Note: Descriptions are shown in the official language in which they were submitted.
CA 02419729 2004-09-23
C~.tXS'1<'AL FOlZM rY OF CLARITH~OM'YCrN
'technical Field
This invention relates to compounds having therapeutic utility and to methods
for
their preparation. More particularly, the present invention concerns the novel
compound 6-
O-methylerytlu~oznycin A crystal Foxltt I and a process fox its preparation
and uses of same.
Further, the present invention conce;txts the novel compound 6-O-
methylerythxoznycin A
crystal Form II, and compositions and uses thereof
Back~ound of the Invention
6-O-methylerythromycin A (Clarithromycin) is a semisyr~thetic macrolide
antibiotic of
formula
~5 0
oc~
6-Qmethyl erythromycin A
which exhibits excellent antibacterial activity against gram-positive
bacteria, some gram-
negative bacteria, anaerobic bacteria, Mycopdasma, and Chlamidia. It is stable
under acidic
conditions and is efficacious when adtniuistered orally, Clarithromycin is a
useful therapy for
infections of the upper respiratory tract in children and adults.
Brief Descn~tion of the Drawings
FIGS, la, lb and lc show, z~espectively, the powder X ray diffraction
spectnutz, the
infrared spectrum, and the differential scanning calorimetric (DSC) thermogxam
of 6-O-
methylerythromycin ,A, Form I.
CA 02419729 2004-09-23
-2-
FIGS. 2a, 2b and 2c show, respectively, the powder X ray diffraction spectrum,
the
infrared spectrum and the differential scanning calorimetric (DSC)
thermogra~c~n, of 6-O-
methylerythromycin A Form II.
Summary of the Invention
We have discovered that G-O-methylerythromycin A can exist in at least two
distinct
crystalline forms, which for the sake of identification are designated "Form
I" and "Form II".
The crystal forms are identified by their infrared spectrum, differential
scaxazting caloxi~metric
thermogram and powder x ray diffraction pattern. Form I and Form II crystals
have an
identical spectrum of antibacterial activity, but Forra 1 crystals
unexpectedly have an intrinsic
to rate of dissolution about three times that of Form II crystals.
Investigations in our laboratory
have revealed that 6-D-methylerythromycin A when recrystallized from ethanol,
tetrahydrofuran, isopropyl acetate, and isopropanol, or mixtures of ethanol,
tetrahydmfuran,
isopropyl acetate, or isopropanol with other common organic solvents results
in exclusive
formation of Form I crystals, not identified hitherto.
i s Drugs currently on the market are formulated from the thermodynamically
more
stable Form ZI crystals. Therefore, preparation of the current commercial
entity requires
converting the Form I crystals to Form II. Typically this is done by heating
the Form I
crystals under vacuum at ten~,perature of greater than 80°C. Therefore,
the discovery of a
novel form of 6-O-methylerythromycin A which can be prepared without the high
2o temperature treatment results in substantial processing cost savings. In
addition, the
favorable dissolution characteristics of Form I relative to Form II increases
bioavailability of
the antibiotic and provides significant formulation advantages.
The present invention in one embodiment provides, in a process fox the
production of
6-O-methylerythmmycin A Form I by conversion of erythromycin A to 6-O-
25 methylerythromycin A, with intermediate protection and deprotection
reactions and
subsequent crystallization or recrystallization of the 6-O-
methylerytltxozxtycin A to 6-O-
xnethylerythromycin A Fortxi I, that step comprising erystalliaing 6-O-
methylerythromycin A
Forrtt I from a syrup or semisolid containing at least ox~e residual solvent
from the
deprotection reaction.
3o In another embodiment, the aforementioned intermediate protection and
deprotection
reactions are carried out on an erythromycin A 9-oxime derivative.
CA 02419729 2004-09-23
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xn a further embodiment, in the aforementioned crystallizing step, at least
one solvent
additional to the residual solvent is utilized. Preferred additional solvents
are selected from
one or more ox combinations of ethanol, isopropyl acetate, isopropanol,
tetrahydrofuran, a
hydrocarbon of from 5 to 12 carbon atoms, a ketone of from 3 to 12 carbon
atorxxs, a
carboxylic ester of from 3 to 12 carbon atoms, an ether of from 4 to I O
carbon atoms,
benzene, benzene substituted with one or more substitutents selected from the
group
consisting of alkyl of from I to 4 carbon atoms, alkoxy of from 1 to 4 carbon
atoms, vitro,
and halogen, and a polar aprotic sovlent, A particularly preferred additional
solvent is
ethanol.
1o In a yet further embodiment, there is provided the use of such 6-O-
methylerythromycin A, Form I as an antibiotic and also in the manufacture of
an antibiotic
medicament, as well as 6-O-rnethyleryeltromycin A Form I when prepared by the
process of
the present invention.
