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(19) 



(12) 



Europaisches Patentamt 
European Patent Office 
Office europeen des brevets ^ Q Q58 481 B2 

NEW EUROPEAN PATENT SPECIFICATION 



(45) Date of publication and mention 
of the opposition decision: 
21.05.2003 Bulletin 2003/21 

(45) Mention of the grant of the patent: 
01.10.1986 Bulletin 1986/40 

(21) Application number: 82300416.3 

(22) Date of filing: 27.01 .1982 



(51) mtci7: A61 K 38/02, C08G 63/08 
// C07K7/06, C07K7/08, 
C07K16/06, A61K31/765, 
A61K9/22 



CM 

CD 

CO 

oo 
in 
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in 



(54) Continuous release pharmaceutical compositions 

Pharmazeutische Zusammensetzungen fur die kontinuierliche Freigabe des Wirkstoffes 
Compositions pharmaceutiques pour la liberation continue de la substance active 



(84) Designated Contracting States: 

AT BE CH DE FR GB IT LI LU NL SE 

(30) Priority: 16.02.1981 GB 8104734 

(43) Date of publication of application: 
25.08.1982 Bulletin 1982/34 

(73) Proprietor: AstraZeneca AB 
151 85 Sodertalje (SE) 

(72) Inventor: Hutchinson, Francis Gowland 
Lymm Cheshire WA1 3 0BL (GB) 

(74) Representative: 

Lawrence, Peter Robin Broughton et al 

GILL JENNINGS & EVERY, 

Broadgate House, 

7 Eldon Street 

London EC2M 7LH (GB) 



(56) References cited: 
EP-A- 0 025 698 
GB-A-2 008135 
US-A- 3 887 699 



GB-A- 1 351 409 
US-A- 3 773 919 
US-A- 4 011 312 



• Chemical Abstracts vol. 88, no. 12, March 1978 
Columbus, Ohio, USA T.M.S. CHANG 
"Biodegradable semipermeable microcapsules 
containing enzymes, hormones, vaccines, and 
other biologicals" page 79044, column 2, 
abstract no. 79041 n 

• Chemical Abstracts vol. 91, no. 2, 1979 
Columbus, Ohio, USA D. WISE et al. "Results on 
biodegradablecylindrical subdermal implants 
for fertility control" page 275, column 2, abstract 
no. 9442g 

• Polymer, Volume 20, pages 1459-1464. 1979 



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Printed by Jouve, 76001 PARIS (FR) 



EP 0 058 481 B2 



Description 

[0001] This invention relates to solid pharmaceutical compositions of the pharmacologically- active acid-stable 
polypeptide IC1 1 88,630 which provide continuous release of the polypeptide over an extended period when thecom- 

5 position is placed in an aqueous, physiological-type environment 

[0002] It has long been appreciated that the continuous release of certain drugs over an extended period following 
a single administration could have significant practical advantages in clinical practice, and compositions have already 
been developed to provide extended release of a number of clinically useful drugs, after oral dosing (see, for example, 
Remington's Pharmaceutical Sciences, published by Mack Publishing Company, Easton, Pennsylvania, U.S.A., 15th 

10 Edition, 1975, pages 1618 — 1631), after parenteral administration (ibidem, pages 1631 — 1643), and after topical ad- 
ministration (see, for example, United Kingdom Patent Number 1 ,351,409). A suitable method of parenteral adminis- 
tration is the sub-dermai injection or implantation of a solid body, for example a pellet or a film, containing the drug, 
and a variety of such implantable devices has been described. In particular, it is known that, for many drugs, suitable 
implantable devices for providing extended drug release may be obtained by encapsulating the drug in a biodegradable 

?5 polymer, or by dispersing the drug in a matrix of such a polymer, so that the drug is released as the degradation of the 
polymer matrix proceeds. 

[0003] Suitable biodegradable polymers for use in sustained release formulations are well known, and include pol- 
yesters, which gradually become degraded by hydrolysis when placed in an aqueous, physiological-type environment. 
Particular polyesters which have been used are those derived from hydroxycarboxylic acids, and much prior art has 

20 been directed to polymers derived from a-hydroxycarboxylic acids, especially lactic acid in both its racemic and optically 
active forms, and glycolic acid, and copolymers thereof — see, for example, United States Patents Numbers 3,773,91 9 
and 3,887,699; Jackanicz et a/. ; Contraception, 1 973, 8, 227—234; Anderson et at., ibidem, 1 976, 1 1, 375 — 384; Wise 
et al., Ufe Sciences, 1976, 19, 867—874; Woodland et a/., Journal of Medicinal Chemistry, 1973, 16, 897—901 ; Yolles 
et a/., Bulletin of the Parenteral Drug Association, 1976, 30, 306 — 312; Wise etai, Journal of Pharmacy and Pharma- 

25 cology, 1978, 30, 686—689 and 1979, 31, 201—204. 

[0004] In this specification, the term "polylactide" is used to include copolymers of lactic acid and glycolic acid as 
defined in claim 1 and mixtures of such copolymers, the lactic acid being either in racemic or in optically active form. 
Also, the term "acid-stable" is to be understood as meaning that the polypeptide is not significantly hydrolysed under 
the conditions encountered within the claimed formulations during the period of use envisaged, that is, at pH 2 at 

30 mammalian body temperature, say up to 40°C, for up to six months. 

[0005] United Kingdom Patent Specification Number 1,325,209 (equivalent to United States Patent Specification 
Number 3,773,919) and United States Patent Specification Number 3,887,699 is the only prior art known to us which 
makes any reference to extended or sustained release of polypeptides, the latter mentioning insulin only, but it contains 
no specific example of any such formulation, and the reference to polypeptides is apparently entirely speculative, 

35 appearing, as it does, only in an extensive listing of very many different classes of drugs which can allegedly be incor- 
porated into formulations of the kind described therein. In fact, essentially all of the other drug types referred to in that 
specification, apart from polypeptides, are relatively hydrophobic in character and of relatively low molecular weight, 
and the disclosure of that specification displays no recognition of the difficulties which we have encountered when 
seeking to obtain satisfactory sustained release formulations of polypeptides, many of which are relatively hydrophilic, 

40 and of relatively high molecular weight 

[0006] It is to be appreciated that "sustained" or "extended" release of a drug may be either continuous or discon- 
tinuous. We have now discovered, in fact, that in many cases when the teaching of the prior art, and in particular the 
teaching of United Kingdom Specification No. 1 ,325,209, is applied to the manufacture of a formulation of an acid- 
stable polypeptide, the release of the polypeptide from the formulation, although occurring over an extended period of 

45 time, may also be discontinuous. For example, the release of a polypeptide from a polylactide polymer as described 
in the said Specification is often preceded by a significant induction period, during which no polypeptide is released, 
or is biphasic, and comprises an initial period during which some polypeptide is released, a second period during which 
little or no polypeptide is released, and a third period during which most of the remainder of the polypeptide is released. 
By contrast, it is an object of the present invention to provide compositions of the acid-stable polypeptide from which, 

50 apart possibly from a relatively short initial induction period, the polypeptide is released continuously, with no periods 
during which little or no polypeptide is released. The words "continuous release" are used in this specification solely 
to describe a release profile which is essentially monophasic, although it may have a point of inflection, but certainly 
has no "plateau" phase. 

[0007] In Journal of Bioengineering, 1, 25 — 29 (1976) (Chemical Abstracts, 88, 7904/n, 1978), two formulations of 
55 insulin are disclosed which show an essentially monophasic release profile, but substantially all the insulin is released 
within about 48 hours. 

[0008] Thus, according to the present invention, there is provided a solid pharmaceutical composition as defined in 
claim 1 . 



