(12) United States Patent
`Tice et al.
`
`I 1111111111111111 11111 111111111111111 111111111111111 IIIII 1111111111 11111111
`US006306425Bl
`US 6,306,425 Bl
`Oct. 23, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54)
`
`INJECTABLE NALTREXONE
`MICROSPHERE COMPOSITIONS AND
`THEIR USE IN REDUCING CONSUMPTION
`OF HEROIN AND ALCOHOL
`
`(75)
`
`Inventors: Thomas R. Tice, Birmingham; Jay K.
`Staas, Alabaster; Teresa M. Ferrell,
`Vestavia Hills, all of AL (US)
`
`(73)
`
`Assignee: Southern Research Institute,
`Birmingham, AL (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`(21) Appl. No.: 09/545,064
`
`(22) Filed:
`
`Apr. 7, 2000
`
`Related U.S. Application Data
`(60) Provisional application No. 60/128,477, filed on Apr. 9,
`1999.
`
`(51)
`
`Int. Cl.7 ................................ A61F 2/00; A61K 9/00;
`A61K 9/14; A61K 47/30
`(52) U.S. Cl. .......................... 424/426; 424/400; 424/486;
`424/489; 514/872; 514/811; 514/772.3;
`514/812; 514/964
`(58) Field of Search ..................................... 424/426, 423,
`424/425, 486, 449, 451, 489, 501, 502;
`514/772.3, 810
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,568,559
`4,623,588
`4,874,612
`4,897,267
`4,897,268
`4,902,515
`4,981,696
`5,100,669
`5,407,609
`5,486,362 *
`5,736,152 *
`5,945,115
`
`2/1986
`11/1986
`10/1989
`1/1990
`1/1990
`2/1990
`1/1991
`3/1992
`4/1995
`1/1996
`4/1998
`8/1999
`
`Nuwayser et al. ....................... 427/3
`Nuwayser et al. .............. 428/402.24
`Deasy ................................... 424/425
`Bontemps et al. ................... 424/422
`Tice et al. ............................ 424/422
`Loomis et al. ....................... 424/486
`Loomis et al. ....................... 424/486
`Hyon et al. .......................... 424/426
`Tice et al. .............................. 264/46
`Kitchell et al. ...................... 424/426
`Dunn .................................... 424/426
`Dunn et al. .......................... 424/422
`
`OTHER PUBLICATIONS
`
`Falk, et al., J. Controlled Release (1997), 44(1):77-85.
`Yolles, et al. Acta Pharmaceutica Suecica (1976), 13(32).
`Jalil
`and Nixon.,
`(1990),
`J. Microencapsulation
`7(3):297-325.
`Sharon and Wise, NIDA Res Monogr (1981), 28:194--213.
`Schwope, et al., Life Sciences (1975), 17(12):1877-85.
`Woodland, et al., J. Med Chem (1973), 16(8):897-901.
`* cited by examiner
`
`Primary Examiner-Blessing Fubara
`(74) Attorney, Agent, or Firm-Barbara Rae-Venter;
`Jennifer Wahlston; Rae-Venter Law Group P.C.
`
`(57)
`
`ABSTRACT
`
`An injectable slow-release naltrexone formulation is pro(cid:173)
`vided comprising naltrexone in a poly(D,L-lactide) matrix
`with a small amount of residual ethyl acetate. Upon intra(cid:173)
`muscular injection of the composition, naltrexone is released
`in a controlled manner over an extended period of time. The
`composition finds use in the treatment of heroin addicts and
`alcoholics to reduce consumption of the abused substances.
`
`3,773,919
`3,887,699
`
`11/1973 Boswell et al. ........................ 424/19
`6/1975 Yolles
`.................................... 424/19
`
`26 Claims, No Drawings
`
`APOTEX EXHIBIT 1009
`Apotex v. Alkermes
`IPR2025-00514
`
`

`

`US 6,306,425 Bl
`
`1
`INJECTABLE NALTREXONE
`MICROSPHERE COMPOSITIONS AND
`THEIR USE IN REDUCING CONSUMPTION
`OF HEROIN AND ALCOHOL
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This application claims priority to provisional application
`serial No. 60/128,477, filed Apr. 9, 1999, which disclosure
`is herein incorporated by reference.
