Note: Descriptions are shown in the official language in which they were submitted.
~148165
DESCRIPTIOII OF THE INVENTION
The present invention concerns new esters of aryl-
propionic acids characterized by the general formula (I)
CH
~ ' 3
R~ ~
R" (I)
where R represents the -(CH2CH2O)3-CH-2CH2OH residue; R' may
be a hydrogen atom, in which case R" represents the isobutyl,
benzoyl, 2-tenoyl or 1-oxo-2-isoindolinyl residue or
alternatively R' may be a phenyl group in which case R"
represents a fluorine atom or still R' and R" may together
represent a benzene ring orthocondensated on the former and
carrying a methoxyl group. Preferably, R' and R" are such
that (I) represents esters of tetraethylene glycol with
2-(4-isobutyl-phenyl)-, 2-[4-2-(tenoyl)-phenyl]-, 2-[4-(1-oxo-
2-isoindolinyl)phenyl]-, 2-(3-benzoyl-phenyl)-, 2-(3-fluoro-
4-phenyl-phenyl) and 2-(6-methoxy-2-naphthyl)-propionic acids,
all known for their anti-inflammatory properties. The present
invention also concerns the enantiomers of the esters of
formula (I).
The compounds (I), comparable to the corresponding
acids with respect to their properties of low toxicity and
gastric injuring effects, present with an anti-inflammatory
activity that, although showing an equivalent intensity,
differs markedly for a more prolonged duration. This
evidence represents a considerable advantage since the corres-
ponding acids are characterized generally by a short-term
- 1 - ~
~816S
action. Also pharmacokinetic investigations show a bio-
availability markedly higher, even of a 100 percent rate,
than that shown by the corresponding acids.
Therefore, a further object of the present invention
is represented by pharmaceutical compositions endowed with
an anti-inflammatory activity, containing as active ingredient
at least one ester of formula (I), in the form of a racemus
or of enantiomers.
A further object of the present invention is re-
presented by a procedure for the preparation of the esters
(I), that consists in reacting compounds of formula (II)
CH3
CH-COX (II)
R"
(where R' and R" have the above stated significance while X
represents either a hydroxyl group or preferably an activating
group such as alkoxyl, Cl, l-imidanolyl group or still a
residue apt to form an anhydride function with the remaining
moiety of the molecule) with an excess of tetraethylene
glycol. Preferably, the compounds (II) are reacied with
tetraethylene glycol, in a molar ratio at least equivalent
to 1:3.5, in order to ensure the maximum yield of monoester.
The below reported example illustrates the invention, con-
stituting however no limitation to its scope.
EXAMPLE
Monoester o~ 2-(4-isobutyl-phenyl)propionic acid with tetra-
ethylene glycol
~f~;
'~
1148165
3 \ ~ CH3
CH-CH2 ~ / ~ CH-C-O(CH2CH2O)3-CH2CH2OH
CH3
20 grams (0.09 moles) of 2-(4-isobutyl-phenyl) propionic
acid (ibuprofen) are dissolved in 250 ml of anhydrous
CHC13. The resulting solution is added with 20 g of carbonyl-
diimidazole (CDI, 0.12 moles, 33 percent excess) under
agitation, at room temperature. As soon as the effervescence
is terminated (30 minutes approximately), the reaction mixture
is added with 55.2 ml of tetraethylene glycol (0.32 moles,
250 percent excess approximately), previously dried on
CaSO4. The reaction is caused to occur in a thermostatized
bath at 60C for 48 h.
The solution is concentrated in a rotary evaporator,
and diluted thereafter with ethyl ether (250-300 ml). The
ether solution is then washed two times with 100 ml of water,
two times with 100 ml of 0.1 N HCl, two further times with
100 ml of water, two times with 100 ml of 0.1 N NaOH, and
finally three times with 100 ml of water.
After drying on Na2SO4, the resulting solution is
filtered and evaporated to dryness. The residue is purified
by washing with anhydrous n-heptane (500 ml approximately),
duly cooling in order to reduce to a minimum the solubility
of the product, appreciable also in apolar solvents.
n-Heptane is then decanted, and the product is dried under
vacuum (0.1 mmHg).80 percent yield.
On the basis of the NMR spectrum (see attached
figure), the overall rate of esterification results to
correspond to 50 percent approximately in weight of
. ~
~14~3165
2-(4-isobutyl-phenyl) propionic acid likely to be liberated.
