FUNCTIONALITY

FIELD OF THE INVENTION

The invention is in the field of recombinantly produced non-natural Gly-

Xaa-Yaa-proteins, such as non-natural gelatins, and methods of their production. In particular the invention relates to non-natural Gly-Xaa-Yaa-proteins that can be produced in high yields. These non-natural Gly-Xaa-Yaa-proteins have improved resistance to certain proteases found in commonly used expression systems. The high stability towards proteases leads to improved yields and improved uniformity of the particular non-natural Gly-Xaa-Yaa protein.

BACKGROUND OF THE INVENTION

There is an increasing interest in recombinant Gly-Xaa-Yaa-proteins, (wherein Gly is glycine and Xaa and Yaa are independently any amino acid) such as gelatins. The widespread use and possibilities for use of these Gly-Xaa-Yaa proteins in medical and clinical applications means that economically viable production processes are required. This has prompted careful consideration of process variables and variations in protein sequences that could influence expression properties, and hence yields of the desired Gly-Xaa-Yaa- proteins.

Naturally occurring Gly-Xaa-Yaa-proteins such as gelatins, which are obtained by hydrolyzing collagen derived from animal tissues, are actually mixtures of a very large number of peptides and polypeptides. The molecular weight range of these (poly)peptides depends on the tissue from which the gelatin was derived and the processing conditions.

In principle, the recombinant production of Gly-Xaa-Yaa-proteins yields products in which all the component molecules have the same length (the same number of amino acid residues), since a particular gene typically encodes a single protein (barring genes that contain introns). The coding sequence of the gene determines the length of the nascent polypeptide. Secretory proteins also typically contain a signal sequence (signal peptide, preprotein sequence) that is removed during secretion. The remaining polypeptide is then considered to be the mature polypeptide.

Gly-Xaa-Yaa-proteins are sensitive to various proteases. Thus, Gly-Xaa- Yaa-proteins that are secreted by commonly used expression hosts such as Pichia pastoris or Hansenula polymorpha are heterogeneous in size due to (partial) digestion by intracellular and extracellular proteases.

In a strict interpretation only the mature full length polypeptide is considered to be the product. However in the field of repetitive biopolymers often both the mature polypeptide and its proteolytic fragments as considered the final product.

In the first interpretation, proteolysis can lead to a significant reduction in the yield of the product and the degradation products may pose a significant problem during purification of the mature protein (because of the similarity between the mature protein and its degradation products). The product in the sense of the second interpretation has some similarity to animal-derived gelatins: a product that comprises polypeptides with various lengths. However, the heterogeneity of this product can be disadvantageous in some applications.

Therefore, prevention of proteolysis will benefit both the yield and the quality of the product. Proteolysis can be avoided by inactivation of particular protease genes or by excluding target sites for these proteases in the product. Examples of both approaches can be found in the literature. EP926543 and Werten et al. 1999 (Yeast 15, 1087-1096) describe a production method of Gly- Xaa-Yaa proteins using the methylotrophic yeast Pichia pastoris, where the Gly- Xaa-Yaa proteins corresponding to fragments of the helical domains (consisting of Gly-Xaa-Yaa triplet repeats) of mouse type I collagen (encoding a 21 kDa and 28 kDa, calculated MW, COL1 A1 peptide and a 53 kDa COL1A2) and rat type III collagen (COL3A1 ) are produced. A factor such as the fermentation pH was in certain cases found to influence the stability of the expressed product. The presence in the expressed sequence of target sites for certain proteases was also thought to be relevant.

In US 2006/0241032 XRGD-enriched gelatin-like proteins with a minimum (increased) level of XRGD motifs and with a certain distribution of said XRGD motifs are disclosed that were found to be highly suitable for cell adhesion and cell binding in medical and biotechnological applications. The cell binding peptides described therein have good cell attachment properties. However, susceptibility to degradation has been a limiting factor in the ability to produce large amounts of specific Gly-Xaa-Yaa-proteins. In EP21 12997 XRGD-enriched gelatin proteins are disclosed that have an improved stability. This was achieved through avoidance of the use of particular amino acid residues (Asp, Pro, Hyp) as the X in the XRGD motifs in the sequence. However further improvement of the stability of recombinantly produced gelatin-like Gly-Xaa-Yaa proteins is desired.

The proteases in most expression systems are not known. Even less information is available on the targets of these proteases and their substrate specificity. Therefore, in most cases, sequences that are resistant to proteolytic attack must be determined empirically. In the current patent application we disclose new Gly-Xaa-Yaa-proteins that can be produced with improved yields and quality by the exclusion of proteolytic target sites that have not been previously identified SUMMARY OF THE INVENTION

The present invention provides a non-natural Gly-Xaa-Yaa-protein having a molecular weight of at least 5 kDa, wherein at least 80% of the amino acids are present as Gly-Xaa-Yaa-triplets, wherein Gly is glycine and Xaa and Yaa are, independently, any amino acid, wherein said protein lacks the sequences GLA and GAA and has a calculated iso-electric point of at least 7.

Preferably the non-natural proteins essentially entirely consist of Gly-Xaa- Yaa-triplets. The sequences of these non-natural proteins are similar to naturally occurring gelatin which has a glycine residue as every third amino acid and a relatively large proportion of proline residues in the Xaa and Yaa positions, particularly in the Yaa position. The present inventors surprisingly found, that the proteins according to the present invention are secreted by microorganisms in high yields with low levels of accompanying proteolytic degradation products.

It is advantageous, for various end-use applications, to include an RGD motif in the non-natural Gly-Xaa-Yaa-proteins. The non-natural Gly-Xaa-Yaa- proteins according to the current invention are therefore preferably enriched in RGD sequences. Thus, in one embodiment the non-natural Gly-Xaa-Yaa-proteins comprise one or more RGD motifs. A definition of RGD-enriched is given below, however it is, for example, preferred for a gelatin with a length of about 300 amino acids, to comprise at least 2 RGD motifs, more preferably at least 3 RGD and especially at least 4 or more RGD motifs.

The inventors have surprisingly found that the recombinant non-natural Gly-Xaa-Yaa proteins of the present invention are more stable during recombinant production in certain microorganism and during the subsequent isolation and purification procedures. This results in a higher yield of the desired molecular species of the gelatin polypeptides with fewer accompanying fragments.