`
`INTRODUCTION
`
`10
`
`2
`the temptation is avoided and the drug is released in accor(cid:173)
`dance with a predetermined schedule over an arranged
`period of time. One can have implantable rods, which are
`introduced surgically and must be removed surgically or
`5 microspheres, which are injectable and are devised to release
`the drug over an extended period of time in a controlled
`manner.
`Various slow-release microspheres (or microparticles)
`have been developed for a variety of drugs, a few have been
`commercialized. There are many constraints on a satisfac(cid:173)
`tory slow-release injectable formulation: the release of the
`drug must be over an extended period of time; during the
`time of treatment, the level of drug maintained in the subject
`must be an effective level, without reaching any hazardous
`15 level; the drug must be released slowly without a cata(cid:173)
`strophic dumping of the drug; the polymeric matrix used for
`the microspheres must be biocompatible and biodegradable;
`any residual chemicals must be below the maximum accept(cid:173)
`able level; the microspheres must be small and capable of
`20 being delivered by a syringe with a needle which is accept(cid:173)
`able to patients; the results must be reproducible, which
`requires that the process can be accurately controlled and is
`not unduly sensitive to minor changes in conditions; the
`injectable formulation must be capable of being sterilized;
`25 the metabolites that are produced must be acceptable levels;
`as well as other characteristics which may be general or
`specific to the particular medicament. The properties of the
`microspheres are sensitive to many properties of the drug
`and matrix, as well as the selection of the process and the
`30 conditions under which the microspheres are prepared and
`subsequently processed.
`
`BRIEF DESCRIPTION OF THE PRIOR ART
`
`Background
`The disease of substance abuse remains a scourge on
`society. As it becomes more evident that there is a substan(cid:173)
`tial genetic contribution to becoming addicted, helping
`addicted individuals to terminate their dependency or at least
`achieve a level of becoming a functional member of society,
`rather than treating substance abuse as a moral issue, has
`become increasingly accepted policy. Various programs
`have been put in place in the public and private sectors. In
`the private sectors, there are such organizations as Alcohol-
`ics Anonymous and Narcotics Anonymous, which play an
`important role in psycho-social support. In addition there are
`many private clinics which serve to provide both psycho(cid:173)
`social support and medicinal support, using the somewhat
`limited repertoire of drugs which are available. In the public
`arena, there are the extensive programs to bring to the
`attention of young people and parents the hazards of sub(cid:173)
`stance abuse and discourage the young people from embark(cid:173)
`ing on drug use. Also, there are the methadone programs,
`which are primarily public supported.
`The number of substance abusing subjects in the United
`States is quite staggering. There are estimated to be about 15
`million people who abuse alcohol, about 1.3 million who 35
`abuse cocaine in its many manifestations, about 0.8 million
`who abuse amphetamines and about 0.5---0.8 million who
`abuse heroin, in addition to the use of other drugs, such as
`the psychedelic drugs. Efforts to reduce the numbers of
`scheduled substances and alcohol users have been continu- 40
`ous and relatively unavailing. Those subjects who have
`entered programs have had a dismal record of relapse, so
`that only a small proportion of the people who do enter
`programs and are retained in the programs remain clean long
`after the completion of the program.
`One significant factor in lack of retention and relapse is
`compliance. A repetitive act, such as taking a pill daily, is not
`a simple matter, even where the subject has no qualms about
`taking the pill. With the substance abuser, who may have
`physiological and emotional needs for the abused substance,
`the sustaining of the therapeutic routine is substantially more
`difficult. Therapeutic techniques, which require persever(cid:173)
`ance on the part of the subject, decrease the likelihood of
`success of the treatment. It is therefore of great importance
`to be able to reduce the level of involvement of the subject
`where medicinal treatments are involved, particularly
`treatments, which may involve frequent scheduling, moni(cid:173)
`toring of compliance, and sustaining a particular regimen.
