FIELD OF THE INVENTION

The present invention relates to the manufacture of a medicament for the treatment of a corneal wound using a composition comprising one or more hyaluronic acid (or salt thereof) fraction with a certain average molecular weight and to the treatment of a corneal wound with such a medicament or composition.

BACKGROUND OF THE INVENTION Hyaluronic acid (HA) is a natural and linear carbohydrate polymer belonging to the class of non-sulfated glycosaminoglycans. It is composed of beta-1 ,3-Λ/-acetyl glucosamine and beta-1 ,4-glucuronic acid repeating disaccharide units with a molecular weight (MW) up to 6 MDa. HA is present in hyaline cartilage, synovial joint fluid, and skin tissue, both dermis and epidermis. HA may be extracted from natural tissues including the connective tissue of vertebrates, from the human umbilical cord and from cocks' combs. However, it is preferred today to prepare it by microbiological methods to minimize the potential risk of transferring infectious agents, and to increase product uniformity, quality and availability (U.S. Patent No. 6,951 ,743; WO 03/0175902).

Numerous roles of HA in the body have been identified. It plays an important role in biological organisms, as a mechanical support for cells of many tissues, such as skin, tendons, muscles and cartilage. HA is involved in key biological processes, such as the moistening of tissues, and lubrication. It is also suspected of having a role in numerous physiological functions, such as adhesion, development, cell motility, cancer, angiogenesis, and wound healing. Due to the unique physical and biological properties of HA (including viscoelasticity, biocompatibility, and biodegradability), HA is employed in a wide range of current and developing applications within cosmetics, ophthalmology, rheumatology, drug and gene delivery, wound healing and tissue engineering.

SUMMARY OF THE INVENTION The experiments showed herein demonstrate improved healing over 48 hours of rabbit corneal wounds when different hyaluronic acid fractions of 3 average molecular weights, 51 kDa, 320 kDa and 774 kDa were applied to the wound. In particular the two fractions having the lowest average molecular weight were surprisingly effective.

Accordingly, in a first aspect the invention relates to the use of a composition comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 - 1 ,000 kDa; or 30 - 800 kDa; or 35 - 600 kDa; or most preferably in the range of 40 - 400 kDa, for the manufacture of a medicament for the treatment of a corneal wound.

In a second aspect, the invention relates to a method of treating a corneal wound with a composition comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 - 1 ,000 kDa; or 30 - 800 kDa; or 35 - 600 kDa; or most preferably in the range of 40 - 400 kDa.

A third aspect of the invention relates to a contact lens multipurpose solution or a liquid preparation for a contact lens comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 - 1 ,000 kDa; or 30 - 800 kDa; or 35 - 600 kDa; or most preferably in the range of

40 - 40O kDa.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows the rabbit corneal wound healing of a circular mechanical wound of 6 mm diameter (n=3, mean + SD) expressed as percentage of fluorescent corneal surface (measured by confocal microscopy). The effects on wound healing of hyaluronic acid of four different molecular weights (51 kDa, 320 kDa, 774 kDa, and 1500 kDa) applied three times a day for 4 days in the form of a hydrogel are compared with a saline solution ('vehicle') and the absence of treatment (without treatment).

DETAILED DESCRIPTION OF THE INVENTION

"Hyaluronic acid" is defined herein as an unsulphated glycosaminoglycan composed of repeating disaccharide units of N-acetylglucosamine (GIcNAc) and glucuronic acid (GIcUA) linked together by alternating beta-1 ,4 and beta-1 ,3 glycosidic bonds. Hyaluronic acid is also known as hyaluronan, hyaluronate, or HA. The terms hyaluronan, hyaluronic acid and HA are used interchangeably herein.

