DK174120B1 - Poly(lactide-co-glycol)polymer comprising at least 25 mol per cent lactic acid units and up to 75 mol per cent glycolic acid units and method for production thereof - Google Patents

Description

• _ _ _ DK 174120 B1 i

The present invention relates to a heterogeneous wide molecular weight distribution polylactide-co-glycolide polymer and to a process for its preparation.

The poly (lactide-co-glycolide) polymer is characterized in that it comprises at least 25 mol% lactic acid units and up to 75 mol% glycol acid units, is insoluble in benzene and has a logarithmic viscosity number (1 g / 100). The solution for preparing the poly (lactide-co-glycolide) polymer is peculiar to the ring-opening process, for example, in chloroform or dioxane solution equal to or greater than 0.09 dl / g. polymerization of a cyclic dimer of lactic acid and optionally in the presence of a cyclic dimer of glycolic acid at an elevated temperature in the presence of a polymerization catalyst selected from zmk-oxide, zmcarbonate, basic zinc carbonate, diethyl zinc, organotin magnesium, tributylaluminum, barium compounds or lead oxide and in the presence of a chain growth regulator Such poly (lactide-co-glycolide) polymers are suitable for use in pharmaceuticals containing armacologically active acid-stable polypeptides which provide continuous release of the polypeptide over a long period of time when the agent is placed in a physiological type aqueous environment

It has long been recognized that continuous release of 25 certain drugs over a long period of time after a single administration could have significant practical benefits in clinical practice, and agents have already been developed that provide prolonged release of a number of clinically useful drugs after oral dosing ( see, for example, Remington's Pharmaceutical Sciences, 30 published by Mack Publishing Company, Easton, Pennsylvania, USA, 15th edition, 1975, pages 1618-1631), after parenteral administration (ibidem, pages 1631-1643) and after topical administration (see e.g. British Patent Specification No. 1 351 409) DK 174120 B1 2

A suitable method for parenteral administration is subdermal infection or implantation of a solid body, e.g., a pill or film containing the drug, and various such implantable organs have been described. In particular, it is known that for many drugs, suitable implantable organs for provide prolonged release of drug is achieved by encapsulating the drug in a biodegradable polymer or by distributing the drug in a matrix of such polymer so that the drug is released as degradation 10 of the polymeric matrix progresses

Suitable biodegradable polymers for use in sustained release compositions are well known and include polyesters which are gradually degraded by hydrolysis when placed in a physiological type aqueous environment. Particular polyesters which have been used are those derived from of hydroxycarboxylic acids, and much known technique has related to polymers derived from α-hydroxycarboxylic acids, especially lactic acid in both its racemic and optically active forms, and glycolic acid and copolymers thereof (see, e.g., U.S. Patent Nos. 3,773,919 and 20,888,699, Jackanicz et al., Contraception, 1973, 8, 227-234,

Anderson et al, ibidem, 1976, 11, 375-384, Wise et al Life Sciences, 1976, 19, 867-874, Woodland et al, Journal of Medicinal Chemistry, 1973, 16, 897-901, Yolles et al, Bulletin "of the Parenteral Drug Association, 1976, 30, 306-312, Wise 25 et al, Journal of Pharmacy and Pharmacology, 1978, 30, 686-689, and 1979, 31, 201-204) In the present specification, the term" polylactide "generally to include lactic acid polymers alone, lactic acid and glycolic acid copolymers, mixtures of these polymers and mixtures of such copolymers, and mixtures of such polymers and copolymers, wherein the lactic acid is either in racemic form or in optically active form. "acid stable" is understood to mean that the polypeptide is not substantially hydrolyzed under the conditions occurring within the present compositions during the period of use, i.e. at pH 2 at mammalian body temperature, e.g. up to 40 ° C, for up to 6 months

British Patent Specification No. 1,325,209 (equivalent to U.S. Patent No. 3,773,919) and U.S. Patent No. 5,888,669 are the only prior art known to applicants which discloses prolonged release of polypeptides, the latter mentioning only insulin but containing no concrete examples of such a preparation and the mention of polypeptides are apparently entirely speculative in that they appear only in a comprehensive list of many different classes of drugs which are claimed to be incorporated into preparations of the kind described therein, substantially all of the other drug types. In fact, the disclosure disclosed in this specification, except polypeptides, is relatively hydrophobic in character and of relatively low molecular weight, and the patent specification shows no recognition of the difficulties encountered when seeking to obtain satisfactorily maintained release of polypeptide preparations, many of which are relatively hydrophilic and me d is relatively high molecular weight

From U.S. Patent No. 4,011,312, 5 x 0.5 cm bougies are known for insertion into cows' udder channels for the treatment of mastritis comprising an antimicrobial drug and a lacid / glycolide copolymer having a molecular weight below 2000, corresponding to 25 a logarithmic viscosity number of less than 0.093 Such a preparation does not continuously release a polypeptide drug for a long time. In Chemical Abstracts, 88, 79041 n, microcapsules are disclosed wherein a core of drug is enclosed in a sheath of 30 polylactide. Such a microcapsule is not a preparation. wherein the drug is uniformly dispersed in the polylactide

It will be understood that "sustained" or "extended" release of a drug may be either continuous or discontinuous It has now been discovered that in many instances where the teachings of the prior art, and particularly that of British Patent Specification No. 325329 contained in the preparation of a composition of an acid-stable polypeptide, the release of the polypeptide from the composition, although occurring over an extended period of time, may also be discontinuous. for example, polylactide polymer, as described in said specification, often undergoes a significant induction period, during which no polypeptide is released, or the release is biphasic, and includes an initial period during which some polypeptide is released, and another period during which no or little polypeptide is released, and a third period during which most of the remainder of the polypeptide is released. In contrast, it is an object of the present invention to finding novel polymers for use in the preparation of agents containing acid-stable polypeptides from which, except for a relatively short initial induction period, the polypeptide is continuously released, with no periods during which no or little polypeptide is released. In the present specification, "release" is used only to describe a release profile which is substantially single-phase, although it may have a turning point, but which has at least no plateau phase DK Patent Application No. 591/82 This application relates to a pharmaceutical agent comprising (a) from 50% to 99.9% of a polylactide which is a polymer of lactic acid alone, a copolymer of lactic acid and glycolic acid, wherein limic glycolide and lactide units are from 0 up to 3 liters, a mixture of such polymers or a mixture of such polymers and copolymers, the lactic acid being either in rac emic or optically active form and wherein the polylactide is either insoluble in benzene and has a logarithmic viscosity number from 0.093 (1g per 35 ml in chloroform) to 0.5 (1 g per 100 ml in benzene) or insoluble in benzene and has a logarithmic viscosity number from 5 (1 g per 100 ml in chloroform) to 4 (1 g per 100 ml in chloroform or dioxane), and (b) from 0.1% to 50% of a pharmacologically active polypeptide which are not sufficiently hydrolyzed under the conditions occurring within the agent 5 during the intended use period, which polypeptide is uniformly dispersed in the polylactide

