Radioiodinated dechloro-4-iodofenofibrate: A hydrophobic model drug for molecular imaging studies

Article abstract of DOI:10.1016/j.ijpharm.2012.04.039

Radiolabeling is a valuable option for tracking drug molecules in biodistribution experiments. In the development of innovative drug delivery systems the influence of the pharmaceutical formulation on the drugs' pharmacokinetics has to be investigated. Th

Full text of DOI:10.1016/j.ijpharm.2012.04.039

International Journal of Pharmaceutics 431 (2012) 78–83
Contents lists available at SciVerse ScienceDirect
International Journal of Pharmaceutics
journal homepage: www.elsevier.com/locate/ijpharm
Radioiodinated dechloro-4-iodofenofibrate: A hydrophobic model drug
for molecular imaging studies
Sandra Breyera,1, Angelika Semmlera,1, Tobias Millerb, Alexandra Hillb, Simon Geisslerb,
Uwe Haberkorna, Walter Miera,∗
a Department of Nuclear Medicine, University Hospital Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany
b CMC Development/Exploratory Pharmaceutical Development, Merck KGaA, Frankfurter Strasse 250, 64293 Darmstadt, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Radiolabeling is a valuable option for tracking drug molecules in biodistribution experiments. In the
development of innovative drug delivery systems the influence of the pharmaceutical formulation on the
drugs’ pharmacokinetics has to be investigated. The hypolipidemic agent fenofibrate is an ideal model
drug for testing the performance of drug delivery systems designed for poorly soluble compounds. Herein,
we report a de novo synthesis of a fenofibrate derivative, dechloro-4-iodofenofibrate, as well as its conver-
sion into its radioiodinated derivatives containing 125I or 131I. The enzymatic stability of the radiolabeled
compounds synthesized was determined in vitro. A scintigraphic imaging study supplemented by biodis-
tribution experiments and analysis of excreted metabolites revealed the stability required for in vivo
applications and its similarity to fenofibrate. Therefore a convenient method is presented to synthesize
radioiodinated derivatives of fenofibrate. These tracers show excellent in vitro and in vivo properties to
study the behavior of lipophilic drugs.
Received 10 November 2011
Received in revised form 3 April 2012
Accepted 10 April 2012
Available online 19 April 2012
Keywords:
Drug delivery
Radiolabeling
Fenofibrate
Hydrophobic drugs
Iodination
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
To investigate the effect of various formulations of hydrophobic
drugs on their pharmacokinetics, it would be of interest to syn-
Many new candidate drugs display a low aqueous solubility,
hence solubilizing delivery systems have received increasing atten-
tion during the last decades (Strickley, 2004). Improving solubility
is often required to reach therapeutic drug concentrations at the
target site of action in vivo.
The hydrophobicity of fenofibrate (1) (Scheme 1) makes it a
model drug to evaluate innovative drug delivery systems (Kalivoda
et al., 2012; Vogt et al., 2008). Fenofibrate is an established hypolipi-
demic agent and has been successfully used for over thirty years
(Cornu-Chagnon et al., 1995; Guichard et al., 2000; Guivarc’h
et al., 2004). The compound shows a high lipophilicity (log P = 5.24)
(Munoz et al., 1994) and is consequently practically insoluble in
water (Mochalin et al., 2009; Penn et al., 2006). The pharmacoki-
netic profile of fenofibrate is well understood (Adkins and Faulds,
1997). About 40% of the drug development candidates show a
very low aqueous solubility and therefore need technologies for
bioavailability enhancement (Patel et al., 2010).
thesize fenofibrate derivatives that are readily detectable in vitro
and by molecular imaging methods. Radiolabeling is the method of
choice for such applications (Eisenhut and Mier, 2003). The aim of
this work was to obtain fenofibrate with a radioactive iodine label.
This compound is suited for in vitro as well as in vivo biodistribution
studies by introducing different iodine isotopes into the molecule.
