Pharmaceutical compositions for ophthalmic administration comprising a combination of hyaluronic acid fractions and ophthalmic drugs

PHARMACEUTICAL COMPOSITIONS FOR OPHTHALMIC ADMINISTRATION COMPRISING

A COMBINATION OF HYALURONIC ACID FRACTIONS AND OPHTHALMIC DRUGS

FIDIA SPA

PHARMACEUTICAL COMPOSITIONS

FOR OPHTHALMIC ADMINISTRATION COMPRISING

A COMBINATION OF HYALURONIC ACID FRACTIONS

AND OPHTHALMIC DRUGS

Background And Field Of The Invention

This invention relates to ophthalmic compositions comprised of molecular weight fractions of hyaluronic acid (hereinafter referred to as ״HA) and ophthalmic drugs, based on the finding that the HA fractions are useful as vehicles for ophthalmic drugs providing formulations compatible with the corneal epithelium and enhancing the activity of ophthalmic drugs.

Hyaluronic acid is a naturally occurring heteropolysaccharide consisting of alternating residues of D-glucuronic acid and N-acetyl-D-glucosamine. HA is a linear polymer of high molecular weight, generally up to about 8 to 13 million, and has been found in cell coats, the extracellular ground substance of connective tissues of vertebrates, in the synovial fluid in joints, in the endobulbar fluids of the eye, in human umbilical cord tissue, and in rooster combs.

Detailed Description Of The Invention

The present inventors have found that hyaluronic acid, and particularly molecular weight fractions of HA, provides an excellent carrier for various known drugs having activity and usefulness in ophthalmic applications. Various fractions of hyaluronic acid can be utilized in the invention, but of particular usefulness are those fractions described in the applicants' co-pending parent application, Israeli Patent Application No. 73217. That application describes the preparation of HA fractions which are free of inflammatory activity, and are substantially free of low molecular weight HA having a molecular weight of less than 30,000. The fractions of that application broadly have a molecular weight of between 30,000 and 730,000. In addition, specific fractions of hyaluronic acid are differentiated and separated according to molecular filtration techniques.

The first fraction isolated by the applicant has been named HYALASTINE, and has an average molecular weight of from about 50,000 to about 100,000. The second fraction isolated by the applicant has been named HYALECTIN, and has an average molecular weight of about 500,000 to about 730,000. While all of the fractions described in the applicants' parent application are useful for combination with ophthalmic drugs, the HYALECTIN fraction is particularly suitable for use in ocular surgery as a substitute for endobulbar liquids and is especially useful as a vehicle for ophthalmic drugs according to the present invention.

Therefore, the capacity and efficiency of hyaluronic acid as a vehicle for various molecules has been investigated, in particular, use as a vehicle for opthalmic drugs, guaranteeing perfect tolerability and compatibility (i.e., absence of sensitization phenomena) with the corneal epithelium. Hyaluronic acid is considered of particular interest as an ophthalmic vehicle. As discussed previously, HA is a glycosaminoglycan present in various connective tissues and biological liquids (such as the synovial fluid and in particular the vitreous humor) where, because of its chemical and physical nature and its striking visco-elastic characteristics, it plays a structural and biological role of fundamental importance.

Thus, a study was conducted to investigate the use of HA fractions having different molecular weights, particularly the hyalastine and hyalectin fractions, and a mixture of the same, for the preparation of different pharmaceutical forms, such as collyrium, gel, cream, inserts or dry powders. Therefore, opthalmic drugs of different types were studied in order to obtain a broad understanding of the potential use of this biological polymer in its different fractions as a vehicle.

The experiments reported hereafter were aimed at determining whether formulations containing hyaluronic acid as an excipient are capable of enhancing the bioavailability of vehicled drugs or producing a synergistic effect in combination with the vehicled drugs, particularly with drugs having ophthalmic activity or utility.

