it 5"
`
`K$21:A
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`Pharmaceutical Dry Powder Aerosol Delivery’
`
`Nora YJ‘L Chew and Huh-Kim Chan
`
`thntfy ofle mow, Heisman: wflydnef
`
`Abstract
`
`The exigent? fior on inhalation system that does not contribute to ozone—depletion, but is suitable
`for the delivery offioth molt molecules and macromolecules. has led to the booming interest in pow
`der aerosols delivery in the last decade. Successful delivery ofo’mgs via powder aerosol depends on
`both the powderfinmatatioo and aerosol inhaler This rei'iewficoses on fire mowing technologies 69‘
`these two determinants in optimising powder aerosol delivery
`
`1. Dry powder aerosols: the logical choice to
`deliver small and large molecules
`
`Chlorolluorocarbon (CFC) propelltult-driven meter-
`eddosc inhaler (pMDI) has been the dominant inhala—
`tion system in the 20‘“ century. This 'lung—wiuning’
`dosage form has gained remarkable popularity due to
`its effectiveness. safely and convenience to patients.
`Although only low fractions (10 to 3D 96) of the emit-
`ted dose can penetrate the deep lung (even with
`spacer devices) [1, 2}, the number of prescriptions
`written by physicians for the CFC-pMDI still re
`maimed high.
`15 years the prospective ofthe
`During the last 10
`CFC-pMDIs has been radically charmed due. to the
`proven damage to the ozone layer by CFCs. While
`scientists are searching for alternatives to the (SPC-
`pMDIs, the even greater compulsion for new meth—
`ods is, in fact. the delivery of macromolecules to the
`lung.
`The high cost. dosage requirement and payload
`versatility (to. flexibility to deliver a range of differ-
`ent doses) are some of the factors that are unique to
`the delivery of macromolecules compared With small
`molecular drugs. Some proteins and polypeptides for
`deep lung delivery may need milligram-level doses
`versus micrograms per do so for the most potent bron-
`chodilutors and sleriods for the treatment of asthma.
`
`An aerosol system that exhibits payload velsatility is
`especially important because macromolecular drugs
`vary widely in potency from a few micrograms to tens
`
`° gyclney 2006,. New Scum Wales Australia
`"lel $12 9351 3001
`Fax 512 93514391
`Email: kimc-fipharmcsydeduau
`* Accepted: August 1?, 2001
`
`of milligrams per dose [3}. Th us, the delivery of macro
`molecules to the lung must be precise and consistent
`at every inspiration.
`Even though manufacturers have developed CFC-
`fi'ee propellant inhalers containing hydrolluoroalltane
`[such as HFA134a} to replace the CFC-plums. direct
`switching between CFC- and HFA-containing formula-
`tions may not be plausible {4l.'111e conventional neb»
`uliser systems are rather inconvenient for patients to
`use on a daily basis. Powder aerosols. which do not
`consume propellants. are an ideal alternative. More
`importantly, powder aerosols exhibit
`the following
`advantages for the delivery of macromolecules:
`' A greater amount of drug ran be contained in dry
`powders than in liquid forms: Dry powder aerosols
`can carry more drug per unit volume than the CFC
`pMDls and the nebulisers. The closing frequency
`can therefore be reduced With a dry powder System
`for protein drugs that require higher doses, such as
`insulin or alpha-1 antitrypsin.
`0 Minimised microbial growth: Dry-powder formula-
`tions minimise the risk of microbial growth.
`to
`which liquids are more susceptible than solids.
`' Greater drug stability: Drugs can be susceptible to
`biochemical and physical instability in organic sol-
`vents such as the CFC propellants (5. 6). Prepara-
`tion of the actives as dry powders could be far more
`stable in the solid than in the liquid state (F) and
`has been shown to be a promising approach for
`delivering drugs to the respiratory tract (8‘ 9).
`
`2. Dual to multiple challenges. from small mol-
`ecules to macromolecules
`
`Powders for inhalation delivery must he of particle
`size 0.5 — 5 urn and they must flow well during manu-
`
`45
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`
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`KONA No.19 (2001)
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`Liquidia's Exhibit 1040
`Page 1
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`is if
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`K$21:A
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`facture, filling and emptying [mm the inhaler device.