2. Materials and methods
General: All reagents and solvents were purchased from com-
mercial sources and used without further purification. Sodium
[
131I] and [125I] iodide were purchased from Perkin Elmer (Rodgau,
Germany). Radioactivity was measured with an Isomed activime-
ter (Dresden, Germany). 1H and 13C NMR spectra were measured
at room temperature on a 500 MHz Varian spectrometer. Chemical
shifts are reported as ı parts per million (ppm). 1H chemical shifts
are referenced to residual protic solvent (CDCl3, ı H = 7.26 ppm;
DMSO-d6, ı H = 2.50 ppm). 13C chemical shifts are referenced to the
solvent signal (CDCl3, ı C = 77.0 ppm).
HPLC: An Agilent series 1100 HPLC system coupled to a raytest
Gabi star ␥-detector was used to monitor reactions and check for
purity. The following conditions were used unless otherwise noted:
Chromolith Performance column (Merck), RP-18e, 4.6 × 100 mm,
0.1% aqueous trifluoroacetic acid (solvent A) and acetonitrile
∗
Corresponding author at: University Hospital Heidelberg, Radiologische Klinik,
Abt. Nuklearmedizin, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
Tel.: +49 622156 7720.
E-mail address: walter.mier@med.uni-heidelberg.de (W. Mier).
These authors contributed equally to this work.
1
0378-5173/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ijpharm.2012.04.039

S. Breyer et al. / International Journal of Pharmaceutics 431 (2012) 78–83
79
163.4 (COCH3), 137.6, 137.5, 132.5 (CH), 131.2, 129.7 (CCO), 113.7
(CH), 99.3 (CI), 55.5 (OCH3) ppm.
2.1.2. Synthesis of (4-iodophenyl)(4-hydroxyphenyl)methanone
(8) (derived from Britton, 2005; Hartmann and Gattermann,
1892)
To
a
stirred
solution
of
(4-iodophenyl)(4-
methoxyphenyl)methanone (7) (5.17 g, 15.00 mmol), in toluene
(150 mL), AlCl3 (5.00 g, 37.50 mmol, 2.5 eq.) was slowly added.
The reaction mixture was heated to reflux for 1 h. After cooling to
room temperature, the mixture was slowly poured into 10% HCl
(400 mL). The mixture was then transferred to a separatory funnel
and the layers were separated. The aqueous phase was sequen-
tially extracted with ethyl acetate (4 × 100 mL). The combined
organic layers were washed with brine (2 × 100 mL), dried over
anhydrous Na2SO4 evaporated into dryness. The obtained solid
was suspended in hexane, filtered and dried in vacuum to yield
the product 8 (5.04 g, quantitative yield) as a white solid.
HPLC: tR = 3.42 min, LC–MS (method A): tR = 23.17 min, m/z
found 324.9724, calc. C13H10IO2 324.9720. 1H NMR (DMSO-d6,
500 MHz): ı = 7.91 (d, J = 8.4 Hz, 2H, Ar H), 7.65 (d, J = 8.7 Hz, 2H,
Ar H), 7.43 (d, J = 8.4 Hz, 2H, Ar H), 6.89 (d, J = 8.7 Hz, 2H, Ar H)
ppm. 13C NMR (CDCl3, 125 MHz): ı = 194.9 (CO), 160.2 (COH), 137.5,
137.4, 132.9 (CH), 131.2, 129.7 (CCO), 115.3 (CH), 99.4 (CI) ppm.
Scheme 1. Chemical structure of fenofibrate (1) and the dechloro-4-iodofenofibrate
derivatives studied.
containing 0.1% trifluoroacetic acid (solvent B), linear gradient
from 0 to 100% solvent B in 5 min, additional 3 min 100% sol-
vent B, 4 mL/min, absorbance ꢀ = 214 nm. The preparative RP-HPLC
separation was performed on a Gilson/321 pump HPLC system.
For purification the following conditions were used: Chromolith
SemiPrep-column (10 × 100 mm); gradient elution from 0.1% TFA
in water to 0.1% TFA in acetonitrile/water = 70/30 over 10 min; flow
rate 10 mL/min; absorbance ꢀ = 214 nm.