These potential capacities of HA as a vehicle were investigated in the rabbit eye with four ophthalmic drugs of different types and actions, in particular, pilocarpine nitrate, triamcinolone, epidermal growth factor (EGF) and an antibiotic such as streptomycin and gentamicine. All of these drugs are known to have miotic, anti-inflammatory, healing and anti-microbial efficiency. Moreover evaluation of the activity of the antibiotic streptomycin, vehicled in hyaluronic acid, is very important because it is one of the most widely used antibiotics in ocular infections.

The experimental models studied and the experiments effected were as follows:

1) miotic activity of pilocarpine nitrate, vehicled in hyaluronic acid in rabbit eye;

2) anti-inflammatory activity of triamcinolone, vehicled in hyaluronic acid in the model of dextran-induced inflammation in rabbit eye;

3) healing activity of epidermal growth factor (EGF) vehicled in hyaluronic acid in a model of epithelial lesion of rabbit cornea.

4) antimicrobial activity of streptomycin vehicled in hyaluronic acid against Bacillus subtilis 6633 in agar plates.

I. Miotic Activity of Pilocarpine Nitrate Vehicled In Hyaluronic Materials

The following materials were used as excipients of pilocarpine for the various pilocarpine nitrate formulations:

hyaluronic acid sodium salt, hyalastine fraction, (m.w., approximately 100,000), at a concentration of 10 mg/ml and 20 mg/ml;

hyaluronic acid sodium salt, hyalectin fraction (m.w. 500,000 - 730,000), at a concentration of 10 mg/ml and 20 mg/ml;

5% polyvinyl alcohol as a comparative ophthalmic excipient.

Various 2% formulations (collyrium or gel) of pilocarpine nitrate were prepared and vehicled by adding the two different fractions of HA sodium salt at a concentration of 10 and 20 mg/ml.

The following solutions were prepared:

Formulation 1 - saline with pilocarpine nitrate (PiNO₃) (2%) , used as reference.

Formulation 2 - solution of PiNO₃ (2%) vehicled in 5% polyvinyl alcohol (used as reference).

Formulation 3 - solution of PiNO₃ (2%) vehicled in hyalastine fraction sodium salt (10 mg/ml).

Formulation 4 - solution of PiNO₃ (2%) vehicled in hyalastine fraction sodium salt (20 mg/ml).

Formulation 5 - solution of PiNO₃ (2%) vehicled in hyalectin fraction sodium salt (10 mg/ml).

Formulation 6 - solution of PiNO₃ (2%) vehicled in hyalectin fraction sodium salt (20 mg/ml). Method

Albino New Zealand rabbits were used (2 - 2.5 kg). The formulation to be tested was instilled in one eye by microsyringe (10 1); the other eye served as a reference. The diameter of the pupil was measured in all cases at suitable time intervals. Each solution was tested on at least 8 rabbits. Each eye was treated not more than three times and a rest period of at least a week was observed between each treatment.

Parameters Measured

The pupil diameters were measured at various intervals in order to determine the miotic activity curve in time. The following activity parameters were subsequently calculated from the miosis/time graphs: Imax - maximum difference in pupil diameter between the treated eye and the reference. Peak time = time taken to reach I_max, Duration = time taken to restore basal conditions. Plateau -ב period of absolute miotic activity.

AUG = area under miosis/time curve .

Results

The results of the tests are reported in Table 1. It can be seen from the data for the various parameters determined from the miotic activity time curve for all the solutions tested that the addition of hyaluronic acid to a 2% pilocarpine nitrate solution gives rise to an increase in miotic activity of the drug. In fact, the bioavailability of the drug may be as much as 2.7 times greater than that of the aqueous solution containing 2% pilocarpine nitrate (Formulation 1).

It should also be noted that there is a statistically significant increase in activity when the hyalectin fraction of hyaluronic acid both at 10 and 20 mg/ml is used as a vehicle (Formulations 5-6), in contrast to the pilocarpine nitrate solution vehicled in polyvinyl alcohol (Formulation 2).