2 



EP 0 058 481 B2 



[0009] By "an aqueous physiological-type environment* we mean the body, particularly the musculature or the cir- 
culatory system, of a warm-blooded animal, although in laboratory investigations such an environment may be mim- 
icked by aqueous liquids, optionally buffered to a physiological pH, at a temperature of between 35 and 40°C. 
[0010] The continuous release composition of the invention may be placed in the body of an animal which it is desired 
5 to treat with the polypeptide by, for example, intramuscular or subcutaneous injection, or by sub-dermal surgical im- 
plantation, in conventional clinical or veterinary manner. 

[001 1 ] We have discovered that a pharmaceutical composition according to the invention may be designed to provide 
continuous release of the polypeptide by the appropriate choice or control of various parameters, for example by varying 
the polylactide composition, particularly the proportion of lactic acid to glycolic acid in copolymers; by controlling the 
10 molecular weight of the polylactide, both the weight-average molecular weight, and the molecular weight range of 
polydispersity, measured by the ratio of the weight-average molecular weight, (M w ), to the number-average molecular 
weight (M n ), i.e. 



15 




by choice of the proportion of polypeptide to polylactide; or by choice of the geometry of a solid formulation for implan- 
tation, or of the particle size in a formulation for injection. The release characteristics of such compositions are also 
20 controlled to some extent by the nature of the polypeptide itself. In particular, there is less freedom of choice in defining 
the parameters mentioned above when designing a composition of the invention for a polypeptide of high molecular 
weight, (say, greater than 6000), than there is when designing a composition for a polypeptide of lower molecular 
weight, (say, less than 6000). 

[0012] We have further discovered that the release of polypeptide from a composition comprising polylactide and 

25 polypeptide proceeds by two distinct and independent mechanisms, namely first a diffusion -dependent release of 
polypeptide out of the polylactide-polypeptide matrix comprising leaching from the surface, and, for low molecular 
weight polypeptides, some partition-dependent diffusion of polypeptide per se; and subsequently, as the polylactide 
becomes degraded, diffusion of aqueous polypeptide solution out of the composition through aqueous channels. 
[0013] In general, the compatibility of polypeptides in polylactide polymers is limited, except in the case of low mo- 

30 lecular weight (up to, say, 6000 molecular weight) polypeptides which are capable of having some specific interaction 
with the polylactide, for example a low molecular weight polypeptide which is basic, and which therefore interacts with 
the terminal carboxylic acid groups in the polylactide. Because of this limited compatibility of polypeptide in polylactide, 
a polypeptide/polylactide formulation, when placed in an aqueous environment, releases very little polypeptide by 
diffusion through the polymer matrix. While this is broadly true for all combinations of polypeptide and polylactide, 

35 matrix diffusion is at a minimum for high molecular weight polypeptides in high molecular weight polylactides. Even 
when some matrix diffusion resulting in polypeptide release occurs initially on placing the composition in an aqueous 
environment, by 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 inside-the composition to its surface. 
[0014] When a polypeptide/polylactide composition is placed in an aqueous environment, water diffuses into the 
matrix, and is partitioned between polypeptide and polylactide to form domains of aqueous polypeptide solution. This 
aqueous polypeptide, obtained when absorbed water is partitioned between polypeptide and polylactide, is incompat- 
ible with, and insoluble in, polylactides, particularly those of high molecular weight, so that absorption of water by the 
composition still further reduces initially any likelihood of matrix diffusion of polypeptide out of the composition. If the 
aqueous domains of polypeptide so formed are discrete and isolated, then thecompositions are incapable of releasing 

45 polypeptide. However, the possibility of the aqueous polypeptide domains having some continuity increases with in- 
creasing concentration of polypeptide in the composition, and with increasing absorption of water, and when the con- 
tinuity of aqueous polypeptide domains reaches a sufficient level to communicate with the exterior surface of the com- 
position, polypeptide starts to be released from the formulation by diffusion, not through the polylactide matrix, but 
through aqueous polypeptide channels. Even when some aqueous polypeptide domains near the surface have ex- 

50 tended so as to reach the exterior of the composition, that aqueous polypeptide which exists in still isolated domains 
is not released, and is only released when a secondary hydrophilic path for diffusion becomes available. For high 
molecular weight polylactides, this secondary hydrophilic diffusion path arises when the polylactide has undergone 
sufficient degradation for the rate of absorption of water to increase significantly. When this occurs, aqueous pores or 
channels are generated in the polylactide matrix, which allow a continuous and significant release of polypeptide, as 

55 aqueous solution, from previously discrete and isolated domains. 

[0015] As indicated above, we have discovered that, when sustained release compositions of the prior art, and par- 
ticularly those described in United Kingdom Patent Specification Number 1 ,325,209, are used for the release of 
polypeptides, the initial matrix diffusion phase of polypeptide release, and the secondary release of polypeptide con- 



3 



EP 0 058 481 B2 



sequent upon degradation of the polylactide, are separated in time with the result that the release of polypeptide is not 
continuous, but is biphasic and discontinuous, comprising a small first release of polypeptide, a dead phase during 
which essentially no polypeptide is released, and subsequent second release phase, during which substantially all of 
the remaining polypeptide is released. We have now discovered that, by appropriate choice of the parameters of the 
5 composition, the matrix diffusion phase of release, and subsequent degradation induced phase of release, can be 
made to overlap in time. 

[0016] The two phases of release can be made to overlap by either extending the initial diffusion phase, or making 
the degradation-induced phase commence earlier, or both. 

[0017] The initial matrix release phase is difficult to extend, but is sensitive to the concentration of the polypeptide 
10 in the matrix, and to a limited extent, to the nature of the polypeptide, especially its hydrophilicity. 

[0018] The degradation-induced release phase can be made to start sooner by appropriate choice of polylactide 
composition (more glycolide-rich polymer molecules, which degrade more quickly than lactide-rich molecules), M w 
(molecules of low molecular weight degrade more quickly to a level at which aqueous channels appear in the matrix), 
and polypeptide concentration (a higher polypeptide concentration allows more rapid absorption of water and conse- 
*5 quently more rapid generation of continuous aqueous channels which facilitate polypeptide release). 

[0019] However, as well as requiring the degradation induced release phase to start earlier, it is also necessary to 
control 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 purpose. One method of extending the duration of the degradation-induced release 
phase, is to use potylactides which contain lactide-rich molecules, which degrade more slowly than glycolide-rich mol- 
£0 ecutes, or alternatively, polylactides containing molecules of high molecular weight, which take longer to degrade to a 
level at which aqueous channels are formed, can be used. 

[0020] It is apparent, therefore, that since glycolide-rich polymer molecules, and/or molecules of low molecular 
weight, are preferred if the degradation phase is to start quickly, and lactide-rich molecules, and/or molecules of high 
molecular weight are preferred if the degradation-induced release phase is to last for a sufficient period of time, preferred 
25 polylactides are those with a high degree of heterogeneity, in respect of glycolide-rich and lactide-rich molecules, or 
of high polydispersity. 

[0021] Alternatively, the same characteristics can be obtained by blending two or more different polylactides, which 
differ in lactide/glycolide content, and/or in M w . In addition, the blending of a minor proportion of polylactide of high M w 
with a polylactide of low M w , confers desirable physical properties upon compositions according to this invention pro- 

30 duced therefrom, making them easier to fabricate and process. 

[0022] We have further discovered that the profile of polypeptide release from both prior art polylactides and novel 
polylactides is almost exactly parallelled by the profile of water absorption. That is to say, when polypeptide release is 
discontinuous, water absorption is also discontinuous in essentially the same manner, and conversely, when polypep- 
tide release is continuous, so is water absorption. Furthermore, variation of the parameters referred to above for con- 

35 trolling the polypeptide release characteristics of the composition have been found to affect water absorption by the 
composition in an exactly parallel manner. 

[0023] The effect of the various parameters, referred to above, on the polypeptide release and/or water absorption 
characteristics of compositions of the invention is illustrated by the following experiments, which do not necessarily 
illustrate compositions of the invention. 