It has also been found that this monodispersity is further improved in non- natural Gly-Xaa-Yaa-proteins that have a calculated iso-electric point of at least 7, preferably at least 8, more preferably at least 9, and especially 10 or greater.

Preferably the non-natural Gly-Xaa-Yaa-proteins according to the present invention also have a low aspartic acid residue content apart from those residues which are present in the RGD motifs. Preferably the number percent of aspartic acid residues, apart from those residues which are present in the RGD motifs, is below 1.

It is also preferred that one or more RGD sequences in the recombinant non-natural Gly-Xaa-Yaa-proteins are not preceded by a proline (P) or hydroxyproline (O).

In one embodiment of the invention a non-natural Gly-Xaa-Yaa-protein is provided, comprising at least one XRGD motif per 5 kDa molecular weight of sequence, wherein X is any amino acid with the exception of D (Asp) and P (Pro) or O (hydroxyproline).

Preferably, X is selected from the group consisting of Y, W, F, C, M, K, L, I, R, H, V, A, G, N and E, especially E. Preferably each 5 kDa part of the non- natural Gly-Xaa-Yaa-protein comprises at least two XRGD motifs.

A high and stable expression level of non-natural Gly-Xaa-Yaa-protein sequences (and variants thereof and fragments of any of these) can be obtained in genetically engineered micro organisms. In selected micro organisms these proteins are secreted in high yields. Especially suitable microorganisms are methylotrophic yeasts, which are modified by the engineered nucleic acid sequences (DNA or RNA). These modified yeasts allow large scale fermentations for producing the artificial RGD comprising non-natural Gly-Xaa-Yaa-protein at high yields. GENERAL DEFINITIONS

The non-natural Gly-Xaa-Yaa-proteins are polypeptides that comprise segments with consecutive Gly-Xaa-Yaa-triplets, where Gly is a glycine residue and Xaa and Yaa are independently any amino acid residue. The non-natural Gly-Xaa-Yaa-proteins can comprise components of sequences that can be found in nature. Gelatins constitute a well known class of Gly-Xaa-Yaa-proteins that are derived from animals, however, Gly-Xaa-Yaa-proteins can also be found in prokaryotes.

Whereas often the terms 'collagen', 'collagen-related', 'collagen-derived' or the like are also used in the art, the term 'gelatin' or 'gelatin-like' protein will be used throughout the rest of this description. Natural gelatin is a mixture of individual polymers with MW's ranging from 5,000 up to more than 400,000 daltons.

The terms "cell adhesion" and "cell attachment" are used interchangeably. The terms "RGD sequence" and "RGD motif and "Arg-Gly-Asp" are used interchangeably. The term "RGD-enriched" refers herein to amino acid sequences comprising at least one RGD motif. The term "RGD-enriched" in the context of this invention means that a certain level of RGD motifs, calculated as a percentage of the total number of amino acids per molecule is present and that there is a certain, more or less, even distribution of RGD sequences in the amino acid sequence. The level of RGD sequences can be expressed as a percentage. This percentage is calculated by dividing the number of RGD motifs by the total number of amino acids and multiplying the result with 100. Also, the number of RGD motifs is an integer starting from 1 , 2, 3, ... etc.

In particular "RGD-enriched" refers herein to amino acid sequences wherein the percentage of RGD motifs related to the total number of amino acids is at least 0.4 and if the amino acid sequence comprises 250 amino acids or more, each stretch of 250 amino acids contains at least one RGD motif. Preferably the percentage of RGD motifs is at least 0.6, more preferably at least 0.8, more preferably at least 1 .0, more preferably at least 1 .2, more preferably at least 1 .5 and most preferably at least 1 .8. Preferably "RGD-enriched" refers to polypeptides having at least one RGD sequence per 5 kDa of molecular weight. In the context of the present invention the molecular weight refers to the calculated molecular weight, in particular of the primary amino acid sequence, thus not taking into account possibly post-translational modifications of the particular host-micro-organisms wherein the present polypeptides were recombinantly produced. It is noted that of the preferred micro-organisms herein indicated, in particular yeasts, it is assumed no post-translational modifications of the Gly-Xaa-Yaa proteins occur. It is preferred that the present non-natural Gly- Xaa-Yaa proteins do not contain a part of 5 kDa without an RGD sequence.

A percentage of RGD motifs of more than at least 0.4 corresponds with more than at least 1 RGD sequence per 250 amino acids. The number of RGD motifs is an integer, thus to meet the feature of 0.4%, an amino acid sequence consisting of 251 amino acids should comprise at least 2 RGD sequences. Preferably the RGD-enriched GXY-proteins of the invention comprise at least 2 RGD sequences per 250 amino acids, more preferably at least 3 RGD sequences per 250 amino acids, most preferably at least 4 RGD sequences per 250 amino acids. In a further embodiment an RGD-enriched gelatin-like protein according to the invention comprises at least 4 RGD motifs per calculated molecular weight of 30 kD, preferably at least 6 RGD motifs per 30 kD.

"A relatively large proportion of proline residues in the Xaa and Yaa position" means that at least one third of the Gly-Xaa-Yaa triplets contains a proline residue.

A "fragment" is a part of a longer nucleic acid or polypeptide molecule. "Native" or "natural" collagens or collagenous domains refer to those nucleic acid or amino acid sequences found in nature, e.g. in humans or other mammals.

"A non-natural polypeptide or protein" according to the present invention may have a certain degree of homology with polypeptide sequences of the same length which are part of natural molecules such as collagen. The recombinant non-natural Gly-Xaa-Yaa proteins as such however do not occur in nature.

The terms "protein" or "polypeptide" or "peptide" are used interchangeably and refer to molecules consisting of a chain of amino acids, without reference to a specific mode of action, size, 3-dimensional structure or origin. An isolated protein is a protein not found in its natural environment, such as a protein purified from a culture medium. The term "support" or "cell attachment support" refers herein to any support which can be used to facilitate cell attachment and/or growth, such as culture dishes, microcarriers (e.g. microcarrier beads), stents, implants, plasters, etc.