In another aspect of the invention, there is provided 6-O-
rnethylerythron~;ycirr A Form
15 II produced from the aforesaid 6-O-methylerykhromycin A Form I by heating
the latter.
In a further embodimtent, there is provided an antibiotic pharmaceutical
composition
comprising the aforesaid 6-O-xnethylerythromycin A Form II together with a
pharmaceutically acceptable carrier. Preferred is a solid pharmaceutical
dosage form for oral
administration comprising such 6-O-methylerythromycin A Form II in combination
with one
20 or more pharmaceutically acceptable excipients, selected froixt one or more
of fillers, binders,
humectants, disintegrating agents, solution retarding agents, absorption
accelerators, wetting
agents, absorbents and lubricants.
In a fiuther embodiment, there is provided the use of such 6-O-
xnethylerythromycin A
Form II as an antibiotic and also in the manufacture of an antibiotic
medicament.
25 Detailed Descrivtion
6-O-methylerythromycin A is prepared by methylation of the 5-hydroxy group of
erythrorr~ycin A. I~owe~rer, in addition to the fi position, erythromycin A
contains hydroxy
groups at the 1 l, 12, 2' and 4" positions, and a nitrogen at 3' position, all
of which are
potentially reactive witlt alkylatin~g agents. 'therefore, it is necessary to
protect the various
3o reactive functionalities prior to alkylation of the 6-hydroxy group.
Representative 6-O-
CA 02419729 2004-09-23
-4-
methylerythromycin A preparations are described in U.S. Pat. Nos. 4,331,803,
4,670,549,
4,672,109 and 4,990,602 and European Patent Specification 260 938 B 1.
Following final removal of the protecting groups, the 6-O-methylerythromycin A
may
exist as a solid, a semisolid, or a syrup containing residual solvents from
the deprotection
reactions, inorganic salts, and other impurities. 6-O-methylerythromycin A
Form Z zxxay be
crystallized directly from the syrup or semisolid using the solvents described
above.
Alternatively, if the crude reaction product solidifies, the solid zx~ay be
recrystallized from
aaay of the solvents described above. Pure 6-O-methylerythromycin A Form I
rnay also be
obtaizted by recxystallizing Form II or mixtures of Form I and Norm II from
any of the solvent
1o systems described above. The term "6-O-methylerythromycin A" as used herein
is meant to
include 6-O-methylerythromycin A Form I or II in any state of purity, ox
mixtures thereof.
The term "treating" refers to crystallizing or recrystallizing 6-O-
methylerythromycin A as defined above from any of the solvents described
above.
The term "hydrocarbon" as used herein refers to straight chain or branched
alkanes
t5 having the formula C"Hz"+z. Hydrocarbons useful in the solvent mixtures of
the present
invention include hexane, heptane, octane and the like.
The term "alkyl" refers to a monovalent group derived from a straight or
branched
chain saturated hydrocarbon by the removal of a single hydrogezt atoxrr. Alkyl
groups are
exemplified by methyl, ethyl, n- send iso-propyl, n-, sec-, iso- and tent-
butyl, and the like,
20 The term "ketone" refers to a solvent of formula RC(O)R' where R and R' are
straight
or branched alkyl. Ketones useful in the solvent mixtures of the present
invention include
acetone, methyl ethyl ketone, 2- , and 3-pentanone, and the like.
The term "carboxylic ester" means a solvent of formula RCOzR' where R and R'
are
straight ox branched alkyl. Carboxylic esters useful in the solvent mixtures
of the present
25 invention include methyl acetate, ethyl acetate, isobutyl acetate, and the
like.
The term "ether" means a solvent of formula ROR' where R and R' are straight
or
branched alkyl. Ethers useful in the solvent mixtures of the present invention
include ethyl
ether, diisopropyl ether, xx~.ethyl tert-butyl ether, and the like.
CA 02419729 2004-09-23
-5-
The tear "polar aprotic" refers to solvents which do not contain hydroxy
groups but
have a relatively high dipole moment. Polar aprotic solvents useful in the
solvent mixtures of
the present invention include aaetonitrile, N',N dimethylformamide (DMI~,
dimethyl
sulfoxide (DMS4), 1,1- dimethoxyethane (DME), hexamethylphosphoric triamide
(HIVj~A),
and the like,
By "pharmaceutically acceptable salt" it is meant those salts which are,
within the
scope of sound rt~edical judgment, suitable for use in contact with the
tissues of humans and
lower animals without undue toxicity, irritation, allergic response and the
like, and are
commensurate with a reasonable benefitlrisk ratio. Pharmaceutically acceptable
salfis are well
ao known m the art. For example, S_ M Beige, et al, describe pharmaceutically
acceptable salts
in detail in J. Pharmaceutical Sciences, 1977, 66: 1-19 . 'fhe salts can be
prepared in situ
during the final isolation and purification of the compounds of the invention,
or separately by
reacting the free base function with a suitable organic acid. Representative
acid addition salts
include acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate,
benzoate, bisulfate,
15 borate, butyrate, camphorate, camphersulfonate, citrate,
cyclopentanepropionate, digluconate,
dodecylsulfate, ethanesulfonate, fumarate, glucoheptonate, glycerophosphate,
hemisulfate,
heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, 2-hydroxy-
ethanesulfonate,
lactobionate, lactate, laurate, lauryl Sulfate, malate, maleate, malonate,
methanesulfonate, 2-
naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate,
pamoate, pectinate,
20 persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate,
steaxate, succinate,
sulfate, tartz-ate, thiocyanate, toluenesulfonate, undecanoate, valerate
salts, and the like.