LC–MS: High resolution LC–MS measurements were obtained
on a mass spectrometer supporting orbitrap technology (Exactive,
Thermo Fisher Scientific). An Agilent 1200 system using a Hyper-
sil Gold C18 column (0.21 × 200 mm) served as HPLC system. A
mixture of caffeine, MRFA and Ultramark 1621 was used for mass
calibration in the positive-ion mode. Full scan single mass spec-
tra were obtained by scanning from m/z = 100–1000 for 30 min.
The HPLC conditions were the following: (method A) linear gra-
dient of 0.1% TFA in water to 0.1% TFA in acetonitrile in 30 min,
flow rate 200 ␮L/min, 60 ◦C, absorbance ꢀ = 214 nm. (method B)
linear gradient of 0.1% TFA in water to 0.1% TFA in acetonitrile in
10 min followed by 20 min 100% 0.1% TFA in acetonitrile, flow rate
200 ␮L/min, 60 ◦C, absorbance ꢀ = 214 nm.
2.1.3. Synthesis of
2-[4-(4-iodobenzoyl)phenoxy]-2-methylpropanoic acid
isopropylester (2)
5.00 g (15.40 mmol) of the crude (4-iodophenyl)(4-
hydroxyphenyl)methanone (8) were dissolved in 60 mL
dimethylformamide. To the solution 6.38 g (46.20 mmol,
3
eq.) K2CO3, 1.85 g (15.40 mmol, 1 eq.) dried MgSO4 and 9.80 mL
(46.20 mmol, 3 eq.) isopropyl-2-bromo-2-methylpropanoate were
added. The suspension was stirred and heated to 75 ◦C for 10 h fol-
lowed by stirring overnight at room temperature. The precipitate
was filtered off and washed with dichloromethane. The filtrate
was sequentially washed with 0.1 N HCl (3 × 100 mL), brine and
dried over anhydrous Na2SO4. After evaporation of the solvent the
oily residue obtained was dissolved in dichloromethane (5 mL)
and precipitated with hexane (50 mL). The solid was filtered and
recrystallized from isopropanol to yield 4.39 g (9.70 mmol, 63%) of
a white solid.
HPLC: tR = 4.70 min, LC–MS (method A): tR = 28.75 min, m/z
found 453.0551, calc. C20H22IO4 453.0557. 1H NMR (CDCl3,
500 MHz): ı = 7.83 (d, J = 8.3 Hz, 2H, Ar H), 7.72 (d, J = 8.7 Hz, 2H,
Ar H), 7.47 (d, J = 8.3 Hz, 2H, Ar H), 6.86 (d, J = 8.7 Hz, 2H, Ar H),
5.08 (sept, J = 6.3 Hz, 1H, (CH3)2CH), 1.65 (s, 6H, C(CH3)2), 1.20 (d,
J = 6.3 Hz, 6H, (CH3)2CH) ppm. 13C NMR (CDCl3, 125 MHz): ı = 194.6
(CO), 173.1 (CO2), 159.8 (COC(CH3)2), 137.5, 137.4, 131.9 (Ar CH),
131.2, 130.1 (CCO), 117.3 (Ar CH), 99.4 (CI), 79.4 (C(CH3)2), 69.3
(CH(CH3)2), 25.4 (C(CH3)2), 21.5 (CH(CH3)2) ppm.
2.1. Synthesis of [125/131I]
2-[4-(4-iodobenzoyl)phenoxy]-2-methylpropanoic acid
isopropylester
2.1.1. Synthesis of (4-iodophenyl)(4-methoxyphenyl)methanone
(7) (derived from Davies et al., 2009)
To a suspension of 4-iodobenzoic acid (3.44 g, 13.87 mmol) in
dichloromethane (35 mL) thionylchloride (1.50 mL, 18.00 mmol,
1.5 eq.) and dimethylformamide (50.0 ␮L) were added. The result-
ing reaction mixture was stirred at 40 ◦C overnight. The yellow
suspension obtained was concentrated in vacuum to provide a
tan solid that was used in the subsequent reaction without fur-
ther purification. The crude acid chloride (6) then was dissolved
in dichloromethane (60 mL), cooled in an ice bath, and anisole
(1.89 mL, 17.40 mmol, 1.25 eq.) was added. The mixture was stirred
at 0 ◦C for 2 min whereupon AlCl3 (2.28 g, 17.40 mmol, 1.25 eq.)
