Pharmacokinetics of oral fumarates in healthy subjects

DOI:10.1111/j.1365-2125.2004.02145.x Pharmacokinetics of oral fumarates in healthy subjects Nicolle H. R. Litjens, Jacobus Burggraaf,1 Elisabeth van Strijen, Co van Gulpen, Herman Mattie, Rik C. Schoemaker,1
Jaap T. van Dissel, H. Bing Thio2 & Peter H. Nibbering
Department of Infectious Diseases, Leiden University Medical Centre and 1Centre for Human Drug Research, Leiden, and 2Department of
Dermatology and Venereology, Erasmus Medical Centre, Rotterdam, the Netherlands
Correspondence
To characterize the pharmacokinetics of fumarates in healthy subjects.
Infectious Diseases, C5-P, Leiden University Medical Centre, 2300 RC Ten subjects received a single fumarate tablet (containing 120 mg of dimethylfuma- rate and 95 mg of calcium-monoethylfumarate) in the fasted state and after a standardized breakfast in randomized order. Prior to and at fixed intervals after the dose, blood samples were drawn and the concentrations of monomethylfumarate,the biologically active metabolite, as well as dimethylfumarate and fumaric acid weremeasured using high-performance liquid chromatography.
Keywords
After a lag time, a transient increase in serum monomethylfumarate concentrations in the blood was observed, whereas dimethylfumarate and fumaric acid concentra- tions remained below the detection limit. The tlag was 240 min [range 60–603 min; 95% confidence interval (CI) 139, 471] shorter when the tablet was taken after anovernight fast (90 min; range 60–120 min; 95% CI 66, 107) than when taken withbreakfast (300 min; range 180–723 min; 95% CI 0, 1002). The tmax was 241 min(range 60–1189 min, 95% CI 53, 781) shorter when the tablet was taken after anovernight fast (182 min; range 120–240 min; 95% CI 146, 211) than when taken Received
with breakfast (361 min; range 240–1429 min; 95% CI 0, 1062). The mean C for monomethylfumarate in the blood of fasting subjects was to 0.84 mg l-1 (range Accepted
0.37–1.29 mg l-1; 95% CI 0.52, 1.07) and did not differ from that in fed subjects (0.48 mg l-1; range 0–1.22 mg l-1; 95% CI 0, 5.55).
Conclusions
The pharmacokinetics of monomethylfumarate in healthy subjects after a single tablet
of fumarate are highly variable, particularly after food intake. Further experiments
exploring the pharmacokinetics of oral fumarates are warranted in order to elucidate
the mechanisms underlying variability in reponse in patients.
Introduction
be circumvented using mixtures of dimethylfumarate Psoriasis vulgaris is an autoimmune skin disease char- and monoethylfumarate in enteric-coated tablets [7–12].
acterized by epidermal hyperplasia and the presence of There is some variability in the response to these fuma- inflammatory cells in affected lesions. Current long- rates among psoriasis patients. The reason for this is term (anti-inflammatory) therapies for psoriasis cause unknown and may involve both pharmacokinetic and serious adverse effects [1–5]. Fumaric acid is effective pharmacodynamic factors. There are few data on the against psoriasis [6], but its main drawback is that it pharmacokinetics of fumarates in humans [13]. Animal causes gastric ulcers. However, this adverse affect can studies indicate that fumarates are completely absorbed from the gastrointestinal tract within 2 h after adminis- metaphosphoric acid followed by extraction with dieth- tration and that dimethylfumarate is rapidly hydrolysed ylether and pH adjustment to pH 0.5. Sodium chloride in the intestinal mucosa to monomethylfumarate. This was added before centrifugation at 12 000 ¥ g. Thereaf- bioactive intermediate is further metabolized into ter, the ether layer was transferred to a glass vial and fumaric acid, which enters the citric acid cycle (personal after evaporation the residue reconstituted in methanol: communication, Joshi et al. Fumapharm AG, Switzer- 0.1 M potassium phosphate buffer (KH2PO4/K2HPO4; land). As a first step in understanding why patients with pH 7.5) supplemented with 5 mM tetrabutylammonium psoriasis vary in their response to fumarates we have characterized the pharmacokinetics of fumarates in The HPLC instrument (Spectra SERIES P100) was healthy individuals following a single dose taken on an equipped with an Alltima C18 column (5m 5250 ¥ empty stomach as well as with a meal.
