(12) United States Patent
`Tice et a1.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,306,425 B1
`Oct. 23, 2001
`
`US006306425B1
`
`(54) INJECTABLE NALTREXONE
`MICROSPHERE COMPOSITIONS AND
`THEIR USE IN REDUCING CONSUMPTION
`
`4,568,559
`4,623,588
`
`2/1986 Nuwayser et a1. ..................... .. 427/3
`11/1986 Nuwayser et a1. ..
`428/402.24
`gee? ------ --t----i - - - - -
`- - - -
`
`0F HEROIN AND ALCOHOL
`
`
`
`, 4,897,268 ,
`
`
`
`
`
`on emps e a. 1/1990 Tice et a1. . . . . . . . .
`
`. . . .. 424/422
`
`_
`
`(75) Inventors ghomaAslRk; TICEf113HmmgMhaIE’ Jall'lK'
`taas>_ a 35169 eresa
`- erre >
`Vestavla H1118 all OfAL (Us)
`
`.
`
`.
`
`.
`
`_
`
`4,902,515
`
`2/1990 Loomis et a1.
`
`1/1991 Loomis 61 a1.
`4,981,696
`424/486
`3/1992 Hyon 61 a1. ..
`5,100,669
`424/426
`4/1995 T106 61 a1.
`5,407,609
`..... .. 264/46
`5,486,362 * 1/1996 K116h61161a1
`424/426
`5,736,152 * 4/1998 Dunn . . . . . . . . . . .
`. . . .. 424/426
`5,945,115
`8/1999 Dunn et a1. ........................ .. 424/422
`
`424/486
`
`(73) Assignee: Southern Research Institute,
`Birmingham, AL (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`Patent 15 extended or adlusted under 35
`U'S'C' 154(k)) by 0 days‘
`
`(21) Appl. N0.: 09/545,064
`.
`_
`(22) Med‘
`
`Apr‘ 7’ 2000
`Related U S Application Data
`(60) lljgg‘gisional application No. 60/128,477, ?led on Apr. 9,
`
`OTHER PUBLICATIONS
`Falk, et al., J. Controlled Release (1997), 44(1):77—85.
`Yolles, et a1. Acta Pharmaceutica Suecica (1976), 13(32).
`Jalil
`and NiXon., J.
`Microencapsulation (1990),
`7(3):297—325.
`Sharon and Wise, NIDA Res Monogr (1981), 28:194—213.
`s6hw6p6, 61 a1., Life Sciences (1975), 17(12):1877—85.
`Woodland, et al., J. Med Chem (1973), 16(8):897—901.
`* Cited by examiner
`
`_
`7
`92/1043,
`(51) Int. Cl. .............................. ..
`(52) U S C]
`424/426_ 424N200 424/486_
`424/489; 514/872; 514/811; 514/772.3;
`
`_
`
`Primary Examiner—Blessing Fubara
`(74) Attorney) Agent) Or Firm_Barbara Rae_venter;
`Jennifer Wahlston; Rae-Venter LaW Group PC.
`(57)
`ABSTRACT
`
`514/812; 514/964
`(58) Field of Search ................................... .. 424/426 423
`424/425 486 449 451 489 501’ 502?
`’
`’
`’
`’514/’7723’ 816
`'
`’
`
`(56)
`
`References Cited
`
`Us PATENT DOCUMENTS
`
`_
`_
`.
`.
`An mlectable slow'release naltrexone formulanon 15 pro‘
`vided comprising naltrexone in a po1y(D,L-1actide) matrix
`With a small amount of residual ethyl acetate. Upon intra
`muscular injection of the composition, naltreXone is released
`in a controlled manner over an extended period of time. The
`composition ?nds 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 a1. ...................... .. 424/19
`6/1975 Yolles .................................. .. 424/19
`
`26 Claims, N0 Drawings
`
`AMN1015
`IPR of Patent No. 7,919,499
`
`

