Note: Descriptions are shown in the official language in which they were submitted.
8~
DESCRIPTION OF THE INVENTr
The present invention concerns. new esters of aryl-
propionlc acids, characterized by the general formula (I)
IH3 3
R' ~ CH-C-0-(CH2CH~O)n-C-IH - ~
R" 1~"
(I)
where n represents a number ranging between 4 approximately
and 100 approximately while R' may be a hydrogen atom (in
which case R" represents the isobutyl, benzoyl, 2-tenoyl or
l-oxo-2-isoindolinyl residue) or R' may be a phenyl group
(in which case R" represents a fluorine atom or still R' and
R" represent together a benæene ring orthocondensated on the
first ring, and carrying a methoxyl group. R' and R",
preferably, are such as that tI) represents diesters of
polyethylene glycols with the 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 that are all known
for their anti-inflammatory properties. Preferably, moreover,
_ takes mean values ranging between 10 approximately and 50
approximately. The present invention, moreover, also concerns
the enantiomers of the esters characterized by the 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
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evidence constitutes a considerable advantage since the
corresponding acids are generally characterized by a short-
texm action. Also pharmacokinetic investigations show a
bioavailability 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-
An additional object of the present invention is
represented by a procedure for the preparation of the esters
(I), that consists in reacting the compounds of formula (II)
CH3
CH-~OX (II)
R"
where R' and R" have the above stated significance while X
represents either a hydroxyl group or preferably an activating
group such~an alkoxyl, Cl, l-imidazolyl group or still a
residue apt to form, with the remaining moiety of the mole-
cule, an anhydride function), with a polyethylene glycol,
characterized by the formula HO-(CH2CH2O)n-H, where n has
the above stated significance, preferably ranging (as mean
value) between 10 approximately and S0 approximately. Pre-
ferably, the compounds (II) are brought into reaction with
polyethylene glycols in a molar ratio of 2:1 approximately,
preferably around 2.5:1, in order to ensure the maximum diester
yield.
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The below reported example duly illustrates the
invention, constituting however no limitation to its scope.
_.MPLE 1
Die~ster of 2-(4-isobutyl-phenyl)propionic acid with poly-
ethylene glycol 1000 (n=20, 3 in the mean).
CH3 CH
~ ~ cH c o(cH2cH2o)n c cH ~ 7 R
where R=isobutyl; n=20.3 (in the mean)
21 grams (0.102 moles) of 2-(4-isobutyl-phenyl)propionic acid
(ibuprofen) are dissolved in 300 ml of anhydrous CHC13. The
resulting solution is added with 21 g of carbonyl-diimidazole
(CDI, 0.13 moles) under agitation, at room temperature. As
soon as the effervescence is terminated (half-an-hour
approximately), the reaction mixture is added with 40 g of
polyethylene glycol 1000 (0.4 moles) previously dried under
vacuum at 30C and dissolved in 200 ml of anhydrous CHC13.
The reaction is caused to occur in a thermostatized bath at
60C for 48 hours. The excess of ibuprofen results to be
25 percent approximately with respect to the quantity
- required for the formation of the diester.
The resulting solution is washed two times with
20 100 ml of water, two times with 100 ml of 0.1 N HCl, two
further times with 100 ml of water, still two times with 100 ml
of 0.1 N NaOH, and finally three times with 100 ml of water.
After drying on Na2SO4, the solution is filtered
and concentrated under vacuum. The concentrated solution is
shaken with anhydrous n-heptane (about 1000 ml); n-heptane
is then decanted, and anhydrous ethyl ether (500 ml approxi-
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mately) is added cooling down to 0-5C in order to reduce
to a minimum the solubility of the diester.
After further decantation, the product is dried
under vacuum (0.1 mm Hg). The product solidifies, taking a
waxy consistence, only after elimination of any trace of
solvent. Yield 40 g (73 percent).
On the basis of the NMR spectrum (Figure 1) the
overall rate of esterification results to correspond to 25
percent in weight of ibuprofen that can be liberated. This
datum proves comparable with the one provided by the indirect
titration (theoretical: 1.67 meq; practical: 1.525 meq.,
equivalent to 27.3 percent of ibuprofen that can be liberated);
moreover, the direct titration indicates the absence of un-
bound ibuprofen.
The resulting product (that for brevity's sake
shall be from now on called with the code name MR-654) is
scarcely soluble in water, in aliphatic hydrocarbons and in
diethylether, soluble in methanol, ethanol and acetone. Its
TLC characteristics shall be reported further on.