`These small particles. however. are cohesive and ad-
`hesive. matting them difficult to disperse and empty
`from the device. Coupled with these two opposing
`requirements, the delivery of therapeutic macromole-
`cules by inhalation presents additional problems: the
`fragility of proteins imposes certain restrictions dur-
`ing manufacture and storage in order to maintain not
`only their dispersibility as an aerosol. but also their
`biochemical and physical stabilitios.
`In this article, we review the challenges confronted
`in the deliver),r of both small molecules and macro-
`nioclcules via inhalation powder aerosols. Specifically,
`this review focuses on the emerging technologies of
`both the powder formulation and inhaler devices that
`are used to optimise pulmonary drug delivery.
`
`3. Cohesiverless of dry powders
`
`Powder cohesiveness affects their flow and dis-
`persion.
`it
`is dependent on the physicochemical
`properties. such as particle size1 dielectric constant.
`morphology. moisture
`content
`and
`electrostatic
`charge. The three major cohesion forces between two
`particles are the universal van der Wasls force. capilv
`lary force and electrostatic charge interaction (10,
`11‘}. The van der Waals force {Fowl arising between
`two identical spheres is given by (12}:
`
`FM... = A [U12 [12
`
`{equation it
`
`where A is the molecular interaction constant, R is the
`radius of the particles and H is the separation dis-
`tance between the particles. Because the mass of the
`particle increases with the third power of the diame
`ter, the force of attraction per strait mass of particles is
`inversely proportional to the square of the particle
`size [i.e. FundinassIIJ'E. where D is the diameter of
`the particle) (1.2, 13). Thus finer particles are more
`cohesive and are more difficult to disperse.
`The molecular interaction constant A is referred to
`as the Harnaker constant. AH, based on the London-
`van der Wasls theory (tat). Thus. the molecular inter-
`action of two particles. 1 and 2 is:
`
`A}: = II? Cl: '12 the
`
`(equation 2)
`
`where q] is the number of atoms per unit volume of
`particle l. q; is the number of atoms per unit volume
`of particle 2. It” is the London—van der 1t'l'aals constant
`for the interaction between two atoms of the interact-
`
`ing particles. and is related to the polarisability of
`the. atom [12). When A is derived from the dielectric
`properties of the interacting materials. it is referred to
`
`as the lifshitz-van tier Waais constant that), and the
`intermolecular interaction thong} for two particles, 1
`and 2. in vacuum is expressed as:
`
`hi012=hl {Ts tie—lirieloooi (E2 (lo—or
`(6211:.) U- die-3'
`[equation 3]
`
`where E (15.) is the dielectric constant of the material.
`1.. and h is the Planck's constant. The Lifshitzrvan der
`Weals interaction constant is related to the Hanialter
`constant via:
`
`AH = 34’e1 I'Lhtti
`
`(equation 4]
`
`The interaction constant is hence strongly depen-
`dent on the physicochemical property of the interact-
`ing material.
`When the separation distance in equation 1 van-
`ishes (ll approaches zero}, [)erjaguin proposed that
`the cohesion force. F.- becomes (12)
`
`FE : 2 rm'R
`
`{equation 5)
`
`where or is the surface tension of the particles or of
`any adsorbed film present on the particles. and R is
`the particle radius. According to equation 1. the pres-
`ence olan adsorbed moisture film would decrease the
`
`F“... by increasing the separation distance H. How-
`ever. moisture can contribute to the capillary force
`through surface tension according to equation 5. as
`well as increasing the area of contact (15). In general.
`at high relative humidities (265 it). capillary force
`due to condensation of liquid between the particles
`will dominate the interparticuiate force {16).
`Surface roughness and asperities will also con-
`tribute to the Fm... Depending on the nature of the
`roughness. the of iective particle contact per unit area
`may either decrease or increase (1?). It has also been
`suggested that R in equation 5 should be replaced by
`the size of surface asperities if their radii are larger
`than 0.1pm (18).
`When particles come into contact. plastic deforma-
`tion (versus elastic deformation. which has negligiv
`ble effect on particle cohesion (10)] at their contact
`points may occur depending on their relative hard-
`ness. This effect may increase the true area of contact
`and hence the cohesion force. Amorphous materi-
`als are generally more deformable,
`thus giving a
`stronger cohesion (13).