Representative alltali or alkaline earth metal salts include sodium,
lithiurr~, potassium,
calcium, magnesium, and the like, as well as nontoxic amrrtonium, quaternary
ammonium,
and amine cations, including, but not limited to ammonium,
tetramethylammonium,
2s tEtxaethylammonium, nnethylamine, dimethylamine, trimethylamine,
triethylamine,
ethylamine, and the like.
CA 02419729 2004-09-23
-S-
6-O-methylerythxomycin A is prepared from erythromycin A by a variety of
synthetic
routes. In ante method, erythromycin A is converted to 2'-O-3'-N
bis(benzyloxycarbonyl)-N
o
H=O O
,aH ~ z' oa=
,
OH
1o Q
demethylerythromycin A (I).
'flte 6-hydroxy group is then methylated by reaction with an alkylating agent
such as
bromomethane or iodomethane and a base. Removal of the benzoyl groups by
catalytic
t 5 hydrogenation arid reductive methylatiort of the 3' N' gives b-O-
xrtethylerythrotnycin A, See
U.S, Pat. No. 4,331,803.
An alternative synthetic route involves methylatlon of 6-O-
methylerythrortlycin A-9-
oxime. 6~0-methylerythromycin A-9-oxime is prepared by methods well hrtovvn in
the art
such as reaction of erythromycin A, with hydroxylamine hydrochloride in the
presence of
20 base, or by xeactior~ with hydroxylamine in the presence of acid as
described ixt US Pat. No.
5,274,085. Reaction oFthe oxime with RX wherein R. is ahyl or benzyl and X is
halogen
results in formation of 2'-0,3'-N-diallyl or dibettzylerythromycin A-9-O-allyl
or bextzyloxime
halide. lvJ;ethylation of this quaternary salt as described above, followed by
elinnination of the
R groups and deoximation gives 6-O-methylerythromycin A. See U.S. Pat. hIo.
4,670,549.
2s Methylation of 6-O-~nethyletythromycin A oxime derivatives of formula ZI,
pa ~ 1~'~ Ra
-,cue 1 s'
.,
--.,,, g ,,.",
30 HO~ ~ O - OCHs
O
t.
O
rI
CA 02419729 2004-09-23
wherein R is alkyl, alkenyl, substituted or unsubstituted berlzyl, oxyalkyl,
ox substituted
phenylthioalkyl, RZ is benzoyl, and R3 is methyl or benzoyl, followed by
deprotection,
deoximation, and reductive methylation when R3 is benzoyl gives 6-O-
rnethylerythromycin
A. See U.S. Pat. No. 4,672,109.
A particularly useful preparation of 6-O-methylerytllromycin A involves
methylation
of the
RIO z q2 \ 1~
9 . ,r.OH
O
no.,,, J-.,,,~ s~_.,,,.
~ ~ O ~ ~3
OR9
p 4.
oxim,e derivative III, wherein R1 is alkenyl, substituted or unsubstituted
bexlzyl, or
alkoxyalkyl, RZ is substituted silyl, and R3 is RZ or H. Removal of the
protecting groups and
deoximation is then accomplished in a single step by treatment with acid to
give 6-O
methylerythrolnycin A. See European Patent Specification 260 938 >31 and U.S.
Pat. No.
4,990,602.
A preferred route to 6-O-methylerythromycin A is outlined in Scheme 1.
Erythromycin A, prepared by fermentation of Streptomyces erythreus is oximated
to give
oxime 4 wherein Rl is alkoxyalkyl. The group R' may be introduced by reaction
of
erythromycin A with the substituted hydroxylamine R~ONHz> or by reaction of
etytl>rom.ycin
A with hydroxylamine hydrochloride in the presence of base, or hydroxylamine
in the
presence of acid, followed by reaction with R1X. The two hydroxy groups are
then protected
2s simultaneously, in which RZ or R3 are the same, or sequentially in which Rz
and R3 are
different. Particularly useful protecting groups are substituted silyl groups
such as
trimethylsilyl, tent-butyldimethylsilyl, tert-butyldiphenylsilyl and the like.