40 

A. Molecular weight of the polylactide component 
A.1 . Low molecular weight polypeptide. 

45 A.1 .1. Formulations were manufactured comprising 20% w/w of the gastric peptide fragment tetragastrin 

hydrochloride, Trp-Met-Asp-Phe-NH 2 . HCI, molecular weight=633, in a polylactide comprising equimolar 
proportions of D,L-lactide and glycolide units, in the form of a film 0.2 mm thick. The films were placed 
individually in water at 37°C, which was changed daily, and the ultraviolet absorption at 277 nm was 
measured to assay the tetragastrin released by the formulation that day. 

50 With a prior art type of polylactide of M w approximately 240,000 (intrinsic vrscosity=1 .36), there was 

an initial release of tetragastrin, then a "dead period" from about day 5 to day 21 during which little was 
released, followed by the main release from day 24 onward. 

With a polylactide of M w approximately 15.000 (intrinsic viscosity=0;25), the release pattern was sim- 
ilar, but the dead period lasted only from day 4 or 5 to day 8 or 9. 

55 With a polylactide of low M w (inherent viscosity of a 1 g/100 ml solution in chloroform=0.11), there 

was no dead period, and tetragastrin was released continuously from time zero (T c ). 

A.1. 2. Similar formulations were manufactured using 10% by weight of the synthetic luliberin analogue 



4 



EP 0 058 481 B2 



ICI. 11 8,630, 



CI 



Iu-His-Trp-Ser-Tyr>D*Ser(0-tBu)-Leu*Arg-Pro-Azgly-NHt. 



10 



molecular weight^ 1269, in place of tetragastrin. 

With a prior art polylactide of M w ~240,000 (intrinsic viscosity=1 .36), the release of the polypeptide 
was biphasic, with a dead period of about 15 days. 

With a polylactide of M w ~- 1 5,000 (intrinsic viscosity=0.25), there was a short induction period, followed 
by continuous release. 

With a polylactide of low M w (inherent viscosity of a 1 g/100 ml solution in chloroform=0.11), there 
was continuous release from T n . 



15 



20 



A.2. Medium molecular weight polypeptide. 

Formulations were manufactured comprising 0.1% by weight of mouse epidermal growth factor (EOF), 
molecular weight=6041 , in polylactides comprising equimolar proportions of D,L-lactic acid and glycolic acid 
units, and of different M w , and placed in pH 7,4 buffer. Release of EGF was monitored by radio-immunoassay. 

With a prior art polylactide of M w -200,000 (intrinsic viscosity=1 .08), there was no initial release, and no 
significant release of polypeptide until between 13 and 20 days after T 0 , after which release was continuous. 

With a polylactide of M w ~- 80,000 (intrinsic viscosity=0.58), there was also no initial release, and significant 
release did not occur until between 6 and 10 days after T 0! after which release was continuous. - 

With a polylactide of low M w (inherent viscosity of a 1 g/100 ml solution in chloroform=0.11), there was 
continuous release from T n . 



25 



30 



35 



40 



A.3. High molecular weight polypeptide 

A formulation was manufactured comprising 20% w/w of bovine prolactin, molecular weight -22,000, in 
a polylactide comprising equimolar proportions of D,L-lactic acid and glycolic acid units, and of low M w (inherent 
viscosity of a 1 g/100 ml solution in chloroform=0.11). As expected from previous experiments A.1.1., A. 1.2. 
and A.2.. this formulation also released polypeptide continuously from T 0 when tested in vivo in rats, and 
circulating bovine prolactin assayed by radio-immunoassay. 

Experiments A.1 . to A.3. thus demonstrate that reducing the molecular weight, M w . or viscosity of the 
polylactide used in the manufacture of a composition reduces the biphasicity of polypeptide release, for 
polypeptides of low or medium molecular weight, or the initial delay in release of polypeptides of medium or 
high molecular weight, and achieves a continuous release of the polypeptide from T Q . 

B. Ratio of lactide/glycolide in the polylactide 

Compositions were manufactured in the form of implants containing 1 00 ng (3% w/w) of the luliberin analogue 
ICI. 118,630 in polylactides of M w -300,000 but of different lactide/glycolide ratios. All of these formulations when 
tested in wo in adult female rats exhibiting normal oestrous behaviour, gave biphasic release of the polypeptide, 
comprising release for about 6 days post-treatment, followed by a dead period, during which there was no significant 
polypeptide release. The length of this dead period decreased with decreasing lactide/glycolide ratio (L/G), as 
follows: — 



4$ 



50 



UG 


Dead period (days) 


100/0 


no release 


75/25 


51 


67/33 


34 


50/50 


15 



This experiment thus indicates that a composition exhibiting a biphasic release of polypeptide can be improved 
in the direction of achieving continuous release by Increasing the proportion of glycoiideto lactide in the polylactide 
used, up to about 50% glycolide. 



55 C. Ratio of polypeptide to polylactide 

Compositions in the form of Implants were manufactured using different concentrations of the synthetic luliberin 
analogue, ICI.1 18,630, in a prior art 50/50 lactide/glycolide polylactide of M w ~200,000, and tested in vivo in rats 



5 



EP 0 058 481 B2 

as described above. At 5% and 10% w/w incorporation, the release of polypeptide was biphasic, but at 15% and 
20% incorporation, the biphasicity disappeared. 

This experiment thus demonstrates that a polylactide of high molecular weight, which gives biphasic release 
of polypeptide when the polypeptide is incorporated only at low levels, can be used to make satisfactory continuous 
5 release formulations if the proportion of polypeptide is increased sufficiently. 

D. Molecular weight distribution 

A solution of a polymer blend of wide molecular weight distribution (polydispersity) was obtained by mixing 
solutions of a 50/50 D,L-lactide/glycolide polylactide of low M W! (reduced specific viscosity of a 1 g/1 00 ml solution 

10 chloroform=0.115), (3 parts by weight) and a 50/50 D,L-lactide/glycolide polylactide of M w =200,000, (intrinsic vis- 

cosity^. 08), (1 part by weight). Tetragastrin (1 part by weight) was added, and the mixture was cast to give a 
polylactide/ietragastrin composition containing 20% by weight of tetragastrin, and this was then moulded to give 
a slab 0.02 cm thick. The slab was placed in water at 37°C and the release of tetragastrin was found to be continuous 
from T 0 , and to continue for at least 44 days. 

15 Potyiactides of wide molecular weight distribution may be obtained either by mixing preformed polymers of 

different molecular weights, or by appropriate control of the polymerisation process in generally known manner, 
and such polylactides confer important advantages, for example the lower molecular weight polylactide species 
allow an essentially immediate release of some polypeptide, while the higher molecular weight polylactide species 
both extend the release period and slow down the overall rate of release of the polypeptide. In addition, the blending 

20 of low and high M w fractions modifies the water absorption characteristics of the polylactide in a parallel manner. 

E. Thickness of the implant 

E.1 , A solution of 1 0% by weight of tetragastrin in a polylactide comprising equimolar proportions of D,L-lactic 
25 acid and glycolic acid units, and of M w - 1 5000 was cast into films 0.02, 0.06 and 0.12 cm thick. All three films 

showed continuous release of tetragastrin from T Q1 and at 28 days, the three films had released respectively 
85, 75 and 66% of their tetragastrin content. 

E.2. The uptake of tritiated water from pH 7.4 buffer by slabs of polylactide comprising equimolar proportions 
30 of D.L-lactic acid and glycolic acid units of M w -~200,000 ; and intrinsic viscostty=1 .08 and of thickness 0.02, 

0.06, 0.12 and 0.20 cm was measured by removing such slabs from the buffer solution successively after 
varying times of immersion, and measuring the tritium content by scintillation counting. After 5 weeks, the 
different thickness slabs had absorbed respectively 44, 20, 15 and 11% by weight of water. 

These experiments show how the thickness of the implant can be used to control the absorption of water 
35 by, and thus the rate of release of polypeptide from, a composition of the invention, thicker implants releasing 

the polypeptide more slowly than thinner ones. 