`In a low relatively humidity environment. electro-
`static forces will contribute to the cohesion of par-
`titles. The similar or different surface charges of
`particles. that lead to either repulsion or attraction of
`the particles, can be generated through either tribu-
`
`KONA No.19 {2001}
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`rt?
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`Liquidia's Exhibit 1040
`Page 2
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`fist.
`KO!NA
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`elcclrificalion (frictional charging) and! or contact
`charging. The latter usually occurs when particles of
`different work functions are brought
`into contact
`(16). The force due to triboclectr'tlieation can be
`quantified by Coulomb's law (equation 6)
`
`Ftrihoelectn'i:
`
`= Q il—HftR2+H2)mlf16 Its, Iri2
`(equation 6)
`
`where Q are the charges on the particles in Coulomb,
`H is the separation distanoe between two particles. R
`is the particle radius and so is die permittivity of a vac-
`uum. Contact charging is usually applicable to parti-
`c]es of different compositions (if). 19). The work
`function of solid particles is defined as the energy
`required to remove an electron from the particle to
`infinity, and is related to the particle size and dielec-
`tric constant of the substance (20). The work function
`decreases with the particle size. Also, materials with
`higher dielectric constants are easier to ionjse. There-
`fore. when two materials of different work functions
`come into contact, electrons will tend to transfer from
`the material with a higher work function to the mater-
`iai with a lower work function. This effect results in
`
`the formation of a contact potential between die two
`materials, giving rise to electrostatic charges. liumid
`environmcnts will reduce the electrostatic interaction
`among particles by dissipating the charge.
`
`4. Overcoming powder cohesion
`
`4.1 Formulation: the traditional approach
`Two traditional ways that have been used to opli—
`mist: powder flow are {it formation of a drug blends
`with coarse ('non-respirable’t carrier particles leg.
`lactose), and (ii)
`formation of loose agglomerates
`from the primary drug particles.
`lCarrier particles should be physiologically inert
`and large in size (>50 urn}. They are not intended to
`be delivered to the lung. The most commonly used
`carrier is lactose. Drugs blended with carriers are
`believed to adhere to file carrier to form an ordered
`
`mix (2t). Because of the large carrier size, the pow-
`der flow is improved. Upon inhalationr the carrier
`should ideally be retained in the inhaler device or
`impacted on the patient’s throat. whereas the drug
`should be released from the carrier and deposited in
`the lung. Therefore the interaction between the drug
`and the carrier should be strong enough to form an
`uniform ordered mix. but weak enough to be over—
`come by the patient's inspiratory flow to release the
`drug particles. This approach was first employed for
`the Spincap'n' used with the Spinhalera.
`
`Excipient carriers can also improve the availability
`of fine drug particles in the aerosol cloud. Depending
`on the nature of the active drug and the carrier, it is
`possible to generate desirable amount of fine drug
`particles with a minimal
`inspiratory effort
`(8, 22).
`Traditionally, the blend is a binary systemr consisting
`of a drug and a coarse carrier. Recent studies have
`shown that the addition of fine carrier particles (4: 10
`um) {such as lactose or magnesium stcar'ate) can fur-
`ther enhance the amount of drug particles in the ser-
`osol cloud (23, 24). The fine earlier particles appear
`to retluee the drugstarrier interaction by occupying
`possible drug binding sites on the larger carrier parti-
`cles. The formation of multiplcts between fine carrier
`and drug may also occur in the presence of excess
`fine carrier, thereby hindering direct contact between
`the drug and the coarse carrier, and promoting drug
`particle detachment from the carrier surface during
`powder dispersion. Magnesium stearate at concentra-
`tion as low as {1.1 96 was found to be sufficient to
`
`increase the fine particles of salbutamo] sulphate in
`the acrosol cloud (34).
`Instead of being an external entity to the drug parti-
`cles, excipient carrier may be co-spray dried with the
`active. This results in the excipient existing with the
`drug in the same particle. Chan and workers show-
`ed that the fine particle fraction of thNase in the
`aerosol was enhanced linearly with the amount of
`crystalline Natl] present as an excipient. Such an in-
`crease was correlated With the degree of crystallinily
`of the powder {8}.