The protecting
groups are then removed and the compound is deoximated to produce 6-O-
methylerythromycin A. The order of deprotectionldeoximation is zlot critical.
'V'Vhen the
3o protecting groups are substituted silyl, deprotection and deoximatiort can
be accomplished in
a single step by treatment with acid, for example using formic acid or sodium
hydrogen
sulfite. See U.S. Pat. No. 4,990,602.
CA 02419729 2004-09-23
.$_
Scheme 1 ~'
'=. :~'~ _'~> v...'~..
p \ ~ ~1Q
r
'OOH 2 9 ',OOH 2
.~y~ HD O a . HO O
~1,,~ '~p,~ 6 ~-.W1 ~Ib~ '-b,' ~..N
Oximation
HDI~ -~ OCE'~8 HO~ - OCHa
a ~ o
~oe~ ~off
0 0~ o 0'\4
iv
Ernhrumycin A
i o R,o 2 ~ N'
s ~~a-r ~ z~
....,. ~ o
Protection Methulation
n.._ _
~.Ip~~ O ~ OCHa
Ir ,O ORs
4'
15 O
V
RIO fi2 ~~ O OH ~N~
9 ,,OCH3 ~ 2~ a g '~~ 1"b r O
O HOie.. '~~,,r ,,.,w
doprotoction
20 ~u.. «~...
HO ~ O OCH3
O ORa O OH
r 1 -°
~ O 4.
0 O' \ ' O
V 1 6-O-molhylorythromycin A
25 In accordance with the process aspect of the present invention, 6-O-
methylerythromycin A prepared by any of the methods described above is
suspended in the
desired solvent and heated to about the reflux temperature of the solvent.
);Ieating is then
continued and the suspension is stirred fox an amount of time sufficient to
dissolve most of
the solid, generally about 10 minutes to 2 hours. The suspension is then f
ltered hot. If
3o necessary, the filtrate may be heated to at or about the refltlx
terriperature of the solvent to
form a clear solution. The filtrate is then slo~uvly cooled to ambient
temperature with optional
further cooling in an ice water bath. For purposes of this specification,
ambient temperature is
from about 20 °C to about 25 °C. Crystalline 6-O-
methylerythroxnycin A, is then isolated,
preferably by Filtration, and the vcret solid is converted to 6-O-
methylerythroznyciza A Form T
CA 02419729 2004-09-23
-9-
by drying in a vacuum oven at a temperature of betaveen ambient temperature
and about 70
°C, preferably from about 40 to about 50 °C and a pressure of
between about 2 inches of
mercury and atmospheric pressure to remove any remaining solvent.
In accordance with the asgects of this invention wherein 6-O-
methylerythromyein A
is recrystallized from solvent mixtures, 6-O-nnethylerythromycin A is
suspended izt the first
solvez~t and heated to about the reflex temperature of the solvent. I-Ieating
is then cozttinued
and the suspension is stirred for an aritiount of time sufficient to dissolve
most of the solid,
generally about 10 minutes to 2 hours. The suspension is then filtered hot.
The filtrate may be
heated to reflex to form a clear solution if necessary. A second solvent is
then added to the
1o hot f ltrate and the mixture is cooled slowly to ambient temperature with
optional further
cooling in an ice bath. Representative second solvents include, but are not
limited to, he~tane,
heptane, octane, acetone, methyl ethyl ketone, 2-, and 3-pentanone, methyl
acetate, ethyl
acetate, isobutyl acetate, ethyl ether, diisopropyl ether, methyl tert-butyl
ether, acetonitrile,
N,N dimethylformamide, d,imethyl sulfoxide, 1,1-dimetho~cyethane,
hexarnethylphosphoric
z5 triamide, benzene, toluene, and chlorobenzene, Hydrocarbons of from, 5 to
12 carbon atoms
are preferred second solvents. The most preferred secoztd solvent is heptane.
After cooling, 6-
O-xr~ethylerythromycin A crystal Form I is isolated by filtration and drying
as described
above. The amount of second solvent added is dependent on the solubility of
the drug in the
first solvent and the second solvent, and can be readily determined by one
o~ordinary skill in
2o the art. Typical ratios fall in the range of about 1:10 to about 2:1 parts
by volume of second
solve:at, A preferred ratio of first solvent to seco~td solvent is 1:1 parts
by volume.
Preferred solvents for the isolation of 6-O-methylerythromycin A Form T are
ethanol,
isopropyl acetate, tetrahydrofuran, and isopropanol.
The xnost preferred solvent for the isolation of 6-O-methylerythrornycin A
Forum I is
25 ethanol.
