CA2028665A1 - Bioavailability of pharmaceutical active compounds with peptide linkages - Google Patents

Abstract

Abstract of the Disclosure: Pharmaceutical active com-pounds which contain peptide linkages and are therefore sensitive are protected from degradation, during passage through the stomach and intestines, by micronization.
This improves the absorption and bioavailability. In the micronization the active compounds are extremely finely divided, and each particle is provided with a colloid protective envelope.

Description

2~Qi) o.z. ooso/41212 ,, Improvement in the bioavailability of pharmaceutical active compounds with pe~tide linkaqes Pharmaceutical active compounds which contain peptide linkages and are therefore sen~itive are, accord-ing to the invention, protected from degradation,especially duriny pas~age through the ~tomach and intes-tines, by micronization. This improves the ab orption and bioavailability. In the micronization the active com-pounds are extremely finely divided, and each particle i~
provided with a colloid protective envelope.
Pharmaceutical active compound~ with peptide linkage~ are usually unstable during pa~sage through the stomach and intestine~. This is why relatively large quantities of ac~ive compound have to be ~aken in order to achieve adequate plasma levels. An enteric coating does not ~olve the problem because the peptide linkages are also rapidly degraded in the intestines. A relatively complex solution is described by M. Saffran and G.S.
Rumar in 5cience 233 (1986) 1081, but this e~tails undesired ~lowing of absorption. In addition, the ab~orp-tion promoter~ employed therein are not physiologically acceptable.
It is an ob~ect of the pre~ent invention to devQlop dry pharmaceutical product~ containing active compound~ with peptide linkages, which are more ~table than conventional~ones during pa sage through the stomach and intestines and therefore are absorbed to a greater extent.
~ We have found that thi~ ob~ect is achieved by micronizing the active compound, ie. dissolving it together with a sur~actant in a volatile, water-miscible organic solven~ at from 5 to 200C, where appropriate under superatmo~lpheric pressure, within le~s than 10 sec-onds, immediately converting the active compound into co}Ioidal form by rapidly mixing tha resulting molecular solution with an aqueous solution of a swellable colloid at ~rom a to 'iOC,~ and removing the solvent and the . ~

- 2 - O.Z. 0050/41212 dispersing medium in a conventional manner from the resulting dispersion.
The micronizing process is described for caroten-oids and retinoids in EP-A-65 193 for producing colorant~
for human and animal foods. It was not to be expected that this process could be used to achieve the present object. The active compounds which have been micronized according to the invention are, ~urpri~ingly, stable to hydrolysis or enzymatic degradation of the peptide linkages, despite being extremely finely divided. The active compounds are, moreover, absorbed rapidly and to a large extent so that even relatively low dose~ result in relatively high plasma levels.
~xamples of active compound~ with peptide link~
ages are doreptide, polypeptide antibiotics such as tyrothricin and polymyxin B, TNF, immunomodulator~ such as in~erferon-~, renin inhibitors, and ACE inhibitors.
Examples of suitable water-miscible volatile organic solvents are alcohols such as ethanol, n-propanol and iso-propanol, ethers such as 1-methoxy-2-butanol or l-n-propoxy-2-propanol and ketones such a~ acetone. They should be a~ least 10 % water-miscible, boil below 200~
and contain fewer than 10 carbon atoms. Examples of suitable water-solublQ or swallable colloid~ are gelatin, starch, dextrin, dextran, pectin, gum arabic, ca3ein, ca~einate, whole milk, skim milk, milk powder, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulo~e, carboxy-methylcelluloqe,hydroxypropylcellulose,microcrystalline callulo3e and alginates. For further detail~ on colloids, reference may be made to R.A. Morton, Fast Soluble Vitamins, Intern. Encyclopedia of Food and Nutrition, Volume 9, Pergamon Press 1970, pages 128-131. In order to increase the mechanical stability of the final product it i4 po~ible to add to the colloid a softener, for example a sugar ~uch as sucrose, glucose, lactose or invert sugar, or sugar alcohol such as sorbitol or mannitol, or maltodextrin or glycerolO Minor amount~ of, for example, ,.