`Formation of loose agglomerates for terbutaline
`sulphate and budcsonide from drug particles (and
`excipients) to enhance the flow of powders has been
`employed with the proprietary product. Turbuhalerg
`The aim is that these agglomerates should be robust
`enough to withstand filling and packing in the deliv-
`ery device but at the same time they should readily
`be redispersed by the shear stress provided by the
`inhaler and die inspiratory energy ofthe patient. The
`size of these agglomerates. however. should not be
`too large, otherwise they could become trapped with-
`in the inhaler and would not be delivered to the long
`(25].
`Loose agglomerates can be. formed by a variety of
`processes including low shear granulation, roller corn-
`paetioo or extrusion. The formation of such agglom-
`erates often requires binding liquids that will not
`dissolve the powders and hence minimise crystalline
`bridges formation between particles upon drying.
`Commonly used liquids such as alkanois, however,
`can denature the actives cg. proteins. Fluorocarbon
`
`48
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`RONA No_l9 [Zilflil
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`Page 3
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`(FC) liquids. such as pertluorodecalin and perfluo-
`rooctyl bromide. have been found useful because
`they dissolve neither lipophilie nor hydrophilic com-
`pounds. PC has a low surface tension, which forms a
`relatively weal: bond between the fine particles oi the
`loose agglomerates. so that the agglonierates can he
`redispersed easily as an aerosol. The high vapour
`pressure of FC also renders it easy to remove from
`the agglomerate particles {25).
`
`4.2 Formulation: the novel approach
`(See Section 5.1.4.)
`
`4.3 Inhaler Device - new design’ new
`technology
`The dry-powder inhaler provides storage and pro
`tcction to die medicament. More importantly, it aids
`the transfer of the powder from the device into the air
`stream and disperses the powder into fine particles
`for inhalation. It is known that the degree of disper-
`sion of the powder depends not only on Lhc powder
`cohesiveness. but also on the inhaler device and the
`energy input from the patient. Because different in-
`halers offer different resistances to air flow through
`the device, the inspiratory flow attained by a patient
`will, dlcreforE. be dependent on the device used.
`Insufficient air flow through the inhaler will result in
`imprecise dosing to the patient and affect drug depo-
`sition. This behaviour is especially important with
`devices of high resistance (26 — 28]. Some recent in-
`ventions. therefore. aim at improving; the inhaler‘s dis-
`persion efficiency by reducing the resistance of the
`device and the influence of patient’s inspiration on
`powder dispersion.
`
`4.3.1 Orbital“
`
`()rbitalfi Inhalation System {BrinTeeh International,
`Nottingham. UK} is a low resistance unit-dose device,
`with the dose contained within a hollow disk, which is
`perforated by a series of small evenly spaced open-
`ings arranged around the outside edge (Figure 1}
`(29). During inhalation. the disk rotates following an
`'orbital’ path and the drug powder is released through
`the openings. The particles undergo rapid accelera-
`tion and deAaggTegation as they are released under
`the influence of centrifugal force. The device has
`demonstrated aerosol performance comparable to the
`relatively high resistance Tu rbuhalcrig'.
`
`4.3.2 Tovisthaiercm
`
`The ’T‘WJ's1halet"“-c {filtering-Plough. Kenilworth, N ,
`USA} features specially designed nozzle geometry
`
`
`
`RONA No.13 (2001)
`
`
`
`Dose
`containing
`"pill”
`
`i,
`
`intakes
`
`grid
`
`Rumour-thin
`
`Fig. 1
`
`Schematic diagram of the Orbital“ inhalation System.
`[Reprinted with permission. Scrcntec Press. Raleigh. NC.
`All rights reserved).
`
`to optimise deagglomeration of powders. but at the
`same time minimises drug caught in the inhaler noz-
`zle and mouthpiece {30). The design of the nozzle
`creates an airflow pattern which carries the small par-
`doles out of the device via the fluted chimney, while
`the larger particles or agglomerates wiil be spun into
`a centrifugal pattern which deagglomerates into fine
`particles for inhalation (Figure 2).
`
`
`
`air passage
`
`
`inhalation
`
`ehannei
`
`swirl non]:-
`
`rcscr vuir
`
`Err
`air passagea
`
`
`
`Fig.2
`
`Inhalation through the AWEX'" 'IWIE—i’l‘l-IAIJ-IK'"
`UPI.