Sa:id datum is comparable with the one resulting from the
indirect titration (theoretical:1.319 meq; practical:l.33 meq,
equivalent to 50.4 percent of acid likely to be liberated);
moreover, the direct titration states the absence of unbound
acid.
The resulting produ~t (that, for brevity's sake
shall be indicated from now on with the code name MR-653) is
practically insoluble in water, and soluble on the other hand
in methanol, diethyl ether, acetone and chloroform.
The MeOH/CHCl3/glacial acetic acid (70:35:4)
mixture was used for the elution on 60 Merck Kieselgel plates.
MR-653, the starting acid and tetraethylene glycol
show the following retention coefficients:
Rf
MR-653 0.8
Acid 0.78
Tetraethylene glycol 0.6
CHROMATOGRAPHIC TESTS
-
A single spot characterizes the presence of MR-653.
TLC does not show in any case the presence of unbound
2-(4-isobutyl-phenyl) propionic acid. A related perfect
reproducibility was observed repeating the preparations of
the compound MR-653. This evidence also proved valid in all
the cases in which the chloride of 2-(4-isobutyl-phenyl)-
propionic acid or its mixed anhydride with ethyl chloro-
carbonate are used in replacement of imidazolide.
The pharmacotoxicologic properties of the esters
(I) are herein described on the basis of the example provided
by MR-653.
~148~65
ACUTE TOXICITY: in the mouse, the oral LD 50 of MR-653
proved higher than 2000 mg/kg.
ANTI-INFLAMMATORY ACTIVITY
_
The anti-inflammatory activity of MR-653 was
assessed versus the one of ibuprofen, i.e. 2-(4-isobutyl-
phenyl)-propionic acid, at equimolar doses by the carrageenin
edema test in the rat (Wistar males and females, bodyweight
160-200 g, twelve animals per compound and per experiment).
1 percent carrageenin in saline was given, at the rate of
0.1 ml subcutaneously, into the plantar area of the left paw.
Ibuprofen was given at doses of 100 mg/kg/os(in 5 percent
gum arabic); MR-653 in doses equivalent to ibuprofen 100 mg/
kg/os, i.e. 200 mg/kg/os respectively.
The compounds were administered 1, 3 and 6 hours
respectively before the carrageenin injection; the related
values were always read 4 hours after the carrageenin
injection, duly assessing the percent swelling of the paw
versus the value at the time 0 (carrageenin inocula). The
results are expressed as percent protection considering the
swelling in the control group as equal to 100.
The protection exerted by the two compounds, versus
the edema induced by carrageenin, proved rapid and effective.
A comparable peak of activity is observed for both treatments
around the first hour; said peak, while undergoing in the
case of ibuprofen a rapid and progressive decrease even
starting from the second hour, proves on the contrary markedly
slower in the.case of MR-653, with a typical action prolonged
in the course of time, as results from the attached Table 1.
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Table 1 - Percent protection from the carrageenin edema
considering.the.control .gro.ups a.s eqN.al. to..l.00..
-
Drug Detection after hours
12 3 4 6
Ibuprofen 6044 28 24 20
MR-653 6459 47 44 34
ANALGESIC ACTIVITY
Abdominal squirmings were induced by an intraperitoneal
injection in saline, given at the dose of 4 mg/kg/20 ml.
The compounds ibuprofen and MR-653 had been given
one hour before, orally, at the dose of 100 mg/kg (equimolar
doses).
In the course of the 20 minutes subsequent to the
injection of phenylquinone, all animals were observed in
order to detect any squirming: the animals, presenting with
no squirming, were considered as protected. A 20 percent
protection (10 animals per group), versus the control group.
Acetylcholine Test
Squirmings were induced by an intraperitoneal injection of
aCetylcholine (200 ml; 0.5 ml per mouse); both compounds
were given orally one hour before the administration of
acetylcholine at the dose of 10 mg/kg, in equimolar doses.
After the administration of acetylcholine the animals were
observed for the subsequent 4 minutes, and considered
protected when presenting with no squirming. The below
reported results were obtained in comparison with the control
group:
Ibuprofen: 50 percent protection
MR-653 : 48 percent protection
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Gastric Injuring Effects
The possible gastric injuring effect of MR-653,
versus ibuprofen, was assessed on Wistar rats of either sex,
bodyweight ranging between 160 and 200 g, fasted for 24 hours
at the time of treatment. The compounds were given intra-
peritoneally at the equimolar dose of 500 mg/kg.
The animals were killed 5 hours after the treatment
in order to assess the conditions of the gastric mucosa, and
the possible presence of bleedings and ulcers.