was added portion wise over a period of 20 min. The resulting
reaction mixture was allowed to stir between 0 ◦C and room tem-
perature for 4 h. The yellow suspension was poured into ice-water
(200 mL), stirred for 15 min, acidified with 1 N HCl and diluted
with dichloromethane. The phases were separated and the aque-
ous layer was extracted with dichloromethane (3 × 100 mL). The
combined organic layers were washed with 1 N NaOH, dried over
anhydrous Na2SO4 and concentrated in vacuum. The crude prod-
uct was crystallized from dichloromethane/hexane (1/10) to afford
4.49 g (13.27 mmol, 96%) of a white solid.
2.1.4. Synthesis of
2-[4-(4-tri-n-butylstannylphenyl)phenoxy]-2-methylpropanoic
acid isopropylester (9)
Compound 2 (25.0 mg, 55.3 ␮mol) was dissolved in diox-
ane (2 mL) under argon. Hexabutyltin (27.9 ␮L, 0.33 mmol, 6
eq.) and dichlorobis(triphenylphosphine)palladium(II) (38.8 mg,
27.8 ␮mol, 0.5 eq.) were added, and the mixture was heated to
reflux. After 3 h the mixture was filtered over silica and concen-
trated in vacuum. The crude product was purified by preparative
RP-HPLC to give 8.1 mg of the pure product 9 (13.3 ␮mol, 24%).
HPLC: tR = 5.43 min, LC–MS (method B): tR = 17.9 min, m/z found
617.2662, calc. C20H22IO4 617.2652 (1.6 ppm).
HPLC: tR = 4.14 min, LC–MS (method A): tR = 25.76 min, m/z
found 338.9871, calc.
C
14H12IO2 338.9877. 1H NMR (CDCl3,
500 MHz): ı = 7.83 (d, J = 8.5 Hz, 2H, Ar H), 7.79 (d, J = 9.0 Hz, 2H,
Ar H), 7.47 (d, J = 8.5 Hz, 2H, Ar H), 6.96 (d, J = 9.0 Hz, 2H, Ar H),
3.89 (s, 3H, OCH3) ppm. 13C NMR (CDCl3, 125 MHz): ı = 194.6 (CO),

80
S. Breyer et al. / International Journal of Pharmaceutics 431 (2012) 78–83
O
O
O
a
b
OH
Cl
I
I
I
O
5
6
7
O
O
c
d
O
I
OH
I
O
O
2
8
Scheme 2. Synthesis of dechloro-4-iodo-fenofibrate. Reagents and conditions: (a) SOCl2, dimethylformamide, CH2Cl2, 40 ◦C, 18 h; (b) AlCl3, anisole, CH2Cl2, 0 ◦C to rt, 4 h;
(c) AlCl3, toluene, 100 ◦C 1 h; (d) BrCMe2CO2iPr, K2CO3, MgSO4, dimethylformamide, 75 ◦C, 10 h.
2.1.5. Synthesis of [125/131I]
2-[4-(4-iodobenzoyl)phenoxy]-2-methylpropanoic acid
isopropylester (3, 4)
Wildbad, Germany). The results were expressed as the percentage
of the injected dose per gram (%ID/g) and injected dose (%ID) of
blood and organs.
Approximately 1 ␮L (13 MBq = 0.351 mCi) iodine-125 or iodine-
131 (formulated as sodium iodide in 0.05 M NaOH) and 5 ␮L 4.5%
H2O2 in acetic acid were added to the stannyl precursor 9 (15.4 ␮g,
5 mM) in 5 ␮L absolute ethanol. After 15 min the reaction mixture
was diluted with 50 ␮L ethanol and purified by RP-HPLC. After
evaporation of the solvent 5.06 MBq of the radiolabeled product
could be obtained.