The poly (lactide-co-glycolide) polymers are useful in pharmaceuticals comprising acid-stable polypeptides generally without any restriction in structure or molecular weight, but are most useful for relatively hydrophilic polypeptides and the following list which does not must be considered exhaustive, showing polypeptides which can be used with the poly (lactide-co-glycolide) polymers of the invention

Oxytocin, vasopressin, adrenocorticotropic hormone (ACTH), epidermal growth factor (EGF), prolactin, lulibenn or lutemizing hormone-releasing hormone (LH-RH), insulin, somatostatin, glucagon, interferon, gastrin, tetragastrm, penile tagastrin, urogastron, secretin, calcitonin, enkephalins, endorphins, angiotensins, renin, bradykimn, bacitracmer, 20 polymyxins, colistins, tyrocidin, gramicidms and synthetic analogs and modifications and pharmacologically active fragments thereof

However, it has been found that polypeptides which are not stable under acidic conditions are unsuitable for use in the agents as they are degraded in the acidic environment produced in the polymeric matrix when the polylactide begins to degrade by hydrolysis, thereby producing carboxylic acid end groups

By the term "a physiological type aqueous environment" is meant the body, especially the muscular system and circulatory system, of a warm-blooded animal, although in laboratory studies such an environment may be mimicked by aqueous fluids optionally adjusted to a physiological pH at a temperature between 35 and 40 ° C

DK 174120 B1 6

Continuous release agents may be placed in the body of an animal that is desired to be treated with polypeptide, for example by intramuscular or subcutaneous infection, or by sub-dermal surgical implantation in the usual clinical or veterinary manner.

It has been found that a pharmaceutical agent containing a polylactide as defined in the second paragraph of page 4 can be designed to provide continuous release of the polypeptide by appropriate selection or regulation of various parameters, e.g., 10 by varying the polylactide composition. , especially the ratio of lactic acid to glycolic acid in copolymers, by controlling the molecular weight of the polylactide, both the average molecular weight by weight and the molecular weight range or polydispersity, as measured by the ratio of average molecular weight by weight

15 (Μω) and the average molecular weight by number (Mn), d v s M

ω

Mn in choosing the ratio of polypeptide to polylactide or in choosing the geometry of a solid preparation for implantation or of the particle size of a preparation for infection The release properties of such agents are also regulated to a certain extent by the nature of the polypeptide itself. for defining the above parameters when preparing a high molecular weight polypeptide (e.g. greater than 6000) than there is when preparing a lower molecular weight polypeptide 25 (e.g. less than 6000)

Furthermore, it has been found that the release of a polypeptide from an agent comprising a polylactide and a polypeptide proceeds by two distinct and independent mechanisms, namely, first a diffusion-dependent release of polypeptide from the base mass of polylactide and polypeptide consisting in leaching from and for low molecular weight polypeptides any distribution-dependent diffusion of polypeptide as such, and afterwards as the polylactide degrades, diffusion of aqueous polypeptide solution out of the agent through aqueous channels is generally the compatibility of polypeptides in polylacid polymers are limited, except in the case of low molecular weight polypeptides (e.g., up to a molecular weight of 5,6000), which are capable of having any specific reaction with the polylactide, e.g., a low molecular weight polypeptide, and which therefore reacts with the terminated carboxylic acid groups in the polylactide Due to this limited polypeptide similarity in polylactide releases a preparation of 10 polypeptide and polylactide when applied in an aqueous environment, very little polypeptide by diffusion through the polymeric matrix This is pretty much true for all polypeptide and polylactide combinations, but matrix diffusion is at a minimum for High Molecular Polypeptides in High Molecular Poly Lactides Although there is some matrix diffusion which results in an initial polypeptide release upon application of the agent in an aqueous environment upon release from or very near the surface, this soon ceases because the diffusion of polypeptide into polylactide is insufficient to result in continuous transport of polypeptide from the interior of the agent to its surface When an agent of polypeptide and polylactide is placed in an aqueous environment, water diffuses into the matrix and is distributed between polypeptide and polylactide to form regions of 25 aqueous polypeptide solution This problem Polypeptide produced when absorbed water is distributed between polypeptide and polylactide is incompatible with and insoluble in polylactides, especially those of high molecular weight, so that the absorption of water by the agent initially reduces a probability of matrix diffusion of polypeptide from of the agent If the thus-formed polypeptide regions are separated and isolated, the agents are unable to release polypeptide. However, the possibility that the aqueous polypeptide regions have some continuity grows with increasing concentration of polypeptide in the agent and with increasing absorption of water. and when the continuity of aqueous polypeptide regions reaches a sufficient level to contact the outer surface of the agent, polypeptide begins to be released from the composition by diffusion, not through the polylactide matrix, but through 5 aqueous polypeptide channels. some aqueous polypeptide areas near the surface expanded so that when they reach the exterior of the agent, the aqueous polypeptide existing in still isolated regions is not released, it is only released when a secondary hydrophilic pathway for diffusion becomes available. For high molecular weight polylactides, this secondary hydrophilic diffusion pathway is formed. when the polylactide has undergone sufficient degradation for the rate of water absorption to increase significantly When this occurs, aqueous pores or channels develop in the polylactide matrix which enable a continuous and substantial release of polypeptide as aqueous solution from previously separated and isolated regions.

