WO1999027897A9 - Site-specific preparation of polyethylene glycol-grf conjugates - Google Patents

Abstract

A method is described for the site-specific preparation of hGRF-PEG conjugates containing one or more PEG units (per mole of hGRF) covalently bound to Lys12 and/or Lys21 and/or Nα, characterized in that the conjugation reaction between the hGRF peptide and activated PEG is carried out in solution and the desired hGRF-PEG conjugate can be purified by chromatography. The conjugates prepared by this method, as well as their use in the treatment, prevention or diagnosis of growth hormone deficiency, are also an object of the present invention.

Description

SITE-SPECIFIC PREPARATION OF POLYETHYLENE GLYCOL-GRF CONJUGATES

FIELD OF THE INVENTION

The present invention relates to a method for the site-specific preparation of hGRF-PEG conjugates containing one or more than one PEG units (per hGRF) covalently bound to Lys¹² and/or Lys²¹ and/or N^α, characterized in that the conjugation reaction between the hGRF peptide and activated PEG is carried out in solution and the desired hGRF-PEG conjugate is purified by chromatographic methods.

The conjugates prepared by this method, as well as their use in the treatment, prevention or diagnosis of growth-hormone related disorders, are also an object of the present invention.

BACKGROUND OF THE INVENTION

In the early 1980's several groups isolated and characterized growth hormone releasing factor (GRF).

GRF (also called Somatorelin) is a peptide secreted by the hypothalamus which acts on its receptor and can promote the release of growth hormone (GH) from the anterior pituitary. It exists as 44-, 40-, or 37-amino acid peptide; the 44-amino acids form may be converted physiologically into shorter forms. All three forms are reported to be active, the activity residing mainly in the first 29 amino acid residues. A synthetic peptide corresponding to the 1-29 amino acid sequence of human GRF [hGRF(l-29)], also called Sermorelin, has been prepared by recombinant DNA technology as described in European Patent EP 105 759.

Sermorelin has been used in the form of acetate for the diagnosis and treatment of growth hormone deficiency.

GRF has indeed a therapeutic value for the treatment of certain growth-hormone related disorders. The use of GRF to stimulate the release of GH is a physiological method in promoting long bone growth or protein anabolism.

One problem associated with the use of GRF relates to its short biological half-life (about 12 to 30 minutes). The hGRF(l-29)-NH₂ is subject to enzymatic degradation and is rapidly degraded in the plasma via dipeptidylpeptidase IV (DPP-IV) cleavage between residues Ala² and Asp³.

It is therefore advantageous to develop biologically stable, long-acting GRF analogues using specific chemical modification of GRF, in order to prevent or slow down enzymatic degradation.

Polyethylene glycol (PEG) is a hydrophilic, biocompatible and non-toxic polymer of general formula H(OCH₂CH₂)„OH, wherein n > 4. Its molecular weight could vary from 200 to 20,000 daltons.

It has been demonstrated that the chemical conjugation of PEG in its mono- methoxylated form to proteins and/or peptides significantly increases their duration of biological action. Like carbohydrate moieties in a glycoprotein, PEG provides a protective coating and increases the size of the molecule, thus reducing its metabolic degradation and its renal clearance rate.

PEG conjugation is an already established methodology for peptide and protein delivery pioneered by the fundamental studies of Davis and Abuchowski (Abuchowski et al., 1977a and 1977b). PEG conjugation to peptides or proteins generally resulted in non-specific chemical attachment of PEG to more than one amino acid residue. One of the key issues with this technology is therefore finding appropriate chemical methods to covalently conjugate PEG molecule(s) to specific amino acid residues.

For example, the trichlorotriazine-activated PEG, which was found to be toxic and reacted in a non-specific way, was later on replaced by various PEG reagents with chemical linkers that could react specifically to amino groups (Benchamp et al., 1983; Veronese et al., 1985; Zalipsky et al., 1983; Zalipski et al., 1990; and Delgado et al., 1990), to sulphydryl groups (Sartore et al., 1991; and Morpurgo et al., 1996) or to guanidino residues (Pande et al., 1980).

Various PEG-protein conjugates were found to be protected from proteolysis and/or to have a reduced immunogenicity (Monfardini et al., 1995; and Yamsuki et al., 1988).

Another technical difficulty in protein pegylation arises from the fact that PEG- protein conjugates usually have various number of PEG molecules attached and result in a mixture of conjugates with different PEG:protein stoichiometries. Site-specific pegylation remains a chemical challenge The conjugation of PEG to GH represents a typical example of such problem (Clark et al., 1996) It was demonstrated that Lys- residues of GH were pegylated at random positions

To avoid or reduce the loss of enzyme activity, the active site could be protected in advance, thus allowing enzyme pegylation to occur at non-active site(s) (Caliceti et al , 1993)

Another approach was recently proposed for the site-specific conjugation of PEG to low molecular weight peptides, such as GRF, which was prepared by solid- phase peptide synthesis In these conjugates a pegylated amino acid, prepared in advance, was introduced into the peptide sequence during the solid-phase synthesis This procedure, however, dramatically complicates product purification that is known to be the critical step in solid phase synthesis The presence of PEG, for its high molecular weight and its polydispersivity, is likely to yield final products with unacceptable impurities and/or products with missing amino acids, the latter being considered to occur commonly in the Merrifield procedure

Mono-pegylation, meaning that only one PEG molecule is attached, using solid- phase synthesis to specific amino acid residues of [Ala¹⁵]-hGRF(l-29)-NH₂ has been recently reported in the literature (Felix et al , 1995) This study shows that [Ala¹⁵]-hGRF(l-29)-NH₂ pegylated at residues 21 or 25 retains the full in-vitro potency of the parent [Ala¹⁵]-hGRF(l-29)-NH There is however no in-vivo data to show whether these pegylated conjugates exhibit a longer duration of action with respect to the non-pegylated counterpart

More recently, it has been demonstrated (Campbell et al , 1997) that the attachment of PEG with different molecular weights to the C-terminus of several analogs of hGRF, again using solid-phase synthesis, had enhanced duration of action in both pig and mouse models as compared to the non-pegylated counterpart

DESCRIPTION OF THE INVENTION

In contrast to the solid-phase preparation of mono-pegylated hGRF mentioned above, the present invention relates to site-specific pegylation of hGRF in solution phase hGRF was found to have a low solubility in a neutral/alkaline buffer solution, a chemical condition whereby most efficient pegylation reaction occurs. In a diluted hGRF solution, the hydrolysis of the activated PEG (such as the PEG ester) tends to decrease the yield of the pegylation reaction.

It was discovered by the Applicant that, in a suitable solvent whereby hGRF has a high solubility, it is possible to carry out a site-specific pegylation reaction in solution phase. In this way, even if the starting hGRF peptide is non-protected, the PEG chains will bind with high yields and almost exclusively to the primary amino groups (ε-amino groups) of Lys¹², Lys²¹ and/or N^α, depending upon the reaction conditions. The following four conjugates, which are also covered by the present invention, were obtained, the hGRF:PEG stoichiometric ratio in the conjugates mainly depending on the molar ratio of PEG to hGRF: hGRF-PEG conjugate, in which 1 PEG molecule is covalently bound to Lys¹², hGRF-PEG conjugate, in which 1 PEG molecule is covalently bound to Lys²¹, hGRF-2PEG conjugate, in which 2 PEG molecules are covalently bound to both Lys¹² and Lys²¹; and hGRF-3PEG conjugate, in which 3 PEG molecules are covalently bound to both Lys¹² and Lys²¹ and also to N^α.

"N^α" through out the present invention means the amino group at the N-terminal position of the peptide (Tyr).