The term "substantially identical", "substantial identity" or "essentially similar" or "essential similarity" means that two polypeptide, when aligned pairwise using the Smith-Waterman algorithm with default parameters, comprise at least 60%, 70%, 80% more preferably at least 85%, 90%, 95%, 96% or 97%, and particularly at least 98%, 99% or more amino acid sequence identity. Sequence alignments and scores for percentage sequence identity may be determined using computer programs, such as the GCG Wisconsin Package, Version 10.3, available from Accelrys Inc., 9685 Scranton Road, San Diego, CA 92121 -3752, USA or using in EmbossWIN (e.g. version 2.10.0). For comparing sequence identity between two sequences, it is preferred that local alignment algorithms are used, such as the Smith Waterman algorithm (Smith TF, Waterman MS (1981 ) J. Mol. Biol 147(1 ); 195-7), used e.g. in the EmbossWIN program "water". Default parameters are gap opening penalty 10.0 and gap extension penalty 0.5, using the Blosum62 substitution matrix for proteins (Henikoff & Henikoff, 1992, PNAS 89, 915-919).

The term "comprising" is to be interpreted as specifying the presence of the stated parts, steps or components, but does not exclude the presence of one or more additional parts, steps or components.

In addition, reference to an element by the indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

"Monomer" refers to a polypeptide unit (or nucleic acid sequence encoding it) which can be used to generate a "multimer" (or "polymer", which is used interchangeably) by repeating the unit in a linear fashion to generate a longer polypeptide. The monomer units are preferably repeated without intervening amino acids, although optionally 1 , 2, 3, 4, 5 or more linking amino acids may be present between monomer units.

The term "improved stability" means that a protein is not hydrolysed or is hydrolysed to a lesser extent, preferably by at least 10% or higher, under usual culture conditions of the yeast expression host and usual conditions under which the proteins are isolated compared to the corresponding sequences derived from natural occurring structures.

"Free of triple helix" structure refers to essentially the absence of the positive peak characteristic of the collagen triple helix in a circular dichroism spectrum. Circular dichroism spectrometry can be carried out as described in Werten et al. (2001 , Protein Engineering 14:447-454).

DETAILED DESCRIPTION OF THE INVENTION

It was found, surprisingly, that it is possible to obtain high yields of improved, highly stable peptides or polypeptides. This is of great benefit to render the production process of Gly-Xaa-Yaa-proteins economically viable. The instant invention thus concerns non-natural Gly-Xaa-Yaa-proteins. The stability of the present proteins is beneficial for applications where gelatin has been used, in particular for applications that rely on the integrity of the gelatin/Gly-Xaa-Yaa- proteins. The polypeptides also do not display any health related risks, as they have a low antigenicity meaning that these polypeptides can be used with minimal risk of transferring pathological factors such as viruses, prions and the like. The present invention is directed to peptides, polypeptides or proteins, in particular to gelatins or gelatin-like proteins, which are highly suitable to be used in clinical, medical and/or biotechnological applications. For example the use as a plasma expander whereby intact molecules are kept in circulation is of interest and an application for which the present proteins are advantageously suited. Also, in particular, their uses in haemostats, dermal fillers and cell adhesion are areas of interest. In one embodiment the invention is directed to cell binding peptides or polypeptides that have improved properties compared to known Gly-Xaa-Yaa- RGD-comprising polypeptides, such as those described in US 2006/0241032, in particular the sequence designated as SEQ ID NO: 2 therein.

Although the non-natural proteins of the present invention are different from naturally occurring sequences they can display some homology to collagen. Thus, it is possible, that the non-natural protein sequence can exhibit more than 50% homology with a native collagen amino acid sequence. The majority of triads of amino acids in the Gly-Xaa-Yaa-proteins, preferably at least 80%, should have the sequence Gly-Xaa-Yaa, but an occasional deviating triad such as A-XaaYaa (A = alanine) does not alter the required properties. A substantial number of Gly- Xaa-Yaa-triplets should have the sequence Gly-Xaa-P or Gly-P-Yaa (wherein P is proline), Preferably more than half of the Gly-Xaa-Yaa triplets contains a proline residue. Preferably cysteine is avoided.

According to the invention recombinant gelatins are provided with excellent cell attachment properties and which demonstrate advantages such as improved stability, improved cell attachment and tissue support properties

In one embodiment the non-natural Gly-Xaa-Yaa-protein has at least 60% sequence identity to SEQ ID NO:1 . This sequence is also referred to herein as ICP-monomer. In one embodiment the non-natural Gly-Xaa-Yaa-protein can also be defined as a protein comprising or consisting of an amino acid sequence having at least 70%, preferably at least 80%, and more preferably at least 90% or more amino acid sequence identity to SEQ ID NO: 1 or to a fragment thereof, more preferably at least 92%, 95%, 96%, 98%, 99% sequence identity or more. "Fragments" are parts of less than 000 amino acids, such as 800, 600, 500, 300, 250, 200, 100, 50, 30 or less consecutive amino acids, but preferably at least 10, 1 5 or 20 amino acids.

In one embodiment the present invention provides non-natural recombinantly produced Gly-Xaa-Yaa-proteins which have a molecular weight of at least 5 kDa and which comprise at least one RGD sequence per 5 kDa of molecular weight. Preferably the non-natural Gly-Xaa-Yaa-protein has a calculated molecular weight of at least 15 kDa, preferably at least 20 kDa and more preferably at least 25 kDa.

Preferably each part of the non-natural Gly-Xaa-Yaa-protein of 5 kDa comprises at least one RGD sequence. Preferably the molecular weight is less than 200 kDa, more preferably less than 150 kDa. Such non-natural Gly-Xaa- Yaa-proteins were found to have an even further improved stability.

In order to obtain the present non-natural proteins, for example, nucleic acid sequences encoding natural gelatin sequences may be modified by site directed mutagenesis to give sequences having RGD motifs as defined herein. Of course it is also possible to simply design amino acid sequences comprising consecutive Gly-Xaa-Yaa-motifs, such as at least 5, 10, 1 5, 20, 30, 50, 100, 200, 300 or more consecutive Gly-Xaa-Yaa-motifs, whereby at least one, but preferably more RGD motifs are included in the sequence. Such designed polypeptides can be made by making nucleic acid sequences encoding these (using routine molecular biology techniques) and expressing these in a recombinant host cell. Preferably the spacing of the RGD-motifs is such that at least about 0, 10, 1 5, 20, 25, 30 or more intervening amino acids are present. When several RGD-motifs are present in the sequence, these can be spaced regularly or irregularly, depending on the application under consideration.