As stated above, it has been found that when sustained release agents of known kind, and especially those described in British Patent No. 1,325,209, are used to release polypeptides, the initial matrix diffusion phase of the polypeptide release and the second release of polypeptide following degradation of the polylactide separated in time with the result that the release of polypeptide is not continuous but two-phase and discontinuous and comprises a small first release of polypeptide, a dead phase during which substantially no residual polypeptide is released and a subsequent second release phase during which substantially all of the remaining polypeptide is released It has now been found that by appropriate selection of the agent parameters, the matrix diffusion phase of the release and the subsequent degradation induced phase can be caused to overlap in time

A pharmaceutical agent comprising a polylactide as defined above and an acid-stable polypeptide exhibits two consecutive phases of polypeptide release when placed in a physiological type aqueous environment, the first phase being release by matrix diffusion, and the second phase is release due to degradation of polylac time, which is peculiar in that the diffusion phase and the 5 degradation-induced phase overlap in time.

The two phases can be overlapped by either prolonging the first diffusion phase or by causing the degradation induced phase to begin earlier or both. The first matrix release phase is difficult to extend, but is sensitive to the concentration of polypeptide in the matrix and to a limited extent for the nature of the polypeptide, especially its hydrophilicity

The degradation-induced release phase can be started earlier by appropriate selection of polylactide (more glycolide-rich polymer molecules which degrade faster than late-rich molecules), Μω (low molecular weight molecules decompose faster to a level where aqueous channels appear in the matrix) and polypeptide concentration (a higher 20 polypeptide concentration enables faster absorption of water and consequently faster development of continuous aqueous channels facilitating polypeptide release)

In addition to the need for the degradation-induced release phase to begin earlier, it is also necessary to regulate the rate of polypeptide release during this phase and to ensure that the total duration of this phase is sufficient for its intended clinical or veterinary purposes. of the degradation-induced release phase is to use polylactides containing 30 lactide-rich molecules that degrade more slowly than glycolide-rich molecules, or alternatively, high-molecular-weight polylactides can be used which take longer to degrade to a level. , where aqueous ducts are formed in DK 174120 B1 10

Therefore, it is clear that since glycolide-rich polymer molecules and / or low molecular weight molecules are preferred if the degradation phase is to begin rapidly and lactide-low molecules 5 and / or high molecular weight molecules are preferred if the degradation-induced release phase is to last. for a sufficiently long time, preferred polylactides are those with a high degree of heterogeneity with respect to glycolide and lactide-rich molecules or high polydispersity. Alternatively, the same properties can be obtained by mixing two or more different polylactides which are different with respect to lactide / glycolide. addition and / or with respect to Μω Mixture of a smaller amount of high Μω polylactide with a low Μω polylac time also provides desirable physical properties for 15 agents made therefrom, facilitating their preparation and processing.

Furthermore, it has been found that the profile of the polypeptide release from both known lactides and novel polylactides is almost exactly paralleled by the profile of water absorption. That is, when the polypeptide release is discontinuous, water absorption is also substantially discontinuous. in the same way, and conversely, when polypeptide release is continuous, water absorption is also Variation of the above-mentioned parameters for controlling the polypeptide release properties of the agent has also been shown to affect the water absorption of the agent in a precisely parallel manner.

The effect of the various parameters mentioned above on the polypeptide release and / or water absorption properties is illustrated by the following experiment 30 A Molecular weight of the polylactide component A 1 Low molecular weight polypeptide 11 DK 174120 B1

All Preparations comprising 20% w / w of the gastric peptide fragment tetragastrm hydrochloride, Trp-Met-Asp-Phe-NH 2, HCl, molecular weight = 633, were prepared in a polylactide comprising equimolar amounts of D, L-lactide-5 and glycol units in the form of a 0.2 mm thick film. Films were placed individually in water at 37 ° C, which was changed daily, and the ultraviolet absorption at 277 nm was measured to determine the tetragastration of the preparation in question. Day 10 With a known type of polylactide with Μω of about 240,000 (intrinsic viscosity = 1.36), there was an initial release of tetragastone, then a dead period ... from about 5 days to 21 days, during which very little was captured , followed by a major release from the 24 15th day onwards

With a new polylactide with Μω of about 15,000 (limit viscosity = 0.25), the release pattern was similar, but the dead period only lasted from day 4 or 5 to day 8 or 9 20 With a new low-polω polylactide (limit viscosity number).

of a 1 g / 100 ml solution in chloroform of 0.11) was no dead period and tetragastn was continuously released from time zero (TQ) A 1 2 Similar preparations were prepared using

25 of 10% by weight of the synthetic luliberin analog, ICI

118 630, µlu-His-Trp-Ser-Tyr-D-Ser (O-tBu) Leu-Arg-Pro - Azgly-NH 2, molecular weight * 1269, instead of tetragas-tnn

With a known polylactide having Μω about 240,000 (limit viscosity number = 1.36), the release of the polypeptide was two-phase with a dead period of about 15 days.

With a new polylactide with Μω about 14,000 (intrinsic viscosity = 0.25) there was a short induction penode followed by continuous release

With a new low Μω polylactide (intrinsic viscosity 5 of a 1 g / 100 ml solution in chloroform of 0.11) was

there a continuous release from TQ

A 2 Medium molecular weight polypeptide

Medium molecular weight polypeptide preparations were prepared comprising 0.1% by weight of mouse epidermal growth factor (EGF), molecular weight = 6041, in polylactides comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having different Μω and placed. in a buffer of pH 7.4 Release of EGF was monitored by radioimmunoassay 15 With a known polylactide having Μω about 200,000 (intrinsic viscosity = 1.08), there was no release at the beginning and no appreciable release of polypeptide until between 13 and 20 days after TQ <after which the release was continuous 20 With a new polylactide with Μω about 80 000 (limit viscosity = 0.58), there was also no release at the beginning, and significant release only occurred between 6 and 10 days after T0 '. after which the release was continuous 25 With a new low Μω polylactide (intrinsic viscosity

of a 1 g / 100 ml solution in chloroform of 0.11) there was continuous release from TQ