EXAMPLE 2
Diester of 2-(4-isobutyl-phenyl)propionic acid with poly-
ethylene glycol 2000 (n = 43.04 in the mean)
C~3 C~
R __ ~ H-c-O(c~2cH2o)~-c-cH -
where R = isobutyl; n = 43.04 (in the mean)
As analogously as in Example 1, 11 g of ibuprofen
(0.053 moles) are dissolved in 150 ml of anhydrous CHC13.
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The resulting solution is added with 11 g of CDI (0.068 moles),
under agitation at room temperature.
As soon as the effervescence is terminated (half-
anwhour approximately), the reaction mixture is added with
40 g of polyethylene glycol 2000 (0.02 moles), previously
dried under vacuum at 30C, dissolved in 200 ml of anhydrous
CHC13. The excess of ibuprofen results to be 33 percent
approximately with respect to the desubstitution of poly-
ethylene glycol 2000. The reaction is caused to occur in a
thermostatized bath at 68C for 48 hours.
The chloroform solution is 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, still two times with
100 ml of 0.1 N NaOH, and finally three times with 100 ml
of water. After drying on Na2S04, the resulting solution is
filtered and concentrated under vacuum. The product is
precipitated by addition, to the concentrated solution, of
1 liter of a 2:1 n-heptane/ether mixture (anhydrous solvents).
The precipitate is filtered by pump and dried under vacuum
(0.1 mmHg). Yield 42 g (88 percent).
On the basis of the NMR spectrum (FIGURE 2) the
overall esterification rate results to correspond to 15~percent
approximately, in weight, of Ibuprofen that can be liberated.
This datum coincides with the datum resulting from the in-
direct titration (theoretical:0.85 meq; practical:0.75 meq.);
moreover the direct titration proves the absence of unbound
ibuprofen.
The resulting product (that, for brevity's sake
shall be defined from now on with the code name MR-655) is
scarcely soluble in aliphatic hydrocarbons and in diethyl-
..~,i~
1~48~6~
ether, soluble in water, alcohols and acetone. The diesters
MR 654 and MR-655 were subjected to chromatography on Merck
60 Kieselgel plates; the elution was carried out wi~h a MeOH/
CHC13/glacial AcOH in a 70:35:4 ratio.
Ibuprofen, polyglycols and diesters present with
the following coefficients of retention:
Rf
MR-654 0.68
MR-655 0.47
~buprofen 0.78
PEG 1000 0.4
PEG 2000 0.32
The spots, pertaining to the two oligomeric
derivatives (I) are single. TLC does not reveal in any case
the presence of unbound ibuprofen. The replication of the
preparations of the products MR-654 and MR-655 allowed to
remark their reproducibility.
The pharmacotoxicologic properties of the diesters
(I) are hereinbelow described on the basis of the examples
provided by the compounds MR-654 and MR-655.
ACUTE TOXICITY
The acute toxicity of the two products, established
orally in the mouse, provided LD50 values higher than 2a00
mg/kg. Also the gastric injuring effects of MR-654 and
MR-655 result to be very low, i.e. mildly lower than those
induced by ibuprofen.
ANTI-INFLAMMATORY ACTIVITY
The anti-inflammatory activity of MR-654 and MR-655
was assessed in comparison with that of ibuprofen, at equi-
molar doses, by the carrageenin edema test in the rat (Wistarmale and female animals, bodyweight of 160-200 g; twelve
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animals for each compound and for each experiment). One
percent carrageenin in saline was injected, at the dosage
rate of 0.1 ml, subcutaneously, into the plantar area of
the left paw. Ibuprcfen was given at doses of 100 mg/kg/os
(in 5 percent gum arabic); MR-654 and MR-655 were given
in doses equivalent to 100 mg/kg/os of ibuprofen, i.e. of
370 and 625 mg/kg/os.
The products were administered 1, 3 and 6 hours
respectively before the carrageenin injection; the values
were always read 4 hours after the injection of carrageenin
assessing the percent swelling of the paw versus the value
observed at the time O (carrageenin inocule). The results
were expressed in terms of percent protection considering
the swelling, observed in the control group, as equal to
100 .
The protection exerted by the investigational com-
pounds is expressed in the attached Table 1, which enables
to remark that the anti-inflammatory action of MR-654 and
MR-655 is exerted according to a typical slow release effect.
TABLE 1
Percent protection from the carrageenin edema after oral
administration, in the rat, of ibuprofen, MR-654 and MR-655,
control groups being made equal to 100.