Further to this step, it is possible to carry out a simple chromatographic fractionation of the conjugates obtained in the reaction either by gel filtration or by direct application to a C18 HPLC column eluted by water/acetonitrile gradient. The second method is preferred, since large scale preparation and purification of the products could be obtained.

Therefore, the main embodiment of the present invention is a method for the site- specific preparation of different hGRF-PEG conjugates containing one or more than one PEG units (per hGRF) covalently bound to Lys¹² and/or Lys²¹ and/or N^α, characterized in that the pegylation reaction is carried out in solution and the desired hGRF-PEG conjugate is purified, for example, by chromatographic methods. hGRF-PEG conjugates containing one or more PEG units (per mole of hGRF) covalently bound to Lys¹² and/or Lys²¹ and/or N^α are also covered by the present invention. The hGRF-PEG conjugates, in which 1 PEG molecule is covalently bound to

Lys¹² or to Lys²¹, are the preferred products of the present invention.

According to another embodiment of the present invention, if one or more of these three amino groups to which PEG chains bind, are reversibly protected by certain chemical groups from pegylation, the pegylation reaction will give directly the desired conjugate with specific pegylation sites, which can then be isolated from the reaction mixture, for example, by ultrafiltration or other chromatographic methods. In this case, the preparation method can further, optionally, comprise a de-protection reaction.

The de-protection reaction is preferably carried out according to known methods and depending on the chemical protective group to be removed.

According to this invention the term "hGRF", unless otherwise specified, is intended to cover any human GRF peptides, with particular reference to the 1-44, 1-40, 1-29 peptides and the corresponding amides thereof (containing an amide group at the N-terminus or C-terminus). The preferred hGRF peptide is hGRF(l-29)-NH₂. whose amino acid sequence is reported in SEQ ID NO: 1.

The "activated PEG"(or "pegylating agent") is any PEG derivative, which can be used as protein modifier, because it contains a functional group capable of reacting with some functional group in the protein/peptide to produce the PEG-protein/peptide conjugates. A review of PEG derivatives useful as protein modifiers can be found in Harris (1985). The activated PEG can be an alkylating reagent, such as PEG aldehyde, PEG epoxide or PEG tresylate, or it can be an acylating reagent, such as PEG ester.

The activated PEG is preferably used in its mono-methoxylated form. It has preferably a molecular weight between 2,000 and 20,000. Mono-methoxylated PEG5_.000 is particularly preferred for the preparation of the activated PEG according to the present invention.

If activated PEG is an acylating agent, it preferably contains either a norleucine or ornithine residue bound to the PEG moiety via an amide linkage. These residues allow a precise determination of the linked PEG units per mole of peptide (see for example Sartore et al., 1991). Therefore, more in particular, the preferred activated PEG is mono- methoxylated PEG_5,ooo linked by means of an amide bond to the alpha amino group of norleucine, that is activated at the carboxy group as succinimidyl ester

Branched PEGs are also in common use The branched PEGs can be represented as R(-PEG-OH)_m in which R represents a central core moiety such as pentaerythritol or glycerol, and m represents the number of branching arms The number of branching arms (m) can range from three to a hundred or more The hydroxyl groups are subject to chemical modification

Another branched form, such as that described in PCT patent application WO 96/21469, has a single terminus that is subject to chemical modification This type of PEG can be represented as (CH₃O-PEG-)_pR-X, whereby p equals 2 or 3, R represents a central core such as lysine or glycerol, and X represents a functional group such as carboxyl that is subject to chemical activation Yet another branched form, the "pendant PEG", has reactive groups, such as carboxyl, along the PEG backbone rather than at the end of PEG chains

All these branched PEGs can be "activated" as indicated above

"Chromatographic methods" means any technique that is used to separate the components of a mixture by their application on a support (stationary phase) through which a solvent (mobile phase) flows The separation principles of the chromatography are based on the different physical nature of stationary and mobile phase

Some particular types of chromatographic methods, which are well-known in the literature, include liquid, high pressure liquid, ion exchange, absorption, affinity, partition, hydrophobic, reversed phase, gel filtration, ultrafiltration or thin-layer chromatography

"Pegylation" is the reaction by which a PEG-protein/peptide conjugate is obtained starting from the activated PEG and the corresponding protein/peptide

The molar ratio PEG hGRF can be 1 1, 2 1 or 3 1, depending on which conjugate is sought at high yields

The solvent of the pegylation reaction is selected from the group consisting of a highly concentrated nicotinamide aqueous solution, a buffered aqueous solution of a defolding agent (such as urea) or a polar organic solvent selected among dimethyl sulfoxide, dimethyl formamide/buffer or acetonitrile/buffer

The pH of the solution is usually kept between 7 and 9

A non-limitative list of protective chemical groups for Lys¹² and Lys²¹ includes Alloc (allyloxycarbonyl), Dde (l-(4,4-Dimethyl-2,6-dioxocyclohex-l-ylidene)ethyl), Adpoc (l-(l'-Adamantyl)-l-methyl-ethoxycarbonyl) or 2-Cl-Z (2- Chlorobenzyloxycarbonyl) Alloc is the preferred protective group for the lysine group

After pegylation Alloc can be removed according to one of the methods described in Greene T W et al , 1991) Dde can be removed with 2% hydrazine in DMF (see W C Chan et al , 1995) Adpoc can be removed similarly to Alloc (see also Dick F et al , 1997) 2-Cl-Z can be requires a stronger acid deprotection (HF, TFMSA, HBr) or hydrogenation (see also Tarn et al , 1 87)

The protective groups for N^α can be an alkyl group, such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, benzyl or cyclohexyl Isopropyl is the preferred one These alkyl groups can be introduced by reductive alkylation (see Murphy et al , 1988 or Hocart et al , 1987)

[N^α-isopropyl-Tyr¹,Lys(Alloc)¹²]-hGRF and [Lys(Alloc)^1Z21]-hGRF are also covered by the present invention, as useful and new intermediates of the pegylation reaction

It has also been discovered that the pegylation of the present invention

1 does not modify the conformation of the peptide,

2 increases the resistance to the proteolytic degradation,

3 does not affect, or only slightly decreases, the biological activity, depending upon the extent of pegylation and

4 allows to obtain products (the conjugates), which are more soluble in aqueous buffered solutions

Another object of the present invention is to provide the hGRF-PEG conjugates in substantially purified form in order for them to be suitable for use in pharmaceutical compositions as active ingredients

In a further aspect, the present invention provides the use of the conjugates of the invention in the manufacture of a medicament for treatment, prevention or diagnosis of growth hormone-related disorders, such as for example growth hormone deficiency(GHD), in particular pediatric growth hormone deficiency.

The medicament is preferably presented in the form of a pharmaceutical composition comprising the conjugates of the invention together with one or more pharmaceutically acceptable carriers and/or excipients. Such pharmaceutical compositions form yet a further aspect of the present invention.

An embodiment of the invention is the administration of a pharmacologically active amount of the conjugates of the invention to subjects at risk of developing a growth hormone-related disease or to subjects already showing such pathology.

A further object of this invention is a method of treatment, prevention or diagnosis of growth hormone-related disorders, comprising administering an effective amount of the conjugates of the invention, in the presence of one or more pharmaceutically acceptable excipients.

An "effective amount" refers to an amount of the active ingredients that is sufficient to affect the course and the severity of the disorders described above, leading to the reduction or remission of such pathology. The effective amount will depend on the route of administration and the condition of the patient.

"Pharmaceutically acceptable" is meant to encompass any carrier, which does not interfere with the effectiveness of the biological activity of the active ingredient and that is not toxic to the host to which is administered. For example, for parenteral administration, the above active ingredients may be formulated in unit dosage form for injection in vehicles such as saline, dextrose solution, serum albumin and Ringer's solution.