A 3 High molecular weight polypeptide

A composition comprising 20% w / w was prepared in a new polyolactxd comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a low Μω (intrinsic viscosity of A Ig / 100 ml solution in chloroform of 0.11) As expected from the previous experiments All, A 1 2 and A 2, this preparation also released polypeptide continuously from T0 when tested in vivo in rats and circulating bovine prolactin. was determined by radioimmunoassay 10 Experiment A1-A3 thus shows that reducing the molecular weight Μω or the viscosity of the polylactide used to prepare an agent reduces the two-phase nature of polypeptide production for low or medium molecular weight polypeptides or the starting delay. in the release of the medium or high molecular weight polypeptides and obtains a continuous release of the polypeptide from T0 B Ratio of lactide / alycolide in the polylactide

Preparations in the form of implantable organs 20 containing 100 µg (3% w / w) of the lulibenn analogue, ICI, were prepared.

118 630, in polylactides with Μω about 300,000, but with different lactide / glycolide ratios When tested in vivo in adult female rats exhibiting normal estrus behavior, they all produced two-phase release of the polypeptide comprising release for approximately 6 days after treatment, followed by a dead period during which there was no appreciable release of polypeptide The length of this dead period decreased with decreasing lactide / glycolide ratio (L / G) as follows DK 174120 B1 14 L / G_ Dead period (days) 100/0 No release 75/25 51 67/33 34 5 50/50 15

Thus, this experiment demonstrates that an agent exhibiting a two-phase polypeptide release can be improved toward continuous release by increasing the amount of glycolide relative to lactide in the polylactide 10 used up to about 50% glycolide C The molecular weight distribution

A wide molecular weight distribution (polydispersity) polymer blend solution was prepared by mixing solutions of a 50/50 D, L-lactide / glycolide polylactide with 15 low Μω (viscosity of a lg / 100 ml solution in chloroform of 0.115) (3 parts by weight) and a 50/50 D, L-lactide / glycolide polylactide with Μω about 200,000 (intrinsic viscosity = 1.08) (1 part by weight) Tetragastin (1 part by weight) was added and the mixture was cast to form a polylacid / tetragastrin material containing 20 wt% tetragastrm, which was then formed into a 0.02 cm thick plate. The plate was placed in water at 37 ° C and the release of tetragastrin was found to be continuous from Tq and continue for at least 44 days. Wide molecular weight distribution polylactides can be obtained, one by mixing pre-formed polymers with different molecular weights or by appropriately regulating the polymerization process in a well-known manner, and such polylactides provide important advantages. eg m the lower molecular weight polylactides disprove a substantially immediate release of any polypeptide, while the higher molecular polylacid times both prolong the period of completion and decrease the overall rate of release of the polypeptide. The mixture of low and high} Μω fractions in addition, it modifies the water absorption properties of the polylactide in a parallel manner. 5 From the foregoing, it is clear that it is desirable to prepare polylactides having an M range, especially low to medium Μω, in the range up to 60,000 and with high polydispersity. site / Μω \

The prior art regarding polylactides in general and 10 copolymers containing lactic acid and glycol moieties in particular says nothing about the preparation of such low molecular weight copolymers and nothing about methods of obtaining high polydispersity in such copolymers. In general, they have Μω 15 greater than about 30,000 - 60,000 (an intrinsic viscosity greater than 0.5) and have low polydispersity due to their preparation under anhydrous conditions and without any added chain stoppers. that, due to the different degrees of reactivity under polymeric conditions of the cyclic dimers of lactic acid and glycolic acid, copolymers of high heterogeneity with respect to polymer types can be obtained by ring-opening polymerization of a mixture of the two cyclic dimers in the presence of chain growth regulators so as to obtain polylactides with a vi -25 mucosal numbers less than 0.5 The cyclic dimer of glycolic acid is the most responsive under polymerisation conditions, and the first copolymer molecules formed by the polymerization are therefore glycolic acid. As a result, the later formed copolymer molecules are necessarily lactic acid-rich so that a copolymer is produced. of lactic acid and glycolic acid having the desired high heterogeneity

In addition, according to the invention, the polymerization to produce copolymers in the desired low Μω range is regulated by performing the ring-opening copolymerization of the mixed DK 174120 B1 16 cyclic dimers in the presence of water, lactic acid-containing water or other known chain growth regulator in accordance with general knowledge in the art. polymer chemistry

Suitable polymerization catalysts are zinc oxide, zinc carbonate, basic zinc carbonate, diethyl zmk, organotin compounds, e.g., stannous octanoate, tinbutyl aluminum, titanium, magnesium or barium compounds, or lead oxide, and of these, stannous octanoate is preferred.

The copolymerization of the mixed cyclic dimers is generally carried out in a conventional manner with respect to time and temperature.

Low molecular weight polylactides can also be obtained by copolymerizing the hydroxy acids themselves instead of the cyclic dimers. Although less heterogeneous polymers are obtained by this method, suitable matrixes for continuous release of polypeptides 15 can be obtained by mixing such polylactides with different compositions prepared by this method or by mixing a polylactide prepared in this way with one or more polylactides prepared by ring-opening polymerization of the cyclic dimers. By a "heterogeneous polylactide" is meant polylactides having a high degree of heterogeneity with respect to glycolide and lac time. -molecular molecules or with high polydispersity or mixtures of two or more different polylactides which are different in terms of lead time / glycolide content and / or 25 Μω as described above