`In order to reduce the vicissitudes of compliance, there
`have been efforts to provide sustained-release methodolo(cid:173)
`gies. These have involved pumps, patches, depots and the
`like. Where the release implement is accessible to the
`subject, there is always the temptation to remove the imple(cid:173)
`ment during a craving episode. This opportunity, which may
`be an indication of will power, nevertheless, puts the subject 65
`at risk that succumbs to the temptation. By providing for a
`slow-release medicament, which is introduced into the body,
`
`50
`
`Krantzler, et al., Alcoholism: Clin and Exp Res 1998,
`22:1074-1079 report the treatment of alcoholics with a
`slow-release naltrexone particle injectable formulation. A
`number of studies were carried out by Reuning's laboratory
`concerning naltrexone and its use in a slow-release form:
`Renning, et al., NIDA Re: Monograph Series, January 1976,
`(4) p43-5; Renning et al., J. Pharmacokinet Biopharm,
`August 1983, 11 (4), p369-87; Renning, et al., Drug Metab
`Dispos November-December 1989, 17( 6) p583-9; MacGre(cid:173)
`gor et al., J. Pharm Pharmacol, January 1983, 35(1) p38-42;
`Renning et al., NIDA Res Monograph Series 1980, 28,
`45 p172-84. See also, Schwope et al., NIDA Res Monograph
`Series, 1975, (4), p13-8; Yolles et al., J Pharm Sci Febuary
`1975, 64(2) p348-9; Thies, NIDA Res Monograph Series,
`1975 (4), p19-20; Schwope et al., NIDA Res Monograph
`Series, January 1976, 4, p13-18; Chiang et al., Clin Phar-
`macol Ther Nov. 1984 36(5) p704-8; Pitt et al., NIDA Res
`Monograph Series 1981, 28, p232-53; Chiang et al., Drug
`Alcohol Depend (SWITZERLAND), September 1985, 16
`(1) pl-8; Yoburn et al., J. Pharmacol Exp Tuer, April 1986,
`237 (1) p126-130; Cha and Pitt, J. Control Release, 1989,
`8(3), p259-265; Yamaguchi and Anderson, J. Control
`Release, 1992, 19(1-3), p299-314.
`The use of naltrexone in the treatment of alcoholism is
`described in O'Malley et al., Psychiatric Annals, November
`60 1995, 11, p681-688, as well as numerous other publications.
`Patents of interest include U.S. Pat. Nos. 4,568,559;
`4,623,588; 4,897,267; and 5,486,362. U.S. Pat. No. 5,407,
`609 describes a process applicable to the process employed
`in the subject invention.
`The use of polylactide in the preparation of drug contain(cid:173)
`ing microspheres is described in Benita et al., J Pharm Sci,
`December 1984, 73(12) p1271-4; Speniehauer et al., ibid,
`
`55
`
`

`

`US 6,306,425 Bl
`
`3
`August 1986, 75(8), p 750---5; and Nihant et al., October
`1994, 11(10), p1479-84.
`
`SUMMARY OF THE INVENTION
`
`Injectable, slow-release naltrexone formulations are pro(cid:173)
`vided comprising a therapeutically effective amount of nal(cid:173)
`trexone released over an extended period of time and a
`matrix consisting of the polymer poly(D,L-lactide). The
`microspheres are under 100 µm in diameter and can be
`readily injected intramuscularly. Different release profiles
`are obtained depending upon the molecular weight of the
`polymer, molecular-weight homogeneity of the polymer,
`matrix size of the microspheres, and the weight percentage
`of naltrexone. The microspheres are prepared by solvent
`extraction of a oil-in-water emulsion, the dispersed oil phase
`being an organic solution of naltrexone and the polymer.