3. Results and discussion
A new method of labeling fenofibrate for in vivo monitoring
was investigated. For this purpose fenofibrate was labeled with
iodine. As attempts of direct labeling of fenofibrate (Kometani
et al., 1985a,b) or substituting the chlorine by iodine (Klapars and
Buchwald, 2002) or metal (Sheppard, 2009) failed, a de novo syn-
thesis of the iodinated analogue of fenofibrate 2 (Scheme 1) was
developed. To our best knowledge this compound had not been
described previously. Dechloro-4-iodofenofibrate can be obtained
via a Williamson type etherification of benzophenone 8 and
isopropyl-2-bromo-2-methylpropanoate (see Scheme 2).
The benzophenone 8 was prepared according to the literature
using a Friedel-Crafts acylation of anisole with 4-iodobenzoyl chlo-
ride (Davies et al., 2009) followed by deprotection of the phenolic
group with AlCl3 (Britton, 2005; Hartmann and Gattermann, 1892).
Etherification with isopropyl-2-bromo-2-methylpropanoate using
a Williamson type ether synthesis (Gustafsson et al., 2008) led to
the literature unknown cold precursor 2 which was obtained in
63% yield after two crystallization steps. The synthesis protocol cir-
cumvents the need of time consuming column purification steps.
All compounds can be purified by precipitation or crystallization.
Consequently, it is possible to run the synthesis in a multigram
scale.
The transformation of the cold iodine (Scheme 3) was done by
a halogen–metal–halogen exchange in a similar route as shown
by Mühlhausen et al. (2006). The stannyl precursor 9 was puri-
fied by preparative RP-HPLC. It has been proven that relinquishing
the acidic additive in the eluent buffer is necessary. As a last step
destannylation of compound 9 was performed under very mild
conditions using dihydrogen peroxide in acetic acid. Besides, the
radiolabeling could also be done using the HPLC-eluate. The final
compound 3 could be easily identified by RP-HPLC due to a shift in
the retention time caused by the decreased polarity of the stan-
nylated compound 9 compared to the iodinated ones 2, 3 or 4
(Fig. 1).
Fenofibrate is used as a prodrug that is metabolized into the
active drug fenofibric acid. Consequently, saponification experi-
ments were performed with the modified model drug 2. A solution
of 2 in methanol was treated with NaOH and heated to 95 ◦C. HPLC
analysis showed a complete conversion to the corresponding iod-
ofenofibric acid after 1 h. This product was characterized by high
2.2. Serum and liver stability
A solution of [125I]-dechloro-4-iodo-fenofibrate (fraction of
HPLC, 40 ␮L) was added to 12.5 amounts of human serum (500 ␮L)
or homogenized mouse liver and incubated at 37 ◦C. After various
times, samples of 50 ␮L were mixed with 50 ␮L acetonitrile. The
samples were centrifugated and the supernatant was added again
to 50 ␮L acetonitrile. The stability of the compound was determined
by HPLC analysis.
2.3. Scintigraphic imaging and biodistribution in mice
For scintigraphic imaging and biodistribution experiments, the
labeled
[ [
125I]-dechloro-4-iodo-fenofibrate or 131I]-dechloro-4-
iodofenofibrate were purified by HPLC. Female NMRI (a non-inbred
Swiss-type model) mice, weighing 20–29 g, were used for imaging
and biodistribution studies according to the microdosing con-
cept (Wagner and Langer, 2011). All experiments were performed
in compliance with German laws. For imaging purposes [125I]-
dechloro-4-iodo-fenofibrate (5 MBq, ∼20 ␮g) was formulated in
100 ␮L of a mixture of solvents containing 60% propylene gly-
col, 20% phosphate buffered saline, 10% dimethyl sulphoxide and
10% ethanol and injected intravenously via the tail vein. Scintigra-
phies (␥-imager/Biospace Lab, Paris, France) of the whole animal
were performed 5 min, 10 min, 30 min, 1 h, 2 h, 6 h and 24 h after
injection. During the first 2 h the animal was kept in anesthe-
sia. At the following points in time, the mouse was anesthetized
for each measurement. After 24 h the mouse was sacrificed by
cervical dislocation. For the biodistribution study [131I]-dechloro-
4-iodo-fenofibrate (approximately 4 ␮g, corresponding to 2 MBq)
formulated as described above was injected intravenously via the
tail vein. After 30 min, 6 h and 24 h post injection the animals were
sacrificed. For each time point n = 3 was used. Samples of blood
and organs of interest were removed, weighed and counted in an
automatic ␥-counter (Berthold LB 951G/Berthold Technologies, Bad

S. Breyer et al. / International Journal of Pharmaceutics 431 (2012) 78–83
81
O
O
O
a
b
O
I
Bu3Sn
X
O
O
X = 125I 3; X = 131I 4
2
9
Scheme 3. Synthesis of the radiolabeled dechloro-4-iodo-fenofibrates. Reagents and conditions: (a) (SnBu3)2, [Pd(PPh3)2Cl2], dioxane, 100 ◦C, 3 h; (b) Na125I or Na131I, 4.5%
H2O2 in CH3COOH, ethanol, rt, 15 min.