Besides the pharmaceutically acceptable carrier, the compositions of the invention can also comprise minor amounts of additives, such as stabilizers, excipients, buffers and preservatives.

Any route of administration compatible with the active principle can be used. The preferred is the parenteral administration, such as subcutaneous, intramuscular or intravenous injection. The dose of the active ingredient to be administered depends on the basis of the medical prescriptions according to age, weight and the individual response of the patient. The dosage of the active ingredient for the human therapy can be between 5 and

6,000 μg/Kg body weight and the preferable dose is between 10 and 300 μg/Kg body weight

The present invention has been described with reference to the specific embodiments, but the content of the description comprises all modifications and substitutions which can be brought by a person skilled in the art without extending beyond the meaning and purpose of the claims

The invention will now be described by means of the following Examples, which should not be construed as in any way limiting the present invention The Examples will refer to the Figures specified here below

DESCRIPTION OF THE FIGURES

Figure 1 shows the amino acid sequence of hGRF(l-29)-NH Arrows indicate the possible site(s) of pegylation

Figure 2 shows the reversed-phase HPLC chromatography of the mixture obtained after the pegylation reaction in DMSO carried out as described in Example 1 The first two major peaks are the conjugates containing 1 PEG chain per mole of hGRF The following minor peak is the conjugate hGRF 2PEG and the last minor peak the conjugate hGRF 3PEG

Figure 3 a reports the degradation of hGRF(l-29) and of the PEG conjugates of the present invention by subtilisin

Figure 3b reports the degradation of hGRF(l-29) and of the PEG conjugates of the present invention by chymotrypsin

Figure 4 shows the spectroscopic characterization of [Lys(MPEG₅,ooo -CH -CO-Nle-

CO) ' '-hGRF(l-29)-NH₂] carried out by circular dichroism The spectra are superimposable with those of "native" hGRF

Figure 5 shows the biological effect of various hGRF-PEG conjugates (from a 1 st

DMSO preparation) in the CHO-hGRFR-LUC in vitro assay Data represent the average of three independent experiments Figure 6 reports the biological effect of various hGRF-PEG conjugates (from a 2nd

DMSO preparation) in the CHO-hGRFR-LUC in vitro assay Data represent the average of two independent experiments

Figure 7 shows the biological effect of various hGRF-PEG conjugates (from a nicotinamide preparation) in the CHO-hGRFR-LUC in vitro assay Data represent the average of two independent experiments

Figure 8 illustrates the biological effect of various hGRF-PEG conjugates (1st DMSO preparation) on the GH release from rat pituitary cell in vitro

Figure 9 shows the biological effect of various hGRF-PEG conjugates (from a 2nd

DMSO preparation) on the GH release from rat pituitary cell in vitro

Figure 10 shows the time-response curve of plasma hGRF and serum GH levels following hGRF (400 μg/rat) i v injection in male rats Each point represents the mean

± SEM value obtained from nine rats

Figure 11A (see the first graph on the page) shows the time-response curve of serum GH levels after the i v injection of 400 μg/rat of hGRF-PEG conjugates (DMSO preparation) in male rats Each point represents the mean value obtained for three rats

Figure 11B (see the second graph on the page) shows the time-response curve of plasma hGRF levels after the i v injection of 400 μg/rat of hGRF-PEG conjugates (DMSO preparation) in male rats Each point represents the mean value obtained for three rats

Figure 12 represents the restriction map of plasmid pcDNA3-hGRF-R used in the reporter gene assay for the evaluation of GRF activity

Figure 13 shows the restriction map of plasmid pTF5-53 LUC used in the reporter gene assay for the evaluation of GRF activity

EXAMPLES Abbreviations

Acetonitrile (ACN), allyloxycarbonyl (Alloc), Benzyl (BZL), tert-Butyloxycarbonyl (Boc), Dichloromethane (DCM), Diisopropylethylamine (DIEA), Dimethyl Formamide (DMF), dimethyl sulphoxide (DMSO), 9-Fluorenylmethyloxycarbonyl (FMOC), 2-[ lH-Benzotriazole- 1 -yl]- 1 , 1 ,3,3-tetramethyluronium hexafluorophosphate (HBTU), 1-hydroxybenzotriazole (HOBt,), methyl-t-butyl ether (MTBE), norleucine (Nle), N-methyl pyrrolidone (NMP), 2,2,5,7,8-Pentamethyl-chroman-6-sulfonyl (Pmc), tert-Butyl (tBu), Trifluoroacetic Acid (TFA), Triphenylmethyl (Trt)

EXAMPLE 1: Solution-phase pegylation of hGRF

In these experiments mono-methoxylated PEG5.000 (MPEG5.000) linked by means of an amide bond to the alpha amino group of norleucine, that is activated at the carboxy group as succinimidyl ester, was used as pegylating reagent It can be prepared for example as described in Lu et al , 1994

Human GRFι_-29 hGRF(l-29)-NH₂ supplied by Bachem was used as hGRF peptide

Given the low solubility of hGRF(l-29) in water solution at neutral or slightly alkaline pH needed for the pegylation, alternative reaction conditions A to E have been adopted

A Dimethyl sulphoxide 20 mg of peptide were dissolved in 1 ml DMSO and proper amounts of pegylating reagent were added at once

B Dimethyl formamide/0 2 M borate buffer pH 8 0 in a volume ratio of 1 1 peptide and proper amounts pegylating reagent were added at once

C Highly concentrated nicotinamide aqueous solution (200 mg/ml) 200 mg of nicotinamide were added to a solution of 40 mg of hGRF(l-29) in 1 ml of 10 mM acetic acid 1 ml of 0 2 M borate buffer at pH 8 0 was added to the acidic solution to reach the desired pH, before the addition of proper amounts of pegylating reagent

D Acetonitrile /0.2 M borate buffer pH 8.0 in a volume ratio of 1 1 and proper amounts of pegylating reagent were added at once

E 0 2 M borate buffer . 5 M urea. pH 8 0 and proper amounts of pegylating reagent were added at once

The dry PEG reagent was added under stirring to reach final PEG hGRF molar ratios of 1 1, 2 1 or 3 1 A 2 1 ratio is the preferred one

The use of different PEG hGRF molar ratios allowed the preparation of a reaction mixture with a predominant conjugate being the desired conjugate The reaction solution was left standing for 5 hours at room temperature before purification.

The following 4 hGRF-PEG conjugates (A1-A4) are obtained Al [Lys(MPEG_5,ooo-CH₂-CO-Nle-CO)¹²-hGRF(l-29)-NH₂], A2 [Lys(MPEG₅.ooo-CH₂-CO-Nle-CO)²¹-hGRF(l-29)-NH₂], A3 [Lys(MPEG₅.ooo -CH₂-CO-Nle-CO)¹²"²¹-hGRF(l-29)-NH₂] and A4 N^α-(MPEG_5.ooo-CH₂-CO-Nle-CO)[Lys(MPEG₅ ooo-CH₂-CO-Nle-CO)¹²²¹-hGRF(l - 29)-NH₂]

The excess of DMSO, dimethyl formamide, acetonitrile or urea and the side- product of reaction (hydroxysuccinimide) were removed by gel ultrafiltration using a 1,000 D cut-off membrane The volume was brought to 10 ml with 10 mM acetic acid and then reduced to 1 ml The procedure was repeated three times

The hGRF-PEG conjugates were isolated by gel filtration chromatography or alternatively by reversed-phase chromatography