[0024] As indicated above the composition of the invention is a solid composition for sub-dermal injection or implan- 
tation or as a liquid formulation for intramuscular or subcutaneous injection. 
40 [0025] Suitable solid compositions for sub-dermal injection or implantation are, for example, rods, spheres, films or 
pellets, and cylindrical rods which can be injected through a hypodermic needle or trochar are preferred. Such com- 
positions are manufactured by conventional techniques which are well known in the pharmaceutical art. 
[0026] Preferred solid compositions of the invention are as shown in Table 1 . Each entry in Table 1 thus defines a 
further feature of this invention. 

45 



TABLE 1 



50 



No. 


Polypeptide 


Polylactide inherent viscosity* 


Glycolide 
Lactide 


% Polypeptide 


1 
2 


ICI.1 18630 
ICI.1 18630 


0.2—0.5 
<0.2 


0.2—3 
0—3 


5—50 
0.1—50 



* dl/g (1 g per 100 mt in chloroform or dtoxan). 



[0027] From the foregoing, it is clear that it is desirable to manufacture polylactides of a range of M w , particularly of 
low to medium M w in the range up to 60,000, and of high polydispersity 

55 



6 



EP 0 058 481 B2 



"n" 

5 these being particularly valuable in the compositions of this invention. The prior art relating to polylactides in general, 
and to copolymers containing lactic acid and gly colic acid units in particular, is largely silent as to the manufacture of 
such copolymers of low molecular weight, and as to methods of achieving high polydispersity in such copolymers. 
Indeed, it is inherent in the prior art disclosure of polylactides that they are generally of M w greater than about 
30,000—60,000 (an inherent viscosity of greater than 0.5) and of low polydispersity, due to their manufacture under 

10 anhydrous conditions and without any added chainstoppers. 

[0028] Certain polylactides within this range have, however, been disclosed. For example, United States Patent 
Number 4,011,312 discloses copolymers having molecular weights in the range 1200—1800, and Polymer, 20, 
1459— 1 464 (1 979), United States Patent Number 3,773,91 9, United Kingdom Patent Number 1 ,351 ,409 and Chemical 
Abstrats., 91, 9442 g (1979) discloses polymers having a molecular weight upward of about 35,000, corresponding to 

*5 an inherent viscosity of greater than about 0.5. 

[0029] We have realised that, because of the different reactivities under polymerisation conditions of the cyclic dimers 
of lactic acid and glycolic acid, copolymers of high heterogeneity in respect of polymer species may be obtained by 
ring opening polymerisation of a mixture of the two cyclic dimers in the presence of chain-stopping agents, to give 
polylactides having an inherent viscosity of less than 0.5. The cyclic dimer of glycolic acid is the more reactive under 

20 polymerisation conditions, and thus the first copolymer molecules formed in the polymerisation are glycolic acid-rich. 
Consequentially, the later copolymer molecules formed are necessarily lactic acid-rich, thus producing acopolymer of 
lactic acid and glycolic acid of the desired high heterogeneity. 

[0030] In addition, we control the polymerisation to produce copolymers in the desired low M w range by carrying out 
the ring opening copolymerisation of the mixed cyclic dimers in the presence of water, of lactic acid containing water, 
25 or of some other known chain growth regulator, in accordance with the general knowledge in the polymer art. 

[0031] Suitable polymerisation catalysts are zinc oxide, zinc carbonate, basic zinc carbonate, diethylzinc, organotin 
compounds, for example stannous octanoate, tributylaluminium, titanium, magnesium or barium compounds, or lith- 
arge, and of these stannous octanoate is preferred. 

[0032] The copolymerisation of the mixed cyclic dimers is otherwise carried out in conventional manner, known in 

30 the polymer art, as regards time and temperature. 

[0033] According to a preferred feature of the invention the polylactide is a heterogeneous polymer containing from 
25 to 1 00% molar of lactic acid units and from 0 to 75% molar of glycolic acid units, and which has an inherent viscosity 
(1 g/100 ml solution in chloroform or dioxan) equal to or greater than 0.09 and has an intrinsic viscosity -equal to or 
less than 0.33. By a "heterogeneous polymer we mean polymers with a high degree of heterogeneity, in respect of 

35 glycolide-rich and lactide-rich molecules, or of high polydispersity, or blends of two or more different polylactides which 
differ in lactide/glycolide content and/or M w , as hereinbefore described. 

[0034] Whether or not a particular copolymer is heterogeneous or not, in this sense, may be readily determined from 
inspection of the 25 MHz 13 C nuclear magnetic resonance spectrum of the copolymer in, for example, deuterated 
dimethyl sulphoxide. In a homogeneous copolymer such as is obtained in the prior art copolymerisation of lactic acid 
<o and glycolic acid monomers, the resonance of the glycolic acid unit carbonyl carbon, atS=T66.0 — 166.2 approximately, 
appears as two doublets, as a consequence of the four different, approximately equally probable molecular environ- 
ments in which this carbon atom can exist, namely G q G, L qG, G q L and L q L (G=a glycolic acid unit, L=a lactic acid 
unit and the asterisk indicates the glycolic acid unit under consideration), In a heterogeneouscopolymer, on the other 
hand, such as is used in the present invention, the sequence LGL is unlikely to occur, so that one of the doublet signals 

6 in the spectrum of the homogeneous copolymer appears as a singlet. In fact, we find that in the spectrum of hetero- 
geneous copolymers, this glycolic acid unit carbonyl carbon signal often appears as two singlets. Thus, a "heteroge- 
neous copolymer" as herein defined is a copolymer for which the glycolic acid carbonyl carbon signal in the 13 C n.m. 
r. appears as other than a pair of doublets. 

[0035] The heterogeneity or homogeneity of lactic acid/glycolic acid copolymers can also be demonstrated by an 
so examination of their degradation. Thus, when a copolymer is placed in pH 7.4 buffer at 37°C, removed periodically, 
dried and sampled, and the ratio of lactic acid to glycolic acid units in the samples is determined by n.m. r., for a het- 
erogeneous copolymer, the ratio L/G increases with time, as the glycolic acid sequences hydro lyse preferentially. For 
a homogeneous copolymer, on the other hand, the ratio of L/G remains essentially constant as degradation progresses . 
[0036] The lactic acid content of the copolymer is preferably in the racemic (D.L) form, or in the optically active L form. 
55 [0037] According to the invention the polylactide is made by a process, which comprises the ring openingcopolym- 
erisation of the cyclic dimer of lactic acid and in the presence of the cyclic dimer of glycolic acid, at elevated temperature 
in the presence of one of the above-mentioned polymerisation catalyst and in the presence of a chain stopping agent. 
[0038] A suitable chain stopping agent is, for example, water, lactic acid, glycolic acid or other hydroxy acids, alcohols 



7 



EP 0 058 481 B2 



or carboxylic acids generally. 

[0039] The invention is illustrated but not limited by the following Preparations and Examples: — 
Preparation 1 

5 

[0040] Zinc oxide (16 g) was added to D.L-lactic acid (800 g) in a 2 13-necked round bottom flask-equipped with a 
stirrer, a thermometer and a distillation head connected to a water condenser. The mixture was stirred and heated to 
about 135 C C, at which temperature water started to distil over. Heating was continued for 8 h, during which time the 
temperature rose to about 190°C. When distillation of water ceased, the pressure was reduced, and distillation was 
10 continued until solid began to collect in the condenser. At this stage the water condenser was replaced by an air 
condenser and the residue was cooled and then distilled under high vacuum [2.66 — 1 0.64 mbar (2 — 8 mm of mercu- 
ry)], the fraction (about 300 g) distilling between 130 and 160°C being collected, this being D.L-lactide (3,6 - dimethyl 
-1 ,4 - dioxan - 2,5 - dione), the cyclic dimer of D.L-lactic acid. 