The level of hyaluronic acid may be determined according to the modified carbazole method (Bitter and Muir, 1962, Anal Biochem. 4: 330-334). The method of choice to determine the absolute molecular weight and polydispersity of hyaluronic acid is to use Size Exclusion Chromatography combined with refractive index coupled to multi angle laser light scattering detection (SEC-MALLS-RI). For separation of hyaluronan into different molecular weight fractions, a hydrophilic column with the appropriate pore size is required (Standard guide for characterization and testing of hyaluronan as starting materials intended for use in biomedical and tissue engineered medical product applications, ASTM International, F 2347- 03). Accordingly, the chromatography system consisted of a Waters Alliance HPLC (Waters 2695, Milford, MA, USA) equipped with Wyatt's Multi Angle Laser Light Scattering (Dawn EOS, Santa Barbara, CA, USA) and Wyatt's Optilab rex Refractive Index (Rl) detector (Optilab rEX, Santa Barbara, CA, USA). Three TSK columns (4000, 5000, and 6000 PWXL) connected in series were eluted with a buffer of 50 mM NaH ₂ PO ₄ and 150 mM NaCI at a flow rate of 0.5 mL/min at 30 ⁰ C. Dn/dc and A2 values used were 0.153 and 2.3 ^χ 10 ^"3 , respectively. All data were calculated in Astra software v. 5.1.3.0. (Wyatt, 1993, Anal. Chim. Acta 272: 1- 40).

The first aspect of the invention relates to the use of a composition comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 - 1 ,000 kDa; or 30 - 800 kDa; or 35 -

600 kDa; or most preferably in the range of 40 - 400 kDa, for the manufacture of a medicament for the treatment of a corneal wound.

In a preferred embodiments the the composition comprises at least two hyaluronic acid fractions having different average molecular weights that differ by at least 250 kDa; preferably by at least 200 kDa; more preferably by at least 150 kDa; still more preferably by at least 100 kDa; and most preferably by at least 50 kDa. In another preferred embodiment, the composition further comprises at least one additional hyaluronic acid fraction, or salt thereof, with a average molecular weight in the range of 600 - 10,000 kDa; preferably in the range of 650 - 5,000 kDa; more preferably in the range of 700 - 2,500 kDa.

In a preferred embodiment the medicament provides a corneal wound surface area below 22% or a reduction in the corneal wound surface area of at least 32% compared to a control treatment when measured at 48 hours in the rabbit corneal wound healing model defined herein.

It is preferred that the composition comprises at least 0.01 % (w/w) of the at least one hyaluronic acid fraction, or salt thereof; preferably at least 0.1% (w/w) of the at least one hyaluronic acid fraction, or salt thereof.

Likewise, it is preferable that the medicament also comprises at least one pharmaceutically active compound, preferably an antibiotic compound, a bacteriostatic compound or an anaesthetic compound.

The second aspect of the invention relates to a method of treating a corneal wound with a composition comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 -

1 ,000 kDa; or 30 - 800 kDa; or 35 - 600 kDa; or most preferably in the range of 40 - 400 kDa.

It is preferred that the composition comprises at least two hyaluronic acid fractions having different average molecular weights that differ by at least 250 kDa; preferably by at least 200 kDa; more preferably by at least 150 kDa; still more preferably by at least 100 kDa; and most preferably by at least 50 kDa. Preferably the composition further comprises at least one additional hyaluronic acid fraction, or salt thereof, with a average molecular weight in the range of 600 - 10,000 kDa; preferably in the range of 650 - 5,000 kDa; more preferably in the range of 700 - 2,500 kDa.

A preferred embodiment relates to the method of the second aspect, which provides a corneal wound surface area below 22% or a reduction in the corneal wound surface area of at least 32% compared to a control treatment when measured at 48 hours in the rabbit corneal wound healing model defined herein.

It is also preferred that the composition comprises at least 0.01% (w/w) of the at least one hyaluronic acid fraction, or salt thereof; or preferably at least 0.1 % (w/w) of the at least one hyaluronic acid fraction, or salt thereof.

In another preferred embodiment the composition comprises at least one pharmaceutically active compound, preferably an antibiotic compound, a bacteriostatic compound or an anaesthetic compound.