EXAMPLE 2: Gel Filtration Chromatography

By gel filtration chromatography the products were fractionated on the basis of the different molecular weight of the components (in this case, conjugates hGRF-PEG 1 1 MW = 8,358, hGRF-PEG 1 2 MW= 13,358, and hGRF-PEG 1 3 MW = 18,358 Unconjugated hGRF MW = 3358) The separation was performed by using a serial column system Superdex 75-Superose 12 resin (Biotech, Pharmacia) eluted with 10 ml acetic acid at a flow rate of 1 5 ml/min

The collected fractions of 1 ml were analysed by OD at 280 nm for protein content and by iodine test for PEG content (Sims et al , 1980)

After pegylation in DMSO using a hGRF PEG molar ratio of 1 1, three peaks were obtained a hGRF-PEG conjugate at an elution volume of 132 ml (major peak), a hGRF-PEG conjugate at an elution volume of 108 ml (minor peak), and unconjugated hGRF at an elution volume of 108 ml (minor peak)

After pegylation in DMSO using a hGRF PEG molar ratio of 1 2, three peaks were obtained a hGRF-PEG conjugate at an elution volume of 108 ml (major peak), a hGRF-PEG conjugate at an elution volume of 132 ml (minor peak), and a hGRF-PEG conjugate at an elution volume of 73 ml (minor peak)

After pegylation in DMSO using a hGRF PEG molar ratio of 1 3, two peaks were obtained a hGRF-PEG conjugate at an elution volume of 73 ml (major peak), and a hGRF-PEG conjugate at an elution volume of 108 ml (minor peak)

The eluted peaks were collected, concentrated by ultrafiltration using a 1,000 D cut-off membrane, lyophilised, dissolved in 10 mM acetic acid and characterised as herein after reported for their identification and quantification

The peak at the elution volume of 73 ml was found to correspond to compound A4

The peak at the elution volume of 132 ml was found to correspond to compound A3

The peak at the elution volume of 108 ml was found to correspond to a mixture of compounds A2 and Al

The peak eluted at 232 ml was found to be unconjugated hGRF

However, this method of purification does not allow to separate hGRF-PEG conjugates having the same molecular weight but different pegylation site (positional isomers)

EXAMPLE 3: Reversed-Phase Chromatography

A more specific fractionation was carried out by hydrophobic chromatography using an RP-HPLC C18 column This procedure can separate eventual isomers having the same molecular weight In fact, with this method the single peak corresponding to the conjugates with 1 PEG covalently bound obtained by gel filtration was found to split in two peaks

The reversed-phase chromatography was carried out using a RP-HPLC C18 preparative column (Vydac) eluted with a gradient of H₂O/0 05%TFA (Eluent A) and acetonitrile/= 05% TFA (Eluent B), as follows 0-5 min 35% A

5-35 min 35% A → 2% A

35-38 min 2% A

38-40 min 2%A → 35% A

Flow rate 10 ml/min, loop 1 μl, UV-Vis Detector at 280 nm

After pegylation in DMSO using a hGRF PEG molar ratio of 1 1, 4 peaks were obtained

1 13 2 min major peak,

2 13 7 min major peak,

3 14 4 min minor peak, and

4 8 9 min minor peak

After pegylation in DMSO using a hGRr⁷ PEG molar ratio of 1 2, 4 peaks were obtained

1 13 2 min minor peak,

2 13 7 min minor peak,

3 14 4 min major peak, and

4 15 5 min minor peak

After pegylation in DMSO using a hGRF PEG molar ratio of 1 3, 2 peaks were obtained

1 14 4 min minor peak, and

2 15 5 min major peak

The eluted peaks were collected, evaporated to eliminate acetonitrile and TFA and then lyophilised The dry product was dissolved in 10 mM acetic acid solution and analysed as reported herein after for identification and quantification of the isolated species

The hGRF-PEG conjugate eluted at 13 2 min was found to be compound Al (GRF- 1 PEG, 1st peak)

The hGRF-PEG conjugate eluted at 13 7 min was found to be compound A2 (GRF-1PEG, 2nd peak)

The hGRF-PEG conjugate eluted at 14 4 min was found to be compound A3 (GRF-2PEG) The hGRF-PEG conjugate eluted at 15.5 min. was found to be compound A4

(GRF-3PEG).

The peak eluted at 8.9 min. was found to be unconjugated hGRF. As a typical example, the reversed-phase chromatography of the pegylation products obtained using a 2: 1 PEG:hGRF molar ratio is reported in Figure 2.

The dry products were obtained by solvent evaporation/lyophilization.

EXAMPLE 3a: Solution-phase pegylation of hGRF, using PEGm nnn

In this example a branched monomethoxy PEG having a molecular weight of 10,000 Dalton with lysine as spacer (supplied by Shearwater Polymers, Inc.) was used. This branched PEG has been obtained by linking to each amino group of lysine a

The carboxy group of the spacer lysine, activated as succinimidyl ester, was reacted in DMSO to the amino groups of hGRF(l-29)-NH₂ using a molar ratio of 0.9 moles of PEG to 1 mole of GRF.

The solvent was removed and the residue fractionated by gel exclusion chromatography in a preparative column Superose 12 TM. Two peaks, corresponding to two hGRF-PEG conjugates were eluted. The first minor peak corresponded to the conjugate having two PEGio.ooo units bound to hGRF, the second major peak corresponded to the conjugate containing one PEGιo,ooo unit per hGRF.

EXAMPLE 3a: Solution-phase pegylation of hGRF, using PEG , 000

In this example a branched monomethoxy PEG having a molecular weight of 20,000 Dalton with lysine as spacer (supplied by Shearwater Polymers, Inc.) was used.

This branched PEG has been obtained by linking to each amino group of lysine a PEGιo,ooo-

The carboxy group of the spacer lysine, activated as succinimidyl ester, was reacted in DMSO to the amino groups of hGRF( 1 -29)-NH₂ using a molar ratio of 0.9 moles of PEG to 1 mole of GRF. The solvent was removed by lyophylization and the residue fractionated by gel exclusion chromatography in a preparative column Superose 12 TM A single peak was obtained, corresponding to the conjugate containing one PEG₂₀,ooo unit per hGRF

EXAMPLE 4: Analytical Characterization of the hGRF-PEG conjugates

The products, obtained as previously reported, were examined for the bound PEG chains on the basis of the following assays

1 Colorimetric method based on trinitrobenzene sulphonate was used for free amino groups determination (as described in Habeed et al , 1966),

2 Colorimetric method based on iodine assay was used for PEG content determination (as described in Sims et al , 1980),

3 PEG chain number based on norleucine as chain reporter in amino acid analysis was used (as described in Sartore et al , 1991),

4 Mass spectroscopy was used to determine the molecular weight of the conjugates

The MALDI- mass spectrometry was used to reveal the molecular weight of the conjugates and their polydispersivity resulting from the polydispersivity of the starting PEG

The PEG attachment site analysis of the hGRF-PEG conjugates was evaluated by amino acid sequence Each sample was diluted 100-fold Then 10 μl of this solution (about 50 pmol) loaded into the sequencer

The purity of the final product was also confirmed by RP-HPLC analytical chromatography

The analysis was carried out using a C 18 analytical column (Vydac) eluted with a gradient H₂O/0 05% TFA (Eluent A) and acetonitrile/0 05% TFA (Eluent B) as follows

0-5 min 80% A

5-50 min 80% A → 5% A

50-52 min 5% A

52-54 min 5%A → 80% A

Flow rate 1 ml/min, loop 20 μl, UV-Vis Detector at 226 nm

The unconjugated hGRF eluted at 20 7 min Compound Al eluted at 22.9 min, compound A2 eluted at 23.4 min, compound

A3 at 24.4 min, and compound A4 at 25.5 min.