[0041] The crude D,L-lactide was crystallised from ethyl acetate (approximatey 600 ml) three times, and the recrys- 
15 tallised product was finally dried at 45°C under reduced pressure [2.66 mbar (2 mm of mercury)] for 24 — 48 hours, 
after which it had m.p. 124 — 125°C. 

Preparation 2 

20 [0042] Glycolide (1 : 4-dioxan-2,5-dione), the cyclic dimer of glycolic acid, was prepared by the method described in 
Preparative Methods in Polymer Chemistry by W. R. Sorenson and T. W. Campbell, second edition, published by 
Interscience (1968), page 363. The crude glycoiide was purified by three successive crystallisations from dry ethyl 
acetate, then dried at 45°C under reduced pressure [2.66 — 10.64 mbar (2 — 8 mm of mercury)1 for 24 — 48 h, m.p. 
82— 84°C. 

25 

Examples 1 to 13 

[0043] Polymers of D,L-lactide and glycolide were prepared as follows: — 

[0044] Pure dry D,L-lactide (Preparation 1), pure dry glycolide (Preparation 2) totalling 42 g, commercial D.L-lactic 
30 acid containing about 12% by weight of water, and 1 ml of an 8% by weight solution of stannous octanoate in hexane, 
were placed in a pre-dried glass tube. The hexane was evaporated under reduced pressure, and the tube was heated 
at 160°C for 6 hours with constant agitation if possible. The tube was cooled in powdered solid carbon dioxide, and 
the polylactide was removed, broken into small pieces and dissolved in chloroform (400ml). The chloroform solution 
was filtered, and the filtrate was poured into methanol (2 I) to precipitate the polylactide, which was filtered off and 
35 dried under vacuum at 40°C for 24 hours, then at 80 C C for 24 hours. All the polylactides so produced were soluble in 
chloroform and dioxan, and polylactides 1 to 9 in the following Table were soluble in benzene, but polylactides 10 to 
13 were insoluble in benzene. 

[0045] The following particular polylactides were prepared by this method: — 



40 



45 



Ex. 


D.LIactide (L) 


Glycolide (G) 


L/G Molar 


D,L-lactic acid 


Intrinsic 


M w (approx.) 




(g) 


(g) 


proportion 




viscosity <dl/g) 




r* 


42.0 


0 


100/0 


0 


1.385 


440,000 


2** 


33.5 


9.0 


75/25 


0 


1.084 


400,000 


3 


32.4 


8.7 


75/25 


920 pi 


O.108* 


low 


4" 


30.0 


12.1 


67/33 


0 


0.97 


370,000 


5** 


30.0 


12.1 


67/33 


0 


0.94 


214,000 


6** 


30.0 


12.1 


67/33 


30 \i\ 


0.67 


107,000 


7** 


30.0 


12.1 


67/33 


60 uj 


0.51 


63,000 


8 


30.0 


12.1 


67/33 


120 u I 


0.37 


33,000 


9 


30.0 


12.1 


67/33 


920 ul 


0.121* 


low 


10** 


23.0 


18.5 


50/50 


0 


1,045 


300,000 


11 


23.0 


18.5 


50/50 


400 ul 


0,25 


15,200 



55 M w are relative to polystyrene standard 

4 are reduced specific viscosities of a 1 c/100 ml solution in chloform. 
** are outside the scope of the invention 



8 



EP 0 058 481 B2 



(continued) 



Ex. 


D,L lactide (L) 


Glycolide (G) 


L/G Molar 


D.L-lactic acid 


Intrinsic 


M w (approx.) 




(g) 


(9) 


proportion 




viscosity (dl/g) 




12 


23.0 


18.5 


50/50 


920 til 


0.126* 


low 


13 


23.0 


18.5 


50/50 


1380 u.l 


0.108* 


low 



M w are relative to polystyrene standard 

* are reduced specific viscosities of a 1 g/100 ml solution in chlofomn. 



10 

[0046] Alternatively, the lactide, glycolide and lactic acid if present, may be heated at 1 60°C and 0.08 g of stannous 
octanoate then added to initiate the polymerisation. 

Example 14 (outside scope of invention) 

15 

[0047] A polylactide comprising equimolar proportions of glycolic acid and D,L-lactic acid units, and having an intrinsic 
viscosity of 1 .36 (50 mg) was dissolved in dioxan (1 ml), and 50 uJ of a solution of ICI.11 8630, 

20 ^lu-His-Trp-Ser-Tyr-D-Ser(0-tBu)-Leu-Arg-Pro-Azgly-NH a 

(233 mg per ml of the acetate salt, equivalent to 200 mg per ml of base) in distilled water was added. The resultant 
ha2y 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 C under reduced pressure [0.027 mbar (0.02 mm of mercury)] for 48 hours. The mixture, containing -17% 
25 by weight of ICI. 118630 in the polylactide was homogenized by three successive compression mouldings at 110°Cfor 
10 seconds, and was finally compression moulded into implants 0.038 cm thick, each weighing 1 .5 mg and containing 
309±7 ^g (-17% by weight) of ICI. 118630. 

[0048] The continuous release of ICI. 118630 from such implants was demonstrated by placing them in female rats 
exhibiting normal oestrous behaviour. After implantation, the rats went into a period of dioestrus, detected by the lack 
30 of cornified vaginal smears, lasting from 31 to 40 days : thus indicating that ICI. 11 8630 was being continuously released 
during that period. 

[0049] The process described above was repeated, using 50 uJ of ICI.11 8630 acetate solution (150 mg of pure 
peptide per ml of water) and implants were made similarly, weighing 2 mg, containing 306±6 ug of ICI. 118630 (13% 
by weight), and 0.038 cm in thickness. In the rat oestrus test described above, these implants released ICI. 118630 
35 continuously over a period of 30 to 38 days, as evidenced by the period of dioestrus in the rats. 

[0050] For use in human therapy, implants containing 1 to 100 mg of ICI 118630 (5 — 50% by weight), weighing 2 
mg — 1 g, and in the form of cylindrical rods suitable for implantation by trochan were manufactured by the process 
described above. 

40 Example 15 

[0051] The process described in Example 14 was repeated, but using polylactides comprising equimolar proportions 
of D,L- lactic acid and glycolic acid units, and having intrinsic viscosities of 0.33 and 0,25, instead of 1 .36, to prepare 
implants containing 10% by weight of ICI. 118630, weighing about 3 mg, and 0.08 cm thick. 

45 [0052] These implants were placed in female rats (5 per group) which, prior to implantation , exhibited regular oestrous 
behaviour. The implants prepared from polylactide of intrinsic viscosity 0.33 exhibited an induction period of 5 days 
followed by a dioestrus period of about 26 days; and the implants prepared from polylactide of intrinsic viscosity 0.25 
exhibited an induction period of 3—4 days, followed by a dioestrus period of about-25 days. 
[0053] Similar implants, but containing 20% by weight of ICI. 118630 were prepared in the same way, and these 

50 exhibited a similar dioestrus period, but no induction period, in the rat test described above. 

[0054] For use in human therapy, implants containing 1 to 100 mg of ICI. 118630 (5 — 50%-by weight), weighing 2 
mg — 1 g, and in the form of cylindrical rods suitable for implantation by trochar were manufactured similarly. 

Example 16 (outside scope of invention) 

55 

[0055] The process described in Example 14 was repeated, using a polylactide comprising equimolar proportions 
of D,L-lactic acid and glycolic acid units, and having intrinsic viscosity of 1.36, to prepare mixtures of ICI.11 8630 and 



9 



EP 0 058 481 B2 



polylactide containing 3% and 1% by weight of ICi. 118630. The mixture was micronised at room temperature in an 
ultracentrifuge mill fitted with a 125 nm (120-mesh) screen, and the micronised particles were suspended in propylene 
glycol for injection at a concentration of 100 mg per ml. 