The use of hyaluronic acid as a vehicle is particularly interesting because the miotic activity of pilocarpine nitrate lasts longer when it is vehicled with this substance. That is, for the hyaluronic acid containing formulations the time taken to restore pupil diameter to basal conditions is up to 190 minutes (Formulation 6) as compared to 110 minutes for pilocarpine in saline alone (Formulation 1).

II. Anti-Inflammatory Activity Of Triamcinolone Vehicled In Hyaluronic

Materials

The following were used:

solution of hyaluronic acid sodium salt-hyalectin fraction, m.w. between 500,000 and 730,000, 10 mg/ml in saline;

solution of triamcinolone (10% in saline).

Method

The experiments were carried out on male New Zealand rabbits (average weight 1.6 kg). After an adaptation period of 5 days, intraocular inflammation was induced in the rabbits by intraocular injection of dextran (10%, 0.1 ml). The administration was effected in both eyes under local anaesthetic with 4% Novesina, inserting the needle of the syringe by 4 mm into the anterior chamber, at a distance of 2 mm from the limbus of the cornea. The test was conducted on 10 animals.

Treatment

Treatment was effected in each animal both in the right and left eyes, by instillation of 3 drops 3 times a day for 6 days in all, of the following:

a solution of triamcinolone (10% in saline) in the left eye (LE);

a solution of hyaluronic acid sodium salt, hyalectin fraction, (10 mg/ml) + triamcinolone (10%) in the right eye (RE).

Parameters

The anti-inflammatory effect on the phlogistic reaction induced by dextran was evaluated by observing the eye with a slit lamp at the following intervals: 0, 1 hr, 3 hr, 24 hr, 48 hr, 3 days, 4 days, 5 days and 6 days.

Table 1: Biological Activity of Ophthalmic Vehicles Containing Hyaluronic Acid’

<td> Formulation</td><td> Vehicle</td><td colspan="2"> I¹״ mm Peak time (+ LF 95%)(minutes)</td><td colspan="4"> Duration Plateau ADC, cm² Relative (minutes) (minutes) (+ LF 95¾) AUC</td>

<td> 1</td><td> saline</td><td> 1.93 + 0.35</td><td> 20</td><td> 110</td><td></td><td> 117 + 28</td><td> 1</td>

<td> 2</td><td> 5% polyvinyl alcohol</td><td> 2.33 + 0.28</td><td> 20</td><td> 140</td><td></td><td> 192 + 32</td><td> 1.64</td>

<td> 3</td><td colspan="2"> hyalastine (10 mg/ml) 2.50 + 0.42</td><td> 20</td><td> 120</td><td></td><td> 240 + 40</td><td> 2.05</td>

<td> 4</td><td colspan="2"> hyalastine (20 mg/ml) 2.58 + 0.38</td><td> 30</td><td> 150</td><td></td><td> 208 + 41</td><td> 1.78</td>

<td> 5</td><td> hyalectin (10 mg/ml)</td><td> 2.50 + 0.38</td><td> 15</td><td> 170</td><td></td><td> 242 + 48</td><td> 2.06</td>

<td> 6</td><td> hyalectin (20 mg/ml)</td><td> 2.70 + 0.38 Μ»</td><td> 20</td><td> 190</td><td> 45</td><td> 320 + 45</td><td> 2.73</td>

* Reported values represent a mean value for 8 runs.

At the intervals, the eye examination evaluated the following observations: the state of the cornea and conjunctiva for the possible presence of hypermia, edema, and especially observation of the iris which is normally sensitive to phlogistic processes after intraocular injection of inflammatory agents; the Tyndall effect, in which the presence of more or less intense opacity (nubecula) is indicative of the presence of corpusculating (inflammatory) elements in the anterior chamber.

The result of the observation was expressed in terms of subjective scoring (from 0 to 3) related to the gradualness of the effect noted.

Results

It can be seen from the results as reported in Table 2 that administration of triamcinolone has an anti-inflammatory effect on the iris and causes the disappearance of opacity (Tyndall effect) in the anterior chamber. The inflammatory process which is evident from the lst-3rd hour until the 3rd to 4th day progressively decreases until almost normal conditions are restored, with perfect limpidness of the eye by the 6th day. On the other hand, administration of hyaluronic acid sodium salt, hyalectin fraction, together with triamcinolone reduces intraocular inflammation observed at the times discussed above relating to administration of triamcinolone alone.