The conformational characterization of the "native" and polymer-bound peptides was performed by circular dichroism analysis.

The spectroscopic characterization of the unconjugated hGRF and hGRF-PEG conjugates was carried out by circular dichroism analysis in the range of 190-300 nm. The samples (50 μg/ml) were dissolved in 10 mM acetic acid or methanol/10 mM acetic acid in 30:70 and 60:40 molar ratios. In all the above solutions the unconjugated hGRF and the hGRF-PEG conjugates presented a superimposable behavior, as shown in Figure 4 for compound A3. In acetic acid solution the peptides were in random conformation, whereas by increasing the methanol content the peptide assumed an α-helix structure.

The results demonstrate that the PEG conjugation does not change markedly the structural properties of the peptide.

EXAMPLE 5: Stability Evaluation of the hGRF-PEG Conjugates

The proteolytic stability of hGRF and of the hGRF-PEG conjugates was investigated using proteolytic enzymes, such as subtilisin and chymotrypsin.

The study with subtilisin was performed by incubation at 4°C of a 0.297 mM peptide solution in 0.1 M Tris HCl 0.05 M CaCl₂ pH 8.0 with a peptide/protease molar ratio 1 :50,000.

In the case of chymotrypsin the peptide was dissolved in 0.08 M Tris HCl, 0.1 M CaCl₂ pH 7.8 and a peptide/protease molar ratio of 1:15,000 was used.

The degradation behavior was followed by analytical RP-HPLC using C18 column eluted under the same conditions as reported in Example 4. The height corresponding to the peak of the starting compound was calculated before incubation with the proteolytic enzyme and after scheduled times of incubation. The percentage of residual height at the scheduled times was estimated and is reported in Figures 3a and b.

EXAMPLE 6: Pegylation with Alkylating PEG hGRF was conjugated with mono-methoxylated PEG activated with different acylating groups as well as alkylating groups.

The alkylating PEG presents the advantage of yielding conjugates that maintain the positive charge at the lysine residue.

The isolation and characterisation were carried out as described in Examples 1-4.

EXAMPLE 7: Evaluation of The Activity of hGRF-PEG Conjugates Materials

Test compounds

Human GRFι_-29 hGRF(l-29)-NH₂, batch 1299201, supplied by Bachem;

Human GRF_3-29 hGRF(3-29), supplied by Bachem;

Human GRF_3-29, supplied by ISL; and hGRF-PEG Conjugates prepared as described above.

Reagents

CHO-hGRFR-LUC in vitro assay

MEM alpha medium with ribonucleosides and deoxyribonucleosides (Gibco) supplemented with 10% fetal bovine serum (Gibco) plus 600 μg/ml geneticin G418 sulfate (Gibco);

Cell culture lyses reagent (Promega);

Luciferase assay reagent (Promega); and

Lu elite (Packard).

In vitro rat pituitary cell bioassay

Earle's Balanced Salts (EBSS) (Gibco), supplemented with 50 μg/ml of gentamycine sulfate (Sigma).

Medium 199 (Ml 99) with Earle's Salts (Gibco) with 12.5 % of fetal bovine serum

(FBS) (Gibco) and 50 μg/ml of gentamycine sulfate.

Rat GH assay kit supplied by Amersham.

Enzyme solution for tissue digestion (make up to 30 ml of EBSS):

120 mg Collagenase (Sigma) 30 mg Hyaluronidase (Sigma)

30 mg Dnase I (Sigma)

900 mg BSA (Sigma)

After reconstitution, the solution was filter- sterilized and placed at 37°C

In vivo bioassay

Rat GH radioimmunoassay kit supplied by Amersham

Human GRF(l-44) radioimmunoassay kit supplied by Phoenix Pharmaceutical

Animals

SPF adult male Sprague-Dawley rats, 200-250 g b w, supplied by Charles River, are used after an acclimatisation period of at least 7 days

Methods

CHO-hGRFR-LUC in vitro assay

CHO-hGRFR-LUC (clone 1-1 1-20) is a cloned cell line that had been obtained by cotransfection of the pcDNA3-hGRF-R and pTF5-53 LUC vectors into CHO-DUKX cell line

The plasmid pcDNA3-hGRF-R was constructed by inserting the human growth hormone releasing factor receptor (hGRF-R) cDNA into pcDNA3 expression vector The Bluescript plasmid containing hGRF-R cDNA was kindly provided by Dr B Gaylinn (University of Virginia) the pcDNA3 mammalian expression vector was obtained from Invitrogen The hGRF-R coding sequence was driven by the human cytomegalovirus (CMV) promoter Its restriction map is reported in Figure 12

The plasmid pTF5-53LUC was constructed by inserting the c-fos cAMP response element along with its endogenous promoter upstream of the luciferase coding sequence in plasmid poLuc The cAMP response element and the c-fos promoter were obtained from the plasmid pTF5-53 (described in Fish et al, 1989) The promoterless reporter gene vector (poLuc) with multiple cloning sites upstream of the luciferase coding sequence was obtained from Dr Brasier (University of Texas, Galveston) Its restriction map is reported in Figure 13 These CHO-DUKX cells obtained by the above co-transfection were routinely grown in MEM alpha medium containing ribonucleosides and deoxyribonucleosides and supplemented with 10% fetal calf serum plus 600 μg/ml geneticin G418 sulfate

The cells were seeded (40,000 cells/well) in white 96-well plates (Dynatech) and incubated for 16-18 hrs in 200 μl growth medium before the assay

The next day, the medium was removed and replaced with a medium containing different concentrations of hGRF(l-29) in-house reference standard (Bachem) or different hGRF-PEG conjugates before incubating the plates at 37°C, 5% CO₂ for two hours At the end of incubation, CHO-hGRFR-LUC cells were washed twice with 200 μl of PBS (Sigma) and then lysed by adding 50μl of a cell culture lyses reagent (Promega) to each well After a further 15-minute incubation at room temperature, the plates were read in a luminometer (Dynatech) after introducing 150 μl of a luciferase assay reagent (Promega)

As an alternative method, CHO-hGRFR-LUC cells, seeded at 50,000cells/well, at the end of incubation with different hGRF-PEG conjugates , were washed with PBS, as above discussed To each well 100 μl PBS containing calcium and magnesium ions was added, prior to addition of 100 μl of Luclite (Packard) After 10 minutes incubation at room temperature, plates were read in luminometer (Lumicount - Packard)

Results were expressed as relative light unit (RLU)

In vitro rat pituitary cell bioassay for hGRF(l-29)

The animals (SPF male Sprague-Dawley rats 200 g, b w ) were sacrificed by CO₂ inhalation and the pituitaries removed The tissue was finely minced and put into a bottle with the enzyme solution for tissue digestion The bottle was placed in an incubator at 37°C for 1 hour

The digested tissue was recovered and the cells washed twice, counted and adjusted to a concentration of 5xl0⁵/ml The cells were plated out in a 48-well plate (200 μl/well) and the plate placed in an incubator for 72 hrs

After 72 hrs the cells were incubated with different concentrations of hGRF for 4 hours At the end of the incubation period the supernatants were collected and stored at - - 80°C The GH content in each sample was assayed by a commercial rat GH radioimmunoassay kit

In vivo assay

The animal was injected i v with hGRF(l-29) (400 μg/rat) A few minutes before blood collection, the animal was anaesthetized (ketamine-xylazine) Two ml of blood were withdrawn from the inferior vena cava from each rat The sample was divided into two aliquots 1 ml was collected as such and serum was obtained after an incubation period of about 3 hours at 37°C and subsequent centrifugation, the remaining 1 ml was collected into a vial containing 50 μl of a 4 mg/ml heparin solution, immediately stored on ice and plasma was obtained after centrifugation at 4°C