Whether a given copolymer is heterogeneous or e) in this sense can easily be determined by examining the 25 MHz13C chemomagnetic resonance spectrum of the copolymer, e.g., deuterated dimethyl sulfoxide, in a homogeneous copolymer obtained in the prior art by copolymerization of lactic acid - and glycolic acid monomers, the resonance of the carbonyl carbon of the glycolic acid unit at δ = 166.0 - 166.2 shows itself as two doublets as a result of the four different approximately equally probable molecular states in which this carbon atom can exist, namely GGG , lSg, G ^ T1 and LGL (G = a glycolic acid unit, L = a lactic acid unit, and the star indicates the glycolic acid unit in question) in a heterogeneous copolymer as used in the present invention In contrast, it is unlikely that the order l £ l occurs, so that one of the duplicate signals in the spectrum of the homogeneous copolymer appears as a singlet. In fact, in the spectrum of h etherogenic copolymers, this signal from the glycolic acid unit's carbonyl carbon often appears as two singlets. A "heterogeneous copolymer" as defined in the present disclosure is therefore a copolymer for which the carbonyl carbon signal of the glycolic acid in say the heterogeneity or homogeneity of lactic acid / glycolic acid copolymers can also be detected by examining their degradation. Thus, when a copolymer is placed in a buffer of pH 7.4 at 37 ° C, it is periodically removed, dried, and samples are taken and the ratio of lactic acid and glycolic acid units 20 in the samples is determined by NMR, the ratio L / G increases with time for a heterogeneous copolymer, as preferably the glycolic acid sequences hydrolyze. For a homogeneous copolymer, however, the ratio L / G becomes constant as the decomposition proceeds 25 The lactic acid content of the copolymer is preferably in the racemic (D, L) form or in the optically active L form.

A suitable chain growth regulator for use in the process of the invention is, for example, water, lactic acid, glycolic acid or other hydroxy acids, alcohols or carboxylic acids in general.

The invention is illustrated by the following preparations and examples DK 174120 B1 18

Preparation 1 16 g of zinc oxide was added to 800 g of D, L-lactic acid in a 2-liter 3-necked round bottom flask, equipped with a stirrer, thermometer and distillation kit connected to a water condenser. The mixture was stirred and heated to about 135 ° C. at which temperature water began to distill over Heating was continued for 8 hours, during which the temperature rose to about 190 ° C. When distillation of water ceased, the pressure was reduced and distillation continued until solid began to accumulate in the condenser. at this stage, the water condenser was replaced with an air condenser and the residue was cooled and then distilled under high vacuum (2-8 mm of mercury) and the fraction (about 300 g) distilling between 130 and 160 ° C was collected. was D, L-lactide (3,6-dimethyl-1,4-dio-15-xane-2,5-dione), the cyclic dimer of D, L-lactic acid

The crude D, L-lactide was crystallized from ethyl acetate (about 600 mL) three times, and finally the recrystallized product was dried at 45 ° C under reduced pressure (2 mm of mercury) for 24-48 hours, after which it had the melting point 124 - 125 ° C

Preparation 2

Glycolide (1,4-dioxane-2,5-dione), the cyclic dimer of glycolic acid, was prepared in the manner described in Preparative Methods in Polymer Chemistry by WR Sorenson & TE Campbell, 2nd Edition, published by Interscience (1968), page 363 25 The crude glycolide was purified by three successive crystallisations of dry ethyl acetate, then dried at 45 ° C under recuperated pressure (2-8 mm of mercury) for 24-48 hours, mp 82 - 84 ° C

EXAMPLES 1-8 30 Polymers of D, L-lactide and glycolide were prepared as follows DK 174120 B1 19

Pure dry D, L-lactide (Preparation 1), pure dry glycolide (Preparation 2), a total of 42 g, industrial D, L-lactic acid containing about 12 wt% water and 1 ml of an 8 wt% solution of stan -Noctanoate in hexane was placed in a pre-dried glass tube. 5 The hexane was evaporated under reduced pressure and the tube was heated to 160 ° C for 6 hours with constant stirring, if possible. The tube was cooled in powdered solid carbon dioxide and the extracted, broken up into small pieces and dissolved in chloroform (400 ml) The chloroform solution was filtered and the filtrate was poured into methanol (2 L) to precipitate the polylacid which was filtered off and dried under vacuum at 40 ° C for 24 hours. and then at 80 ° C for 24 hours. All the polylactides thus prepared were soluble in chloroform and dioxane but insoluble in benzene. The following polylactides were prepared in this way D, L-L / GD, L-Limit-Μ-ω

Ex lactide Glycolide mol- Milk viscosity (ca) __ (L) (g) (G) (g) ratio of acid__tet__ 1 __23.0__18.5 50/50 400 µl 0.25 15 200 2 23.0 18.5 50 / 50 920 ul 0.126 low ______ X) __ 3 23.0 18.5 50/50 1380 ul 0.108 low ______ x) __ 20 4__23.0__18.5__50 / 50 ___ 0.33__ 5 __23.0__18.5__50 / 50 ___ 0.25__ 6 __23.0__18 , 5__50 / 50 ___ 0.115 * __ 7 __23.0__18.5 50/50 ___ 0.11 ** __ 8 23.0 18.5 50/50 0.11 * 25 Μω is in relation to polystyrene standard x) is viscosity number of a 1 g / 100 ml solution in chloroform xx) logarithmic viscosity number (1 g / 100 ml in chloroform)

Alternatively, if present, the lactide, glycolide and lactic acid may be heated to 160 ° C and 0.08 g of stannous octanoate may then be added to initiate the polymerization EXAMPLE A (not according to the invention)

A polylactide comprising equimolar amounts of glycolic acid and 5 D, L-lactic acid units and having an intrinsic viscosity of 1.36 (50 mg) was dissolved in 1 ml of dioxane and 50 μΐ of a solution of ICI 118 630, C luHis-Trp-Ser-Tyr-D-Ser (O-tBu) -Leu-Arg-Pro-Azgly-NH 2 (233 mg per ml of the acetate salt, equivalent to 200 mg per ml of base) in distilled water was added. turbid solution was cast as a film, the solvents were evaporated in a stream of nitrogen in the dark, and the film was dried at 40 ° C under reduced pressure (0.02 mm of mercury) for 48 hours The mixture containing about 17% by weight of ICI 118,630 in the polylactide was homogenized at three consecutive 15 pressure casts at 110 ° C for 10 seconds and was finally pressurized to implantable organs 0.038 cm thick, each weighing 1.5 mg and containing 309 ± 7 µg (about 17% by weight) of ICI 118 630