`
`DESCRIPTION OF THE SPECIFIC
`EMBODIMENTS
`
`Injectable, slow-release naltrexone formulations are pro(cid:173)
`vided for use in the treatment of alcoholics and heroin
`addicts and such other indications for which naltrexone has
`been found to be efficacious. Small sterilized particles,
`microspheres, are provided which can pass through a 25
`syringe needle and be administered intramuscularly and
`remain at the site of injection for an extended period of time,
`while continuously releasing and maintaining a therapeuti(cid:173)
`cally effective amount of naltrexone for at least about 28
`days. The release profile is found to be sensitive to the 30
`amount of naltrexone in the microspheres, the use of the free
`base as compared to the salt and the inherent viscosity and
`homogeneity (molecular-weight profile) of the poly(D,L(cid:173)
`lactide ). The release profile appears to be less sensitive to the
`conditions under which the microencapsulation process is 35
`operated, the size distribution of the microspheres, as long as
`the composition substantially consists of particles in the
`range of 20 to 100 µm, and the amount of polymer solvent
`retained, so long as the amount of polymer solvent is below
`about 3 weight %.
`The microspheres as observed by SEM are substantially
`uniform with the drug dispersed throughout the matrix. The
`microspheres have less than about 3 weight % of ethyl
`acetate, the organic solvent used in the preparation of the
`microspheres. The content of naltrexone in the microspheres 45
`is from 5 to 50 weight % and may vary in range depending
`upon the inherent viscosity of the poly(D,L-lactide) making
`up the microsphere polymer matrix. The inherent viscosity
`of the polymer is in the range of about 0.3 to 1.2 dL/g
`(Capillary viscometry method, chloroform, polymer concen- 50
`tration of 0.5 g/dl, 30° C.). Where the matrix has an inherent
`viscosity in the range of about 0.3-0.4 dL/g, the amount of
`naltrexone will be in the range of about 5 to 45 weight %,
`usually 10 to 40 weight %, particularly 10 to 30 weight %.
`While when the inherent viscosity is in the range of about 55
`1.0-1.2 dL/g, usually 1.0-1.1 dL/g, the amount of naltrex(cid:173)
`one will be in the range of about 35 to 50 weight %, usually
`35 to 45 weight %. For the most part, polymers having an
`inherent viscosity in the range of 0.45 to 0.95 dL/g will not
`be employed. Mixtures of the polymers and/or microspheres 60
`may be used so as to deliver the desired amount of naltr(cid:173)
`exone over the desired time period. Thus, when mixing two
`polymers (prior to microencapsulation) having different
`inherent viscosities, the weight % of two different polymers
`may range from 1:99 to 99:1, more usually 10:90 to 90:10, 65
`where the polymer with the lower inherent viscosity (i.e., the
`lower-molecular-weight polymer will be in lesser amount
`
`4
`than the polymer with the higher inherent viscosity (the
`higher-molecular-weight polymer)). Similarly, naltrexone
`microspheres made with a low-molecular-weight polymer
`may be mixed with microspheres made with a higher-
`5 molecular-weight polymer, where the drug loading (weight
`% of naltrexone in the microsphere formulation) may vary
`as to the two or more microspheres mixed together. With two
`different microsphere formulations, the mixture will have a
`weight ratio in the range of 5:95 to 95:5, where the micro-
`10 spheres made with the lower-molecular-weight polymer will
`usually be present in from about 10 to 65 weight %.
`Greater than about 90 weight % of the microspheres will
`have a diameter in the range of about 20 to 100 µm and less
`than about 5 weight % will have a diameter greater than
`15 about 100 µm.
`To reduce agglomeration, the microspheres may be coated
`with an antiagglomerating agent, such as mannitol, which
`will be employed in less than about 10 weight %, usually
`less than about 5 weight %, and may be less than about 2
`20 weight %, of the microspheres.
`Desirably, the microspheres release naltrexone over a
`period of at least 4 weeks, where the area under the curve in
`monitoring the plasma level of naltrexone in human subjects
`is less than about 40% in any one week period and at least
`about 10%, preferably at least about 12%. Generally, the
`proportion in at least two of the weeks, preferably 3 of the
`weeks is not greater than 25%, usually not greater than 20%.
`Desirably, at least about 75%, preferably at least about 80%
`and not more than about 95% of the naltrexone, as deter(cid:173)
`mined by the area under the curve, is released in the first 4
`weeks. The area under the curve is determined by a standard
`pharmacokinetics computer program entitled WinNonlin
`Professional (version 2.1, Pharsight, Inc., Mountain View,
`Calif.).