intravenously into a NMRI mouse. The time dependent distribu-
tion of the tracer was visualized on a ␥-camera. Scintigraphies of
the whole animal were performed 5 min, 10 min, 30 min, 1 h, 2 h,
6 h and 24 h after intravenous injection (Fig. 3). Already after 5 min
the 125I-labeled fenofibrate showed a predominant accumulation
in the liver. The high concentration in the liver persisted during
the first 6 h. The images at later points in time also showed the
localization in the gastro-intestinal tract. This might be explained
by an enterohepatical recirculation of 3 and its metabolites. For-
tunately, we observed no accumulation of activity in the thyroid,
which would reveal deiodination.
To correlate the images with quantitative uptake values a
biodistribution study to determine the activity concentrations was
performed at 30 min, 6 h and 24 h post injection. For this purpose
compound 4 was used. Each mouse was dosed with approximately
Fig. 1. RP-HPLC profile of the compounds 2, 9 and 4.
2 MBq (corresponding to 2 ␮g) of 4. The biodistribution data rep-
resented as percent of the injected dose (% ID) are shown in Fig. 4.
According to the imaging experiment most of the activity can be
resolution mass spectrometry and used as a non-radioactive refer-
found in the liver, kidneys and intestinal tract.
ence for the radioactive drug.
Due to the almost complete disappearance of radioactivity
With the radioactive model drug 4, we did first in vitro exper-
iments (Fig. 2). We investigated the stability of compound 4 in
within 24 h the total activity of excretion was determined. This
investigation showed that approximately 80% of the activity had
human serum, homogenized mouse liver and carbonate buffer (pH
been excreted which correlates with data known for fenofibrate
9.6). We observed a high stability of 4 in carbonate buffer and
(Weil et al., 1988). As shown in Fig. 5 during the first 4 h excretion
human serum. First conversion to iodofenofibric acid in human
occurred mainly via urine and up to 24 h predominantly via the
serum could be observed after 43 h. Even after 138 h the main
compound was 4 and not the corresponding iodofenofibric acid. In
feces. HPLC analysis of the recovered urine confirmed the absence of
free iodide and therefore deiodination of 4. This finding reveals that
contrast the whole compound 4 was converted to the correspond-
the iodinated fenofibrate derivatives developed constitute highly
ing iodofenofibric acid after 15 min in homogenized mouse liver.
stable model drugs of hydrophobic drugs, which allow the exami-
These results encourage us to extend the experiments to further
nation of drug delivery systems.
in vivo and in vitro studies.
The lack of compound 4 in the urine indicates its complete
Based on the in vitro experiments an imaging study was per-
conversion into its metabolites. Two more polar compounds,
corresponding to dechloro-4-iodofenofibric acid glucuronide and
formed to determine the distribution of the 125I-labeled tracer in
a mouse model. For this purpose a single dose of 3 was injected
Fig. 2. Stability study of dechloro-4-iodofenofibrate under in vitro conditions. Compound 2 was incubated in carbonate buffer (pH 9.6) at 37 ◦C and RP-HPLC chromatograms
were recorded (at 214 nm) to analyze the stability (chromatogram A). Compound 4 was incubated in human serum (chromatogram B) or in homogenized mouse liver
(chromatogram C) at 37 ◦C and radio-RP-HPLC chromatograms were recorded at the times indicated to analyze the stability of the substance.