The third aspect of the invention relates to a contact lens multipurpose solution or a liquid preparation for a contact lens comprising at least one hyaluronic acid fraction, or salt thereof, with an average molecular weight in the range of 20 - 1 ,200 kDa; preferably in the range of 25 - 1 ,000 kDa; or 30 - 800 kDa; or 35 - 600 kDa; or most preferably in the range of

40 - 40O kDa.

In a preferred embodiment the solution or preparation of the third aspect comprises at least two hyaluronic acid fractions having different average molecular weights that differ by at least 250 kDa; preferably by at least 200 kDa; more preferably by at least 150 kDa; still more preferably by at least 100 kDa; and most preferably by at least 50 kDa.

Preferably, the solution or preparation of the third aspect further comprises at least one additional hyaluronic acid fraction, or salt thereof, with a average molecular weight in the range of 600 - 10,000 kDa; preferably in the range of 650 - 5,000 kDa; more preferably in the range of 700 - 2,500 kDa.

It is also preferred that the solution or preparation of the third aspect comprises at least 0.01 % (w/w) of the at least one hyaluronic acid fraction, or salt thereof; or preferably at least 0.1% (w/w) of the at least one hyaluronic acid fraction, or salt thereof. Finally, it is preferred that the solution or preparation of the third aspect also comprises at least one pharmaceutically active compound, preferably an antibiotic compound, a bacteriostatic compound or an anaesthetic compound.

HA sources Rooster combs are a significant commercial source for hyaluronan. Microorganisms are an alternative source. U.S. Patent No. 4,801 ,539 discloses a fermentation method for preparing hyaluronic acid involving a strain of Streptococcus zooepidemicus with reported yields of about 3.6 g of hyaluronic acid per liter. European Patent No. EP0694616 discloses fermentation processes using an improved strain of Streptococcus zooepidemicus with reported yields of about 3.5 g of hyaluronic acid per liter.

In a preferred embodiment the hyaluronic acid or salt thereof is of microbial origin, preferably from a strain of Streptococcus.

As disclosed in WO 03/054163 (Novozymes), which is incorporated herein in its entirety, hyaluronic acid or salts thereof may be recombinantly produced, e.g., in a Gram- positive Bacillus host.

Hyaluronan synthases have been described from vertebrates, bacterial pathogens, and algal viruses (DeAngelis, P. L., 1999, Cell. MoI. Life Sci. 56: 670-682). WO 99/23227 discloses a Group I hyaluronate synthase from Streptococcus equisimilis. WO 99/51265 and WO 00/27437 describe a Group Il hyaluronate synthase from Pasturella multocida. Ferretti et al. disclose the hyaluronan synthase operon of Streptococcus pyogenes, which is composed of three genes, hasA, hasB, and hasC, that encode hyaluronate synthase, UDP glucose dehydrogenase, and UDP-glucose pyrophosphorylase, respectively (Proc. Natl. Acad. Sci. USA. 98, 4658-4663, 2001 ). WO 99/51265 describes a nucleic acid segment having a coding region for a Streptococcus equisimilis hyaluronan synthase.

Since the hyaluronan of a recombinant Bacillus cell is expressed directly to the culture medium, a simple process may be used to isolate the hyaluronan from the culture medium. First, the Bacillus cells and cellular debris are physically removed from the culture medium. The culture medium may be diluted first, if desired, to reduce the viscosity of the medium. Many methods are known to those skilled in the art for removing cells from culture medium, such as centrifugation or microfiltration. If desired, the remaining supernatant may then be filtered, such as by ultrafiltration, to concentrate and remove small molecule contaminants from the hyaluronan. Following removal of the cells and cellular debris, a simple precipitation of the hyaluronan from the medium is performed by known mechanisms. Salt, alcohol, or combinations of salt and alcohol may be used to precipitate the hyaluronan from the filtrate. Once reduced to a precipitate, the hyaluronan can be easily isolated from the solution by physical means. The hyaluronan may be dried or concentrated from the filtrate solution by using evaporative techniques known to the art, such as lyophilization or spraydrying.