Pharmaceutical Compositions
The present invention also provides pharmaceutical compositions which comprise
6-
O-methylerythromycir~ A Form I formulated together with one or more non-toxic
pharmaceutically acceptable carriers. The pharmaceutical corrrpositions may be
specially
3o formulated for oral administration in solid or liquid form, for paxenteral
inyection, or for rectal
administration.
CA 02419729 2004-09-23
- 10-
The pharmaceutical compositions of this invention can be administered to
humans
and other animals orally, rectally, parenterally, intracisternally,
intravaginally,
intraperitor~eally, topically (as by powders, ointments, or drops), bucally,
or as an oral or
nasal spray. The ternn "parenteral" administration as used herein refers to
modes of
administration which include intravenous, intramuscular, intxaperitoneal,
intrasternal,
subcutaneous and intraarticular injection and infusion.
Pharmaceutical compositions of this invention for parenteral injection
comprise
pharmaceutically acceptable sterile aqueous or nonaqueous solutions,
dispersions,
suspensions or emulsions as well as sterile powders for reconstitution into
sterile injectable
1D solutions or dispersions just prior to use. Examples of suitable aqueous
and nonaqueous
carriers, diluents, solvents or vehicles include ~uvater, ethanol, polyols
(such as glycerol,
propylene glycol, polyethylene glycol, and the like), and suitable mixtures
thereof, vegetable
oils (such as olive oil), and injectable orgaaic esters such as ethyl oleate.
Proper fluidity can
be maintained, for exatx~.ple, by the use of coating materials such as
lecithin, by the
is maintenance of the required particle size in the case of dispersions, and
by the use of
surfactants.
These compositions may also contain adjuwants such as preservatives, wetting
agents,
emulsifying agents, and dispersing agents. Prevention of the action o~
microorganisms may
be ensured by the inclusion of various antibacterial and antifvngal agents,
for example,
2o paraben, chlorobutanol, phenol sorbic acid, and the like. rt may also be
desirable to include
isotonic agents such as sugars, sodium chloride, and the like. Prolonged
absorption of the
injectable pharmaceutical form rnay be brought about by the inclusion of
agents which delay
absorption such as aluminum monostearate and gelatin.
1n some cases, in order to prolong the effect of the drug, it is desirable to
slow the
25 absorption of the drug from subcutaneous or intramuscular injection. This
may be
accomplished by the use of a liquid suspension of crystalline or amorphous
material with
poor water solubility. The rate of absorption of the drug then depends upon
its rate of
dissolution which, in turn, may depend upon crystal size and crystalline form.
Alternatively,
delayed absorption. of a parenterally administered drug form is accomplished
by dissolving or
30 suspending the drug in an oil vehicle.
Injectable depot forms are made by forming microencapsule matrices of the drug
in
biodegradable polyrr~ers such as polylactide-polyglycolide. Depending upon the
ratio of dxug
CA 02419729 2004-09-23
-11-
to polymer and the nature of the particular polymer eznploycd, the rate of
drug release can be
controlled. Examples of other biodegradable polymers include poly(arthoesters)
and
poly(anhydrides). Depot injectable formulations are also prepared by
entrapping the drug ins
liposomes or microemulsions which are compatible with body tissues.
The injectable forrmnlations can be sterilized, for example, by filtration
through a
bacterial retaining filter, or by incorporating sterilizing agents in the form
of stet~ile solid
compositions which can be dissolved or dispersed in sterile water or other
sterile injectable
medium dust prior to use.
Solid dosage forms for oral administration include capsules, tablets, pills,
powders,
1o and granules. In such solid dosage forms, the active compound is mixed
~uvith at least one
inert, pharmaceutically acceptable excipier~t or carrier such as sodium
citrate or dicalcium
phosphate and/or
(a) fillers or extenders such as starches, lactose, sucrose, glucose,
rnannitol, aad
5111C1C aCld,
15 (b) binders such as, for example, carboxymethylcellulose, alginates,
gelatin,
polyvinylpyrrolidone, sucrose, and acacia,
(c) humectants such as glycerol,
(d) disintegrating agents such as agar-agar, calciura carbonate, potato or
tapioca
starch, alginic acid, certain silicates, and sodium carbonate,
zo (e) solution retarding agents such as paraffin,
(fj absorption accelerators such as quaternary ammonium compounds,
(g) wetting agents such as, for example, cetyl alcohol and glycerol
monostearate,
(h) absorbents such as kaolin and bentonite clay, and
(i) lubricants such as talc, calcium stearate, magnesium stearate, solid
25 polyethylene glycols, sodium lauryl sulfate, and mixtures thereof.
In the case of capsules, tablets and pills, the dosage form may also comprise
buffering agents.