82
S. Breyer et al. / International Journal of Pharmaceutics 431 (2012) 78–83
Fig. 3. Time course of the scintigraphic imaging of [125I]-dechloro-4-iodofeofibrate in a NMRI mouse after intravenous application.
A preliminary imaging and biodistribution study demonstrated
the utility of [125I/131I]-dechloro-4-iodofenofibrate as a tracer. The
obtained data for dechloro-4-iodofenofibrate indicate similar char-
acteristics to that of 14C-fenofibrate in literature (Weil et al., 1988).
The introduction of the radiolabel offers an access to further exper-
iments to evaluate the influence of different formulations on the
pharmacokinetic behavior of lipophilic drugs in the body and its
biodistribution.
Acknowledgements
This work was supported by the BMBF (Bundesministerium für
Bildung und Forschung) BioRN Cluster Project No. BioRN-INC-04.
The authors would like to gratefully thank T. Müller and K. Leotta
for assistance in the bioimaging and biodistribution experiments.
Appendix A. Supplementary data
Fig. 4. Results of the biodistribution of [131I]-dechloro-4-iodofenofibrate in NMRI
mice presented as % injected dose (% ID). The data show the activity at 30 min, 6 h
and 24 h post injection.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.ijpharm.2012.04.039.
90
feces
urine
80
70
60
50
40
30
20
10
0
References
Adkins, J.C., Faulds, D., 1997. Micronised fenofibrate: a review of its pharmaco-
dynamic properties and clinical efficacy in the management of dyslipidaemia.
Drugs 54, 615–633.
Britton, J., 2005. Cycloalkylidene compounds as modulators of estrogen receptor,
PCT/US2004/024308.
Chapman, M.J., 1987. Pharmacology of fenofibrate. Am. J. Med. 83, 21–25.
Cornu-Chagnon, M.C., Dupont, H., Edgar, A., 1995. Fenofibrate: metabolism and
species differences for peroxisome proliferation in cultured hepatocytes. Fun-
dam. Appl. Toxicol. 26, 63–74.
Davies, D.R., Mamat, B., Magnusson, O.T., Christensen, J., Haraldsson, M.H., Mishra,
R., Pease, B., Hansen, E., Singh, J., Zembower, D., Kim, H., Kiselyov, A.S., Burgin,
A.B., Gurney, M.E., Stewart, L.J., 2009. Discovery of leukotriene A4 hydrolase
inhibitors using metabolomics biased fragment crystallography. J. Med. Chem.
52, 4694–4715.
2
4
6
24
time (h)
Fig. 5. Results of urinary and fecal excretion study of
iodofenofibrate in NMRI mice presented as % injected dose (% ID). The data show
the activity excreted from 2 h up to 24 h post injection.
[
131I]-dechloro-4-
Eisenhut, M., Mier, W., 2003. Radioiodination chemistry and radioiodinated com-
pounds. In: Rösch, F. (Ed.), Handbook of Nuclear Chemistry, vol. 4. Kluwer
Academic Publishers, New York, NY, pp. 257–278.
Guichard, J.P., Blouquin, P., Qing, Y., 2000. A new formulation of fenofibrate: supra-
bioavailable tablets. Curr. Med. Res. Opin. 16, 134–138.
Guivarc’h, P.H., Vachon, M.G., Fordyce, D., 2004. A new fenofibrate formulation:
results of six single-dose, clinical studies of bioavailability under fed and fasting
conditions. Clin. Ther. 26, 1456–1469.
reduced dechloro-4-iodofenofibric acid glucuronide could be iden-
tified per HPLC (analyzed after 4 h post injection). These compounds
are known as the main metabolites of fenofibrate in urine after oral
dosage (Chapman, 1987).
Gustafsson, T., Ponten, F., Seeberger, P.H., 2008. Trimethylaluminium mediated
amide bond formation in a continuous flow microreactor as key to the synthesis
of rimonabant and efaproxiral. Chem. Commun. (Camb.), 1100–1102.