`(Reprinted with permission. Serentec Press. Ra-
`leigh. NC. All rights reserved}.
`
`49
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`%
`
`4.3.3 Microdose Technology
`The recently patented design (Microdose Tech-
`nologies Inc., Monmouth Junction. NJ. USA) utilises
`electrostatic charging and ultrasonic vibration to facil-
`itate suspension of powder in air (3ll.’l‘he device may
`include a user-actuahle control to allow the user to
`
`choose [he Vibration frequencies and!or amplitudes
`for optimally suspending the drug in air.
`
`4.3.4 Hovine FlowCaps“
`Hovine Flost-Caps? [Hovione SA, Loures, Portugal]
`dry powder inhaler features a tube which receives
`capsule (is) at. one end (Figure 32:) (32, 33}. The cap-
`sule is pierced by two blades (instead of the tradi—
`tional needle piercing} giving rise to a narrow slit
`across each end of the capsule. As the patient inhales
`through the device, most of the air rushes into the
`inhaler tube inlets. whereas only little enters the cap-
`sules. This effect creates a pressure difference within
`
`Random loading
`
`Capsules do not have lo
`be inserted in a proper
`orientation. as in all other
`cap-suit based systems
`A patented ramp will auto
`minimally.r right a capsule for
`loading into the inhalation
`chamber. The patient can
`visually check thatlhis is
`happening.
`Ease of use is fundamental
`
`For patient t'ortipliance.
`
`Figs 3a
`
`llorione HA Flannel—napsit {Inr powder detrire. [Courtesy of
`Hovitnte I'mdtlt'iofi Formation Lit'os 5h, l’orlutral].
`
`
`
`Fig; 3b Photograph shouting the dispersion atrium-dam within the
`capsule in a Hovionc SA FlowCap'i‘ dry' powder inhaler.
`[Courtesy of Iioviour: Proriuclos Farmaceulicos “uh. Por-
`tugall.
`
`the capsule causing very high turbulence for powder
`dispersion within the capsule before emptying from
`the device {Figure 3b).
`
`5. Stabilityr and dispersibility of protein powders
`
`The bioactivily of proteins is governed by their
`secondary and. higher order structures, Therapeutic
`proteins prepared as dry powders have been found
`unstable when dried alone. Inclusion of certain ex-
`
`cipients in the formulation prior to drying has signifi-
`cantl},r improved the stability of the drier] products.
`The choice of eacipients is dependent on the powder
`preparation methods {see below). the protein itself.
`the physicochomieal properties of the excipient. and
`the subsequent storage conditions. Besides the amor-
`phous glassy carbohydrates. other excipients. such as
`polymers (eg. polyvinylpyrrolidone}. Proteins tag.
`human serum albumin) and amino acids or peptides
`(eat. aspartame) have also been used to stabilise pro-
`tein powders.
`Based on the empirical observations, the protective
`effects imparted by the excipients can he explained
`by one or more of die following interrelated factors
`(34);
`(1) formation of an amorphous-glassy protein-
`excipient system:
`(ii)
`increase of the glass transi-
`tion temperature of protein formulation: (iii) residual
`water content; (iv) water replaCernent via hydrogen
`bonding between the excipient and protein molecules;
`and (v) or volallinity of cxcipeint.
`Solid exists as an amorphous glass which is eharao
`terised by the glass tran sition temperature tTg) above
`which fl'tt? glastS)I state softens to the rubbery state. In
`a glassy state. the mobility of protein molecules is
`much slower than those in the rubbery state: thus
`any reactions that may lead to protein degradation are
`almost impeded {35). From this behaviour, it seems
`logical and beneficial to render '1} well above the
`maximum temperature to which the dried product
`will be exposed during powder preparation and stor-
`age in order to preserve the structural integrity of
`protein and to minimise protein degradation. Crown
`and coworkers found that large carbohydrates form a
`glass with a higher Te than the small ones [36).
`Water affects the stabilin of proteins by enhancing
`the mobility of the surface groups of the protein as
`demonstrated by solid-state NMR spectroscopy {37.