That is, the phlogistic process in the iris and the opacity in the anterior chamber is seen to have decreased by the 24th hour, with progressive reduction at 48 hours and with total absence of inflammatory reaction from the 4th day on.

In the conjunctiva and the cornea, essentially no notable reactions were observed after intraocular injection of dextran.

Thus, the administration of triamcinolone, together with the hyaluronic acid fraction, resulted in enhanced activity of the drug as evidenced by the more rapid healing of the rabbit eye.

EFFECT OF THE COMBINATION OF HYALURONIC ACID AND TRIAMCINOLONE

ON INTRAOCULAR INFLAMMATION INDUCED BY DEXTRAN

Observation Interval

Table 2

<td></td><td> 0</td><td> Ihour</td><td> 3hours</td><td> 24hours</td><td> 48hours</td><td> 3days</td><td> 4days</td><td> 5days</td><td> edays</td>

<td></td><td></td><td></td><td></td><td colspan="2"> Evaluated Score</td><td> a</td><td></td><td></td><td></td>

<td></td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td><td> LE RE</td>

<td colspan="2"> Conjunctiva 0.0 0.0</td><td> 0.2 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td>

<td> Cornea</td><td> 0.0 0.0</td><td> 1.0 0.2</td><td> 0.0 0.7</td><td> 0.1 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td><td> 0.0 0.0</td>

<td> Tyndall</td><td> 0.0 0.0</td><td> 1.0 1.2</td><td> 3.0 3.0</td><td> 3.0 2.1</td><td> 3.0 1.2</td><td> 3.0 0.2</td><td> 2.2 0.0</td><td> 1.2 0.0</td><td> 0.4 0.0</td>

<td> Iris</td><td> 0.0 0.0</td><td> 0.5 0.7</td><td> 2.7 2.7</td><td> 3.0 2.5</td><td> 3.0 1.2</td><td> 3.0 0.4</td><td> 2.4 0.0</td><td> 1.5 0.0</td><td> 0.5 0.0</td>

LE = Left eye, treated with triamcinolone.

RE = Right eye, treated with fia/ncinolone and hyalectin.

״ Each value is the mean of seven observations in a total of seven animals, and expressed in terms of subjective scoring between 0 and 3, in relation to the gradualness of the effect observed.

III. Healing Activity of EGF Vehicled in Hyaluronic Acid Materials

The following were used:

Formulation A - EGF (Epidermal growth factor), dissolved in saline (0.5 mg/5 ml)

Formulation B - hyaluronic acid sodium salt, hyalastine fraction, (m.w. approximately 100,000) dissolved in saline (10 mg/ml) Method

The experiments were carried out on male albino New Zealand rabbits (average weight 1.8 kg). The animals, after a period of adaptation of about 5 days, underwent epithelial lesion of the cornea in suitable conditions of local anaesthetic with Novesina (4%). The lesion consisted of a monocular scarification of a circular area in the optic zone effected by a concave glass cylinder (O 3mm) with a sharp edge.

Treatment

The animals were subdivided into groups, each group consisting of 5 animals, and subjected to pharmacological treatment by conjunctival instillation as follows:

Group

Treatment

Group 1 (control) Saline

Group 2 EGF solution (Formulation A)

Group 3 Solution of hyaluronic acid sodium salt, hyalastine fraction, + EGF solution combination of Formulation A + Formulation B at 1:1 ratio to make Formulation C

Treatment was effected on the right eye (RE) by conjunctival instillation of 2 drops every 8 hours for 3 total administrations. Parameters

Healing of the corneal epithelium was evaluated by observation of the eye and photographic documentation with a slit lamp at various intervals after scarification: 0, 8 hours, 16 hours, 24 hours, 32 hours, 40 hours, and 48 hours. Results

Ophthalmological examination 1 as reported in Table 3, revealed that in the controls (Group 1) complete healing was achieved (5/5 animals) 48 hours after lesion. In the animals treated with EGF (Group 2) the healing process was apparent as early as 24 hours after scarification with considerable efficacy (4/5 animals). In the animals treated with the Formulation C comprising hyaluronic acid sodium, salt, hyalastine fraction, + EGF (Group 3) the healing process was complete in all the animals (5/5) as early as 16 hours after scarification.