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- 3 - O.Z. 0050/41212 methylparaben, propylparaben, sorbic acid and/or sodium benzoate can be added as preservatives.
Exc~mples of suitable suxfactsnt3 (disper~ant~) are esters of long-chain fatty acid~ with citric acid, lactic acid, tartaric acid or ascorbic acid, especially ascorbyl palmitate, mono- and diglyceride~ of fatty acids and the ethoxylation product~ thereof, polyglycerol fatty acid esters (eg. the monostearate of triglycerol), sorbitan fatty acid esters, propylene glycol fatty acid esters, salts of 2-(2-stearoyllactyl)lactic acid and le~ithin. Depending on the solubility, the surfactant is dissolved either in the organic solvent (together with the active compound) or in the aqueous phase.
Further pharmaceutical auxiliaries such as binders, disintegrants, flavorings, vitamins, colorants, wetting agents and additives to alter the pH (cf.
H. Sucker et al., Pharmazeutlsche Technologie, Thieme-Verlag, Stuttgart 1978) can also be introduced in the solvent or the aqueou3 phase. It is self-evident that all pharmaceutical auxiliaries must be physiologically accep~able.
The ratio of colloid and softener to solution of active compound and surfactant i~ generally selected to result in a final product which contains from 0.5 to 40, preferably about 20, % by weight of active compound, from Q.l to 30, preferably 5 to 15, % by weight of one or more surfactants, from 10 to 50 % by weight of a swellable colloid, from 0 to 70 % by weight of a softener, all percentage being based on the dry mass of the powder, and, where appropriate, minor amounts of a stabiliz2r, with the powder having a mean particle ~ize of the active compound less than 0.8 ~m and a half-width of the par-ticle ~i2e distribution of le~s than 50 %, and virtually no par~icle3 are over 1 ~m in size.
Examples of suitable stabilizers are -t ophe-rol, butylated hydroxytoluene, butylated hydroxyani~ola and ethoxyquine. Like the ~urfactant, they can be added .. . .