Continuous release of ICI 118 630 from these implanted organs was demonstrated by placing them in female 20 rats exhibiting normal oestrus behavior. After implantation, the rats underwent a period of diarrhea detected by the absence of horny vaginal discharge. lasted from 31 to 40 days, showing that ICI 118 630 was continuously released during this period 25 The procedure described above was repeated using 50 µl ICI 118 630 acetate solution (150 mg pure peptide per ml water) and implantable organs were prepared in a similar manner, weighing 2 mg and containing 306+ 6 µg ICI 118 630 (13 wt%) and at a thickness of 0.038 cm In the rat oestrus test described above, these implantable organs released ICI 118 630 continuously through a period of 30 - 38 days, detected by the diastrous period in the rats 21 DK 174120 B1

For use in human therapy, implantable organs containing 1 - 100 mg of ICI 118 630 (5 - 50% by weight) weighing 2 mg - 1 g and in the form of cylindrical rods suitable for implantation by trocart 5 were prepared. Examples 4-5

The procedure described in Example A was repeated but using polylactides comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a limit viscosity of 0.33 (Ex. 4) and 0.25 (Ex. 5). ) instead of 10 1.36 to produce implantable organs containing 10 wt% ICI 118 630 weighing approximately 3 mg and being 0.08 cm thick

These organs were placed in female rats (5 per group) who exhibited regular oestrus behavior prior to implantation. The implanted organs made of polylactide having a limit viscosity of 0.33 exhibited an induction period of 5 days, followed by a diastolic period. of about 26 days, and the organs made of polylactide having an intrinsic viscosity of 0.25 exhibited an induction period of 3-4 days, followed by a diestrus period of about 25 days. 20 Similar implantable organs but containing 20% by weight of ICI 118,630 were prepared. similarly, and these exhibited a similar diastrous period, but no induction period in the rat test described above.

Similarly, for use in human therapy, readily implantable organs containing 1 - 100 mg of ICI 118,630 (5 - 50% by weight) weighing 2 mg - 1 g and in the form of cylindrical rods suitable for implantation were prepared. with trocart

EXAMPLE B

Tetragastrin hydrochloride (Trp-Met-Asp-Phe-NH 2, HCl) (200 mg) was dissolved in a mixture of 9 ml of dioxane and 1 ml of water and to the solution was added a polylactide as described in Example l (1.8 g) The mixture was cast as a film and the solvents were evaporated in a stream of nitrogen. The resulting film was dried under reduced pressure (0.02 mm of mercury) at 40 ° C for 5 48 hours, then it homogenized at three successive pressure casts at 80 ° C for 10 seconds and molded to form films of 0.02, 0.06 or 0.12 cm thickness, each weighing about 80 mg

The release of tetragastrin was measured by placing a film 10 in distilled water, taking a sample of the distilled water daily, replacing all the remaining distilled water with fresh water and measuring the ultraviolet absorption of the daily samples at 277 nm. which showed continuous release of tetragastrin from films of all three thicknesses

Cumulative% of tetragastrin released

Time (days) __ 0.02 cm film__0.06 cm film__0.12 cm film _1__9j_6__5,6__4j_0_ _4__14,9__10, 5__9j_0_ 20 7__20,3__13,9__11,7_ _9__25,3__17,7__14,8_ _11__33,1__22,6__19,4_ _14__48,6__33 , 2__28,1_ _17__61,9__45, 9__40, 5_ 25 21__74,7__59, 8__53.2_ _24__81,8__68,1__60,2_ _28__85,2__74,9__66,4_ _31__86,9__77,7__70,9_ _36__88,5__82,5__77,5_ 30 39 89 EXAMPLE 6 23 rag tetragastrin hydrochloride was dissolved in aqueous dioxane (1 9 by volume) and added to a solution of (a) a polylactide comprising equimolar amounts of D, L-lactic acid. and glycolic acid units and having a viscosity of 5 0.115 (as a 1 g / 100 ml solution in chloroform) (Ex 6) (120 mg) and (b) a polylactide comprising equimolar amounts of D, L-lactic acid and glycolic acid residues and having a intrinsic viscosity of 0.08 (40 mg) in 2 ml of dioxane 10 The mixed solutions were cast as a film as described in Example A and cast as implantable organs weighing approximately r 50 mg and 0.02 cm thick

The release of tetragastrum from these implantable organs was measured by the procedure described in Example B and the following results showing continuous release were obtained.

Time (then cumulative% free tetragastn) 1 0.6 2 1.0 3 1.6 5 4 2.7 7 8.6 10 17.2 14 29.4 18 43.1 10 23 56.3 28 64.9 32 71 , 36 79.0 39 83.9 15 44 90.5 EXAMPLE 7

A polylactide comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a viscosity of 0.11 as a 1 g / 100 ml solution in chloroform (Ex 7) (50 mg) was dissolved in 20 dioxane (1 ml) and a solution of mouse epidermal growth factor (EGF, 0.05 mg) was added in 0.05 ml of water. The mixture was cast as a film on polytetrafluoroethylene and the solvent was removed in a stream of nitrogen in the dark. The film was dried at 60 ° C under reduced pressure (0.8 mm mercury) for 48 hours. The film was then pressurized at 120 ° C for 10 seconds to form implantable organs 0.02 cm thick and weighing 10 mg

The implantable organs were each placed in a black bottle at 37 ° C with 1 ml of Mcllvain's buffer (pH 7.4) (Documenta 30 Geigy, Scientific Tables, edited by K Diem & C Leutner, published by JR Geigy SA, Basel, Switzerland, 7th edition, 1970, page 280) containing 0.02% by weight sodium azide The buffer was removed daily and replaced with fresh, and EGF released in the buffer by the organ was measured by radioimmunoassay, which showed that the release started immediately and continued for at least 2 weeks, releasing 100 - 200 // g per day EXAMPLE 8

A polylactide comprising equimolar amounts of D, L-lactide and glycolide and having a viscosity number (1 g / 100 ml solution in chloroform) of 0.11 (ex 8) (400 mg) was dissolved in 2 ml of dioxane, and a solution / suspension of bovine prolactin (100 mg) in 0.5 ml of distilled water was added with vigorous stirring. The mixture was poured onto a polytetrafluoroethylene substance and dried, first in a stream of nitrogen and then under reduced pressure (0.01 mm) (mercury) at 40 ° C for 24 hours The resulting heterogeneous mixture was homogenized at four successive pressure molds at 60 ° C and then molded to a plate of 0.2 cm thickness, excised implantable organs weighing 60 mg

