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Background and PurposeWe conducted preclinical and clinical studies to examine the pharmacological, particularly cardiac, effects of amiselimod (MT‐1303), a second‐generation sphingosine 1‐phosphate (S1P) receptor modulator, designed to reduce the bradycardia associated with fingolimod and other S1P receptor modulators.Experimental ApproachThe selectivity of the active metabolite amiselimod phosphate (amiselimod‐P) for human S1P receptors and activation of G‐protein‐coupled inwardly rectifying K+ (GIRK) channels in human atrial myocytes were assessed. Its cardiac distribution was determined in rats, and cardiovascular telemetry was assessed in monkeys. We also examined the pharmacokinetics, pharmacodynamics and safety of amiselimod in healthy humans.Key ResultsAmiselimod‐P showed potent selectivity for S1P1 and high selectivity for S1P5 receptors, with minimal agonist activity for S1P4 and no distinct agonist activity for S1P2 or S1P3 receptors and approximately five‐fold weaker GIRK activation than fingolimod‐P. After oral administration of amiselimod or fingolimod at 1 mg·kg−1, the concentration of amiselimod‐P in rat heart tissue was lower than that of fingolimod‐P, potentially contributing to the minimal cardiac effects of amiselimod. A telemetry study in monkeys confirmed that amiselimod did not affect heart rate or ECG parameters. In healthy human subjects, peripheral blood lymphocyte counts gradually reduced over the 21 day dosing period, with similar lymphocyte count profiles with the highest doses by day 21, and no clinically significant bradycardia observed on day 1 or during the study.Conclusions and ImplicationsAmiselimod exhibited potent therapeutic efficacy with minimal cardiac effects at the anticipated clinical dose and is unlikely to require dose titration.

AimAmiselimod (MT‐1303) is a selective sphingosine 1‐phosphate 1 (S1P1) receptor modulator which is currently being developed for the treatment of various autoimmune diseases. Unlike some other S1P receptor modulators, amiselimod seemed to show a favourable cardiac safety profile in preclinical, phase I and II studies. The aim of the current study was to characterize the cardiac effects of amiselimod by directly comparing it with fingolimod and placebo.MethodsA total of 81 healthy subjects aged 18–55 years were equally randomized to receive amiselimod 0.4 mg, amiselimod 0.8 mg, placebo or fingolimod 0.5 mg once daily for 28 days. The chronotropic/dromotropic and inotropic effects were evaluated using intensive Holter electrocardiogram and echocardiography.ResultsUnlike fingolimod, neither amiselimod dose exerted acute (1–6 h) negative chronotropic effects on Days 1 and 2. The lowest nadir mean hourly heart rate was observed on Day 14 in the amiselimod 0.4 mg group (least squares mean difference: −4.40 bpm, 95% confidence interval −7.15, −1.66) and Day 7 in the 0.8 mg group [−3.85 bpm (−6.58, −1.11)] compared with placebo, but these changes were smaller than those with fingolimod on Day 1 [−6.49 bpm (−8.95, −4.02)]. No clinically significant bradyarrhythmia or cardiac functional abnormalities were observed in either amiselimod group. Both amiselimod doses were well tolerated and no serious adverse events were reported. Fingolimod was also generally well tolerated, although one subject was withdrawn owing to highly frequent 2:1 atrioventricular blocks on Day 1.ConclusionThe study demonstrated a more favourable cardiac safety profile for amiselimod than fingolimod when administered over 28 days in healthy subjects.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• New drugs are expected to undergo rigorous clinical electrocardiographic evaluation ('thorough QT/QTc study') during their early clinical development in order to determine any affect on cardiac repolarization. • The fluoroquinolone antibiotic moxifloxacin (400 mg) has been used as a positive comparator for thorough QT/QTc studies due to its QT prolongation (QTcF) of between 6 and 10 ms. • Positive comparators that are able to produce mean changes close to the regulatory guidelines of 5 ms, and which can be detected by the assay in use, would enable a more rigorous evaluation of the assay conditions used in evaluating new chemical entities. WHAT THIS STUDY ADDS• This thorough QT/QTc study directly compares the effects of two doses of levofloxacin and moxifloxacin on QTc in the same healthy subjects.• Mean QTc was prolonged in subjects receiving levofloxacin compared with placebo as determined by both individual and Fridericia's heart rate correction methods.• The largest time-matched differences in QTc for two doses of levofloxacin compared with placebo suggest the potential for using levofloxacin in more rigorous QT/QTc studies, providing a robust evaluation of the assay conditions used in determining potential effects on cardiac repolarization.• There is evidence to suggest that levofloxacin moderately increases heart rate in a dose-dependent fashion. AIMSTo characterize the effects of levofloxacin on QT interval in healthy subjects and the most appropriate oral positive control treatments for International Conference on Harmonization (ICH) E14 QT/QTc studies. METHODSHealthy subjects received a single dose of levofloxacin (1000 or 1500 mg), moxifloxacin (400 mg) or placebo in a four-period crossover design. Digital 12-lead ECGs were recorded in triplicate. Measurement of QT interval was performed automatically with subsequent manual onscreen over-reading using electronic callipers. Blood samples were taken for determination of levofloxacin and moxifloxacin concentrations. RESULTSMean QTcI (QT interval corrected for heart rate using a correction factor that is applicable to each individual) was prolonged in subjects receiving moxifloxacin 400 mg compared with placebo. The largest time-matched difference in QTcI for moxifloxacin compared with placebo was observed to be 13.19 ms (95% confidence interval 11.21, 15.17) at 3.5 h post dose. Prolonged mean QTcI was also observed in subjects receiving levofloxacin 1000 mg and 1500 mg compared with placebo. The largest time-matched difference in QTcI compared with placebo was observed at 3.5 h post dose for both 1000 mg and 1500 mg of levofloxacin [mean (95%) 4.42 ms (2.44, 6.39) in 1000 mg and 7.44 ms (5.47, 9.42) in 1500 mg]. A small increase in heart rate was observed with levofloxacin during the course of the study. However, moxifloxacin showed a greater increase compared with levofloxacin. CONCLUSIONSBoth levofloxacin and moxifloxacin can fulfil the criteria for a positive comparator. The ICH E14 guidelines recommend a thres...