`The microspheres are formulated in an appropriate
`vehicle to provide from about 150---350 mg of naltrexone,
`usually 250 to 350 mg of naltrexone, particularly 300±15 mg
`of naltrexone, for an administration. The vehicle may be
`40 sterile water, phosphate buffered saline, or other conven(cid:173)
`tional vehicle for administering the microspheres. Additives
`may be present to reduce adhesion of the microspheres,
`diminish discomfort from the injection, reduce edema,
`itching, bumps or other discomfort. Conveniently, mannitol
`may be present in about 2 to 10 weight % of the vehicle,
`particularly 4 to 7 weight % of the vehicle. Other physi-
`ologically acceptable additives may include nonionic
`detergents, e.g. Tween, polysorbate, etc., if present, will be
`present in from about 0.05 to 0.2 weight % of the vehicle,
`viscosity enhancing agents, e.g. carboxymethylcellulose, in
`the range of about 0.1 to 1 weight % of vehicle, and other
`conventional additives, as appropriate. The amount of
`vehicle will generally be in the range of about 1.5 to 5 mL,
`usually 2 to 4 mL, particularly 2 to 3 mL, where the lower
`amounts will generally involve multiple injections, e.g. 2.
`The microspheres are dispersed in the vehicle immediately
`before use. Generally, the microspheres will be stored after
`sterilization in a sterile vial with a septum, where the
`microspheres may be mixed with the vehicle and then
`withdrawn into a syringe. Usually, the needle will not be of
`greater inner diameter than about 18 gauge. With multiple
`injections per administration, they may be at the same,
`adjacent or removed sites.
`The microspheres are prepared by the microencapsulation
`process substantially as described in U.S. Pat. No. 5,407,
`609. The process is an emulsion-based process which
`involves the preparation of an emulsion comprising an
`
`

`

`US 6,306,425 Bl
`
`5
`
`10
`
`5
`aqueous continuous phase (water and a surfactant and/or
`thickening agent) and a hydrophobic dispersed phase
`(polymer solvent, polymer and drug) Shortly after formation
`of the emulsion, the polymer solvent is extracted into an
`aqueous extraction phase. After a sufficient amount of poly-
`mer solvent is extracted to harden the microspheres, the
`microspheres are collected on sieves and washed to remove
`any surfactant remaining on the surface of the microspheres.
`The microspheres are then air dried at room temperature, or
`dried by lyophilization or by other convenient drying pro-
`cesses.
`For the preparation of the subject microspheres, the
`dispersed phase (organic solution) contains about 1 to 10
`weight % naltrexone and about 1 to 20 weight % polymer
`dissolved in ethyl acetate. The continuous phase is an
`aqueous solution of about 1 to 10 weight % of poly(vinyl
`alcohol) and 1 to 7 weight % ethyl acetate. The extraction
`phase is water. Generally, the amount of naltrexone
`employed will be from about 20 to 50 weight % in excess of
`the final amount of naltrexone in the microparticles. Tem(cid:173)
`peratures may be ambient, generally being from about 15 to 20
`30° C.
`After the microspheres have been collected and dried,
`they may be stored at ambient temperatures, particularly in
`the range of about O to 20° C. in an oxygen free and water
`free environment or divided into aliquots into appropriate
`containers and sterilized. Various methods of sterilization
`may be employed, gamma radiation being convenient.
`A relatively simple apparatus may be employed to fabri(cid:173)
`cate the microspheres. Using storage containers to hold the
`different liquids, tubing, pumps, valves and a homogenizer,
`the system is readily assembled. In addition, various moni(cid:173)
`toring devices may be included, such as flow meters, tem(cid:173)
`perature monitors, particle size monitors, etc. The organic
`solution is pumped into a first tube, which fits into the
`homogenizer. Likewise the aqueous solution (to be the
`continuous phase) is pumped into the second tube which
`also fits into the homogenizer. By controlling the rate of flow
`of the two streams in the tubes connecting to the
`homogenizer, the ratio of the two streams can be controlled,
`as well as the residence time in the homogenizer. The 40
`effluent from the homogenizer (an oil-in-water emulsion)
`exits through a third tubing containing flowing water. The
`water extracts the polymer solvent ethyl acetate from the
`emulsion droplets to form microspheres. Again, the ratio of
`flow rates controls the amount of emulsion and water 45
`introduced into the third tubing. The length of the third
`tubing and the rate of flow of the combined streams control
`the residence time of the water-extraction step. The micro(cid:173)
`spheres are then segregated by size by passing them through
`two or more sieves, which reject microspheres outside the 50
`desired size range.