`

`US 6,306,425 B1
`
`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, ?led Apr. 9, 1999, Which disclosure
`is herein incorporated by reference.
`
`INTRODUCTION
`
`Background
`The disease of substance abuse remains a scourge on
`society. As it becomes more evident that there is a substan
`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
`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
`stance abuse and discourage the young people from embark
`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
`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
`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 signi?cant factor in lack of retention and relapse is
`compliance. Arepetitive 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
`dif?cult. Therapeutic techniques, Which require persever
`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
`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
`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
`ment during a craving episode. This opportunity, Which may
`be an indication of Will poWer, nevertheless, puts the subject
`at risk that succumbs to the temptation. By providing for a
`sloW-release medicament, Which is introduced into the body,
`
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`the temptation is avoided and the drug is released in accor
`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
`microspheres, Which are inj ectable 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
`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
`level; the drug must be released sloWly Without a cata
`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
`able level; the microspheres must be small and capable of
`being delivered by a syringe With a needle Which is accept
`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;
`the metabolites that are produced must be acceptable levels;
`as Well as other characteristics Which may be general or
`speci?c 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
`conditions under Which the microspheres are prepared and
`subsequently processed.
`
`BRIEF DESCRIPTION OF THE PRIOR ART
`
`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:
`Reuning, et al., NIDA Re: Monograph Series, January 1976,
`(4) p43—5; Reuning et al., J. Pharmacokinet Biopharm,
`August 1983, 11 (4), p369—87; Reuning, et al., Drug Metab
`Dispos November—December 1989, 17(6) p583—9; MacGre
`gor et al., J. Pharm Pharmacol, January 1983, 35(1) p38—42;
`Reuning et al., NIDA Res Monograph Series 1980, 28,
`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) p1—8; Yoburn et al., J. Pharmacol EXp Ther, 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
`1995, 11, p681—688, as Well as numerous other publications.
`Patents of interest include US. Pat. Nos. 4,568,559;
`4,623,588; 4,897,267; and 5,486,362. US. 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
`ing microspheres is described in Benita et al., J Pharm Sci,
`December 1984, 73(12) p1271—4; Speniehauer et al., ibid,
`
`AMN1015
`IPR of Patent No. 7,919,499
`
`

`

`US 6,306,425 B1
`
`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
`vided comprising a therapeutically effective amount of nal
`trexone released over an extended period of time and a
`matrix consisting of the polymer poly(D,L-lactide). The
`microspheres are under 100 pm in diameter and can be
`readily injected intramuscularly. Different release pro?les
`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
`vided for use in the treatment of alcoholics and heroin
`addicts and such other indications for Which naltrexone has
`been found to be ef?cacious. Small steriliZed particles,
`microspheres, are provided Which can pass through a
`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
`cally effective amount of naltrexone for at least about 28
`days. The release pro?le is found to be sensitive to the
`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 pro?le) of the poly(D,L
`lactide). The release pro?le appears to be less sensitive to the
`conditions under Which the microencapsulation process is
`operated, the siZe distribution of the microspheres, as long as
`the composition substantially consists of particles in the
`range of 20 to 100 pm, 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
`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
`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
`1.0—1.2 dL/g, usually 1.0—1.1 dL/g, the amount of naltrex
`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
`may be used so as to deliver the desired amount of naltr
`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,
`Where the polymer With the loWer inherent viscosity (i.e., the
`loWer-molecular-Weight polymer Will be in lesser amount
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`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
`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
`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 pm and less
`than about 5 Weight % Will have a diameter greater than
`about 100 pm.
`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
`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
`mined by the area under the curve, is released in the ?rst 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 300115 mg
`of naltrexone, for an administration. The vehicle may be
`sterile Water, phosphate buffered saline, or other conven
`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, eg 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, eg 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 US. Pat. No. 5,407,
`609. The process is an emulsion-based process Which
`involves the preparation of an emulsion comprising an
`
`AMN1015
`IPR of Patent No. 7,919,499
`
`

`

`US 6,306,425 B1
`
`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 suf?cient 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 ?nal amount of naltrexone in the microparticles. Tem
`peratures may be ambient, generally being from about 15 to
`30° C.
`After the microspheres have been collected and dried,
`they may be stored at ambient temperatures, particularly in
`the range of about 0 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
`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
`toring devices may be included, such as How meters, tem
`perature monitors, particle siZe monitors, etc. The organic
`solution is pumped into a ?rst tube, Which ?ts into the
`homogeniZer. Likewise the aqueous solution (to be the
`continuous phase) is pumped into the second tube Which
`also ?ts into the homogeniZer. By controlling the rate of How
`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
`effluent from the homogeniZer (an oil-in-Water emulsion)
`exits through a third tubing containing ?oWing Water. The
`Water extracts the polymer solvent ethyl acetate from the
`emulsion droplets to form microspheres. Again, the ratio of
`How rates controls the amount of emulsion and Water
`introduced into the third tubing. The length of the third
`tubing and the rate of How of the combined streams control
`the residence time of the Water-extraction step. The micro
`spheres are then segregated by siZe by passing them through
`tWo or more sieves, Which reject microspheres outside the
`desired siZe range.
`The primary application for the subject formulations is as
`an intramuscular injectable, although subcutaneous injec
`tions may also be used. The subject Will normally be a
`substance abuser, such as alcohol and heroin, but the subject
`compositions may be used for other indications, such as
`obesity. The appropriate amount of the subject formulation
`is directly injected into a convenient site, eg gluteus.
`Thereafter, the subject may be monitored for naltrexone
`plasma concentration to ensure that the amount is in the
`therapeutic range of at least about 1 ng/mL, preferably at
`least about 2 ng/mL. When the naltrexone plasma concen
`tration falls beloW the therapeutic range, a subsequent inj ec
`tion may be made and this process repeated during the
`treatment period.
`For heroin addicts, the subject Will normally be detoxi?ed
`by any one of a number of different Ways, using
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`buprenorphine, clonidine, naltrexone, etc. and checking With
`naloxone. A response to naloxone indicates that the subject
`has not been completely detoxi?ed. It is also found that
`about 10% of the population that has been tested With oral
`naltrexone have adverse reactions, Which may resolve them
`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[3-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
`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
`istered after the ?rst dose, because one continues to obtain
`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
`istered. By providing for microspheres that can continue to
`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
`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
`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
`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
`each batch is >40 pm and <90 pm. In vitro release charac
`teristics are de?ned by % released over the ?rst 72 hours at
`37° C.
`
`AMN1015
`IPR of Patent No. 7,919,499
`
`