4.6 mm) and a precolumn. The mobile phase for dime-thylfumarate was methanol : water 30 : 70 (v/v) and Materials and methods
that for monomethylfumarate and fumaric acid was The Medical Ethics Committee of Leiden University methanol : potassium phosphate buffer supplemented Medical Centre approved this open, randomized, cross- with 5 mM tetrabutylammonium dihydrogen phosphate over study and all subjects gave written informed 20 : 80 (v/v). The limit of detection for all three com- consent. The study was conducted according to the prin- pounds was 0.01 mg l-1, the coefficients of variation for ciples of the Declaration of Helsinki and in compliance monomethylfumarate and dimethylfumarate were 7% with International Conference on Harmonization/Good and 9% at 0.5 mg l-1, respectively, and the recoveries Clinical Practice regulations. The study population con- of monomethylfumarate and dimethylfumarate were sisted of 10 healthy subjects (four male, six female) 75 ± 7% and 98 ± 3% (n = 6).
between 19 and 28 years with a normal weight forheight (body mass index range 18–25 kg m-2).
Data analysisThe pharmacokinetic parameters for monomethylfuma- rate were calculated by noncompartmental analysis using The subjects participated on two study days. On one day WinNonlin software (version 4; Pharsight Corp., Moun- a single tablet was taken after an overnight fast and on tain View, CA, USA). Terminal half-life (t1/2) was esti- the other day the tablet was taken with a standardized mated by log-linear regression of the terminal part of the breakfast (2060 kJ – 45% as protein, 12% as fat and concentration–time curve, where the number of points 43% as carbohydrates). The tablets (Fumaraat 120®) to be included was determined by the program. Lag-time containing 120 mg of dimethylfumarate and 95 mg of (tlag), time at which peak concentrations of monometh- calcium-monoethylfumarate were purchased from Tio- ylfumarate occurred (tmax), and peak concentrations of farma (Oud-Beijerland, Netherlands). Each study day monomethylfumarate (Cmax) are reported for all subjects.
lasted 24 h and was separated from the other days by a Where possible, clearance/F (dose/AUC0–•) was esti- mated. The nonparametric Friedman test was used to Blood was collected shortly before and at fixed inter- determine whether the descriptive pharmacokinetic vals after tablet dosing and placed in 4-ml tubes con- parameters differed between the fed and fasting state.
taining sodium fluoride and potassium oxalate asantioxidant and esterase inhibitors. Immediately after collection, the samples were vortexed, transferred onto Two subjects withdrew consent after the first study day ice for 5 min and centrifuged at 4 ∞C for 10 min at for personal reasons. The fumarate tablets were well 1500 ¥ g. The resulting supernatant was stored at tolerated by all participants, who suffered no serious adverse events. In addition, no abnormalities inhaematology, blood biochemistry and urinalysis were observed. However, peripheral vasodilatation (mainly in The concentrations of the fumarates were determined as the face and the upper part of the body) occurred after described by Litjens et al. (unpublished data). After pre- 10 (out of 18) of the doses and lasted between 1 and 3 h.
cipitation of serum proteins with acetonitrile, dimethyl- This was not accompanied by a decrease in blood pres- fumarate was analysed by high-performance liquid sure, an increase in heart rate or by any other event.
Concentrations of both dimethylfumarate and fumaric The sample preparation for monomethylfumarate and acid were below the detection limit. Serum monometh- fumaric acid required a protein precipitation step using ylfumarate concentrations vs. time profiles were similar in all eight subjects who took the drug after an overnight fumarate (Figure 1A,B) occurred. The tlag and tmax in fast (Figure 1A), whereas subjects who were fed dis- fasting subjects were 240 min shorter [range 60– played either negligible monomethylfumarate concen- 602 min; mean ± SD 305 ± 179 min; 95% confidence trations or values similar to those in fasting subjects interval (CI) 139, 471] and 241 min shorter (range 60– 1189 min; mean ± SD 417 ± 394 min; 95% CI 53, 781), The main pharmacokinetic parameters for monome- respectively (P = 0.008) than in fed subjects (Table 1).
thylfumarate are summarized in Table 1. A transient Moreover, the mean Cmax of monomethylfumarate in increase in the serum concentration of monomethyl- fasting individuals (n = 8) was 0.84 mg l-1 (range 0.37– Figure 1
Concentration–time profiles for monomethylfumarate in the serum of eight healthy subjects after a single Fumaraat® tablet in the fasting (A) and fed
(B) state
Table 1
Serum pharmacokinetic parameters for monomethylfumarate in eight healthy subjects after a single Fumaraat 120® tablet in the
fasting state and after a standardized breakfast
aOwing to undetectable concentrations of monomethylfumarate, no values could be calculated. 1.29 mg l-1; mean ± SD 0.8 ± 0.33; 95% CI 0.52, 1.07), may be useful in distinguishing patients who respond to and did not differ from that in the fed subjects (0.48 mg l-1; range 0–1.22 mg l-1; mean ± SD 0.46 ±0.47 mg l-1; 95% CI 0, 5.55) (Table 1). In four out of This study was financially supported by AstraZeneca eight subjects who took the drug with a breakfast, very R&D Charnwood, Loughborough, UK. low concentrations of monomethylfumarate wereobserved.
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