CA 02419729 2004-09-23
- 12-
Solid compositions of a similar type may also be employed as fillers in soft
and hard-
filled gelatin capsules using such excipients as lactose or milk sugar as well
as high,
molecular weight polyethylene glycols and the like.
The solid dosage forms of tablets, dragees, capsules, pills, and granules can
be
prepared with coatings and shells such as enteric coatings and other coatings
well known in
the pharmaceutical formulating art. They may optionally contain opacifying
agents and ca»
also be of a composition that they release the active ingredients) only, or
preferentially, ixr a
certain part ofthe intestinal tract, optionally, in a delayed manner. Examples
ofembedding
compositions which can be used include polymeric substances and waxes.
to The ac've compounds cart also be in micro-encapsulated form, if
appropriate, with
one yr more of the above-mentioned excipients.
Liquid dosage forms for oral administration include pharmaceutically
acceptable
emulsions, solutions, suspensions, syrups and elixirs. rn addition to the
active compounds, the
liquid dosage forms znay contain inert diluents commonly used in the art such
as, for
15 example, rwater or other solvents, solubilizing agents and emulsifiers such
as ethyl alcohol,
isopropyl alcohol, ethyl carboztate, ethyl acetate, benzyl alcohol, benzyl
benzoate, propylene
glycol, 1,3-butylene glycol, dimethyl formamide, oils (in particular,
cottonseed, groundnut,
corn, germ, olive, castor, and sesame oils), glycerol, tetrahydrofuxfuryl
alcohol, polyethylene
glycols and fatty acid esters of sorbitan, and mixtures thereof.
2o Besides inert diluents, the oral compositions can also include adjuvants
such as
wetting agents, emulsifying and suspending agents, sweetening, flavoring, and
perfuming
agents.
Suspensions, in addition to the active compoutlds, may contain suspending
agents as,
for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and
sorbitan esters,
25 microcrystalline cellulose, aluminurr~ metahydroxide, bentonite, agar agar,
and tragacanth,
and nnixtures thereof.
Compositions for rectal ox vaginal administration are preferably suppositories
which
can be prepared by mixing the compounds of this invention with suitable non-
irritating
excipients or carriers such as cocoa butter, polyethylene glycol or a
suppository wax ~uvhich
CA 02419729 2004-09-23
-13-
are solid at roam temperature but liquid at body temperature and therefore
melt in the rectum
or vaginal cavity attd release the active compound.
Compounds of the present invention can also be administered in the form of
liposvmes. As is ltnown in the art, liposomes are generally derived fz'om
phospholipids or
other lipid substances. Liposomes are for~xred by mono- or nr~ulti-lamellar
hydrated liquid
crystals that axe dispersed in an aqueous medium. Arty non-toxic,
physiologically acceptable
and metaboIizable lipid capable of forming liposomes can be used. The present
compositions
in liposome form can contain, in addition to a compound of the presexxt
invention, stabilizers,
preservatives, excipients, and the like. The preferred lipids are the
phospholipids and the
io phosphatidyl cholines (lecithins), both natural and synthetic.
Methods to forra liposomes are known in the art. See, for example, Prescott,
Ed.,
Methods in Cell Biolo~y. Volume XzV, Academic Press, New 'York, N.Y. (1976),
p. 33 et
seq.
Dosage forms for topical administration of a compound of this invention
include
15 powders, sprays, ointments and inhalants. The active compound is mixed
under sterile
conditions with a pharmaceutically acceptable carrier az~d any needed
preservatives, buffers,
or propellants which may be required. CJgthahnnic fornnulations, eye
ointtxtents, powders and
solutions are also contemplated as being within the scope of this invention.
Actual dosage levels of active ingredients in the pharmaceutical compositions
of this
2o invention may be varied so as to obtain ara amount of the active
cornpound(s) that is effective
to achieve the desired therapeutic response fox a particular patient,
compasitiotr, and mode of
adm,inistratxon. The selected dosage level will depend upon the activzty of
the particular
com~pour~d, the route of administration, the severity of the condition being
treated, and the
condition and prior medical history of the patient being treated. however, it
is within the skill
25 of the art to start doses of the compound at levels lower than required to
achieve the desired
therapeutic effect and to gradually increase the dosage until the desired
effect is achieved.
Generahy dosage levels of about 1 to about 1040, more preferably of about 5 to
about
200 mg of 6-O-methylerythromycin A Form I per kilogram of body weight per day
are
administered to a mammalian patient. If desired, the effective daily dose may
be divided into
3d multiple doses for purposes of administration, e.g. two to four separate
doses per day.
CA 02419729 2004-09-23
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The following Examples are provided to enable one skilled in the art to
practice the
invention and are merely illustrative of the invention. They should not be
read as limiting the
scope of the invention as defined in the claims.