`38}. However, the effect of drying may remove water
`molecules that are hydrogen-bonded to the polar
`groups on file protein surface. This effect maltr alter
`the protein structure via the formation of tone or
`interprolein hydrogen bonds (39). The function of the
`
`
`
`RONA No.19 (2001)
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`fih
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`I%§il
`
`excipienl is to serve as a water substitute to preserve
`the native structure of the proteins as evidenced by
`F'l'IR spectroscopy (40, 41). Maintainingr the protein;f
`excipient combination in an amorphous state allows
`maximal hydrogen-bonding for protein stabilisation
`(39}.
`Crystalline excipients. such as mannitoL were
`found to reduce the stability of proteins [9, 42, d3).
`Excipients, such as glycine and sodium phosphate,
`appeared to inhibit
`the crystallisation of mannitol.
`Water facilitates crystallisation, resulting in the loss
`of amorphous glassy matrix for protein stabilisation
`(39). Since recrystallisation readily leads to interpar—
`ticulate bridging as evidenced in the co-spray dried
`thNase powders (44] during storage at bill} ‘li RH,
`the tlowability and dispersability were adversely
`affected (45). Thus, a balance must be achieved be-
`tween the choice of stabilise-r to maintainjimprove
`protein stability without compromising powder aero-
`sol performance. Controlling the humidity of the envi-
`moment during powder manufacturing and storage is
`aiso critical for the powder formulation s.
`
`5.1 Preparation of powders
`
`5.1.1 Lyophilisntionfmilling
`Lyophilisation is a freezedrying process in 1tvhich
`water is sublimed from the solution after it is frozen.
`
`A particular advantage of the process is that pharma-
`ceuticals, which are relatively unstable in aqueous
`solution tog. proteins). can be dried without being
`subjected to elevated temperatures which may have
`an adverse effect on the product stability. However,
`lyophilised powders are often too large for inhalation.
`Jet milling may reduce the particle size, but a mill-
`ing stabiliser (such as :rnannitol, sorbiiol} is often
`required to reduce the shear. pressure and!or tent-
`perature degradation of the protein during milling.
`Significant loss of activity of interferon was found
`when sorbitol was not included in the formulation (46.
`4?). The adverse effect of the high energy from rnill-
`ing compromises die application of this technique.
`
`5. 1.2 Solvent precipitation
`Precipitation of solids using organic anti-solvents
`often raises health concerns due to residual solvents.
`Non-solvents, such as supercritical carbon dioxide
`{SC C02). which exhibits remarkable solvent power
`for high molecular weight, low vapour pressure sol-
`ids, is an ideal alternative. C02 is particularly attrac-
`tive for operation due to its low critical temperature of
`31.1°C. It is also non-toxic, inexpensive and readily
`
`available. This technique was found feasible to pre—
`pare anti-asth matic drugs such as salmoterol xlnafoate
`(4-8) and cromolyn sodium (49]. Fine-timing of this
`technique may result in particles of desirable size,
`shape and solid state properties for inhalation (50).
`The majority of proteins are soluble in aqueous
`solutions, However, being non-polar and immiscible
`with water, SC C02 cannot be used as an anti-solvent
`to precipitate proteins from aqueous solutions. Meth-
`ods, such as the use of a Ito—axial nozzle to enhance
`mixing of the water—liased protein solution with SC
`C03, were able to overcome this hurdle {51). Alterna—
`tively, protein particles can be produced using a
`supercritical or near critical cog-assisted aerosolisa—
`tion and bubble drying process {49}.
`
`5.1.3 Spray drying
`Spray dl‘yit’ut,f is a one step process, Which involves
`converting the atomised liquid droplets into dry pow-
`ders by hot air. Depending on the concentration of
`the feed solution, the spray temperature, cyclone effi—
`ciency and chemical nature of the feed, spray drying
`can yield powders of narrow particle size distribution
`suitable for inhalation {52).
`Proteins, however, are susceptible to degradations
`due to the tremendous surface area of the atomised
`droplets. The relatively high drying temperatures
`and mechanical stress during atomisation may also
`adversely affect the integrity of the protein. Excipi-
`cots are often co—spray dried with proteins for stabi-
`lisation. For example.