Accordingly, in a preferred embodiment the hyaluronic acid or salt thereof is recombinantly produced, preferably by a Gram-positive bacterium or host cell, more preferably by a bacterium of the genus Bacillus. In another preferred embodiment the hyaluronic acid or salt thereof is recombinantly produced, preferably by expressing a heterologous hyaluronic acid synthase gene(s) in a strain of Bacillus. The host cell may be any Bacillus cell suitable for recombinant production of hyaluronic acid. The Bacillus host cell may be a wild-type Bacillus cell or a mutant thereof. Bacillus cells useful in the practice of the present invention include, but are not limited to, Bacillus agaraderhens, Bacillus alkalophilus, Bacillus amyloliquefaciens, Bacillus brevis, Bacillus circulans, Bacillus clausii, Bacillus coagulans, Bacillus firmus, Bacillus lautus, Bacillus lentus, Bacillus licheniformis, Bacillus megaterium, Bacillus pumilus, Bacillus stearothermophilus, Bacillus subtilis, and Bacillus thuringiensis cells. Mutant Bacillus subtilis cells particularly adapted for recombinant expression are described in WO 98/22598. Non- encapsulating Bacillus cells are particularly useful in the present invention. In a preferred embodiment, the Bacillus host cell is a Bacillus amyloliquefaciens,

Bacillus clausii, Bacillus lentus, Bacillus licheniformis, Bacillus stearothermophilus or Bacillus subtilis cell. In a more preferred embodiment, the Bacillus cell is a Bacillus amyloliquefaciens cell. In another more preferred embodiment, the Bacillus cell is a Bacillus clausii cell. In another more preferred embodiment, the Bacillus cell is a Bacillus lentus cell. In another more preferred embodiment, the Bacillus cell is a Bacillus licheniformis cell. In another more preferred embodiment, the Bacillus cell is a Bacillus subtilis cell. In a most preferred embodiment, the Bacillus host cell is Bacillus subtilis A164Δ5 (see U.S. Patent No. 5,891 ,701 ) or Bacillus subtilis 168Δ4.

Transformation of the Bacillus host cell with a nucleic acid construct of the present invention may, for instance, be effected by protoplast transformation (see, e.g., Chang and Cohen, 1979, Molecular General Genetics 168: 11 1-1 15), by using competent cells (see, e.g., Young and Spizizen, 1961 , Journal of Bacteriology 81 : 823-829, or Dubnau and Davidoff-Abelson, 1971 , Journal of Molecular Biology 56: 209-221 ), by electroporation (see, e.g., Shigekawa and Dower, 1988, Biotechniques 6: 742-751 ), or by conjugation (see, e.g., Koehler and Thome, 1987, Journal of Bacteriology 169: 5271-5278).

In a preferred embodiment the salt of hyaluronic acid is an inorganic salt, preferably sodium hyaluronate, potassium hyaluronate, ammonium hyaluronate, calcium hyaluronate, magnesium hyaluronate, zinc hyaluronate, or cobalt hyaluronate.

EXAMPLES

Example 1 : Production of low molecular weight HA by acid hydrolysis

Hyaluronic acid (0.5 g) was dissolved overnight at room temperature with vigorous agitation in 50 ml MilliQ™ water in 5 x sealable 250 ml bottles. The solutions were pre- warmed to 60 ⁰ C before 4 M HCI was added under vigorous stirring (800 rpm) for 1 minute to give acid concentrations of 0; 0.10; 0.50; 1.0 and 2.0 M. The total HA concentrations were adjusted to 10 mg/ml. The bottles were left at weak shaking at 60 ⁰ C in a water bath for a total of 52 hours. Samples of 5 ml were withdrawn at 1 h10min, 2h17min, 4h10min, 5hO5min, 23h, 48h15min and 52h10min from each solution and neutralized with equimolar amounts of NaOH (1 M solution) before freezing (-20 ⁰ C) and lyophilisation.