`The primary application for the subject formulations is as
`an intramuscular injectable, although subcutaneous injec(cid:173)
`tions may also be used. The subject will normally be a
`substance abuser, such as alcohol and heroin, but the subject 55
`compositions may be used for other indications, such as
`obesity. The appropriate amount of the subject formulation
`is directly injected into a convenient site, e.g. gluteus.
`Thereafter, the subject may be monitored for naltrexone
`plasma concentration to ensure that the amount is in the 60
`therapeutic range of at least about 1 ng/mL, preferably at
`least about 2 ng/mL. When the naltrexone plasma concen(cid:173)
`tration falls below the therapeutic range, a subsequent injec(cid:173)
`tion may be made and this process repeated during the
`treatment period.
`For heroin addicts, the subject will normally be detoxified
`by any one of a number of different ways, using
`
`6
`buprenorphine, clonidine, naltrexone, etc. and checking with
`naloxone. A response to naloxone indicates that the subject
`has not been completely detoxified. It is also found that
`about 10% of the population that has been tested with oral
`naltrexone have adverse reactions, which may resolve them(cid:173)
`selves or exclude the use of naltrexone. In addition, there
`have been some reports of hepatotoxicity resulting from the
`use of naltrexone at high dosages, with the potential that
`high doses of the metabolite, 6~-naltrexol having
`hepatotoxicity, so that subjects who have compromised
`livers, e.g. subjects infected with hepatitis C, may be
`excluded from treatment. Otherwise, naltrexone has been
`found to be safe at administered levels in excess of the levels
`employed with the subject compositions. With alcoholics,
`once it has been determined that the subject does not respond
`15 adversely to naltrexone, the subject formulation may be
`injected into the subject. It is found that naltrexone serves to
`enhance the control of the alcoholic in the amount of alcohol
`consumed and the number of binges.
`By having microspheres which have long-term releasing
`capability, that is, greater than 28 days, particularly greater
`than about 32 days, one can layer the administration, so that
`by giving injections in a periodic manner, one obtains an
`additive effect. In this manner, smaller doses may be admin(cid:173)
`istered after the first dose, because one continues to obtain
`25 release from the prior injected microspheres to which is
`added the release from the lately administered microspheres,
`or one can enjoy enhanced levels of the naltrexone without
`increasing the amount of the microspheres which are admin(cid:173)
`istered. By providing for microspheres that can continue to
`30 release at levels in excess of 1 ng/mL in blood, preferably in
`excess of 1.5 ng/mL in blood, more preferably in excess of
`2 ng/mL in blood, greater than about 28 days after injection,
`frequently at least about 36 days, more frequently at least
`about 42 days. In this way protection is greatly enhanced, as
`35 the subject is continuously protected with a protective level
`of the naltrexone and one can provide levels of naltrexone
`which will inhibit response to a 50-mg challenge dose of
`heroin or an equivalent dose of a different drug, e.g. fenta-
`nyl.
`The following examples are offered by way of illustration
`and not by way of limitation.
`EXPERIMENTAL
`The microencapsulation process involves microencapsu(cid:173)
`lation by solvent extraction. Naltrexone anhydrous base,
`poly(D,L-lactide) and ethyl acetate are combined and added
`to the in-line homogenizer with water and surfactant. An
`emulsion is produced, additional water is added and the
`extraction process is initiated. The product, naltrexone
`microspheres, is dried by lyophilization in jars. Gamma
`sterilization at 2.5 Mrad exposure is used, and bioburden,
`bacteriostasis, and fungistasis are monitored.