The organs were placed subcutaneously in adult female rats, which were then periodically drained from the tail, and the prolactm in the blood samples was measured by radioimmunoassay. A placebo group receiving no prolactin in the implanted organ was similarly examined. and the amounts of circulating prolactin were compared The following results were obtained DK 174120 B1 26 nifRP-nrnlactm in plasma (uq / ml)

Time __Placebo group_Treated 'group 5 1 0.38 24.7 2 0.45 105.9 6 0.54 7.7 9 0.72 17.8 10 13 0.52 65.4 16 0.56 89.7 20 0.75 288 23 0.81 142 26 0.84 562 15 42 1.25 1250

The procedure described in Examples 1-8 was repeated except that the polylactide was dissolved in dioxane instead of in chloroform and similar polylactides were obtained EXAMPLES 9-15

The procedure described in Examples 1-8 was repeated except that the polylactide was dissolved in glacial acetic acid and the resulting glacial acetic acid solution was added dropwise to methanol to precipitate the polylactide which was filtered off. dried under vacuum at 40 ° C for 24 hours, and then at 80 ° C for 24 hours. The following special polylactides were prepared in this way D, Li-L / GD, L-Limit-Mole-Stan.

Ex lactide Glycolide Molecular Milk Sequyl Nooc- <L) (G) (g) Acid Shock Weight Ta- __ (£) ___ Hold ___ Tet __ (ca) Note 9 33.3__26.7 50/50 360µ1 0.234 13 500 93µ1 5 10 11.1__8.9 50/50 120µ1 0.243 14 450 31µ1 11 11.1__8.9 50/50 120µ1 0.265 16 800 31µ1 12 111.0 89.0 50/50 1.2ml 0.257 15 850 0, ________31ml 13 111.0 89.0 50/50 1.2ml 0.239 14 200 0, ________31ml 14 88.8 71.2 50/50 0.96ml 0.262 16 600 0, ________25ml 10 15 22.2__17.8 50/50 1 , 38ml 0.09 ** __ 62µ1 16 11.1__8.9 50/50 ___ 0.126 * ___ 17 __ = __ 67/33 ___ 0.121 * ___ 18 __: __ 75/25 ___ 0.108 * ___ 19 11.1__8.9 50 / 50 ___ 0.126 ** ___ 15 20 11.1__8.9 50/50 ___ 0.093 ** ___ 21 11.1 8.9 50/50 0.11 * 22 __11.1__8.9 50/50 ___ 1, 06___ * Viscosity Figures { lg / 100 ml in chloroform ** logarithmic viscosity number (lg / 100 ml in chloroform)

EXAMPLE C

A polylactide comprising equimolar amounts of glycolic acid and D, L-lactic acid units and having an intrinsic viscosity of 0.25 was dissolved in glacial acetic acid and the solution was lyophilized The lyophilized powder (540.7 mg) and ICI 118 630 (142.1 mg ) of the acetate salt (equivalent to 124 mg base) was dissolved in 6.8 ml of acetic anhydride glacial acetic acid and freeze dried for 24 hours (the glacial acetic acid was refluxed for 2 hours with 1% water to remove the acetic anhydride). The freeze-dried product was extruded under pressure. at 70 ° C to a rod of 30 mm diameter from which implantable organs of DK 174120 B1 28 were cut to the desired weight. The implantable organs were dissolved in a suitable solvent, e.g., acetonitrile, and tested for drug content and Purity The organs were found to contain 16.1% w / w pure 118 630 base 5 Release of 118 630 was assessed by immersing implantable weights approximately 10 mg in Mcllvam's pH 7.4 shock pad at 37 ° C ICI 118 630 was released continuously for at least 5 weeks

In a further experiment, implantable organs weighing approximately 390 μg, 860 μg, 1500 μg, 3000 μg and approximately 6000 μg were implanted subcutaneously in a group of adult female rats with regular cycling for the 28 days following implantation. the animals were essentially free of oestrus intervals, showing that active drug was released continuously during this period

EXAMPLE D

A solution of ICI 118 630 acetate salt was prepared by dissolving 170.8 mg of ICI 118 630 acetate in 5 ml of acetic anhydride - free glacial acetic acid (The glacial acetic acid was refluxed for 2 hours with 1% water to remove acetic anhydride). This solution was shown by high pressure liquid chromatography. (HPLC) containing 25.21 mg of ICI 118,630 base per ml of 442.5 mg of polylactide (prepared as in Example 12) was dissolved in 4.5 ml of the acetic acid solution and the resulting solution was lyophilized for 25 hours. was extruded under pressure at 74 ° C to a 25 mm diameter rod from which implantable organs of the desired weight were excised. The organs were dissolved in a suitable solvent such as acetonitrile and the resulting solution analyzed by HPLC Implant is mgsor The genes are shown to contain 20% w / w pure 118 630 base EXAMPLES 16-18

A polylactide comprising equimolar amounts of D, L-lactic acid and DK 174120 B1 29 glycolic acid units and having a viscosity of 0.126 (1 g / 100 ml solution in chloroform) (Ex 16) (240 mg) was dissolved in glacial acetic acid (5 was added with vigorous stirring. The solution was lyophilized for 24 hours and the resulting solid was pressurized at 50 ° C for 20 seconds to form of implants 0.2 cm thick and weighed 35-40 mg

The above procedure was repeated with the following polymeric 10 (a) A polylactide comprising 67 mole% D, L-lactic acid and 33 mole% glycolic acid units and having a viscosity number of 0.121 (1 g / 100 ml solution in chloroform (Ex 17)) b) A polylactide comprising 75 mole% D, L-lactic acid and 25 mole% glycolic acid units and having a viscosity number of 0.108 (1 g / 100 ml solution in chloroform (Ex 18)) (c) A polylactide comprising 100% D , L-lactic acid and with a viscosity number of 0.100 (1 g / 100 ml solution in chloroform)

The release of tetragastine from these implant members 20 was measured by the procedure described in Example 17, and the following results were obtained.