`thermal degradation of the
`protein, beta—galactosidasc, is minimised in the pres-
`ence of trehalose as excipient (53]. Similarly, the
`presence of sucrose prevents the formation of a
`degradation product, oxyhemoglobin. during spray
`drying {54}. The addition of surfactant polysorbate—20
`In the liquid feed antlfor divalent zinc ion significantly
`reduces the fomlation of insoluble aggregates of the
`recombinant human growth hormone (rhGl-I} (55},
`The formation of the zinc ion dimerised complexes
`with the protein and the occupancy of the surfactant
`at the airfliquicl interface of the spray droplets have
`prevented protein unfolding and aggregation.
`Spray drying of recombinant humanised mono-
`clonal antibody, anli—IgE (rhMAbE25) containing
`trchalose or lactose had less than 1 it of aggregation
`following spraying drying (9). Formulation with tre—
`halose, however, was found too cohesive and thus not
`suitable for aerosol delivery. Mannitoi was less capa-
`ble of stabilising rhMAbE25. with 1 — 3 96 aggregates
`found following spray drying. Upon storage. the pro-
`tein stability and aerosol performance were reduced
`
`
`
`FIONA No.19 {2001)
`
`
`
`Liquidia's Exhibit 1040
`Page 6
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`Liquidia's Exhibit 1040
`Page 6
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`

`

`Eni?
`t
`
`due to the recrystallisation of mannitol. liven though
`lactose improved the protein stability Without com-
`promising the aerosol performance, the antibody was
`subjected to glycation during storage. These results
`imply that each protein}sugar system requires indi-
`vidual characterisation to identify an optimal
`for-
`mulation for protein stability and powder aerosol
`performance,
`
`5.1.4 ‘Tailorcd-made' particles from spray
`drying
`Despite the challenges faced in preparing stable
`protein powders. spray drying still remains the most
`popular method of preparing inhalation dry powders.
`A number of therapeutic proteins have been effec-
`tively prepared by spray drying. as shown in Table l.
`
`5.] .4.1 Pulmosphere'r"
`Spray drying has been applied to non-aqueous sys—
`tems.
`l’ulmospherem (Inhale Therapeutic Systems.
`San Carlos, CA. USA} particles are created by a pro—
`prietary spray—drying procedure in which the feed
`comprises two parts; an aqueous solution contain-
`ing dissolved or dispersed active drug, and a fluroro
`carbon-in—water emulsion, stabilised by a monolayer
`of phospholipid (such as dipalmitoylphosphatidyl-
`choline) (61}. l‘ulmospherc‘“ particles have size be—
`tween 2 and 4 pm, a hollow porous morphology and a
`bulk density of 0.0:") — 0.2 gfcn'f‘ (Figure 4). Pulmos-
`pherem particles can be dispersed more readily than
`the traditional drug—carrier blend with lactose.
`
`5.1 .4.2 Technospl'tcre'“1
`local and systemic inhalation therapies can often
`benefit from a relatively slow controlled release of the
`active drug {62). The invention of 'i‘echnosphere'”
`{Pharmaceutical Discovery Corporation. Elmsford.
`NJ. USA} aims to provide particles with a controlled
`pulsed or sustained release profile. The process is
`
`
`
`Fig.4
`
`Pulrnosphere'“. [Courtesy of inhale Therapeutic 51m ems
`Inc. San Carlos, Carlitornia. USA].
`
`based on the formation of dikctopiperaaine micropar—
`ticles. which is targeted the specific cell types and is
`released only after reaching,r the targeted cells {EB}.
`Microcapsules prepared by spray drying cuntain the
`active drug suspended or dissolved in the polymer
`solution. This solution 0:— suspension is then spray-
`dried to produce particles in which the drug is en-
`trapped in the diketopiperrine matrix,
`
`5.1.4.3 AIR” particles
`NR“ particles (Alkermes. Inc.. Cambridge. MA,
`USA) also aim to release drugs in the airways in a
`controllable manner (ti-‘1). The particles (Figure 5}
`are prfiiared by spray drying solutions containing a
`mixture of drug and biodegradable nnlterial
`leg.
`polyglycolic acid, polylactic acid or copolymers).