Example 1
Prepatatio~n of 6-O-methyler~rthroxnvein Form I
6-O-methylerythromycin A was prepared from erythromycin A by oximation of the
C-9 carbonyl, protection ofthe C-Z' and C-4" hydroxy groups, methylation of
the C-6
hydroxy group, deoximatiori and removal of the protecting groups, and
recrystallization from
ethanol according to the method of U.S. Pat No. 4,990,602. The material
obtained from the
1o recrystallization was dried zn a vacuum oven (40-45 °C, 4-8 in. Hg)
to give 6-O-
methylerythromycirt A Form I.
6-O--methylerythromycin A Form I is characterized by its infrared spectrum,
the
differential sca~uning calorimetric {DSC) thenxsogram acrd the powder x-ray
diffraction
pattern. Tlte differential scanning calorimetric thermogram is obtained by
rrtethods known in
1s the art and is illustrated in Figure lc. hn Figure lc, an exothermic
transition at 132.2 °C can be
seen, which is believed to be due to a phase transition. An endothermic peak
at 223.4 °C,
which may be due to melting, can also be seen. Another endothermic peak at
283.3 °C
followed by an exothermic peak at 306.9 °C may be due to decomposition.
After the DSC
scan the color of the sample was black.
2o The powder x-ray diffraction pattern is obtained by the methods known iu
the art.
Figure la illustrates the powder x-ray diffraction pattern. The 2-theta angle
positions in the
powder x- ray diffraction pattern. of 6-O-methylerythromycin A Form I are
5.16°*0.2,
6.68°t0.2, 10.20°t0.2, 22.28°t0.2, 14.20°t0,2,
15.40°~0.2. 15.72°t0.2, and 16.36°t0.2.
Example 2
i5 Conversion of 6-O-methyler~rthrvmycin Form I Crystals to Form II Crystals
6-O-methylerythxomyci,z~ A Fortn I crystals (0.40 g), prepared as in Example
1, were
placed in a vial and heated in the vacuum oven (4-9 in Hg, 100-110 °C)
for 18 hours to give
6-O- methylerythromycin A Form II crystals. 6-O-methylerythromycin A Form II
melts at
223.4 °C. In the differential scanning calorimetric thermogram of 6-O-
methylerythxomycin A
30 Form II there can be seen an endothermic peak at 283.3 °C which may
be due to
CA 02419729 2004-09-23
-15-
decomposition. After the DSC scan the color of the sample was black. The 2-
theta angle
positions in the powder x-ray diffraction pattern of 6-O-methyleryth~omycin A
Form Iz are
8.52°t0.2, 9.48°~0.2, 10.84°t0.2, 11.48°t0.2,
11.88°10.2, 12.36°~0.2, 13.72°10.2,
14.12°i0,2, 15.16°~0.2. 16.48°~0.2, I6.92°t0.2,
17.32°t0.2, 18.08°~0.2, 18.40°~0.2,
19.04°~0.2, 19.88°~0.2, and 20.48°t0.2.
Example 3
Isolatiozt of 6-O-rnethvler~thromvcin Form T by RecrystalIization
Reerystallization from Tetrahydrofuran
A mixture of 6-O-methyleryyhromycin A (20 g), prepared as described in Example
1,
to in tetrahydrofuran (100 mL) was warmed to reflex and stirred for 15
minutes. The hot
solution was filtered to remove traces of insoluble material and cooled to
ambient
temperature. No crystallization occurred so 10 g of 6-O-methylerythromycizt A
was added to
the solution and the suspension was again heated to reflex, hot filtered, and
cooled in an ice
bath. The resulting solid was collected by filtration and dried in the vacuum
oven, (40-45 °C,
i5 4-S in. Idg) to give 6-O- methylerythromycin A Form I (16.74 g),
Rec~rystallization from Isopropyl Alcohol
A mixture of 6-O-mtethylerythromycin A (15 g), prepared as described in
Example 1,
and isopropyl alcohol (100 rmL) was ~avarmed to reflex and heated for 20
minutes. The hot
solution was filtered to remove traces of insoluble material. The filtrate was
transferred to
2o another flask along with a 50 mL isopropanol rinse, and the solution was
again heated to
reflex. The clear solution was them cooled slowly to ambient temperature and
left standing for
seven hours. The resulting solid was collected by filtration and dried in the
vacuum omen (40-
45 °C, 4-8 in. I~g) to give 6-O methylerythtomycin A Form I (13.3g).
Recrystallization frorr~ Isopropyl Acetate
2s A mixture of 6-CO methylerythromycin A (10 g), prepared as described in
Example 1,
aztd isopropyl acetate (I00 mL) was warmed to 73 °C. The hot solufion
was filtered to
remove traces of insoluble material. The clear solution was then cooled slowly
to ambient
temperature. The resulting solid was collected by filtration and dried in the
vacuum oven (40-
45 °C, 4-8 in. Hg) to give 6-O-methylerythromycin A Form I (3.6 g).