[0056] Female rats showing regular oestro us behaviour were injected subcutaneously with 0.1 ml of the 3% by weight 
propylene glycol suspension described above, or with 0.3 ml of the 1% suspension. Both groups were monitored, by 
examining vaginal smears daily for comification, and exhibited occasional comified smears up to 20 to 24 days after 
dosing, followed by a clear dioestrus period up to days 38 to 42 after dosing, thus demonstrating continuous release 
of ICI. 118630 over that period. 

Example 17 (outside scope of invention) 

[0057] Tetragastrin hydrochloride, (Trp-Met-Asp-Phe-NH 2 * HCI), (200 mg) was dissolved in a mixture of dioxan (9 
ml) and water {1 mi), and to the solution was added a polylactide as described in Example 11 (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 [0.027 mbar (0.02 mm of mercury)] at40°Cfor48 hours, then homogenised by three successive compression 
mouldings at 80°C for 1 0 seconds, and moulded to give films of thickness 0.02, 0.06 or 0.1 2 cm, each weighing about 
80 mg. 

[0058] The release of tetragastrin was measured by placing a film in distilled water, removing a sample of the distilled 
water daily, replacing all the remaining distilled water by fresh, and measuring the ultraviolet absorption of the daily 
samples at 277 nm. The following results were obtained, which demonstrated continuous release of tetragastrin from 
films of all three thicknesses: — 



Time (days) 


Cumulative % tetragastrin released 


0.02 cm film 


0.06 cm film 


0.12 cm film 


1 


9.6 


5.6 


4.0 


4 


14.9 


10.5 


9.0 


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 


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 


39 


89.2 


85.1 


82.6 



Example 1 8 (outside scope of invention) 

[0059] Tetragastrin hydrochloride (40 mg) was dissolved in aqueous dioxan (1 :9 by volume), and added to a solution 
of: 

(a) a polylactide comprising equimolar proportions of D,L-lactic acid and glycolic acid units, and having a reduced 
specific viscosity of 0.115 (as a 1 g/100 ml solution in chloroform), (120 mg), and 

(b) a polylactide comprising equimolar proportions of D,L-lactic acid and glycolic acid residues, and having an 
intrinsic viscosity of 1 .08 (40 mg), in dioxan (2 ml). The mixed solutions were cast as a film, as described in Example 
14, and moulded as implants weighing about 50 mg, and 0.02 cm thick. 

[0060] The release of tetragastrin from these implants was measured by the procedure described in Example 17, 
and the following results showing continuous release were obtained: — 



Time (days) 


Cumulative % tetragastrin released 


1 


0.6 



10 



EP 0 058 481 B2 



(continued) 



Time (days) 


Cumulative % tetragastrin released 


2 


1.0 


3 


1.6 


4 


2.7 


7 


8.6 


10 


17.2 


14 


29.4 


18 


43.1 


23 


56.3 


28 


64.9 


32 


71 .2 ■ ■ - 


36 


79.0 


39 


83.9 


44 


90.5 



20 Example 1 9 (outside scope of invention) 

[0061] A polytactide comprising equimolar proportions of D,L-lactic acid and glycolic acid units, and having an inher- 
ent viscosity of 0.11 as a 1 g/100 ml solution in chloroform, (50 mg), was dissolved in dioxan (1 nil) and a solution of 
mouse epidermal growth factor (EGF, 0.05 mg) in water 0.05 ml) was added. The mixture was cast as a film on poly- 
25 . tetraf luoroethylene cloth, and the solvent was removed in a stream of nitrogen in the dark. The film was dried at €0°C, 
under reduced pressure [0.11 mbar (0.8 mm of mercury)] for 48 hours. The film was then compression moulded at 
120°C for 10 seconds to give implants 0.02 cm thick, weighing 10 mg. 

[0062] The implants were each placed in a black vial at 37°C with 1 ml of Mcllvatn's buffer (pH 7.4), (Documenta 
Geigy, Scientific Tables, edited by K, Diem and C. Leutner, published by J. R. Geigy SA, Basle, Switzerland, 7th Edition, 
30 1 970, page 280), containing 0.02% by weight of sodium azide. The buffer was removed daily, and replaced with fresh, 
and the EGF released into the buffer by the implant was measured by radio-immuno assay, which demonstrated that 
release started immediately, and continued for at least 2 weeks releasing 100 — 200 ng per day. 



Example 20 (outside scope of invention) 

35 

[0063] A polylactide comprising equimolar proportions of D,L-lactide and glycolide and having a reduced specific 
viscosity (1 g/1 00 ml solution in chloroform) of 0.1 1 , (400 mg), was dissolved in dioxan (2 ml), and a solution/suspension 
of bovine prolactin (100 mg) in distilled water (0.5 ml) was added, with vigorous agitation. The mixture was poured 
onto a polytetrafluoroethylene cloth, and dried, first in a stream of nitrogen and then under reduced pressure [0.013 
40 mbar (0.01 mm of mercury)] at 40°C for 24 hours. The heterogeneous mixture thus obtained was homogenised by four 
successive compression mouldings at 60°C, and then moulded into a slab 0.2 cm thick, from which implants weighing 
60 mg were excised. 

[0064] The implants were placed subcutaneously into adult female rats, which were then periodically bled from the 
tail, and the prolactin in the blood samples thus obtained was measured by radio-immune assay. A placebo group, 
45 receiving no prolactin in the implant, was similarly assayed, and the levels of circulating prolactin compared. The fol- 
lowing results were obtained: — 



Time 


Plasma level of bovine prolactin (uxj/ml) 


Placebo group 


Treatment group 


1 


0.38 


24.7 


2 


0.45 


105.9 


6 


0.54 


7.7 


9 


0.72 


17.8 


13 


0.52 


65.4 


16 


0.56 


89.7 


20 


0.75 


288 



11 



EP 0 058 481 B2 



(continued) 



Time 


Piasma level of bovine prolactin (u,g/ml) 




Placebo group 


Treatment group 


23 


0.81 


142 


26 


0.84 


562 


42 


1.25 


1250 



Example 21 (certain examples outside scope of invention as specifed in Examples 1 to 13) 

[0065] The process described in Examples 1 — 13 was repeated, except that the polylactide was dissolved in dioxan 
instead of in chloroform, and similar potylactides were obtained. 

Examples 22 — 29 

[0066] The process described in Examples 1 — 13 was repeated, except that the polylactide was dissolved in glacial 
acetic acid, and the glacial acetic acid solution thus obtained was added dropwise to methanol in order to precipitate 
the polylactide, which was filtered off and dried under vacuum at 40°C for 24 hours, then at 80°C for 24 hours. 
[0067] The following particular polylactides were prepared by this method: — 



12 



EP 0 058 481 B2 




45 

Example 30 

[0068] A polylactide comprising equimolar proportions of glycolic acid andO.L-lactic acid units and having an intrinsic 
viscosity of 0.25 was dissolved in glacial acetic acid, and the solution was freeze-dried. The freeze dried powder {540.7 
so mg) and ICI 118630 (142.1 mg) of the acetate salt (equivalent to >124 mg of base) were dissolved in 6.8 ml of acetic 
anhydride-free glacial acetic acid and freeze dried for 24 h. 

[0069] (The glacial acetic acid was ref luxed for 2 h with 1 % water to remove the acetic anhydride): The freeze dried 
product was extruded under pressure at 70°C to a 1 mm diameter rod, from which implants of the required weight were 
cut. The implants were dissolved in an appropriate solvent, for example acetonitrile, and assayed for drug content and 
55 purity. Implants were shown to contain 16.1% w/w pure 11 8630 base. 

[0070] Release of 1 1 8630 was evaluated by immersing implants weighing approximately 1 0 mg in Mcllvains pH 7.4 
buffer at 37°C. IC1 118630 was released continuously for at least 5 weeks. 