`The appropriate amount of dried, naltrexone microspheres
`are weighed into empty 5-cc vials, closed with rubber
`stoppers, sealed with aluminum seals and sealed into foil
`pouches for transport and sterilization. A vial containing 2
`mL of diluent comprising 0.5% carboxymethyl cellulose,
`0.1 % polysorbate 80 and 5% mannitol is used to resuspend
`the microspheres. The suspension is drawn into a 3-cc
`syringe with an 18-gauge needle. The intramuscular injec(cid:173)
`tion is given immediately to prevent the microspheres from
`settling. The injection may comprise one or two injections of
`from 2 to 4 mL, usually not more than a total of 4 mL.
`Size distribution is controlled such that 90 volume % of
`65 each batch is >40 µm and <90 µm. In vitro release charac(cid:173)
`teristics are defined by % released over the first 72 hours at
`37° C.
`
`

`

`US 6,306,425 Bl
`
`20
`
`35
`
`7
`A description of the microencapsulation of naltrexone is
`included in the following sections.
`
`8
`stopped and the dispersion phase needle valve is closed off.
`This is the end of the batch run. The final amount of
`dispersion phase solution is then homogenized, extracted,
`Step 1: A 2.5 wt % solution of polymer is prepared by
`and filtered though the sieves.
`mixing ethyl acetate with poly(D,L-lactide ), low 5
`Water is then pumped across the sieves for 10 minutes to
`molecular weight, in an 8-liter bioreactor flask
`wash the microspheres. The microspheres on the 20-µm
`equipped with a PTFE-coated stirring shaft. A mini(cid:173)
`sieve are then rinsed into the SO-gallon stainless steel
`mum of 4 hours is required to completely dissolve the
`washing bath tank and continuously stirred at 500±50 rpm
`polymer. The weight of the polymer solution and its
`flask is measured and if needed, additional ethyl acetate 10 for a minimum of 3 hours. The microspheres are then passed
`through another RBF-12 Vorti-Sieve oscillating sieve decks
`is added to return the solution back to it's desired
`containing a 125-µm and a 20-µm sieve in series, using a
`weight.
`centrifugal pump. The microspheres on the 20-µm sieve are
`Step 2: A 2 wt % poly(vinyl alcohol) (PVA) solution is
`then transferred to a collection vessel by rinsing with water.
`prepared by mixing PVA in sterile water, in 3 to 4
`batches, and stirring at 90° C. Each batch is then 15
`Microspheres are diluted with water to make a 15% solids
`suspension based on estimated yield. The suspension is
`allowed to cool to room temperature and then water is
`added back to adjust for evaporation loss. After a
`stirred continuously while dividing contents into one liter
`pre-filter integrity test of a Millipak 200-liter unit is
`lyophilization flasks such that each flask contains an esti(cid:173)
`successfully completed, the solutions are filtered and
`mated 20 gm of microspheres. After lyophilization, micro(cid:173)
`pooled in a 36-liter bioreactor flask. The flask and its
`spheres are dry sieved through a 125-µm sieve. The micro(cid:173)
`contents are then weighed, 2.5 wt % ethyl acetate is
`spheres are then weighed and distributed to amber glass
`added to the PVA solution and a motor driven PTFE
`bottles.
`impeller stirs the solution for a minimum of 30 minutes.
`The bottles are then capped, sealed and packaged in
`Step 3: For every 15 gm of drug product produced, a
`25 plastic bags with silica gel desiccant. Bags are stored at 2 to
`go C.
`minimum of 8 liters of water is transferred to a
`SO-gallon stainless steel tank, covered and stored.
`After the microspheres meet the pre-defined acceptance
`criteria for core loading, size distribution, theoretical yield
`Step 4: The naltrexone dispersed phase solution is pre(cid:173)
`and residual ethyl acetate, they are packaged, as single
`pared by adding naltrexone to the polymer solution
`30 doses, into 5-cc flint glass vials. The vials are then capped
`while stirring. The solution is stirred for a minimum of
`with PTFE-coated rubber stoppers, sealed with open top
`1 hour until the naltrexone is dissolved.