Product Detection after hours
1 2 3 4 6
Ibuprofen 60 4428 24 20
MR-654 45 4954 45 27
MR-655 50 4226 24 32
Actually, the activity of ibuprofen results to be
much higher than that exerted by the other two compounds at
the first hour; but, already starting from the second hour,
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the new related values can be considered almost comparable.
From third hour on, a quite different pattern is
observed, i.e.:
- the activity of ibuprofen decreases markedly and constantly;
- MR-654 attains in these detections a maximum peak of
efficacy that results to be prolonged in the course of
time keeping, despite a dropping parabola, values always
markedly higher than those provided by ibuprofen;
- in the case of MR-655, progressively from the third hour,
the line of activity increases gradually and markedly
through an evident delayed release.
PHARMACOKINETICS
The plasma pharmacokinetics of MR-654 and MR-655
was investigated following oral administration in the albino
rat, Wistar strain, male sex, bodyweight ranging between 180
and 220 grams. Since said compounds liberate ibuprofen into
the body, the kinetics of said latter drug was also investi-
gated at the doses of 58.8 mg/kg and 19.2 mg/kg.
In the case of ibuprofen, the plasma kinetics was
also investigated after oral administration to the purpose
of being provided with an assessment of the rate of intestinal
absorption of this drug.
The investigational compounds were given by oral
gavage, suspended in 0.5 percent gum arabic; an analogous
suspension was also used in the case of intraperitoneal
administration. Blood withdrawals from the animals were
made from a sublingual vein, according to the procedure
described by Ferro Milone M and Barbiera P. ~Atti della Soc.
It.Scienze Veterinarie, 1974, 28, 394).
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The plasma determination o~ ibuprofen was carried
out by a gas chromatographic method accord;`n~ to the
procedure descri~ed by Runci F.M. and Segre G. (Recent
Development in Chromatography and Electrophoresis, A.Frigerio,
L.Renoz Eds., Elsevier, Amsterdam, 1~79, page 199).
Table 2 shows the plasma kinetic patterns after
oral and intraperitoneal administration of 58.8 mg/kg, and
after oral administration of 19.2 mg/kg. The intraperitoneal
kinetics, provided that it can be assimilated to the intra-
venous kinetics, can be expressed by the following biexpon-
ential equation:
X(t) = 468 e~2 1t+32 e-0.23t
where X = concentration as 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 areas under the curve (AUC) are in a first
approximation (for times up to the 7th hour) equivalent to
190 (os) and 325 (ip), in a ratio equivalent to a 60 percent
level.
The kinetic patterns of MR-654 and MR-655 are shown
in Table 2; the content of ibuprofen of the two molecules
is such that the used dose of MR-654, equivalent to 120~mg/kg,
corresponds to 38.8 mg/kg of ibuprofen while the dose of
MR-655, equivalent to 19.2 mg/kg, corresponds to 19.2 mg/kg
of ibuprofen.
On the basis of said content of ibuprofen, the
plasma curves were compared with the curves resulting from
the administration of 58.8 and 1~.2 mg/kg of ibuprofen. In
the case of MR-654 the comparison was also made with said
two doses of ibuprofen since the plasma kinetics of ibuprofen
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had not been investigated at the dose of 38.8 mg/kg. A line
going through the peaks (at the first hourl of the plasma
le~els of ibuprofen at the two tested doses (58.8 and 19. 2
mg/kg) was plotted in order to better assess the kinetic
patterns. It could be stated on the basis of said line that
MR-654 and MR-655 present with a slower drop of the plasma
concentration after the peak (and therefore a longer half-
life) and can therefore be considered as long-acting ibuprofen.
TABLE 2
Plasma concentrations and standard deviations (mcg/ml) of
ibuprofen in the male rat, after intraperitoneal and oral
administration of MR-654, and oral administration of MR-655.
.
Product Dose given 0.5 hour of adm~nistration
mg/k~ 1 2 5 7
Ibuprofen os 19.2 26.2- 10. 5- 0.12+
9.7 1.9 0.03
Ibuprofen i.p, 58.8 215.2-104.7- 18.3- 6.2-
33.4 12.4 11.0 2.4
Ibuprofen os 58.8 71.7- 34.2- 12.1- 9.1-
23.6 7.7 2.2 1.5
MF<-654 os 120(*)116.1-39.3-12.9- 10. 7-
11.7 14.2 3.5 3.0
MR-655 os 120(**) 13.4- 10.9- 7. 5-7. 2-
2.1 2.7 0.30.4 ;
(*) correspondent to 38.8 mg of ibuprofen
(**) correspondent to 19.2 mg of ibuprofen
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