Hartmann, C., Gattermann, L., 1892. Saponification of phenol ethers and their deriva-
tives, as well as acid ethers, by aluminium chloride. Ber. Dtsch. Chem. Ges. 25,
3531–3534.
Kalivoda, A., Fischbach, M., Kleinebudde, P., 2012. Application of mixtures of
polymeric carriers for dissolution enhancement of fenofibrate using hot-melt
extrusion. Int. J. Pharm. http://dx.doi.org/10.1016/j.ijpharm.2012.03.009.
Klapars, A., Buchwald, S.L., 2002. Copper-catalyzed halogen exchange in aryl halides:
an aromatic Finkelstein reaction. J. Am. Chem. Soc. 124, 14844–14845.
Kometani, T., Watt, D.S., Ji, T., 1985a. Iodination of phenols using chloramine T and
sodium iodide. Tetrahedron Lett. 26, 2043–2046.
4. Conclusion
In conclusion we could develop a convenient synthetic access
to dechloro-4-iodofenofibrate (2) in an efficient way and to label it
with either 125I for imaging or 131I for biodistribution experiments.
In vitro experiments showed a high stability of the radiolabeled
compound in human serum and a conversion of the prodrug
into the biological active derivate in homogenized mouse liver.

S. Breyer et al. / International Journal of Pharmaceutics 431 (2012) 78–83
83
Kometani, T., Watt, D.S., Ji, T., Fitz, T., 1985b. An improved procedure for the iodina-
tion of phenols using sodium iodide and tert-butyl hypochlorite. J. Org. Chem.
50, 5384–5387.
Mochalin, V.N., Sagar, A., Gour, S., Gogotsi, Y., 2009. Manufacturing nanosized fenofi-
brate by salt assisted milling. Pharm. Res. 26, 1365–1370.
Mühlhausen, U., Schirrmacher, R., Piel, M., Lecher, B., Briegert, M., Piee-Staffa, A.,
Kaina, B., Rösch, F., 2006. Synthesis of 131I-labeled glucose-conjugated inhibitors
of O6-methylguanine-DNA methyltransferase (MGMT) and comparison with
nonconjugated inhibitors as potential tools for in vivo MGMT imaging. J. Med.
Chem. 49, 263–272.
Munoz, A., Guichard, J.P., Reginault, P., 1994. Micronised fenofibrate. Atherosclerosis
110, 45–48.
Patel, S.K., Lavasanifar, A., Choi, P., 2010. Molecular dynamics study of the encapsu-
lation capability of a PCL-PEO based block copolymer for hydrophobic drugs
with different spatial distributions of hydrogen bond donors and acceptors.
Biomaterials 31, 1780–1786.
Penn, R., Williams, 3rd, R.X., Guha-Ray, D.K., Sawyers, W.G., Braun, S.L., Rains, K.T.,
2006. An open-label, crossover study of the pharmacokinetics of insoluble drug
delivery-microparticle fenofibrate in combination with atorvastatin, simvas-
tatin, and extended-release niacin in healthy volunteers. Clin. Ther. 28, 45–54.
Sheppard, T.D., 2009. Metal-catalysed halogen exchange reactions of aryl halides.
Org. Biomol. Chem. 7, 1043–1052.
Strickley, R.G., 2004. Solubilizing excipients in oral and injectable formulations.
Pharm. Res. 21, 201–230.
Vogt, M., Kunath, K., Dressman, J.B., 2008. Dissolution enhancement of fenofibrate
by micronization, cogrinding and spray-drying: comparison with commercial
preparations. Eur. J. Pharm. Biopharm. 68, 283–288.
Wagner, C.C., Langer, O., 2011. Approaches using molecular imaging technology –
use of PET in clinical microdose studies. Adv. Drug Deliv. Rev. 19, 539–546.
Weil, A., Caldwell, J., Strolin-Benedetti, M., 1988. The metabolism and disposition of
fenofibrate in rat, guinea pig, and dog. Drug Metab. Dispos. 16, 302–309.