Preferably, the XRGD-motifs are part of the Gly-Xaa-Yaa-motifs, i.e. the sequence of Gly-Xaa-Yaa-triplets is not disrupted by the RGD-motif(s). For example in a sequence - GlyXaaYaa-GlyXaaYaa-GlyXaaR-GDYaa-GlyXaaYaa- GlyXaaYaa- the RGD-motif does not disrupt the consecutive Gly-Xaa-Yaa triplets.

Its also preferred that there is at least one XRGD motif (with X not being D or P or O) present in the non-natural Gly-Xaa-Yaa-protein. More preferably, more than 2 XRGD-motifs may be present in the non-natural Gly-Xaa-Yaa-protein, such as 3, 4, 5, 6 or more, wherein X is again any amino acid, except D, P or O. In a further embodiment the invention relates to non-natural Gly-Xaa-Yaa- proteins which are not glycosylated. Glycosylation should be preferably prevented for applications where no immune response is desired. In a preferred embodiment, the non-natural non-natural Gly-Xaa-Yaa-proteins according to the invention are free of serine (Ser, S) and threonine (Thr, T) residues. It is believed that the absence of serine and threonine in the amino acid sequence may be an effective way to prevent the glycosylation in biotechnological production systems using, for instance, yeast cell cultures.

The non-natural Gly-Xaa-Yaa-protein monomer may comprise additional amino acids at one or both ends, e.g at the N- and/or C-terminal. For example, 1 , 2, 3, 6, 9, 12, 15 or more amino acids may be present. These may be in the form of Gly-Xaa-Yaa-triplets. Additional amino acids at the termini, in particular the C- terminus, enhance the stability of the non-natural Gly-Xaa-Yaa-proteins, for example by preventing C-terminal degradation such as one by one cleavage of amino acids. Also additional amino acids at the termini facilitate multimer construction, the multimeric non-natural Gly-Xaa-Yaa-protein polypeptide may comprise N-terminal and C-terminal amino acids that are not part of the repeating amino acid sequence. In one embodiment the non-natural Gly-Xaa-Yaa-proteins according to the present invention, are preceded by a glycine-proline-proline (GPP) triplet and extended with two glycine residues (GG) at the carboxy- terminus.

The above described non-natural Gly-Xaa-Yaa-proteins according to this invention have a good stability to enzymatic and/or chemical proteolysis breakdown.

Preferably, with the non-natural Gly-Xaa-Yaa-proteins according to the present invention, no or reduced degradation or cleavage products, i.e. polypeptides of a smaller size than that of the encoded (full length) non-natural Gly-Xaa-Yaa-protein, are seen in/after a stability assay, e.g. on SDS-PAGE gels or by other methods such as LC-MS. Stability can for example be tested after the polypeptide is secreted into the culture medium of the yeast host, whereby the polypeptide is stable if substantially all (at least 95%, preferably at least 98%, 99% or most preferably 100%) of the recombinant polypeptide is full size. Stability to enzymatic or chemical hydrolysis can also be tested by incubating the polypeptide with one or more proteolytic enzymes or hydrolytic chemicals and by analyzing the resulting molecular weight after a specified period of treatment.

For example, when the molecular weight of recombinant natural gelatins and gelatins according to the invention produced in the same yeast host is compared after fermentation, the non-natural Gly-Xaa-Yaa-protein according to the invention is less degraded than the natural gelatin produced under the same conditions and in the same way. Degradation can also be quantified, e.g. by analyzing band intensities on SDS-PAGE gels loaded with the same amount of sample. See e.g. Werten et al. 1999 (supra).

Genes for non-natural Gly-Xaa-Yaa -proteins of the present invention can be derived from genes that encode natural collageneous sequences, with further modification to fulfill the amino acid sequence criteria described elsewhere herein. Alternatively, the genes for non-natural Gly-Xaa-Yaa proteins of the present invention can be synthesized de-novo. Gene synthesis is offered by various companies. Glv-Xaa-Yaa-protein multimers

In a further embodiment multimers of the monomers described above are provided. Thus, the present invention encompasses a non-natural Gly-Xaa-Yaa- protein comprising or consisting of at least two repeats of the non-natural Gly- Xaa-Yaa-proteins as described above. Such multimers thus comprise or consist of at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 repeats of the monomer sequence. Thus, a non-natural Gly-Xaa-Yaa-protein polypeptide is provided comprising or consisting of a multimer of a monomer sequence described above. Preferably, the monomer repeats are repeats of the same monomer unit sequence (repeats are identical in amino acid sequences), although optionally also combinations of different monomer units (having different amino acid sequences, each falling under the criteria above) may be used.

Preferably the monomer units are not separated by spacing amino acids, although short linking amino acids, such as 1 , 2, 3, 4 or 5 amino acids, may be inserted between one or more of the monomers. Preferably there are less than 7 intervening amino acids between the monomer repeat units more preferably less than 3 amino acids.

In one embodiment the multimers comprise or consist of at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 repeats of a monomer as described above. In one embodiment the multimers comprise or consist of at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 repeats of a sequence having at least 60%, preferably at least 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or more amino acid sequence identity or is substantially identical to SEQ ID NO: 1 or a fragment thereof (wherein the sequence similarity is determined as outlined above). Thus, non-natural Gly-Xaa-Yaa proteins include (SEQ ID NO: 1 ) _n wherein n is an integer selected of 1 and higher, preferably n is 1 to 10 or more. Two repeats of the ICP monomer results in the dimer (SEQ ID NO: 2); four repeats of the ICP monomer results in the tetramer (SEQ ID NO: 3).

In one embodiment the multimer non-natural Gly-Xaa-Yaa-proteins according to the present invention, are preceded by a glycine-proline-proline (GPP) triplet and extended with two glycine residues (GG) at the carboxy- terminus. Thus, non-natural Gly-Xaa-Yaa -proteins according to the present invention include GPP((SEQ ID NO: 1 )) _n GG wherein n is an integer selected of 1 and higher, preferably n is 1 to10 or more. For n = 1 a gelatin according to the present invention called ICP (SEQ ID NO: 4) is obtained. In the above formula for n = 2 the sequence ICP2 (SEQ ID NO: 5) is obtained; in above formula n = 3 results in the sequence ICP3 (SEQ ID NO: 6); in above formula for n = 4 the sequence ICP4 (SEQ ID NO: 7) is obtained.

Such multimers can be generated using known standard molecular biology methods.