Cumulative S released tetragastrm T id ttr1 »50% D, L- 67% D, L- 75% D, L-lactide lactide lactide No. 100% D, L-50% 33% 25% lactide glycolide glycolide glycolide I 6.0 1.0 1.7 1.9 3 12.9 2.1 3.2 3.0 7 23.3 7.1 8.0 5.1 9 27.2 12.2 11.6 6.5 II 30 , 3 20.2 15.8 8.2 15 36.7 40.0 27.0 14.0 17 39.3 45.0 29.7 17.9 21 44.5 51.8 35.1 25.5 24 49.6 55.6 37.9 30.4 28 58.8 59.6 41.1 36.1 31 68.8 62.3 42.8 40.1 35 81.5 67.3 45.0 45 , 6 39 91Ό 74.3 47.6 50.7 42 95.9 81.9 50.6 55.3 46 96 # 5 89.1 55.5 60.4 49 97.5 93.2 60.0 65 , 2 53 95.4 64.8 70.0 56 96.3 68.6 73.6 59 97.0 73.1 77.8 63 97.2 77.1 81.5 70 82.7 86.1 74 85.0 87.5 84 90.4 89.5 DK 174120 B1 31

These results show that continuous release of tetra-gastrm is achieved by using low molecular weight polylactides and that the duration of the release is determined by the composition of the hydrolytically unstable polyester. EXAMPLE 19

A polylactide comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a logarithmic viscosity number of 0.126 (as a 1 g / 100 ml solution in chloroform) (Ex 19) (9.5 mg) was dissolved in distilled dioxane ( 0.25 ml) and a solution of mouse epidermal growth factor (EGF 0.5 mg) in distilled water (0.1 ml) was added. The mixture was cast as a film on polytetrafluoroethylene fabric and the solvent was removed in a stream. of nitrogen in the dark The film was dried at 40 ° C under reduced pressure (0.01 mm of mercury) for 48 hours Fil-15 but then pressurized at 70 ° C for 10 seconds to a planting organ of 0.02 cm thick and weighing about 9 mg A placebo implant was also prepared

The samples were implanted subcutaneously in guinea pigs cannulated in the carotid artery and blood samples were taken periodically and the plasma EGF-20 levels were measured by radioimmunoassay.

Increased plasma EGF levels were observed from day 3 and continued for at least one week

Similar implant organs were prepared as described above, but using a polylactide comprising 25 equimolar amounts of D, L-lactic acid and glycolic acid units and having an intrinsic viscosity of 1.06 Pressure casting of this implant was performed at 120 ° C.

Plasma implantation and examination was performed as described above, but no increased EGF levels were observed in the plasma prior to 17 days after implantation. EXAMPLE 20

A polylactide comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a logarithmic viscosity of 5 0.093 (as a 1 g / 100 ml solution in chloroform) (Ex 20) (40 mg) was dissolved in anhydride-free glacial acetic acid. (1 ml) and a solution of mouse epidermal growth factor (EGF, 8.15 mg) in a mixture of water (0.5 ml) and anhydride-free glacial acetic acid (3 ml) was added. The solution was freeze-dried for 24 hours. 10 was then die-cast at 50 ° C to form a 2 mm x 2 mm x 10 mm implant member weighing 36.1 mg

The sample was implanted subcutaneously in the cannulated cat, blood samples were taken periodically, and the plasma EGF levels were measured by radioimmunoassay. 15 Increased plasma EGF levels were observed from day 3 and continued for at least 40 days. EXAMPLES 21-22

Implant anthers containing bovine prolactin were prepared as described in Example 20 but using 20 (a) a polylactide (400 mg) comprising equimolar amounts of D, L-lactic acid and glycolic acid units and having a viscosity number (1.9 / 100). (b) a polylactide (400 mg) comprising equimolar amounts of D, L-25 lactic acid and glycolic acid units and having an intrinsic viscosity number of 1, 06, (Ex. 22) dissolved in 4 ml of dioxane

This sample was cast at 110 ° C

DK 174120 B1 33

Compositions (a) and (b) were tested in vivo as described in Example 20. Composition (a) released significant amounts of plasma bovine prolactin at least as early as the 4 day and continued to release for at least 85 days, while Preparation 5 (b) released significant amounts at least as early as from the 8 day and for at least 85 days

Claims (3)

1 Heterogeneous poly (lactide-co-glycolide) polymer having a wide molecular weight distribution, characterized in that it comprises at least 25 mole% lactic acid units and up to 75 mole% glycolic acid units, is insoluble in benzene and has a logarithmic viscosity (lg / 100 ml solution in chloroform or dioxane) equal to or greater than 0.09 dl / g and a limit viscosity equal to or less than 0.33 dl / g A process for preparing a heterogeneous polydactide (co-glycolide) polymer having a wide molecular weight distribution comprising at least 25 mole% of lactic acid units and up to 75 mole% of glycolic acid insoluble in benzene having a logarithmic viscosity number (1 g / 100 ml solution in chloroform or dioxane) equal to or greater than 0.09 dl / g and an intrinsic viscosity equal to or less than 0.33 dl / g, characterized by ring-opening polymerization of a cyclic dimer of lactic acid and optionally in the presence of a cyclic dimer of glycolic acid at an elevated temperature in the presence of a polymerization catalyst selected from zinc oxide, zinc carbonate, basic zinc carbonate, diethyl zinc, organotin compounds, tributyl aluminum, titanium, magnesium or barium compounds or lead oxide and in the presence of carbon dioxide in the presence of 30. A wide molecular weight heterogeneous poly (lactide-co-glycolide) polymer having a distribution comprising at least 25 mol% of lactic acid units and up to 75 mol% of glycolic acid insoluble in benzene having a logarithmic viscosity number (lg / 100 ml solution DK 174120 B1 34 in chloroform or dioxane) equal to or greater than 0.09 dl / g and an intrinsic viscosity number equal to or less than 0.33 dl / g prepared by the method of claim 3 or in obvious equivalent manner 5