Example 2: Preparation and characterization of HA-based formulations HA (molecular weight: 51 kDa, or 320 kDa, or 774 kDa, or 1500 kDa) was dissolved in a neutral, isotonic and sterile phosphate buffer solution (PBS) at room temperature and under magnetic stirring to give a final concentration of 0.2% (w/v). The buffer was sterilized by filtration (Sartorius filters of nominal pore size 0.22 microns).

The formulations were freshly prepared for all in vivo experiments to avoid the addition of preservatives and were conditioned in radiation sterilized eye dropper glass bottles of 10 ml_. The PBS buffer had a pH of 7.33 and an osmotic pressure of 282 mθsm/kg. These physico-chemical characteristics measured were compatible with physiological parameters of the tear film, thus allowing topical administration to the cornea.

Example 3: Evaluation of effect of hyaluronic acid on corneal wound healing

New Zealand white rabbit females weighing 3.3 - 5.0 kg (University Medical Center, Geneva, Switzerland) have been used in this study. Animals were individually housed in stainless steel cages and maintained in a 12 hour light/dark cycle at 19 ± 1°C. They were allowed water and food ad libitum. All animals were healthy and free of clinical observable ocular abnormalities. All experiments have been performed in accordance with the Association for Research in Vision and Ophthalmology (ARVO) statement for the use of animals in ophthalmic and vision research (ARVO, 1984) and were approved by the local veterinary authority for animal experimentation.

Mechanical wounds in form of circular superficial epithelial abrasion were performed on rabbit corneas by means of a sterile Algerbrush burr with a 1 mm tip (Jannach, Italy). Animals were anesthetized with an intramuscular injection of a 1 :1 mixture of ketamine hydrochloride (37.5 mg/kg body weight) and xylazine hydrochloride (10 mg/kg body weight). A drop of topical anaesthetic (oxybuprocain hydrochloride 0.4%, NOVESI N ^® , Ciba Vision, Switzerland) was instilled on the cornea prior to the surgical procedure. Circular wounds of 6-mm diameter were generated. The wound size was controlled by applying onto the cornea a sterilized transparent stencil film (PARAFILM ^® M, American Can Company, Greenwich, USA) with a hole cut up by a punch of 6-mm diameter. Immediately after the creation of the mechanical wound, the rabbit eye was thoroughly rinsed with a sterile saline physiological solution (isotonic sodium chloride solution). Twelve rabbits were included in the study, three for each formulation. Each rabbit received only one HA-formulation. The isotonic hydrogel HA-formulations based on 0.2% hyaluronic acid were applied to the right eye immediately after the surgical treatment at the beginning of the experiment. Then the rabbits were treated with the different formulations three times per day at 9:00, 13:00, and 17:00 o'clock till the end of the experiment (that is 96 h after surgery).

The abraded corneal surface was revealed by instilling a sterile isotonic sodium fluorescein solution (0.5%, 25 microliter). After 2 minutes dyeing, the excess fluorescein was washed out during one minute with a sterile NaCI 0.9% solution. The corneas were then observed under confocal microscopy. The HA formulations were compared with a saline vehicle and with absence of treatment.

Microscopic observation was performed using a confocal laser scanning ophthalmoscope (CLSO Zeiss, Oberkochen, Germany) modified by addition of a set of lenses in order to view the cornea instead of the retina. An argon ion laser operating at 488 nm wavelength was used as the excitation light source. The fluorescence signal was detected by a photomultiplier. Images were obtained using Epiplan-Neofluar (2.5x/0.075 NA objective lens (Zeiss, Oberkochen, Germany). Optical sectioning was performed parallel to the corneal surface, at 16 equidistant different focal planes, the focus shifting (from 0 to 470 microns) covering the whole corneal thickness. The images were displayed on a digital video monitor. An image processing system (Analysis SIS, Mϋnster, Germany) carried out the following operation step: addition of the 16 digitized images in one stack to produce a three- dimensional reconstruction, projection of this stack and calculation of the total surface of the fluorescence areas on the projection. No anesthesia of the animals was necessary during the microscopic observation.