Material and compositions comprising the monomers and/or multimers

The present invention is directed to peptides, polypeptides or proteins, in particular to non-natural Gly-Xaa-Yaa-proteins, which are suitable for cell adhesion and can be used in medical or biotechnological applications.

It was found that non-natural Gly-Xaa-Yaa-proteins according to the present invention are very suitable for coating cell culture supports which can be used in biotechnological processes or in medical applications.

RGD sequences in gelatins can adhere to specific receptors on the cell wall called integrins. These integrins differ in their specificity in recognising cell binding amino acid sequences. Although both natural gelatin and, for example, fibronectin may contain RGD sequences, gelatin can bind cells that will not bind to fibronectin and vice versa. Therefore fibronectin comprising RGD sequences cannot always replace gelatin for cell adhesion purposes.

Recombinantly produced gelatin does not suffer from the disadvantage of animal-derived gelatin, e.g. potential contamination with pathogens originating from the animal from which the gelatin was derived.

When used as, or in combination with, a cell culture support, the gelatinlike polypeptides according to the invention function as a cell binding polypeptide. It has the advantage over other polypeptides that it can also be metabolised by the cells growing on it.

A further advantage of recombinantly produced gelatins is that their molecular weight (MW) can be kept uniform. Natural gelatins, in particular gelatins isolated form natural sources, unavoidably have a broad molecular weight distribution with peptides smaller than 5 kDa up to large polymers with a molecular weight larger than 400 kDa. In particular in combination with microcarrier core beads as cell culture support, a disadvantage of smaller peptides is that they will adhere inside finer pores of the microcarrier which cannot be reached by the cells so that part of the added gelatin is not used. With recombinant production methods the gelatin can be designed with the desired molecular weight, preventing this undesirable effect. A cell support comprising a non-natural Gly-Xaa-Yaa -protein according to the invention is provided. Such a cell support may be selected from the group consisting of

1 ) a cell-culture support, such as a core bead (e.g. a microcarrier bead) or a Petri dish or the like, coated with a coating comprising one or more non-natural

Gly-Xaa-Yaa-proteins according to the invention;

2) an implant or transplant device (such as hip-, dental-, or other implants, stents, etc.) coated with a coating comprising one or more of the non-natural Gly- Xaa-Yaa-proteins according to the invention,

3) a scaffold or matrix for tissue engineering, such as artificial skin matrix material, coated with a coating comprising one or more non-natural Gly-Xaa-Yaa- proteins according to the invention;

4) a wound healing product coated with a coating comprising one or more non- natural Gly-Xaa-Yaa-proteins according to the invention;

5) a tissue adhesive comprising or consisting of one or more non-natural non- natural Gly-Xaa-Yaa-proteins according to the invention;

Preferably the cell support is selected from the group consisting of a non- natural Gly-Xaa-Yaa-protein coated implant or transplant material, a non-natural Gly-Xaa-Yaa-protein coated scaffold for tissue engineering, (part of) a dental product, (part of) a wound healing product, (part of) artificial skin matrix material and (part of) a tissue adhesive.

In one embodiment the cell supports provided herein preferably comprise only one non-natural Gly-Xaa-Yaa-protein according to the invention. The product is thus uniform in amino acid sequence, molecular weight, etc. Optionally the peptides may be cross-linked by, for example, chemical cross-linking.

In a different embodiment mixtures of polypeptides according to the invention may be used, such as 2, 3, 4, 5, or more different amino acid sequences according to the invention. The ratios of mixtures may vary, such as 1 :1 , or 10:1 , 50:1 , 100:1 , 1 :100, 1 :50, 1 :10, and ratios in between. Optionally these mixtures of proteins, or parts thereof, may also be crosslinked.

When using the non-natural Gly-Xaa-Yaa -protein monomer(s) and/or multimers for coating porous microcarrier beads, preferably polypeptides with a molecular weight of at least about 30 kDa are used, more preferably at least about, 40 kDa, especially at least about 50 kDa, more especially at least about 60 kDa and particularly at least about 70 kDa or more. The reason for this is that smaller polypeptides may enter the pores on the beads, thereby not contributing to the cell attachment properties of the coated beads. Thus, the coating process may be inefficient, especially if low concentrations of protein are used to coat the beads. Preferably the molecular weight of the non-natural Gly-Xaa-Yaa or gelatinlike protein used is uniform, with more than 75%, preferably more than 85%, more preferably more than 95% and especially at least 98% of the protein having a uniform MW within 20% from the selected molecular weight.

By selecting a molecular weight, within the above specified range, in a coating process the viscosity of the non-natural Gly-Xaa-Yaa or gelatin-like protein coating solution can be accurately controlled. Complete or, more important, partial gelling of such a gelatin solution can be prevented while being able to select a high as possible concentration of the gelatin. The uniform gelatin ensures a process of identically coated microcarriers. The uniform coating process allows the use of a minimum amount of gelatin and the use of a minimum volume of gelatin coating solution. This results in a more efficient coating process than those known in the art.

In one embodiment of the invention non-porous core beads are coated with gelatin of the invention. Suitably non-porous core beads are made of polystyrene or glass. Other suitable non-porous materials are known to those skilled in the art.

A particular advantageous embodiment of the invention is a process wherein porous core beads, such as beads from modified dextran or cross-linked cellulose, or (porous) polystyrene, in particular DEAE-dextran, are coated with the non-natural Gly-Xaa-Yaa-protein of the invention. Other suitable porous materials are known to those skilled in the art, and include, for example, other chemically modified or non-modified polysaccharides.

The size of the beads may vary from 50μιη to 500μηΊ. Typical mean microcarrier bead sizes are about Ι ΟΌμιη, about 150μιη or about 200μιη in physiological saline. Size ranges with at least 90% of the beads lying within the range may vary from 80 to120 μηι, 100 to 150 μητι, 125 to175 μιτι or 150 to 200 μΠΊ.

A wide range of cells may be cultured on microcarriers. For instance, cells from invertebrates, from fish, birds and cells of mammalian origin may all be cultivated. Transformed and normal cell lines, fibroblastic and epithelial cells and even genetically engineered cells may also be cultivated on microcarriers for various biological applications such as for the production of immunologicals like interferons, interleukins, growth factors etc. Cells cultured on microcarriers also serve as hosts for a variety of viruses that are used as vaccines like foot and mouth disease or rabies.