CA 02419729 2004-09-23
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Recrystallization from Isopropyl Acetate-I-Ieptane
A mixture of 6-O-methylerythromycin A (10 g), prepared as described in Example
1,
and isopropyl acetate (100 rnL) was warmed to reflux. A small amount of
insoluble material
was removed by filtration and the filtrate was transferred to anothex vessel.
The filter flask
was rinsed with isopropyl acetate (5 mL) and the filtrate and rinse were
cozrrbined and heated
to reflux. To the resulting clear solution was added heptane (100 mL) and the
clear solution
was cooled to ambient temperature over I , 5 hours during which tizxre a
precipitate Formed.
The solid was collected by filtration and dried overnight in the vacuum overt
(45-50 °C, 4-$
in. Hg) to give G-O-methylerythromycin A Form I (7.0 g).
1o Recrystallization from Isopropyl Acetate-N,N dimethylformamide
A mixture of 6-O-methylerythxomycin A (12 g), prepared as described izr
Example 1,
and isopropyl acetate (100 mL) was warmed to reflux. A small amount of
insoluble material
was removed by filtration and the filtrate was transferred to another vessel.
The filtrate was
heated to reflex and N',N dimethylformamide (30 mL) wa.s added, The clear
solution was
15 cooled to ambient temperature over 1. S hours during which time a
precipitate formed. The
solid was collected by filtration and dried overnight in the vacuum oven (49-
50 °C, 4-8 in.
~Tg) to give 6-O-metlrylerythmmycin A Form I (G.4 g).
Recrystallizativn from Tetrahydrofuran-ldeptane
To a clear solution of G-O-atrethylerythrorttycin A (10 g), prepared as
described in
2o Example 1, in tetrahydrofuran (75 mL) was added heptane (150 mL). The
resulting cloudy
solution was heated to 71.5 °C at which point it turned clear. The
mixture was cooled to
ambient temperature over 2 hours, and then was cooled in an ice-water bath for
0.5 hours,
The resulting solid was filtered and dried in the vacuum oven (45-50
°C, 3-4 in. ~Ig) for four
days to give 6-O- methylerythromycin A Form x (0.50 g).
25 Recrystailization from fithanol-l~eptane
A mixture of G-O-zxiethylerytirromycin A (10 g), prepared as described in
E~tample 1,
and ethanol (100 mL) was warmed to reflex. A small amount of insoluble
material was
removed by filtration and the filtrate was transferred to another vessel. The
~~lter flask was
rinsed with ethanol (20 mL) and the filtrate and rinse were combined and
treated at 78 °C
30 until a clear solution was obtained. To the clear solution was added
heptane (100 mL) and tire
CA 02419729 2004-09-23
- ], 7 _
clear solution was cooled slowly to ambient temperature and stirred for four
days. The
resulting solid was collected by filtration and dried in the vacuunn oven (45-
50 °C, 4-8 in. Hg)
to give 6-O-methylerythromycin A Norm I (4.5 g).
Recrystallization from lsopropanol-Heptan.e
A mixture of 6-O-methylerythromycin A (4.0 g), prepared as described in
Example 1,
and isopropanol (50 mL) was warmed to reflux. Heptane (50 mL) was added and
the solution
was cooled slowly to ambient temperature and then was cooled in an ice-water
bath. The
resulting solids wexe collected by filtration and dried in, the vacuum oven (4-
8 in. Hg) to give
6-O-methylerythtomycin A Form I (3.6 g).
1 o Example 4
Dissolution Rates of 6-O-methylerythromycin Forms I and II
Dissolution studies were carried out at 60 rpm in 300 mL of 0.05 M phosphate
buffer
at 3?°C using a constant surface area (1313x" diameter) drug compact.
Aliquots were
removed periodically and assayed directly by HPLC (Scm x 4.6mm 3p. ODS 2
"Little
i s Champ" (Regis) column; 50:50 acetonitrile-0.05 M pH 4.0 phosphate buffer
mobile phase;
1.0 mLlrnin flow rate). As shown in Table 1, 6-O-methylerytllromycin A Form I
has an
intrinsic rate of dissolution about three times greater than Form II.
Table 1
Intrinsic Dissolution Rates of 6-O-rt~ethylerythromyein A forms I and II
Crystal Form Dissolution Rate ~ S.D.
(~tglmin/cm2)
I 636 ~ 2.5
II 203 ~ 14
The foregoing examples are presented for purposes of illustration and ate not
intended
to limit the scope of the invention. 'Variations and changes which are obvious
to one skilled ire
the art are intended to be within the scope and nature o~the invention as
defined in the
appended claims.
2s