`

`US 6,306,425 B1
`
`7
`A description of the microencapsulation of naltrexone is
`included in the following sections.
`Step 1: A 2.5 Wt % solution of polymer is prepared by
`mixing ethyl acetate With poly(D,L-lactide), loW
`molecular Weight, in an 8-liter bioreactor ?ask
`equipped With a PTFE-coated stirring shaft. A mini
`mum of 4 hours is required to completely dissolve the
`polymer. The Weight of the polymer solution and its
`?ask is measured and if needed, additional ethyl acetate
`is added to return the solution back to it’s desired
`Weight.
`Step 2: A 2 Wt % poly(vinyl alcohol) (PVA) solution is
`prepared by mixing PVA in sterile Water, in 3 to 4
`batches, and stirring at 90° C. Each batch is then
`alloWed to cool to room temperature and then Water is
`added back to adjust for evaporation loss. After a
`pre-?lter integrity test of a Millipak 200-liter unit is
`successfully completed, the solutions are ?ltered and
`pooled in a 36-liter bioreactor ?ask. The ?ask and its
`contents are then Weighed, 2.5 Wt % ethyl acetate is
`added to the PVA solution and a motor driven PTFE
`impeller stirs the solution for a minimum of 30 minutes.
`Step 3: For every 15 gm of drug product produced, a
`minimum of 8 liters of Water is transferred to a
`50-gallon stainless steel tank, covered and stored.
`Step 4: The naltrexone dispersed phase solution is pre
`pared by adding naltrexone to the polymer solution
`While stirring. The solution is stirred for a minimum of
`1 hour until the naltrexone is dissolved.
`Step 5: To set up the continuous microencapsulation
`equipment, the dispersion phase, continuous phase and
`extraction phase and pumps are calibrated to a speci?ed
`?oW rate, for example, 25 gm/min, 125 gm/min, and
`2000 gm/min respectively to prepare Formulation F-1.
`The dispersion phase needle is then primed With dis
`persion phase solution and the dispersion phase pump
`?oW rate is con?rmed on a bypass setting. The extrac
`tion phase pump is then started and the extraction lines
`are ?lled and cleared of bubbles. The continuous phase
`pump is then turned on and PVA is alloWed to ?oW into
`the extraction tubing. The homogeniZer is then turned
`on and set to a stir rate of 650120 rpm. The dispersion
`phase needle valve is then opened and the dispersion
`phase pump is turned on to alloW dispersion phase
`solution to ?oW into the homogeniZer chamber With the
`PVA solution. This is the start of the batch run. Fol
`loWing homogeniZation, the emulsion ?oWs out of the
`in-line homogeniZer and into the extraction line con
`taining ?oWing Water, Which extracts ethyl acetate from
`the microspheres.
`The aqueous suspension of microspheres is then collected
`into a 50-gallon stainless steel holding tank, equipped With
`a stir motor and impeller. The microspheres are stirred at
`500150 rpm until the tank is 25 to 50% full. The micro
`sphere suspension is then moved through a RBF-12 Vorti
`Sieve oscillating sieve deck containing a 125-pm and a
`20-pm sieve in series, using a centrifugal pump. If the sieves
`become clogged, they are removed and replaced With a neW
`set of clean sieves. The 20-pm sieve is then rinsed With Water
`into the 80-gallon stainless steel Washing bath tank and
`continuously stirred While the rest of the run is being
`collected. After the last of the dispersion phase solution
`passes into the homogeniZer, the dispersion phase pump is
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`stopped and the dispersion phase needle valve is closed off.
`This is the end of the batch run. The ?nal amount of
`dispersion phase solution is then homogeniZed, extracted,
`and ?ltered though the sieves.
`Water is then pumped across the sieves for 10 minutes to
`Wash the microspheres. The microspheres on the 20-pm
`sieve are then rinsed into the 80-gallon stainless steel
`Washing bath tank and continuously stirred at 500150 rpm
`for a minimum of 3 hours. The microspheres are then passed
`through another RBF-12 Vorti-Sieve oscillating sieve decks
`containing a 125-pm and a 20-pm sieve in series, using a
`centrifugal pump. The microspheres on the 20-pm sieve are
`then transferred to a collection vessel by rinsing With Water.
`Microspheres are diluted With Water to make a 15% solids
`suspension based on estimated yield. The suspension is
`stirred continuously While dividing contents into one liter
`lyophiliZation ?asks such that each ?ask contains an esti
`mated 20 gm of microspheres. After lyophiliZation, micro
`spheres are dry sieved through a 125-pm sieve. The micro
`spheres are then Weighed and distributed to amber glass
`bottles.
`The bottles are then capped, sealed and packaged in
`plastic bags With silica gel desiccant. Bags are stored at 2 to
`8° C.
`After the microspheres meet the pre-de?ned acceptance
`criteria for core loading, siZe distribution, theoretical yield
`and residual ethyl acetate, they are packaged, as single
`doses, into 5-cc ?int glass vials. The vials are then capped
`With PTFE-coated rubber stoppers, sealed With open top
`aluminum seals , labeled and sealed into individual foil
`pouches.
`A guideline describing the detailed preparation and com
`ponents of the kits is provided beloW.
`1. Using an 18-gauge needle, draW 2.0 cc of diluent up
`into a 3 cc syringe and expel into a vial containing
`microspheres. Discard this needle and syringe.
`2. Shake the vial vigorously for 30 seconds to suspend
`microspheres.
`3. Place a neW 18-gauge needle on a neW 3-cc syringe.
`4. DraW microsphere suspension into syringe While
`inverting vial.
`5
`. Expel microspheres back into vial.
`6
`. Repeat steps 4 and 5 tWo additional times.
`7. Discard this needle and syringe.
`8. Place a neW 18-gauge needle on a neW 3-cc syringe.
`9 . DraW microsphere suspension into syringe While
`inverting vial. WithdraW needle from vial.
`10. Remove air bubbles from suspension and administer
`the dose as soon as possible to prevent settling of
`microspheres.
`The folloWing table indicates speci?c parameters for the
`preparation of the microspheres and the properties and
`performance of the microspheres in vitro and in vivo. In the
`in vivo study, dogs Were injected intramuscularly With an
`18-guage needle With about 2 mL of solution containing the
`microspheres at the Weight indicated in the table. The
`plasma Was monitored for naltrexone at the times indicated.
`For the in vitro study, microspheres Were maintained in 0.01
`M phosphate buffer, pH 7.4 at 37° C. and the residual
`naltrexone in the microspheres determined at the times
`indicated.
`
`AMN1015
`IPR of Patent No. 7,919,499
`
`