Microcarrier cultures have a wide number of applications other than mass cultivation. Cells growing on microcarriers serve as an excellent tool for studying different aspects of cell biology such as cell-to-cell or cell-to-substratum interactions. Cell differentiation and maturation, metabolic studies may also be carried out using microcarriers. Such cells can also be used for electron microscopic studies or for the isolation of cell organelles such as the cell membrane. Also, this system is essentially a three-dimensional system and serves as a good 3-D model. Similarly, co-cultivation of cells can be done using this system. Thus applications include the production of large quantities of cells, viruses and cell products (e.g. interferon, enzymes, nucleic acids, hormones), studies on cell adhesion, differentiation and cell function, perfusion column culture systems, microscopy studies, harvesting mitotic cells, isolation of cells, membrane studies, storage and transport of cells, assays involving cell transfer and studies on uptake of labeled compounds.

Microcarriers may also be used for the depletion of macrophages from a population of spleen cells. DEAE-dextran microcarriers coated with the recombinant non-natural Gly-Xaa-Yaa proteins of this invention can potentiate stimulation of lymphocytes by concanavalin A (con A). Microcarrier beads confluent with allogenic tumour cells can be injected in mice to increase humoral and cell-mediated immunity. Plant protoplasts can be immobilised on DEAE- dextran microcarriers coated with the non-natural Gly-Xaa-Yaa -proteins of this invention.

As a result of the large surface area to volume ratio provided by microcarriers, they can successfully be used for a variety of biological productions on a laboratory scale as well as an industrial scale of for instance even 4000 litres or more.

Large scale production of expressed products can be accomplished with gelatin-coated microcarriers. Loading of microcarriers in production scale bioreactors is generally 20g/l, but may be increased up to 40g/l. Microcarriers may be used in batch and perfusion systems, in stirred cultures, and wave bioreactors, as well as to increase the surface area of traditional stationary monolayers and roller cultures.

In a further preferred embodiment the non-natural Gly-Xaa-Yaa-protein is in essence free of hydroxyproline residues. Hydroxylation of proline is a requirement for the formation of triple helices in collagen and plays a role in gelation of gelatin. In particular less than 10%, preferable less than 5% more preferably less than 3% and especially less than 1 % of the amino acid residues of the non-natural Gly-Xaa-Yaa-proteins are hydroxyprolines. Most preferably the protein is free from hydroxyprolines. In applications where the gelling capability of the non-natural Gly-Xaa-Yaa-protein is unfavorable the hydroxyproline-free proteins can be used in higher concentrations, and the solutions will be less viscous requiring less vigorous agitation, resulting in less shear forces on the cultured cells. As described in WO 02/070000 A1 , non-natural Gly-Xaa-Yaa- proteins which are in essence free from hydroxyprolines do not show immune reactions involving IgE in contrast to natural gelatin. Absence of hydroxyprolines can for example be achieved by expression in Pichia hosts, such as Pichia pastoris, which has not been transformed or does not comprise a functional prolyl- 4-hydroxlase enzyme.

The amount of hydroxyprolines can be determined by any standard amino acid analysis method like, for example, described in HP AminoQuant Series II, operators handbook, 1990, Hewlett-Packard GmbH, Federal Republic of Germany, Waldbronn Analytical Division, HP Part No. 01090-90025.

In one embodiment the present non-natural Gly-Xaa-Yaa-proteins are free of triple helix structure.

In a further embodiment the invention relates to the use of non-natural Gly- Xaa-Yaa-proteins according to the invention to block surface receptors on cells and to make compositions for blocking such receptors. Blocking of receptors of cells is applied in for example inhibiting angiogenesis or in blocking integrins on cardiac fibroblasts.

Cell supports coated with non-natural Gly-Xaa-Yaa-protein according to the invention, on which cells have been grown can be applied during, for example, transplantation of skin or wound treatment or to enhance bone or cartilage (re)growth. It is also possible to coat implant materials with non-natural Gly-Xaa- Yaa -proteins of the invention to adhere cells and so promote implantation.

In one embodiment the present inventions concerns a composition comprising a non-natural Gly-Xaa-Yaa-protein according to the present invention. The composition may be a pharmaceutical composition or a nutritional- or nutraceutical composition. For example the present non-natural Gly-Xaa-Yaa- proteins, in particular the multimers, can be used as a plasma expander in blood substitute liquids.

In yet another embodiment of the invention a controlled release composition comprising a non-natural Gly-Xaa-Yaa-protein is provided. The composition may, thus further comprise one or more drugs. Controlled release formulations can be made as known in the art, for example by using the non- natural Gly-Xaa-Yaa-proteins or compositions comprising these as a coating layer surrounding one or more drugs or for making a matrix in which the drug is enclosed or incorporated. The controlled release composition can be administered by injection (subcutaneous, intravenous or intramuscular) or orally or via inhalation. The controlled release composition can also be implanted via surgery. Yet another suitable route of administering is via an external wound dressing or even transdermally.

The controlled release composition preferably comprises the non-natural Gly-Xaa-Yaa-protein in a cross-linked form, e.g. chemically crosslinked. The invention further provides use of a controlled release composition as described herein for use in the treatment of pain, cancer therapy, cardiovascular diseases, myocardial repair, angiogenesis, bone repair and regeneration, wound treatment, neural stimulation/therapy and diabetics.

Another embodiment of the invention provides a hemostat composition comprising a non-natural Gly-Xaa-Yaa-protein as described above. For use as a hemostat the non-natural Gly-Xaa-Yaa-protein of this invention is preferably transferred into a sponge like material using techniques known in the art. The sponge can be impregnated with suitable anti bleeding compounds. Furthermore the non-natural Gly-Xaa-Yaa-protein sponge can be combined with other sponge like material or the sponge can be made by evaporation of an aqueous solution of the non-natural Gly-Xaa-Yaa-protein of this invention in which the solution can comprise other components to improve sponge properties, like adhesion to the wound, blood take up capacity and the like. Suitable compounds to combine with the recombinant non-natural Gly-Xaa-Yaa-protein of this invention are for example chitosan or oxidized regenerated cellulose (ORC). Optionally the non-natural Gly- Xaa-Yaa-protein of this invention is crosslinked to some extent during or after the sponge formation.