The results were evaluated in three ways. Firstly, the influence of the different treatments on the percentages of fluorescent corneal surface was compared to the vehicle treatment and to the absence of treatment using the Student t test (unpaired sample, level of significance: p>0.05) after the Fisher-Snedecor analysis of variance (supposing a normal distribution of the value). Secondly, using curvefitting in a form of a cubic spline (Maple 10 software, Maplesoft, Ontario, Canada), the mathematical equation of each curve (percentage of fluorescent area as a function of time) was calculated (J. H. Ahlberg, E.N. Nilson et al. 1967; C. de Boor, 1978; G. D. Knott, 2000). Thirdly, using the same software, the Area Under the Curve (AUC) was determined for each curve (integration limits: 0 h and 96 h). The AUC is a parameter indicating the healing rate: the smaller the AUC, the faster the wound healing rate. For biexponential curves, the AUC was calculated taking the interval of integration from 0 h until the time corresponding to the curve minimum point where the first derivative of the curve is zero. The enabled to take into account the first healing phase without the epithelial reorganization one.

Example 4: Evolution of the wound healing and wound healing rate after mechanical corneal injury

The evolution of the wound healing after mechanical corneal injury for different hyaluronic acids (51 kDa, 320 kDa, 774 kDa and 1500 kDa) is detailed in Table 1. The mean area under the curve (AUC) indicating the rate after instillation of the four types of hyaluronic acids is presented in Table 2.

The results were compared to a vehicle (saline solution) and to the absence of treatment ('without treatment') (Figure 1 ). The data showed a healing evolution quite similar for all tested ophthalmic formulations. This evolution consisted of a rapid decrease of the percentage of fluorescent surface in 48 h, followed by a slower decrease between 48h and 96h. Sometimes, the percentage of fluorescent surface even decreased slightly between 72h and 96h. This evolution indicated a two-phase corneal repair mechanism. In the first phase, the wound closed up more or less rapidly, and in the second phase, a rearrangement of the epithelial cells occurred, thus explaining the possible and transient slight increase in the percentage of fluorescent surface. Moreover, due to important standard deviation, the statistical data confrontation of each HA formulation with the saline solution (vehicle) at different times (24h, 48, h, 72h, and 96h after surgery) did not discriminate the performance if the different formulations at 24h. Presumably, at this time, tissue inflammation was too important to be influenced by the instillation of a HA hydrogel. At 48h, formulations based on 51 kDa HA, 320 kDa HA, and 774 kDa significantly stimulated corneal wound healing compared to saline control solution. Low MW HA (51 kDa and 320 kDa) promoted wound healing 48 h after surgery compared to the absence of treatment, suggesting that these HAs covered and protected the corneal wound adequately and accelerated the wound healing rate during the first phase of corneal repair where the wound was closed up by bordering cells. The healing process was enhanced by 50% when applying these two low molecular weight HA-based formulations compared to what it would be when applying no treatment. At 48h, HA can provide additional comfort.

Later, that is 72h and 96h after surgery, the administration of HA of different molecular weights did not seem to accelerate the wound healing rate. During the second phase of wound healing, a cell rearrangement occurred, explaining the slight decrease in fluorescence in a few cases.

No difference was observed between formulations based on 1500 kDa and the control formulations regardless the time of analysis. High molecular weight HA is too viscous and creates a barrier for cells.

Table 1 : Effects of the different HA molecular weights (applied three times per day during 5 days in the form of an hydrogel) on the wound healing rate, compared to a saline solution (vehicle) and the absence of treatment (without treatment). The percentage of fluorescent corneal surface is assessed by confocal microscopy. All values are means of triplicates (n=3). The data is shown graphically in figure 1.

Table 2: Wound healing rate after mechanical corneal injury as measured by the area under the curve (AUC) in a graph plotting the decrease of wound surface over time 0 - 96 hours (n=3).