These results show that utilization of the hyalastine hyaluronic acid fraction as a vehicle for EGF enhances the healing process by promoting more rapid effective healing of corneal lesions.

Table 3

HEALING OF LESIONS IN THE CORNEAL EPITHELIUM

<td colspan="2" rowspan="2"> Group Treatment</td><td rowspan="2"> Hours 0</td><td rowspan="2"> 5 c 8</td><td colspan="3"> ifter scarification</td>

<td> 16</td><td> 24</td><td> 48</td>

<td> 1</td><td> Saline</td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td> 2</td><td> EGF</td><td> +</td><td> +</td><td> +</td><td> —</td><td></td>

<td></td><td colspan="2"> (Formulation A)</td><td></td><td></td><td></td><td></td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td></td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td></td><td></td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> +</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> +</td><td> —</td><td> —</td>

<td> 3</td><td> Hyaluronic acid + EGF</td><td> +</td><td> +</td><td> —</td><td> —</td><td></td>

<td></td><td> (Formulation</td><td> +</td><td> +</td><td> —</td><td> —</td><td> —</td>

<td></td><td> C)</td><td> +</td><td> +</td><td></td><td></td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> —</td><td> —</td><td> —</td>

<td></td><td></td><td> +</td><td> +</td><td> —</td><td> —</td><td> —</td>

<td> = ־4</td><td> unhealed eye</td><td></td><td></td><td></td><td></td><td></td>

<td> — =</td><td> healed eye</td><td></td><td></td><td></td><td></td><td></td>

IV. Antimicrobial Activity of Gentamicins Vehicled in Hyaluronic Materials

The following materials were used: Gentamicine dissolved in saline (50 mg/ml) Hyaluronic acid sodium salt, hyalectin fraction (2 mg/ml) Method

Septic phlogosis was caused in both eyes of 11 rabbits by intraocular injection of a titered suspension of Pseudomonas aeruginosa (0.1 ml). In those rabbits showing septic phlogosis, hyaluronic acid, hyalectin fraction, in combination with gentamicine was administered by instillation in the right eye and gentamicine in a buffered saline vehicle was administered in the left eye. The treatment (3 drops every 6 hours) was begun immediately after injection of the infecting agent and was continued until the infection had disappeared. The rabbits' eyes were observed every day under a slit lamp. Results

Treatment with a combination of gentamicine with hyaluronic acid resulted in a faster disappearance of the septic infection as compared to administration of the antibiotic alone. This conclusion is clear from the data presented in Table 4.

Table 4

EFFECT OF GENTAMICINE VEHICLED IN HYALURONIC ACID

HYALECTINE FRACTION, ON INTRAOCULAR SEPTIC PHLOGOSIS

Treatment

Days from Start of Phlogosis

<td></td><td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td><td> 6</td><td> 7</td>

<td> Gentamicine + Buffer Saline Vehicle</td><td> 0.0</td><td> 0.0</td><td> 0.0</td><td> 0.0</td><td> 0.0</td><td> 36.3</td><td> 100</td>

<td> Gentamicine + Hyaluronic Acid Hyalectine Fraction</td><td> 0.0</td><td> 0.0</td><td> 9.0+</td><td> 27.2+</td><td> 72.7+</td><td> 100</td><td> 100</td>

Values are expressed as percentages (number of eyes cured of phlogosis by the number of eyes treated).