`

`US 6,306,425 B1
`
`10
`
`NalltreXone
`NaltreXone
`loading, target loading, actual
`Wt %
`Wt %
`
`Encapsulation Temperature, Polymer inherent Mean particle
`e?iciency, %
`° C.
`viscosity, dl/g
`size, ,um
`
`50
`
`50
`
`60
`
`38.3
`
`42.5
`
`49.0
`
`77
`
`85
`
`82
`
`22
`
`1.07
`
`1.07
`
`1.07
`
`57.76
`
`44.36
`
`39.78
`
`Lot no. Dog ID
`
`92
`
`2062-HM
`2067-HM
`2073-IM
`142 2063-JM
`2066-JM
`2070-KM
`118a 2065-FM
`2072-FM
`2075-GM
`
`Lot no.
`
`NaltreXone
`dose, mg
`
`Microsphere
`dose
`
`Vehicle, mL
`
`92
`
`142
`
`118
`
`165
`147
`202.5
`135
`165
`191.3
`165
`133.5
`225
`
`430.8
`383.8
`528.7
`317.6
`388.2
`566.5
`336.7
`272.4
`459.2
`
`1.8
`1.8
`1.7
`1.8
`1.8
`1.7
`1.8
`1.9
`1.8
`
`NaltreXone
`in plasma
`ng/mL) (hrs)
`1 hr
`
`6.8
`6.33
`9.66
`6.22
`5.19
`17.28
`15.56
`7.6
`13.02
`
`2 hr
`
`4 hr
`
`8 hr
`
`24 hr
`
`48 hr
`
`2.79
`4.14
`5.28
`4.14
`3.5
`8.79
`7.39
`4.04
`6.62
`
`1.82
`2.34
`2.41
`2.27
`2.33
`3.21
`
`1.77
`3.2
`
`0.73
`0.64
`0.89