Blood sampler were collected at different time points from the injection of the test compound using different animals In each experimental session a total of three rats for each time point was used

Plasma and serum samples were immediately frozen and stored at - 20°C

GH serum levels were measured by a commercial RIA kit, hGRF plasma levels were measured by a commercial RIA kit for hGRF(l-44)

Results

NOTE throughout this section and the related Figures "GRF- 1 PEG 1^st peak' corresponds to [Lys(MPEG₅,ooo-CH₂-CO-Nle-CO)²¹-hGRF(l-29)-NH₂], "GRF-1PEG 2 ,nd peak" corresponds to [Lys(MPEG₅,ooo-CH₂-CO-Nle-CO)¹²-hGRF(l-29)-NH₂], "GRF- 2PEG" corresponds to [Lys(MPEG₅,ooo-CH₂-CO-Nle-CO)¹²'²¹-hGRF(l-29)-NH₂] and "GRF-3PEG" corresponds to N^α-(MPEG₅,ooo-CH₂-CO-Nle-CO)[Lys(MPEG₅,ooo -CH₂- CO-Nle-CO)^1Z21-hGRF(l-29)-NH₂]

CHO-hGRFR-LUC in vitro assay

The activities of two different batches of hGRF-PEG conjugates, both prepared using DMSO, in the CHO-hGRFR-LUC in vitro assay were shown in Figs 5 and 6 All preparations were found to be active although to a lesser extent as compared to "native" hGRF (hGRF subjected to the same purification steps used for the pegylated compounds), with GRF- 1 PEG (both the 1^st and 2^nd peak) being more active than the

GRF-2PEG and GRF-3PEG No difference was observed between hGRF and "native" hGRF (data not shown)

A similar in vitro bioactivity of the hGRF-PEG conjugates from both DMSO- prepared batches (Fig. 5 vs Fig 6) as well as the conjugates from the batch prepared using nicotinamide solution (Fig 7) were observed Fig 6 also shows that two different hGRF(3-29) preparations did not possess a significant in vitro activity as compared to hGRF(l-29)

In both assays performed with hGRF-PEG conjugates from two DMSO preparations, the GRF- 1 PEG 1st peak was found to be the most active compound, followed by GRF-1PEG 2nd peak, GRF-2PEG and then GRF-3PEG (Figs 8 and 9) These findings are in good agreement with those obtained in the reporter gene assay

In vivo assay

In preliminary experiments the serum GH and plasma hGRF levels were determined in rats following i v injection of 400 μg of hGRF The relevant results are illustrated in Fig 10 As shown, both GH and hGRF peaked at 10 min after hGRF injection Thereafter, serum GH concentrations rapidly declined and returned to basal levels after 60 min, whereas the plasma hGRF concentrations maintained a sustained level in the same time-interval

In Fig 11 A and 1 IB the blood levels of GH and GRF at different time-points up to 48 hours in rats treated with 400 μg i v of GRF- 1 PEG 1^st and 2^nd peak, GRF-2PEG and GRF-3PEG (DMSO preparations) are reported

All the pegylated preparations induce a GH serum peak 10 minutes after their i v injection similarly to the hGRF 1.29 However, while the GRF-1PEG 1^st and 2ⁿd peak and GRF-2PEG induce GH levels comparable to those obtained with hGRFj.29_^ GRF- 3 PEG confirms its lower activity as found in vitro For what the GRF plasma levels are concerned, a completely different pattern is observed with GRF-1PEG 1^st and 2^nd peaks as compared to GRF-2PEG and GRF-

3PEG irrespective of the preparation (DMSO or nicotinamide) used At 48 hours following the injection of GRF- 1 PEG 1^st and 2^nd peaks, the GRF plasma concentrations return to basal value, whereas more sustained levels are obtained with GRF-2PEG and

GRF-3PEG

EXAMPLE 8: Solid-Phase Synthesis Of Site-Protected hGRF(l-29 -NH₇ Derivatives As Starting Compounds In The Pegylation Process

A solid-phase synthesis of hGRF(l-29)-NH₂ derivatives containing a specific protection group (the N-allyloxycarbonyl-group) at the primary amino groups of both Lysine 12 and 21 has been carried out This is to allow site-specific pegylation at the N^α-terminus Another amino-protected derivative is prepared by blocking the N -terminus through acylation and the Lysine 12 with the N-allyloxycarbonyl group This derivative is used for site-specific pegylation at Lysine 21

Material and Methods

Peptide Synthesis Procedures

All hGRF derivatives peptide-resins were initially assembled using Fmoc chemistry on an Applied Biosystems Inc Model 431 A Peptide Synthesizer, using a low substitution (0 16 mmol/g) PAL-PEG-PS resin and a double-couple and capping protocol for each residue to optimize the amount and purity of the crude product Additionally [N-isopropyl-Tyr¹, Lys(Alloc)¹²]-hGRF(l-29)-NH₂ peptide-resin was manually treated with a reductive alkylation procedure to add an N-terminal isopropyl group

All peptide resins were cleaved with a mixture of TFA/l,2-ethanedithiol/ thioanisole/water [10 0 5 0 5 0 5 (v/v)] for 2 hours, and the crude peptides isolated by precipitation in MTBE and centrifugation Lyophilized crude peptides were purified by reversed-phase gradient HPLC using a Vydac C18 Preparative column with a 0 1% TFA Water/ Acetonitrile buffer system All purified peptides were characterized by Analytical

Reversed-Phase HPLC and MALDI-TOF Mass Spectrometry

Materials

Fmoc-L-Amino Acids (Bachem Bioscience, Perseptive Biosystems, NovaBiochem), DMF, 20 liter drum (J T Baker), Piperidine (Applied Biosystems, Chem-lmpex), HBTU (Rainin, Richelieu Biotechnologies), NMM (Aldrich), Acetic Anhydride (Applied Biosystems), Resins (Perseptive Biosystems, NovaBiochem) a-Cyano-4-hydroxy-cinnamic acid (Sigma) , Sinapinic acid (Aldrich), acetonitrile (J T Baker) , TFA (Sigma , Pierce), deionized H₂O (Millipore Milli-Q Water System) The other solvents and reagents are listed as follow

REAGENTS/SOLVENTS VENDORS

NMP Applied Biosystems Inc , J T Baker

HBTU Applied Biosystems Inc ,

Richelieu Biotechnologies Inc 0 5 M HOBt in DMF Applied Biosystems Inc

2 0 M DIEA in NMP Applied Biosystems Inc

Piperidine Applied Biosystems Inc

Dichloromethane Applied Biosystems Inc

Acetic Anhydride Applied Biosystems Inc

Amino acids most FMOC amino acids used on the ABI 431 A synthesizer were purchased from Applied Biosystems as pre-weighed 1 0 mmol cartridges FMOC-Lys(Alloc)-OH was purchased from Perseptive Biosystems (Framingham, MA) in bulk and the cartridges filled in house All amino acids used were of the L-configuration

Resins the primary resins used for the hGRF analogs were PAL-PEG-PS (Peptide Amide Linker - Polyethylene Glycol - Polystyrene) resins The PAL-PEG-PS supports, purchased from PerSeptive Biosystems, consistently show superior results in purity and yield of crude product A low substitution resin of 0 16 mmol/g was used for all derivatives Lower substitution resins are commonly used for long, difficult sequences to ensure better coupling by decreasing steric hindrance and β-sheet formation in the growing peptide chains