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~ 4 ~ O.Z. 00~0/41212 either to the aqueous or to the solvent phase, depending on solubility.
The procsss according to the invention is carried out, for example, in an apparatu~ like that depicted in Fig. 1, specifically as follows:
The apparatus comprises parts I, II and III. Part II is the high-temperature zone if required. Parts I and III are generally at below 50C.
A suspension of the active compound in the solvent and possibly one or more surfactants, with or without a small amount of added stabilizers, i8 placed in vessel (1). Particularly rapid dissolution of active compounds which are sensitive to heat or sparingly soluble at room temperature can be achieved by previous milling (particle 8ize ~50 ~m). Ve~sel (2) contains a solvent without active compound. Pumps (3) and (4) deliver the suspen3ion of active compound and the solvent to the mixing chamber, it being possible to choose the mixing ratio by the choice of the delivery rates of each of the pumps ~o that, depending on the solubility of the active compound in the solvent and the desired residence time, the concentration of active compound in the mixin~
chamber i8 from 0.5 ~to 10 ~ by weight based on the solution. In the case of thermolabile active compounds, the volume of the mixing chamber (7) is preferably such that the residence~time in (7) i8 less than 1 second at ~he set delivery rates of pumps (3) and (4). Before the solvent enters the mixing chamber it is brought to the ~ desired temperature in the heat exchanger (6), while the suspension of aotive compound is maintained at below 50C
durin~ transfer throughiths line (5) (which is thermally insulated when the active compound is sensitive to heat).
- Turbulent mixinçl in (7) at from 10 to 240C, preferably from 100 to 200C (for active compounds which are only slightly soluble even~in the bes~ solvent at room temper-ature), causes the active compound and the stabilizer to dissolve, and ~he resulting solution pa~se~ via the ~ ~ ~, iJ ~ 'J; j - 5 - O.Z. 0050/41212 overflow t8) into the second mixing chamber (11~ where, by mixing in an aqueou~ protective colloid/softener solution, which also contain~ the surfactant if this ha~
not been dissolved in the organic solvent, via the pump S (9) and the line (10), a microdispersion of the acti~e compound (micronizate) i8 formed from the molecular solution of active compound and the aqueou~ phase. The disper3ion is then discharged via the line (12) and the pre~sure control valve (13) and collected in the storage vessel (14). It i8 pos~ible, in order to maximize the concentration of active compound, to circulate the dispersion via the ~uction line (15).
When the pres~ure control valve (13) is set at pres~ures above 1 bar, it is even possible in the novel process to use solvents at temperatures above their boiling point (under atmospheric pressure).
It i~ pos~ible to obtain from the dispersion a product in the form of a powder in a conventional manner, eg. a~ de~cribed in DE-A 25 34 091, for example, by spray granulation, spray drying or spray cooling and coating of the particles, removal and drying in a fluidized bed.
For the ~pray drying, either the solvent is fir~t removed from the dispersion by di~tillation, preferably under reduced pressure, or by extraction with a water-immiscible solvent~ or the entire mixtura i3 spray-dried and thu3 water and ~olvent are removed together in the spray tower.
The active compound powder discharged from the spray tower i3 u~ually dry and free-flowing. It may be expedient in some cases to complete the drying by addi-tional treatment in a flùidized bed.
The production of the powder by spray drying can be replaced by ~my other 3uitable methods for converting the act~ve compounds, which are already finely divided in the water/active compound dispersion, into the form of a powder. A conventional process, which can be used when the auxiliaries and-protective colloid~ can be converted .

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- 6 - O.~. 0050/41212 into gel~ comprises, for example, removing the ~olvent from the dispersion and producing a W/O emul~ion in liquid paraffin, converting the emulsion droplets into a gel by cooling, removing the paraffin from the particles, and washing the resulting material with petroleum ~pirit and drying in a fluidized bed. It is also possible to concentrate the disper~ion of active compound by coacer-vation followed by filtration.
In each ca~e, the result is a dry powder which can be dissolved or redispersed in water to achleve a uniform distribution of the active compound in the particle 3iZQ range below 1 ~m.
The powders which can be obtained according to the invention can be converted in a conventional manner into the following pharmaceutical formss uncoated or (film-)coated tablets, cap~ules or instant powders. They can also be used as intermediates for producing lyophil-izates and solutions for in~ection.
Determination of the bioavailability in dogs:
The micronized substance (doreptide) is adminis-tered to dog~ by gavage ~dose 50 mg/kgj~, and blood is taken from the animals at defined times. After the plasma haY baen obtained, the samples are immediately deep-frozen and analyzed later by means of HPLC (reverse phase, fluorescence detection after derivatization). The plasma levels found in this way are compared with those found in the 8am2 dog~ (after a-l-week washout period) afta~ administration of the same dose of doreptide tablets produced in a conventional manner.