`aluminum seals , labeled and sealed into individual foil
`Step 5: To set up the continuous microencapsulation
`pouches.
`equipment, the dispersion phase, continuous phase and
`A guideline describing the detailed preparation and com-
`extraction phase and pumps are calibrated to a specified
`ponents of the kits is provided below.
`flow rate, for example, 25 gm/min, 125 gm/min, and
`1. Using an 18-gauge needle, draw 2.0 cc of diluent up
`2000 gm/min respectively to prepare Formulation F-1.
`into a 3 cc syringe and expel into a vial containing
`The dispersion phase needle is then primed with dis(cid:173)
`microspheres. Discard this needle and syringe.
`persion phase solution and the dispersion phase pump
`flow rate is confirmed on a bypass setting. The extrac- 40
`2. Shake the vial vigorously for 30 seconds to suspend
`tion phase pump is then started and the extraction lines
`microspheres.
`are filled and cleared of bubbles. The continuous phase
`3. Place a new 18-gauge needle on a new 3-cc syringe.
`pump is then turned on and PVAis allowed to flow into
`4. Draw microsphere suspension into syringe while
`the extraction tubing. The homogenizer is then turned
`inverting vial.
`on and set to a stir rate of 650±20 rpm. The dispersion 45
`5. Expel microspheres back into vial.
`phase needle valve is then opened and the dispersion
`6. Repeat steps 4 and 5 two additional times.
`phase pump is turned on to allow dispersion phase
`solution to flow into the homogenizer chamber with the
`7. Discard this needle and syringe.
`PVA solution. This is the start of the batch run. Fol- so
`8. Place a new 18-gauge needle on a new 3-cc syringe.
`lowing homogenization, the emulsion flows out of the
`9. Draw microsphere suspension into syringe while
`in-line homogenizer and into the extraction line con(cid:173)
`inverting vial. Withdraw needle from vial.
`taining flowing water, which extracts ethyl acetate from
`10. Remove air bubbles from suspension and administer
`the microspheres.
`the dose as soon as possible to prevent settling of
`The aqueous suspension of microspheres is then collected 55
`microspheres.
`into a SO-gallon stainless steel holding tank, equipped with
`The following table indicates specific parameters for the
`a stir motor and impeller. The microspheres are stirred at
`preparation of the microspheres and the properties and
`500±50 rpm until the tank is 25 to 50% full. The micro(cid:173)
`performance of the microspheres in vitro and in vivo. In the
`sphere suspension is then moved through a RBF-12 Vorti(cid:173)
`in vivo study, dogs were injected intramuscularly with an
`Sieve oscillating sieve deck containing a 125-µm and a 60
`18-guage needle with about 2 mL of solution containing the
`20-µm sieve in series, using a centrifugal pump. If the sieves
`microspheres at the weight indicated in the table. The
`become clogged, they are removed and replaced with a new
`plasma was monitored for naltrexone at the times indicated.
`set of clean sieves. The 20-µm sieve is then rinsed with water
`For the in vitro study, microspheres were maintained in 0.01
`into the SO-gallon stainless steel washing bath tank and
`M phosphate buffer, pH 7.4 at 37° C. and the residual
`continuously stirred while the rest of the run is being 65
`naltrexone in the microspheres determined at the times
`collected. After the last of the dispersion phase solution
`passes into the homogenizer, the dispersion phase pump is
`indicated.
`
`

`

`US 6,306,425 Bl
`
`9
`
`10
`
`Lot no. Dog ID
`
`Naltrexone
`loading, target
`wt%
`
`Nalltrexone
`loading, actual Encapsulation Temperature, Polymer inherent Mean particle
`CC.
`size, µm
`wt%
`efficiency,%
`viscosity, dl/ g
`
`142
`
`92
`
`2062-HM
`2067-HM
`2073-IM
`2063-JM
`2066-JM
`2070-KM
`118' 2065-FM
`2072-FM
`2075-GM
`
`50
`
`50
`
`60
`
`38