Crosslinking of the non-natural Gly-Xaa-Yaa-protein may be done by any method known in the art. One example is to add a cross-linking agent to the solution of the non-natural Gly-Xaa-Yaa -protein of this invention in water, after which the water is evaporated. The cross-linking agent can also be added after the sponge material is formed by impregnating the sponge with the cross-linking material and evaporating the sponge to dryness. Suitable cross-linking agents are, for example, aldehydes, like glutaraldehyde or a carbodiimide.

The are many medical uses for the sponge according to the invention. The sponge not only can be used for stopping bleeding in very large hemorrhaging areas with a high blood pressure, but also for stopping oozing bleeding. The following internal or external surgical procedures are successfully carried out using the hemostatic sponge according to the invention: general surgery, for instance surgery of parenchymatous organs (liver, kidney, spleen, etc.), cardiovascular surgery, thoracic surgery, transplantation surgery, orthopedic surgery, bone surgery, plastic surgery, ear, nose and throat surgery, neurosurgery, surgery in urology and gynecology as well as haemostasis, such as in wound treatment.

Another embodiment provides a dermal filler comprising the non-natural

Gly-Xaa-Yaa-protein as described above. In this application, the non-natural Gly- Xaa-Yaa-proteins are first dissolved in water and than precipitated from the water solution by adding a less hydrophilic solvent like, for example, acetone. During the preparation a cross-linking agent may be present like for example glutaraldehyde, which crosslinks two lysine residues. Another well known biocompatible crosslinker is 1 -ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC).

These cross-linkers or combination of cross-linkers can comprise agents that start cross-linking spontaneously upon addition to polypeptide solution, or after adjusting for example, pH, or by photo-initiation or other activation mechanisms.

Suitable cross-linking agents are preferably those that do not elicit toxic or antigenic effects when released during biodegradation. Suitable cross-linking agents are, for example, one or more of glutaraldehyde, water-soluble carbodiimides, bisepoxy compounds, formalin, 1 -ethyl-3-(3-dimethylaminopropyl) carbodiimide, N-hydroxy-succinimide, glycidyl ethers such as alkylene glycol diglycidyl ethers or polyglycerol polyglycidyl ether. Very small particles can be obtained (an average size of from 1 to 500 micron).

These small particles are suitable as injectable tissue fillers or for tissue augmentation or cosmetic surgery. For such applications the average particle size is preferably more than or equal to 100 micron. Average particle sizes in the range of from 150 to 500 are also preferred. Other suitable average particle sizes are 220, 250, 300, 350, 400 and 450 micron. Particles suitable as tissue fillers or augmentors should be deformable so that no lump formation occurs, but a natural impression is obtained after injection of the particles.

The invention also provides a non-natural Gly-Xaa-Yaa-protein as described above for use in the inhibition of cancer metastasis and for the prevention of platelet aggregation or for use after surgery to prevent tissue adhesion.

The non-natural Gly-Xaa-Yaa-proteins according to the invention can be produced by recombinant methods as disclosed in EP-A-0926543, EP-A- 014176 or WO01/34646. Also for enablement of the production and purification of the proteins of the invention reference is made to the examples in EP-A-0926543 and EP-A-1014176 which are herein incorporated by reference.

Thus, the non-natural Gly-Xaa-Yaa-proteins can be produced by expression of a nucleic acid sequence encoding the polypeptide by a suitable micro-organism. Fungal and yeast cells are preferred to bacteria as they are less susceptible to improper expression of repetitive sequences. The process can optimally be carried out with a fungal cell or a yeast cell. Suitably the host cell is a high expression host cell such as Hansenula, Trichoderma, Aspergillus, Penicillium, Saccharomyces, Kluyveromyces, Neurospora or Pichia sp. Most preferably the host will not have a high level of proteases that attack the expressed protein. The use of methylotrophic yeast cells, such as Pichia or Hansenula sp. Is preferred. Use of Pichia pastoris as an expression system is disclosed in EP-A-0926543 and EP-A-1014176. In one embodiment the micro- organism is free of active post-translational processing mechanism such as in particular hydroxylation of proline and also hydroxylation of lysine. In another embodiment the host system has an endogenic proline hydroxylation activity by which the non-natural Gly-Xaa-Yaa -protein is hydroxylated in a highly effective way. The selection of a suitable host cell from known industrial enzyme producing fungal host cells specifically yeast cells on the basis of the required parameters described herein rendering the host cell suitable for expression of non-natural Gly- Xaa-Yaa -protein suitable in compositions according to the invention in combination with knowledge regarding the host cells and the sequence to be expressed will be possible by a person skilled in the art.

Thus, in one aspect the invention a method is provided for producing a non-natural Gly-Xaa-Yaa-protein according to the present invention, said method comprising the steps of

a) preparing an expression vector comprising a nucleic acid sequence

encoding a protein as described above operably linked to a suitable promoter,

b) transforming a yeast species with said expression vector,

c) culturing said yeast species under suitable fermentation conditions to allow expression of said nucleic acid sequence;

d) optionally isolating said protein from the culture medium and/or the host cells.

It is preferred that the non-natural Gly-Xaa-Yaa-protein is isolated from the culture medium.

Preferably said non-natural recombinant gelatin is produced at a level of at least 5g/l supernatant, preferably at least 7g/l and more preferably in an amount of more than 9g/l supernatant. Even secretion levels as high as 12, 13, 15 or 17 or 19g/l or more have been achieved. Preferably the present non-natural Gly-Xaa- Yaa-protein is isolated and purified.

Also mutant host strains may be used, e.g. strains deficient in one or more proteolytic enzymes, although this is not necessary according to the present invention, as the recombinant polypeptides are highly stable and resistant to proteolysis.

The invention will be explained in more detail in the following, non-limiting examples:

SEQUENCES

SEQ ID 1 : Sequence of ICP monomer.

SEQ ID 2: Sequence of ICP-dimer.

SEQ ID 3: Sequence of ICP-tetramer.

SEQ ID 4: Sequence of ICP. SEQ ID 5: Sequence of ICP2.

SEQ ID 6: Sequence of ICP3.

SEQ ID 7: Sequence of ICP4.

SEQ ID 8: Sequence of plasmid pFFZa A.

SEQ ID 9: Sequence of ICP3 variant 1 .