Methods

Cham Assembly - Applied Biosystems Inc. Model 431 A Peptide Synthesizer Protected peptide chains are initially assembled using FMOC strategy on an Applied Biosystem Inc Model 431 A Peptide Synthesizer, which utilizes programmed fast FMOC cycles (FastMoc™) HBTU is used for activation and coupling, 20% Piperidine for deprotection, and NMP is the main solvent used during deprotection, amino acid dissolution and washing of the resin Amino acids are introduced in pre-weighed 1 0 mmol cartridges The 0 25 mmol FastMoc™ cycles use 1 0 mmol cartridges and a 40 ml reaction vessel

Chain Assembly - Procedure

The steps for the 0 25 mmole scale programmed cycles can be summarized as follows

1 Piperidine Deprotection - The resin is first washed with NMP, then an 18% piperidine/NMP solution is delivered and deprotects for 3 minutes The reaction vessel is drained and a 20% piperidine solution is delivered and deprotection continued for approx 8 minutes

2 Dissolution of Amino Acid - NMP (2 1 g ) and 0 9 mmol of 0 45 M HBTU/HOBt in DMF (2 0 g ) are added to the cartridge and mixed for 6 minutes

3 NMP washes - The reaction vessel is drained and the resin is washed 5 times with NMP

4 Activation of amino acid and transfer to reaction vessel (RV) - 1 ml of 2 M DIEA in NMP is added to the cartridge to begin activation of the dissolved amino acid, then _ transferred from the cartridge to the RV 5 Coupling and final washing - The coupling reaction between the activated amino acid and the N-terminal deprotected peptide-resin proceeds for approx 20 minutes and then the RV is drained and the resin washed with NMP

6 Capping (if desired) - Approx 12 ml of a 0 5 M Acetic Anhydride, 0 125 M DIEA and 0 015M HOBt in NMP solution is added to the reaction vessel and vortexed for 5 mins This should acetylate any uncoupled sites on the resin, resulting in truncated rather than deletion sequences, which simplifies later purification steps

The complete protocol for these cycles can be found in Applied Biosystems User Bulletin No 35 (FastMoc™ 0 25 and 0 10 on the Model 431 A)

The standard protocol steps for a typical synthesis:

Step 1 Wash resin 3X with DMF

Step 2 Deprotect 2X for 5 minutes with 20% Piperidine/DMF

Step 3 Wash resin 6X with DMF

Step 4 Couple for 45 minutes with Amino Acid activated with HBTU/NMM in DMF

Step 5 Wash resin 3X with DMF

For difficult sequences, an extra capping step can be inserted after coupling, which uses 70% Acetic Anhydride in DMF for 20 minutes to acetylate any uncoupled sites on the peptide-resin, resulting in truncated sequences rather than deletion sequences in the final crude product

Cleavage/Extraction The cleavage cocktail used for removing side-chain protecting groups and releasing the peptide from the resin is a standard mixture used for peptides containing

Arginine and/or Methionine For 0 1-1 5 g peptide-resin, 10 ml Trifluoroacetic Acid, 0 5 ml D I Water, 0 5 ml Thioanisole, 0 5 ml Ethanedithiol (87% Trifluoroacetic Acid, 4 3%

D I Water, 4 3% Thioanisole, 4 3% Ethanedithiol)

Cleavage Procedure

100 mg -1 g of peptide-resin is placed into a 20 ml glass vessel and cooled in an ice bath The cleavage cocktail is prepared and also cooled in an ice bath, then added to the peptide-resin for a final volume of approx 10 ml

The vessel is removed from the ice bath and allowed to warm to room temperature The vessel is capped and the reaction mixture stirred at room temperature for 2 hours

After 2 hours, the solution is vacuum filtered through a medium-to-course porosity filter into approx 30 ml of cold MTBE The reaction vessel is washed with 1 ml TFA and filtered through the same filter funnel into the cold MTBE The entire suspension is then transferred to a 50 ml centrifuge tube and centrifuged for approx 10 minutes at 2,000 rpm at room temperature The supernatant is aspirated, the precipitate re-suspended in 40 ml cold MTBE and centrifuged again This step is repeated once more The final supernatant is aspirated and the precipitate is purged with nitrogen to evaporate most of the remaining ether

The peptide is then dissolved in 20-30 ml of aqueous 1% -10% Acetic Acid, diluted to approx 100-150 ml with deionized water, shell frozen, and lyophilized

Purification

RP-HPLC Methods

System - Waters Delta Prep 4000

Column - Vydac reversed-phase C18, 10 μm, 2 2 x 25 cm (Cat No 218TP1022)

Buffers - A Water/ 0 1%TFA B Acetonitrile/ 0 1%TFA

Flow Rate - 15 ml/minute

Detection - Waters 484 UV detector, 220 nm Gradient - Variable, usually 0 2% B/min up to 1 0% B/min

Lyophilized crude peptides are prepared by dissolving 50-100 mg of peptide in 200 ml of aqueous 0 1 % TFA The peptide solution is then loaded directly onto the preparative column through the "A" buffer reservoir line and the gradient program started

Collected fractions are run overnight on an autosampler analytical HPLC system Overlapping fractions judged to be >92% pure by peak integration are pooled, diluted 4 1 with D I Water, shell frozen, and then lyophilized on a Virtis 25 SL Freezedryer

Characterization

Reversed-phase HPLC

Conditions

System - Waters 510 pumps, 717 Autosampler, 490 Multiwavelength UV Detector

Column - Vydac C18, 5 μm, 0 46 x 25 cm (Cat No 218TP54)

Buffers - A H₂O/0 1 % TFA B ACN/ 0 1 % TFA

Flow Rate - 1 ml/minute

Detection - UV 214 nm, 280 nm

Gradient - 2 % B/minute

Purified lyophilized peptide samples are prepared by dissolving 0 2 - 1 0 mg of peptide in aqueous 0 1% TFA to a concentration of 0 5 - 1 0 mg/ml

15 - 18 μl are injected onto the column and eluted with a gradient program of 0-50% ACN in 25 minutes Chromatogram data is collected and stored with the Waters Expert-Ease software system

Mass Spectrometry

Type MALDI-TOF (Matrix-assisted laser desorption/ionization Time-of-flight)

System Perseptive Biosystems Voyager Elite

Matrices a-Cyano 4-hydroxy cinnamic acid, 10 mg/ml in 67% ACN/0 1% TFA or

Sinapinic Acid, 10 mg/ml in 50% ACN/0 1% TFA

Peptide samples are prepared at 1 - 20 μmol cone in 50% ACN/0 1% TFA 0 5_^ μl of matrix solution, followed by 0 5 μl of peptide sample, is applied to analysis plate wells and allowed to dry The analysis plate is loaded into the machine and the samples scanned and analyzed using a Reflector Delayed-Extraction method optimized for peptides. For each sample, a cumulative data signal from 32 - 128 laser shots is collected and analyzed Each run includes a sample well with a standard peptide for calibration

Specific Synthesis

Preparation of [Lvs( Alloc)¹²²' J-hGRF(l-29)-NH_z

The [Lys(Alloc)¹²"²¹]-hGRF(l-29)-PAL-PEG-PS-resin was initially assembled by Fmoc chemistry on the Applied Biosystems 431 A peptide synthesizer (sec Synthesis Methods above), including deprotection of the N-terminal residue Fmoc group

The peptide-resin was cleaved with a mixture of TFA 1,2-ethanedithiol thioanisole water [10 0 5 0 5 0 5 (v/v) ] for 2 hrs, and the peptide isolated by precipitation in MTBE to give 240 mg of crude peptide Purification by preparative reverse-phase HPLC with a Vydac C18 column (22 x 250 mm) resulted in 60 mg of purified product (>95% by analytical HPLC) MALDI-TOF mass spec Calculated 3523 8, Observed 3524.2