[0071] In a further experiment, implants weighing approximately 390 |ig,.860 1500 ng, 3000 u,g and -6000 u,g 



13 



EP 0 058 481 B2 



were implanted subcutaneously in groups of adult, regularly cycling female rats. In the 28 days following implantation, 
animals were essentially free of oestrus intervals showing that active drug was released continuously over this period. 

Example 31 

5 

[0072] A solution of ICI 118630 acetate salt was prepared by dissolving 170.8 mg of IC1 118630 acetate in 5 ml of 
acetic anhydride-free glacial acetic acid. (The glacial acetic acid was fluxed for 2 h with 1% water to remove acetic 
anhydride). This solution was shown by high pressure liquid chromatography (HPLC), to contain 25.21 mg of IC1 11 8630 
base per ml, 442.5 mg of polylactide (prepared as in Example 25 was dissolved in 4.5 ml of the acetic acid solution, 
10 and the resulting solution was freeze dried for 25 h. The freeze dried product was extruded under pressure at 74°C to 
a 1 mm diameter rod, from which implants of the required weight were cut The implants were dissolved in an appropriate 
solvent, such as acetonitrile, and the resulting solution was analysed by HPLC. The implants were shown to contain 
20% w/w pure 1 1 8630 base. 

'5 Example 32 (outside scope of invention) 

[0073] A polylactide comprising equimolar proportions of D,L- lactic acid and glycolic acid units and having a reduced 
specific viscosity, of 0.126 (1 g/100 ml solution in chloroform), (240 mg), was dissolved in glacial acetic acid (5 ml) and 
a solution of tetragastrin hydrochloride (60 mg) dissolved in glacial acetic acid (5 ml) was added with vigorous agitation. 
20 The solution was freeze dried for 24 h and the resultant solid was compression moulded at 50°C for 20 seconds to 
give implants 0,2 cm thick and weighing 35 — 40 mgs. 
[0074] The above procedure was repeated with the following polymers: — 

(a) a polylactide comprising 67 mole % of D : L- lactic acid and 33 mole% glycolic acid units and having a reduced 
25 specific viscosity of 0.121 (1 g/100 ml solution in chloroform). 

(b) a polylactide comprising 75 mole % of D,L-lactic acid and 25 mole % glycolic acid units and having a reduced 
specific viscosity of 0.108 (1 g/100 ml solution in chloroform). 

(c) a polylactide comprising 100% of D,L-lactic acid and having a reduced specific viscosity of 0.100 (1 g/100 ml 
solution of chloroform). 

30 

[0075] The release of tetragastrin from these implants was measured by the procedure described in Example 17, 
and the following results were obtained: — 



35 



45 



50 



55 



Time (days) 


Cumulative % tetragastrin released 




50%D,L-lactide 


67% D,L-lactide 


75% D.L-lactide 


100%D,L-lactide 




50% glycolide 


33% glycolide 


25% glycolide 




1 


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 


11 


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 


^5.5 


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 


91.0 


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 



14 



EP 0 058 481 B2 



(continued) 



Time (days) 


Cumulative % tetragastrin released 




50% D.L-lactide 


67% D.L-lactide 


75% D.L-iactide 


100%D,L-lactide 




50% glycolide 


33% glycolide 


25% glycolide 




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 



[0076] These results show that continuous release of tetragastrin is obtained using low molecular weight polylactides 
and that duration of release is determined by the composition of the hydrolytically unstable polyester. 

Example 33 (outside scope of invention) 

[0077] A polylactide comprising equimolar proportions of D ,L-lactic acid and glycolic acid units and having an inherent 
viscosity of 0.126 (as a 1 g/100 ml solution in chloroform) (9.5 mg), was dissolved in distilled dioxan (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 cloth, 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 3 mbar (0.01 mm of mercury)] for 48 hrs. The film was then compression 
moulded at 70°C for 1 0 seconds to an implant 0.02 cm thick, weighing about 9 mg. A placebo implant was also prepared. 
[0078] The samples were implanted subcutaneously into carotid cannula ted guinea pigs, blood samples taken pe- 
riodically and the plasma EGF levels were measured by radio-immuno assay. 
[0079] Raised plasma EGF levels were observed from Day 3 and continued for at least 1 week. 
[0080] Similar implants were prepared as described above, but using a polylactide comprising equimolar proportions 
of D,L-lactic acid and glycolic acid units and having an intrinsic viscosity of 1 .06. Compression moulding of this implant 
was done at 120°C. 

[0081] Implantation and plasma assays were done as described above, but raised plasma EGF levels were not 
observed until day 17 after implantation. 

Example 34 (outside scope of invention) 

[0082] A polylactide comprising equimolar proportions of D.L-lactic acid and glycolic acid units and having an inherent 
viscosity of 0.093 as a 1 g/100 ml solution in chloroform (40 mg) was dissolved in anhydrous-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 h. The resulting powder was then 
compression moulded at 50°C to give an implant 2 mmx2 mmx 10 mm weighing 36.1 mg. 

[0083] The sample was implanted subcutaneously into a cannulated cat, blood samples were taken periodically and 
the plasma EGF levels were measured by radio-immuno assay. 

[0084] Raised plasma EGF levels were observed from day 3 and continued for at least 40 days. 
Example 35 (outside scope of invention) 

[0085] Implants containing bovine prolactin were prepared as described in Example 20, but using: — 

(a) a polylactide (400 mg) comprising equimolar proportions of D.L-lactic acid and glycolic acid units and having 
a reduced specific viscosity (1 g/100 ml solution in chloroform) of 0.11, dissolved in 4 ml dioxan; and 

(b) a polylactide (400 mg) comprising equimolar proportions of D.L-lactic acid and glycolic acid units and having 
an intrinsic viscosity of 1 .06 dissolved in 4 ml dioxan. This sample was moulded at 11 0°C. 

[0086] Formulations (a) and (b) were each tested in vivo as described in Example 20. Formulation (a) released 
significant levels of plasma bovine prolactin from at least as early as day 4 and continued to release for at least 85 
days, while formulation (b) released significant levels from at least as early as day 8 for at least 85 days. 



15 



EP 0 058 481 B2 

Claims 

1 . A solid pharmaceutical composition for subdermal implantation comprising a polylactide, which is a copolymer of 
lactic and gtycolic acids made by a ring opening, polymerisation of a mixture of cyclic dimer of lactic acid and cyclic 

5 dimer of glycolic acid in the presence of chain stopping agent or a mixture of such copolymers, and an acid stable 

polypeptide which is not significantly hydrolysed under the conditions encountered within the composition during 
the period of use envisaged, which composition, when placed in an aqueous physiological-type environment, ex- 
hibits a release profile which has two successive phases of release of the polypeptide as an aqueous solution, the 
first phase being released by matrix diffusion and the second phase being released consequent upon degradation 

10 of the polylactide until essentially all of the polypeptide has been released, characterised in that the diffusion 

phase and the degradation phase of the release profile overlap in time, and the release of the polypeptide occurs 
over a period of at least one week, the composition being adapted to achieve the release profile by varying the 
polylactide composition, particularly the proportion of lactic acid to glycolic acid, by choosing the weight average 
molecular weight of the polylactide and its polydispersity, by choosing the proportion of the polypeptide to polylac- 

* 5 tide or by choosing the geometry of the solid formulation for implantation to provide the release profile when taking 

account of the molecular weight of the polypeptide and interaction of basic polypeptides with the terminal carbox- 
ylic-acid groups of the polylactide and wherein either (a) the composition comprises from 5 to 50% by weight of 
ICI 118,630 

20 _ 

(Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (O-tBu) - Lreu ~ Arg- Pro- A2gly- NH 2 ) 

and from 50 to 95% by weight of polylactide wherein the ratio of glycol ide to lactide units is from 0.2 to 3, 
and which has an inherent viscosity of 0.2 to 0.5 dl/g (1 g per 1 00ml in chloroform) or (b) the composition comprises 
25 from 0.1 to 50% by weight of IC1 118,630 

(Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (O-tBu) -Leu-Arg-Pro-Azgly-NH 2 ) 

30 and from 50 to 99.9% by weight of a polylactide wherein the ratio of glycolide to lactide units is up to 3, and which 

has an inherent viscosity of less than 0.2 dl/g (1g per 100ml in chloroform) and excluding a composition in micro- 
capsule form comprising at least one polypeptide which is a naturally occurring luteinising hormone releasing 
hormone (LH — RH), a synthetically prepared material of the same type or synthetically prepared analogues of 
naturally occurring LH — RH which act in some manner on the anterior pituitary gland to affect the release of lutein- 

35 ising hormone (LH) and follicle stimulating hormone (FSH). 