Results
A punctiform ulcer was observed in 14 percent of the cases
in the group given ibuprofen; stomachs were presenting with
an almost normal mucosa with a fair quantity of a yellowish
foamy secretion. A comparable percent incidence of ulcero-
genic punctiform episodes ~16 percent), associated with the
presence of a mildly hyperemic peritoneal exudate, was also
observed in the group given MR-653.
PHARMACOKINETICS
The plasma kinetics of MR-653 was assessed, following
oral administration, in the male albino rat, Wistar strain,
bodyweight of 180-220 grams. Since said compound liberates
in the body a certain amount of ibuprofen, the kinetics'of
said latter drug, at the doses of 58.8 mg/kg and 19.2 mg/kg,
was also assessed. In the direct case of ibuprofen plasma
kinetics was also investigated after intraperitoneal
administration to the purposes of being provided with an
assessment of the rate of the intestinal absorption of this
drug. The investigational drugs were given by oral gavage,
suspended in 0.5 percent gum arabic; an analogous suspension
was used in the case of the intraperitoneal administration.
:1148~65
Blood withdrawals from the experimental animals
were made from a sublingual vein according to the procedure
described by M. Ferro Milone and P. Barbiera (Atti della Soc.
It.Scienze Veterinarie, 1974, 28,394). The plasma deter-
mination of ibuprofen was carried out by a gas chromatographic
method, according to the procedure described by F.M. Runci
and G. Segre (Recent Development in Chromatography and Electro-
phoresis, A. Frigerio, L.Renoz Eds., Elsevier, Amsterdam,
1979, p. 199).
Table 2 shows the plasma kinetic patterns of ibu-
profen after oral and intraperitoneal administration of 58.8
mg/kg.
If the intraperitoneal kinetics can be assimilated
to the intravenous kinetics, it can be expressed by a biex-
ponential equation, i.e.
X(T) = 468 e 2-1t+ 32 e-0.23t
where X = concentration in mcg/ml and t = hours.
The half-life, calculated on the basis of the
second component, results to be equivalent to 3 hours
approximately.
The AUC (areas under the curves) are on first
approximation (for times up to the 7th hour) equivalent-to
190 (os) and 325 (ip) with ratio equivalent to a 60 percent
rate.
Table 2 also shows the kinetics of MR-653; the
ibuprofen content is such that the dose used of MR-653
(128 mg/kg) corresponds to 58.8 mg/kg of ibuprofen.
On the basis of said content of ibuprofen, the
plasma curves were compared with the curves provided by the
administration of 58.8 mg/kg of ibuprofen.
1~8~6S
A line going through the peaks (at the first hour)
of the plasma levels of ibuprofen ~as plotted in order to
better compare the kinetic patterns. It could be therefore
seen, on the basis of said line, that the value results to
be markedly higher in the case of MR-653. Said compound,
therefore, shows an increased bioavailability (ranging on a
100 percent level, as can be assumed by extrapolation).
PHARMACOKINETICS
TAsLE 2 - Plasma concentrations (mcg/ml) and standard
deviation of ibuprofen in the male rat after intraperitoneal
and oral administration, and of MR-653 given orally.
Com~ound Dose given hours
mg/kg 0.5 1 2 5 7
Ibuprofen i.p. 58.8 215.2-33.4 104.7- 18.3- 6.2-
12.4 11.0 2.4
Ibuprofen os 58.8 71.7- 32.2- 12.1- 9.1-
23.6 7.7 22 1.5
MR-653 os 120 (x)118.4- 76.6- 45.2- 36.8-
20.7 12.9 23.7 11.3
X correspondent to 58.8 mg of Ibuprofen
It appears evident from the summation of the results
that MR-653, compared with ibuprofen at equimolar doses
exerts, although maintaining practically unchanged values of
toxicity and gastric injuring effects, a better anti-inflam-
matory activity that becomes evident with an earlier onset
of effects while higher values are kept in the course of time,
especially after the second hour. Actually, while in the
case of ibuprofen the anti-inflammatory activity results to
consist in a curve effect with highly marked drops, the
activity of MR-653 proves quite prolonged with values still
markedly high until the 6th hour, higher in fact, in a 48 per-
g _
, ~
1~8165
cent rate, than those encountered in the case of ibuprofen.
Said higher efficacy, especially in the longint:ervals, is also confirmed by the tests of pharmacokinetics
that demonstrate the higher bioavailability of MR-653 with
respect to ibuprofen for an approximate 100 percent rate.
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