Preparation of /IT-isopropyl-Tyr' ' .Lysf Alloc)' ' AhGRF(l-29)-NH₇ Assembly of initial [Lys(Alloc)'²]-hGRF(l-29)-PAL-PEG-PS-resιn

[Lys(Alloc)¹²]-hGRF(l-29)-PAL-PEG-PS-resin was initially assembled by Fmoc chemistry on the Applied Biosystems 431 A peptide synthesizer (sec Synthesis Methods above), including deprotection of the N-terminal residue Fmoc group

AF-ιsopropylatιon by reductive alkylation

The N^α-isopropyl group was added by reductive alkylation of the peptide-resin using sodium cyanoborohydride and the corresponding ketone (acetone) as described by Hocart, et al , 1987 880 mg peptide-resin (approx 70 μmols) was swelled in 5 ml DCM for 30 mins, then 10 mmol (174 μl) acetone in 7 ml MeOH/ 1% HO Ac added and the mixture swirled intermittently for 2 hrs at ambient temperature 2 mmols (129 mg) sodium cyanoborohydride in 12 ml MeOH/1% HO Ac was then added, the mixture - swirled intermittently for 2 hrs, then allowed to sit overnight (15 hrs) Qualitative ninhydπn monitoring indicated a completed reaction (no blue color) The peptide-resin was cleaved with a mixture of TFA 1,2-ethanedithiol thioanisole water [ 10 0 5 0 5

0 5 (v/v) ] for 2 hrs, and the peptide isolated by precipitation in MTBE to give approx

200 mg of crude peptide Purification by preparative reverse-phase gradient HPLC with

Water/ Acetonitrile/ 0 1 % TFA solvents on a Vydac C 18 column (22 x 250 mm) resulted in 50 mg of pure product (>95% by analytical HPLC) MALDI-TOF mass spec

Calculated 3481 9, Observed 3481 8

EXAMPLE 9: Pegylation Of The Protected hGRFO-29)

The hGRF derivatives prepared as described in Example 8 were conjugated with activated PEG as described in Examples 1 and 6

The purification in this case involved only a separation from excess reagents and side-products, whereas there was no need to carry out the procedure described in Example 2 and 3

References

Abuchowski A et al , J. Bwl. Chem , 252, 3571-3581, 1977a,

Abuchowski A et al , J. Bwl. Chem , 252, 3582-3586, 1977b,

Benchamp C O et al , Anal. Biochem , 131, 25-33, 1983,

Caliceti et al., J. Bioactive Compatible Polymer, 8, 41-50, 1993,

Campbell R et al J. Peptide Res , 49, 527-537, 1997,

Chan W C et al , J. Chem. Soc. Chem. Commun , p 2209, 1995,

Clark R et al , J. Biol. Chem , 36, 21969-21977, 1996,

Delgado C et al , Biotechnology and Applied Biochemistry, 12, 119-128, 1990,

F Dick et al , Peptides 1996, Proceedings of the 24th European Peptide Symposium,

Edinburgh, Scotland, 1997,

Felix A M et al , Int. J. Peptide Protein Res , 46, 253-264, 1995,

Fish et al , Genes and Development, 3, 1989, 198-21 1,

Greene T W et al , Protective Groups in Organic Synthesis, John Wiley and Sons, Inc

Pub , pp 331-333, 1991,

Habeed A S F A et al , Anal. Biochem., 14, 328-336, 1966

Harris J M , Rev. Macromol. Chem. Phys , C25, pp 325-76, 1985,

Hocart et al , J. Med. Chem., 30(4), 739-743, 1987,

Lu et al , Int. J. Peptide Protein Res 43, 1994, 127-138,

Monfardini et al , Bwcon. Chem , 6, 62-69, 1995,

Morpurgo et al , Bwcon. Chem , 7, 363-368, 1996,

Murphy, W A et al , Peptide Research, 1(1), 36, 1988,

Pande C S , et al , Proc. Natl. Acad. Sci. USA, 11, 895-899, 1980,

Sartore L et al , Appl. Biochem. Biotechnol , 27, 45, 1991,

Sartore L , et al , Applied Biochem. Biotechnol , 31, 213-22, 1991,

Sims G E C et al , Anal. Biochem., 107, 60-63, 1980,

Tam, J P et al , Strong acid deprotection of synthetic peptides In The Peptides, 9, S

Udenfriend and J Meienhofer, eds , Academic Press, NY, pp 185-248, 1987,

Veronese F M , et al , Appl. Biochem ,11, 141-152 (1985),

Yamsuki et al , Agric. Bwl. Chem., 52, 2185-2196, 1988, Zalipsky S. et al., Polymeric Drugs and Drug Delivery Systems, adrs 9-1 10 ACS

Symposium series 469, 1990; and

Zalipsky S. et la., Europ. Polym. J., 19, 1177-1183, 1983.

Claims

1 A method for the site-specific preparation of hGRF-PEG conjugates containing one or more than one PEG units (per hGRF) covalently bound to Lys¹² and/or Lys²¹ and/or N^╬▒, characterized in that the conjugation reaction between the hGRF peptide and the activated PEG is carried out in solution and the desired hGRF-PEG conjugate is isolated from the reaction mixture and purified

The method of claim 1, wherein the solution is a concentrated aqueous nicotinamide solution or a buffered aqueous solution of a defolding agent

3 The method of claim 1, wherein the solvent is a polar organic solvent selected among dimethyl sulfoxide, dimethyl formamide/buffer or acetonitrile/buffer.

4 The method of claim 1, wherein the hGRF-PEG conjugate is isolated from the reaction mixture and purified by chromatographic methods

5 The method according to any one of the preceding claims, wherein the hGRF peptide is h-GRF(l-29)-NH₂

6 The method of claim 1, wherein, before the pegylation reaction occurs, the hGRF peptide is protected at one or more of the positions N", Lys¹² and Lys²¹

7. The method of claims 1 or 6, which further comprises a de-protection reaction after pegylation

8 The method according to anyone of the preceding claims, wherein the activated PEG is an alkylating or acylating PEG in its mono-methoxylated form

9 A hGRF-PEG conjugate containing one or more than one PEG units (per hGRF) covalently bound to Lys¹² and/or Lys²¹ and/or N^╬▒ A hGRF-PEG conjugate according to claim 9, in which 1 PEG unit is covalently bound to Lys ╬╣

A hGRF-PEG conjugate according to claim 9, in which 1 PEG unit is covalently bound to Lys²¹

A hGRF-PEG conjugate according to claim 9, in which 1 PEG unit is covalently bound to each of Lys¹² and Lys²¹

A hGRF-PEG conjugate according to claim 9, in which 1 PEG unit is covalently bound to each of Lys¹² , Lys²¹ and N^╬▒

[Lys(Alloc)¹²'²¹]-hGRF, as intermediate in the pegylation reaction of claim 1

[N^╬▒-isopropyl-Tyr¹,Lys(Alloc)¹²]-hGRF, as intermediate in the pegylation reaction of claim 1

Use of the hGRF-PEG conjugates of claims 9 to 13, as a medicament

Use of the conjugates according to any of the claims from 9 to 13, in the manufacture of a medicament for treatment, prevention or diagnosis of growth-hormone related disorders

Use according to claim 17, in the manufacture of a medicament for the treatment or diagnosis of growth hormone deficiency (GHD)

A pharmaceutical composition comprising the conjugates according to any of the claims from 9 to 13 together with one or more pharmaceutically acceptable carriers and/or excipients