Patentansprtiche 

40 1 . Feste pharmazeutische Zusammensetzung fur die subdermale Implantation, die ein Polylactid, das ein Copolymer 
von Milch- und Glykolsaure, das durch ringoffnende Polymerisation einer Mischung des cyclischen Dimeren von 
Milchsaure und des cyclischen Dimeren von Glykolsaure in Gegenwart eines Kettenabbruchmittels hergestellt 
wurde, oder eine Mischung derartiger Copolymerer ist, und ein saurestabiles Polypeptid, das unter den Bedingun- 
gen, die innerhalb der Zusammensetzung wahrend des beabsichtigten Verwendungszeitraums angetroffen wer- 

45 den, nicht nennenswert hydrolisiert wird, umfaBt, wobei die Zusammensetzung, wenn sie in einer waBrigen Um- 

gebung vom physiologischen Typ angeordnet wird, ein Freisetzungsprofil zeigt, das zwei aufeinanderfolgende 
Freisetzungsphasen fur das Polypeptid in Form einer waBrigen Losung aufweist, wobei die erste Phase durch 
Matrixdiffusion freigesetzt wird und die zweite Phase anschlieBend durch Abbau des Polylactids freigesetzt wird, 
bis im wesentlichen das gesamte Polypeptid freigesetzt ist, dadurch gekennzeichnet, dass die Diffusionsphase 

so und die Abbauphase des Freisetzungsprofils zeitlich uberlappen, und die Freisetzung des Polypeptids uber einen 

Zeitraum von wenigstens einer Woche erfolgt, wobei die Zusammensetzung dafur ausgelegt ist, dieses Freiset- 
zungsprofil durch Variation der Polylactidzusammensetzung zu erreichen, und zwar insbesondere des Verhattnis- 
ses von Milchsaure zu Glykolsaure, indem man das gewichtsmittlere Moiekulargewicht des Polylactids und dessen 
Polydispersitat wahlt, das Verhaltnis des Polypeptids zu dem Polylactid wahlt Oder die<aeometrie der festen For- 

55 mulierung fur die Implantation wahlt, urn das Freisetzungsprofil zu emalten, wenn man das Moiekulargewicht des 

Polypeptids und die Wechselwirkung von basischen Polypeptiden mit den terminalen Carbonsauregruppen des 
Polypeptids berucksichtigt, und wobei entweder (a) die Zusammensetzung von 5 bis 50 Gew.-% von ICI 118,630 



16 



EP 0 058 481 B2 



(Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (O-tBu) -Leu-Arg-Pro-Azgly-NH 2 ) 

und von 50 bis 95 Gew.-% Pofylactid umfaBt, wobei das Verhattnis von Glycolid- zu Lactid-Einheiten von 0,2 bis 
3 betragt, und eine inharente Viskositat von 0,2 bis 0,5 dl/g (1 g pro 100 ml in Chloroform) aufweist, Oder (b) die 
Zusammensetzung von 0,1 bis 50 Gew.-% IC1 118,630 



(Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (O-tBu) -Leu-Arg-Pro-Azgly-NH 2 ) 

und von 50 bis 99,9 Gew.-% eines Polylactids umfaBt, wobei das Verhattnis von Glycolid- zu Lactid-Einheiten bis 
zu 3 betragt, und eine inharente Viskositat von weniger als 0,2 dl/g (1 g pro 100 ml in Chloroform) aufweist, und 
wobei eine Zusammensetzung in Mikrokapselform ausgeschlossen ist, die wenigstens ein Polypeptid umfaBt, das 
ein naturlich vorkommendes Release-Hormon eines lutein isierenden Hormons (LH-RH). ein synthetisch herge- 
stelltes Material des gleichen Typs Oder ein synthetisch hergestelltes Analoges des naturlich vorkommenden 
LH-RH ist, die auf irgendeine Weise so auf den Hypophysenvorderlappen wirken, dass die Freisetzung von lute- 
inisierendem Hormon (LH) und follikelstimulierendem Hormon (FSH) bewirkt wird. 



Revendications 

1. Composition pharmaceutique solide pour implantation sous le derme, comprenant un polylactide, qui est un co- 
' polymere d'acide lactique et d'acide glycolique produit par polymerisation, par ouverture de cycle, d'un melange 
d?un dimere cyclique d'acide lactique et d'un dimere cyclique d'acide glycolique en presence d'un agent de termi- 
naison de chaine, ou un melange de tels copolymeres, et un polypeptide stable en milieu acide, qui n'est pas 
hydrolyse de maniere significative dans les conditions rencontrees dans la composition au cours de la p6riode 
d'utilisation envisagee, composition qui, lorsqu'elle est placee dans un environnement aqueux de type physiolo- 
gique, presente un profit de liberation qui comporte deux phases successives de liberation du poly-peptide sous 
forme d'une solution aqueuse, la premiere phase etant une phase de liberation par diffusion a t ravers la matrice 
et la seconde phase etant une phase de liberation suite a ta degradation du polylactide jusqu'ace que pratiquement 
la totality du polypeptide ait ete liberee, caracterisee en ce que la phase de diffusion et la phase de degradation 
du profit de liberation se chevauchent dans le temps, et la liberation du polypeptide se produit pendant une p6riode 
de temps d'au moins une semaine, la composition etant adaptee a presenter te profil de liberation en faisant varier 
la composition de polylactide, en particulier la proportion d'acide lactique par rapport a I'acide glycolique, en choi- 
sissant la moyenne en poids du poids moleculaire du polylactide et sa polydispersite, en choisissant la proportion 
du polypeptide par rapport au polylactide ou en choisissant la geometrie de la formulation solide pour implantation 
afin d'obtenir le profil de liberation lorsqu'on prend en consideration le poids moleculaire du polypeptide et I'inte- 
raction des polypeptides basiques avec les groupes acide carboxylique terminaux du polypeptide, et 
soit (a) la composition comprend 5 a 50 % en poids de ICI 11 8 630 

{Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (OtBu) -Leu-Arg-Pro-Azgly-NH?) 

et 50 a 95 % en poids de polylactide dans lequel le rapport des motifs glycolide aux motifs lactide va de 0,2 
a 3, et possede une viscosite in he rente de 0,2 a 0,5 dl/g (1 g pour 100 ml dans le chloroforme) 
soit (b) la composition comprend 0,1 a 50 % en poids de IC1 118 630 



(Pyro-Glu-His-Trp-Ser-Tyr-D-Ser (O-tBu) -Leu-Arg-Pro-Azgly-NH ? ) 



et 50 a 99,9 % en poids de polylactide dans lequel le rapport des motifs glycolide aux motifs lactide vajusqu'a 
3 et possede une viscosite inherente inferieure a 0,2 dl/g (1 g pour 100 ml dans le chloroforme) 

en excluant une composition sous forme de micro-capsules comprenant au moins un polypeptide qui est 
une hormone de liberation d'hormone luteinisante naturelle (LH-RH), une substance du meme type prepar6e par 
synthese ou des analogues prepares par synthese de la LH-RH naturelle qui agissent d'une certaine maniere sur 



17 



EP 0 058 481 B2 

I'hypophyse anterieure en ayant un effet sur la liberation d'hormone luteinisante (LH) et la folliculostimuline {FSH). 

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