msec
b. Notable resting bradycardia (HR < 50 bpm) or tachycardia (HR > 100 bpm)
c. Personal or family history of congenital long QT syndrome or sudden death;
d. Evidence of atrial fibrillation, atrial flutter, complete branch block, Wolf-Parkinson-White Syndrome, or cardiac
pacemaker
e. Ventricular tachyarrhythmia
f. Atrial tachyarrhythmia, fibrillation or flutter
g. Complete heart block (i.e. third-degree atrioventricular block) or any heart block susceptible to evolve to
complete heart block (first-degree atrioventricular block with markedly prolonged PR interval (≥ 240 ms) and/or
wide QRS complex (≥ 120 ms), second-degree atrioventricular block, bundle branch block, bifascicular and
trifascicular block),
h. Sinus node dysfunction (sinus rate < 50 bpm, sinus arrest of >3.5 sec)
6. Use of any medications (prescription or over-the-counter [OTC]), within 14 days of study drug administration, or
less than 5 half-lives (whichever is longer). Exceptions are paracetamol (up to 4 g/day) and ibuprofen (up to
1g/day). Other exceptions will only be made if the rationale is clearly documented by the investigator.
7. Use of any vitamin, mineral, herbal, and dietary supplements within 7 days of study drug administration, or less
than 5 half-lives (whichever is longer). Exceptions will only be made if the rationale is clearly documented by the
investigator.
8. Participation in an investigational drug or device study within 3 months prior to first dosing, or for more than 4
times a year.
9. History of abuse of addictive substances (alcohol, illegal substances) or current use of more than 21 units
alcohol per week, drug abuse, or regular user of sedatives, hypnotics, tranquillizers, or any other addictive agent
10. Positive test for drugs of abuse at screening or pre-dose.
11. Alcohol will not be allowed from at least 24 hours before screening or pre-dose.
12. Current use of tobacco or nicotine products and unable to abstain from use of these products within the
previous month before the first dose administration.
13. Is demonstrating excess in xanthine consumption (more than eight cups of coffee or equivalent per day).
14. Any confirmed significant allergic reactions (urticaria or anaphylaxis) against any drug, or multiple drug
allergies (non-active hay fever is acceptable).
15. Hypersensitivity to the active substance, mexiletine hydrochloride, or other ingredients (maize starch, colloidal
anhydrous silica, magnesium stearate, gelatin, iron oxide [E 172], titanium dioxide [E 171])
16. Hypersensitivity to any local anaesthetic.
17. Loss or donation of blood over 500 mL within three months prior to screening, or plasma donation within 2
weeks of screening, or intention to donate blood or blood products during the study.
18. Any known factor, condition, or disease that might interfere with treatment compliance, study conduct or
interpretation of the results such as drug or alcohol dependence or psychiatric disease.
19. History of trauma to the lower extremities or other conditions (most importantly neurological or muscle
diseases) that, in the opinion of the investigator, could affect the electrophysiological measurements.
20. Clinically significant abnormalities in coagulation, personal or family history of bleeding disorders.
21. Excessive exercise within 72 hours before study drug administration.
22. Diameter of the upper leg of more than 65 cm, to allow for the induction of ischemia by the blood pressure cuff.

Part B
1. Evidence of any active or chronic disease or condition that could interfere with, or for which the treatment of
might interfere with, the conduct of the study, or that would pose an unacceptable risk to the subject in the opinion
of the investigator (following a detailed medical history, analysis of coagulation). Minor deviations from the normal
range may be accepted, if judged by the Investigator to have no clinical relevance.
2. History of or current conditions that, in the opinion of the investigator, could affect the electrophysiological
measurements, such as trauma to the upper extremity, renal failure, or neuromuscular diseases, including but not
limited to critical illness neuropathy, Anderson Tawil syndrome, channelopathies, erythromelalgia, myotonic
dystrophies, sodium channel myotonias and myotonica congenetica.
3. Positive Hepatitis B surface antigen (HBsAg), Hepatitis C antibody (HCV Ab), or human immunodeficiency virus
antibody (HIV Ab) at screening.
4. Use of any medications (prescription or over-the-counter [OTC]) that could influence the MVRC measurements
(apart from pyridostigmine), within 14 days of study drug administration, or less than 5 half-lives (whichever is
longer), including use of anti-coagulants, sodium channel blockers, dantrolene, anti-epileptic drugs.
5. Participation in an investigational drug or device study within 3 months prior to the study day, or for more than 4
times a year.
6. History of abuse of addictive substances (alcohol, illegal substances) or current use of more than 21 units
alcohol per week, drug abuse, or regular user of sedatives, hypnotics, tranquillizers, or any other addictive agent
7. Positive test for drugs of abuse at screening or the study period. Retesting is allowed at the discretion of the
Investigator.
8. Alcohol will not be allowed from at least 24 hours before the study period.