`AIR” particles have a low lapped density of less than
`-— 04 gfcnrl, with a irregular surface. Low density
`
`Ref
`
`T55r.-
`
`l | ‘
`
`i
`
`58
`
`59
`
`Table 1 Some recent pate-ms for preparing dry DOWdL'IH of macromolecules hr Spray drying
`Prul reins
`|
`
`Spray-teed compositions
`
`linl-t‘lffl (DNAgtlas-mirl)‘ "'-"'—l——'
`I
`'-
`5 PCMVB in 'l'risfn’lannitolfl [AS solution.
`- Insulin
`H _..__.._—
`insulin in citrate buffer (pt-1 55"} containing mannitoi or raftinose or neither.
`
`I
`
`I
`
`[fin- and lgti- antibody H --
`
`EC—ystEt-ibrnsis transmembrane
`conductance {Cl-”1R1 gene
`
`---Antibody was dissolved in citrate buffer containing different excipients {sugarfpolyrnerfprowint
`
`CFI'R gene. Linked With a promoter. was dissolved in phosphate butter saline solution converting;r
`lactose.
`
`Interferon it
`
`interferon [i was dissolved in a solution containing sodium chloride or [nannilnl and spray dried
`accordingly.
`
`
`
`RONA No.19 {2001)
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`Liquidia's Exhibit 1040
`Page 7
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`fik
`KONA
`W
`
`
`
`Fig. 5
`
`All?” particle. [Courtesy oi Alkm'nn's, Inc. Cambridge.
`MA. [IS-ll}-
`
`particles are aerotlynamicallj,r small and are ideal for
`deep lung delivery. The irregular surface of the. par-
`titles may reduce tttil'IPE-tivfittess of particles for pow-
`der dispersion.
`l-‘urthern'iore.
`large particles could
`minimise phantom-tic uptake. thereby providing the
`potential for controlled release of drugs into or via the.
`lungs [65, 65). Addition of surfactants, such as I:
`alpha-phosphatidylcholine dipahnitoyl, to the forlrlulii-
`tion may also improve the dispersion of the AIR”
`particles (5?).
`
`5. 1 AA NanoCi-ystalsi“
`'l‘echnolo
`l“lano(.‘rystalsN tl‘llan Pharmaceutical
`gie5. King of Prussia, PA, USA) are small particles
`(less than ltltllii
`lull
`in diameter) made entirely of
`crystalline drug. stabilised by adsonntion of selected
`polymers tog. l-ll’MC} onto their surfaces. The pen-‘-
`ders are first prepared by a wet-milling process to
`reduce the particle size to the nanometer range and
`are further processed by spray—drying to yield nearly
`spherical aggregates 01' the NanoCrystals‘“ within an
`aerodynamic particie size range suitable. for pulmo-
`nary tlepo-sition.
`'l‘he unique small size of NanoCrystaIs‘“ containing
`huriesoriide {mean diameter of 1.35 pm) leads to a
`nearly twofold increase in the respirahle fraction
`compared to the micronised particles of size. 3.22 pm.
`The close uniformity of hudesonide is also better con-
`trolled with NanoCrystal‘” hndesonidc delivery (RSI)
`8.5 — 11.4]
`than with the micronised powder tRSi)
`13.3 — 13.3) (68].
`
`5.1.4.5 ‘u’t'rinkled particles
`Manipulations of the spraying conditions and pro-
`tein formulations may produce particles of different
`
`
`
`KONA No.19 (2001}
`
`
`
`shape and morphology {59. iii}. Non-porous solid pro-
`tein particles with wrinkled surfaces (Figure 6} have
`recently been prepared in our laboratory. The. wrin-
`kled particles gave a significant improvement in fine
`particle fraction over non-wrinkled spherical particles
`of bovine serum albumin (Figure 7} (Fl). A distinct
`advantage of these particles is that the inhaler choice
`and air flow becomes less critical for the dispersion of
`these particles as an aerosol.
`
`
`
`Fig. I5
`
`Wrinkled brivinl: HI"rlllI'l
`spray-drying.
`
`.3ll'l-llt‘1l1'l particles, product-ti by
`
`5.1.4.6 Spray freeze-dried particles
`Spray freeze-drying involves sprayhng the feed solu-
`tion into liquid nitrogen followed by lyophilisation.
`This process produces light and porous particles of
`rhiii‘tase and anti-lgE with super