12 g of L-prolyl-2-phenyl-L-2-aminobutanoyl-glycinamide (doreptide) were Ru~pended in a vigorously ~tirred mixture of 2.4 g of ascorbyl palmitate and 40 g of isopropanol and, with the pressure control valve (13) set at 25 bar, mixed in the mixing chamber (7) with isoprop nol which had been heated to 200C in the heat exchanger (6). Nith a delivery rate for the suspen~ion of , .. .. ...... . . ........ .
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- 7 - O.Z. 0050/41212 0.2~ l/h and for the solvent of 0.38 l/h, the residence time in the mixing chamber (7) was 0.6 saconds. The resulting molecular solution was then tran~ferred into the mixing chamber (11) where a doreptide dispersion was produced by turbulent mixing with a solution of 15 g of gelatin and 22.5 g of sucrose per liter, which had been ad~uqted to pH 11 with lN NaOH. The tempexature of the dispersion in the collecting vessQl (14) was 30C.
Particle size analysis by photon correlation spectroscopy (B. Chu, Laser Light Scattering Analy~i-q, Academic Pre3s, New York 1974) showed that the mean particle diameter was 370 nm with a distribution range of + 60 %.
Spray drying resulted in an easily handled, water-soluble dry powder which contained 16.5 ~ dorep-tide. Resuspension of the dry powder in cold water yielded a dispersion with a mean particle size of 300 nm + 55 %-10 g of gramicidin S were suspended in a mixture of 1.2 g of ascorbyl palmitatQ and 40 g of isopropanol and micronized in the same way as in Example 1. The particle size distribution of the micronizate correspon-ded to that from Example 1.
. EXAMPLE 3 11 g of N-[(l-ethyl-2-pyrrolidinyl)methyll-2-m~thoxy-5-sulfamoylbQnzamide ~sulpiride) were suspended in a mixture of 2.0 g of ascorbyl palmitate and 40 g of methanol and micronized in the sEme way as in Example 1.
The mean particle size of the micronizate was 390 nm i 40 %.

The activQ compounds listed in the following Table 1 can be converted into micronizates in ~he same way as described in Example 1, the physicochemical propertiQs of the micronizates b~in~ in agreement with thosQ in Exampll3 1.

. . , - 8 - O.Z. 0050/41212 Tl~iLJ3 1 Example Active compound . .

4 Tyxothricin; Merck Index 9640 (lOth edition) Polymyxin B from Fluka, D 7910 Neu-Ulm 6 1-(3-Mercapto-2-m2thyl-1-oxspropyl)-L-proline (~aptopril) 7 1-[N-[(S)-l-Carboxy-3-~phenylpropyl]-L-alanyl]-L-proline-l'-ethyl e~ter maleate (enalapril maleate) 8 2(SJ-~N-(Morpholinocarbonyl)-L-phenylalanyl-N~-methyl-L-hi~tidylamino]-l-cyclohexyl-3(S)-hydroxy-6-methylheptane 9 N Butyl-6-cyclohexyl-4-hydroxy-2-isopropyl-5-tN-t2-(3,3-dLmethyl-2-oxobutyl)-3-phenylpropan-: oyl]-L-hi~tidylamino~-hexanamide ~N-(3-Amino-3-methyl-1-oxobutyl)-4-methoxy-L- ;:
phenylalanyl]-N-~(lS,2R,3S)-l-(cyclohexyl-methyl)-2,3-dihydroxy-5-methylhexyl~-L-histi-dineamide ll 2-Acetamido-3-O-~(R)-l-~[(S)-l-[[(R)-3-Car-bamoyl-l-carboxypropyl]carbamoyl]ethyl]carbam-oyl]ethyl~-2-deoxy-D-glucopyranos:e butyl ester : (murabutide)~
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Claims (2)

1. A process for improving the bioavailability of pharmaceutical active compounds with peptide linkages, which comprises dissolving the particular active compound with or without a surfactant in a volatile, water-mis-cible organic solvent at from 5 to 200°C, where appropri-ate under superatmospheric pressure, within less than 10 seconds, immediately precipitating the active compound in the form of a colloid from the resulting molecular solution by rapid mixing with an aqueous solution or dispersion of a solid or swellable colloid (and of a surfactant if this had not already been dissolved in the organic phase) at from 0 to 50°C, and converting the resulting dispersion into a redispersible powder by removing the solvent and the dispersing medium from it in a conventional manner.

2. A process as claimed in claim 1, wherein the components are employed in amounts such that the result-ing powder has the following composition:
0.5 to 40 % by weight active compound 0.1 to 30 % by weight surfactant to 50 % by weight swellable colloid 0 to 70 % by weight softener 0 to 70 % by weight one or more conventional pharma-ceutical auxiliaries