SEQ ID 10: Sequence of ICP3 variant 2

SEQ ID 1 1 : Sequence of ICP3 variant 3

SEQ ID 12: Sequence of ICP3 variant 4

SEQ ID 13: Sequence of ICP3 variant 6

SEQ ID 14: Sequence of ICP3 variant 7

SEQ ID 15: Sequence of ICP3 variant 8

EXAMPLES

Figure 1 shows SDS PAGE analysis of representative culture supernatants of the host cells (CBS 7435) and of strains that produce ICP3 and its variants ICP3-var6 and ICP3-var8. Arrows indicate the mature protein.

Strains and genetic vectors used

In the examples, Pichia pastoris strain CBS7435 was used as the host strain. Plasmid pFFZa A was used as the vector for the genes that encode synthetic gelatins. It contains the following elements: an origin of replication for plasmid maintenance in E. coli, a zeocin resistance marker that can be used in either E. coli or Pichia pastoris and the AOX1 promoter, the AOX1 terminator and the prepro sequence of the yeast pheromone mating factor alpha from Saccharomyces cerevisiae to control methanol-induced expression and secretion of a gene of interest. The DNA sequence of the plasmid is disclosed as SEQ ID 8.

Preparation of the genetic construct for production of a gelatine-like protein

A synthetic gelatin named ICP3 was designed for enhanced cell-binding.

The sequence of ICP3 is disclosed as SEQ ID 6. The sequence is enriched in the cell-binding sequence RGD.

The codon-optimized gene for the synthetic gelatin ICP3 was synthesized. This gene was subcloned as a Xhol-Xbal fragment in pFFZa A digested with the same enzymes. This resulted in plasmid pFFZ-ICP3. This plasmids contain a gene that encodes MFa-ICP3, in which the ICP3 gelatin sequence is fused to the prepro sequence of mating factor alpha. Host cells that contain this plasmid were used to produce and secrete MFa-ICP3. The principles of the production and secretion of heterologous proteins in Pichia pastoris and their maturation (removal of the secretion signal) are well known in the art. Transformation of the host cells

Plasmid pFFZ-ICP3 was linearized with restriction enzyme Pmel to promote integration in the AOX1 promoter of the host cell. The linearized plasmid was introduced in the host cell by electroporation. Transformants were selected by plating the transformation mixture on YPD agar plates (1 Og/I yeast extract, 20g/l peptone, 20g/l dextrose and 20g/l agar in water) supplemented with zeocin at a concentration of 0.5mg/ml

Recombinant production of the gelatine-like protein

ICP3 production by several transformants was analyzed in shake flask cultures as follows. Erlenmeyers (100 ml_) were filled with 10 mL of YPD medium (1 Og/I yeast extract, 20g/l peptone and 20g/l dextrose in water). These cultures were inoculated with cells from the colonies that appeared after the transformation. The culture was allowed to reach saturation overnight. The next day, the cells were harvested by centrifugation (3000xg, 10 minutes) and the spent medium was decanted. The cells were resuspended in buffered minimal methanol medium (100 mM potassium phosphate, pH 6.0, 1 .34% Yeast Nitrogen Base, 4 x 10 ^"5 % biotin, 0.5% methanol) and grown on this medium overnight. The next two days, methanol was added to each culture to a final concentration of 1 %. On the fifth day, the cells were removed by centrifugation and the supernatant was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), using the Multiphor II electrophoresis system (GE Healthcare). ICP3 production by a few representative transformants is shown in Figure 1 A. For comparison, supernatants of two cultures of the host strain grown under the same conditions are also shown. From Figure 1 , it can be inferred that the ICP3 product is accompanied by several smaller proteolytic degradation products.

Characterization of the degradation products

In order to identify the cleavage sites, it was decided to perform mass spectrometry. Since ICP3 has a very repetitive sequence, mass spectrometry was performed on ICP, rather than on ICP3. The sequence of ICP is disclosed as SEQ ID 4. ICP was produced with the methods described above and was partly purified by anion exchange chromatography. Analytical liquid chromatography coupled mass spectrometry (LC-MS) was used to determine the masses of the intact protein ICP3 and its degradation products. The theoretical mass of ICP is 1 761 7 Dalton.

The molecular masses that were obtained are listed in Table 1 . RT (min) MW (Da) RT (min) MW (Da) RT (min) MW (Da)

15.6 1 1891 17.5 10198 20.8 17583

15.6 9387 17.5 17600 20.8 17092

15.6 1 1450 17.5 9048 20.8 17035

15.6 17664 17.5 9306 20.8 18430

15.6 9458 18.5 17648 21 .4 17616

15.6 8175 18.5 14427 24.8 17206

15.6 14442 18.5 12061 24.8 17617

16.9 12412 18.5 17600 24.8 15344

16.9 12212 19.8 17632 24.8 15342

16.9 14442 19.8 17584

17.5 17648 20.8 17631

The observed masses were compared with the masses that could theoretically be obtained from ICP. This analysis suggested that the sequences GLAG and GAAG are particularly susceptible to proteolytic cleavage. In addition, proteolysis frequently occurs after the sequence GER, depending on amino acids C-terminal of the arginine residue. Proteolysis was also found to occur behind the lysine residue in the sequence PGKEGV. In addition, the LC-MS data suggest that cleavage occurs after certain aspartic acid residues.

Development of variants that are resistant to proteolysis

To develop recombinant gelatine-like proteins more resistant to this proteolytic degradation and to determine which sequences are targeted by proteolytic activity a series of variants of ICP3 (SEQ IDs 9-15) was designed and synthesized. These variants were produced and analyzed by SDS-PAGE as described above.

Variants 1 , 2, 3 and 4 (SEQ IDs 9-12) contain mutations around the RGD and GER sequences. However, these variants showed no significant reduction in the number of degradation bands, as compared to the original ICP3.

ICP3 variant 6 (SEQ ID 13) is identical to ICP3, except that all GLA triplets have been deleted. ICP3 variant 8 (SEQ ID 15) is identical to ICP3 variant 6, except that all GAA triplets have been replaced with GAP triplets. Surprisingly the removal of the GLA triplets and substitution of the GAA triplets by GAP triplets virtually abolishes the degradation bands that were observed for the original ICP3 protein, as can be seen from Figure 1 B. ICP3 variant 7 (SEQ ID 14) is identical to ICP3 with exception of the RGD triplets, which have been deleted to limit the number of aspartic acid residues. However, this variant showed an unwanted increase in degradation, most certainly caused by the increased overall hydrophobicity of this variant.