+ = Significant difference vs buffer vehicle (less than 0.05, Fisher exact T-Test)

Additional samples, although not limitive, of ophthalmic drugs which can be vehicled with HA fractions according to the invention are as follows:

<td> antibiotics:</td><td> chloramphenicol neomycin aureomycin myxin and polymyxin bacitracin mycetins</td>

<td> hormones:</td><td> nandrolone and nandrolone sulfate</td>

<td> anesthetics (local):</td><td> henoxinate and the hydrochloride thereof</td>

<td> antiviral:</td><td> iododeoxyuridine iododeoxycytidine</td>

<td> anti-inflammatories:</td><td> dexamethasone and the phosphate thereof</td>

<td> vasopressors and vasocontrictors:</td><td> synephrine and neosynephrine</td>

Conclusions

On the basis of the results obtained from the experiments discussed above, it can be concluded that solutions of hyaluronic acid sodium salt (in both the hyalastine and hyalectin fractions) can be used as a vehicle for ophthalmic drugs and proves to be efficient as such for various types of drugs having differing biological actions. For example, drugs including anti-glaucoma agents such as pilocarpine nitrate, anti-allergic and anti-inflammatory agents such as triamcinolone, tissue healing and cell proliferation promating agents for promoting healing of eye tissue such as EGF, and antibiotics such as streptomycin and gentamicine, whose miotic, anti-inflammatory, healing and antimicrobial activities respectively are reported, can all be administered effectively utilizing HA as a vehicle.

The formulations of ophthalmic drugs vehicled in hyaluronic acid fractions with various molecular weights prove to be perfectly tolerated by the host, and compatible with the corneal epithelium without, therefore, giving rise to sensitization phenomena.

It is also possible from the data to observe how this biological product, hyaluronic acid, is an efficient vehicle, capable of enhancing the in vivo bioavailability of vehicled drugs, strengthening the pharmacological activity of such drugs. The use of hyaluronic acid fractions as a drug vehicle particularly results in:

an increase in the miotic activity of pilocarpine nitrate while prolonging the activity time of the drug;

an increase in the anti-inflammatory activity of triamcinolone on intraocular inflammation induced by dextran, with a regression of the phlogistic process in shorter times as compared to those obtained with triamcinolone alone;

an increase in the protective action of epidermal growth factor (EGF) on superficial lesions in the cornea with obvious synergism and reduction in healing times as compared to recovery times with EGF alone; and an increase in the in vivo biological activity of antibiotics, such as gentamicine.

The results obtained by using this biological polymer, hyaluronic acid, as a vehicle for drugs with such varied natures and actions, allows for the extrapolation of its potential as a vehicle for numerous other ophthalmic drugs.

Reported below are various examples of different formulations of ophthalmic drugs which may be in the form of powders, collyrium, gel, cream, or inserts, in which hyaluronic acid in its different fractions, hyalastine and hyalectin, is the only excipient used:

Example 1:

a collyrium which may be used as artificial tears, containing:

hyaluronic acid sodium salt hyalectin fraction 10 mg saline buffered with phosphate pH 7.6 M 10 ml

Example 2: a collyrium which may be used as artificial tears containing: hyaluronic acid sodium salt hyalectin fraction 20 mg saline buffered with phosphate pH 7.6M 10 mg

Example 3: a gel containing EGF in which 100 g contain: hyaluronic acid sodium salt hyalastine fraction 55g hyaluronic acid sodium salt hyalectin fraction 30g

EGF 0.5g twice distilled water 23.5g

Example 4:

a 100 mg insert with pilocarpine nitrate containing: hyaluronic acid sodium salt hyalastine fraction 100 mg pilocarpine nitrate2 mg

Example 5:

a powder form for topical application containing streptomycin. 100 g of powder contain: hyaluronic acid sodium salt hyalastine fraction 70 g hyaluronic acid sodium salt hyalectin fraction 28.5 g streptomycin 1.5 g

Although the above-preparations have been described for exemplary purposes, it will be appreciated that the pharmaceutical formulations could be prepared by combining the hyaluronic fractions, particularly the hyalectin or hyalastine fractions or the combined hyalectin/hyalastine fraction, or the potassium or sodium salts thereof, with other active drugs, and at various dosages depending upon the particular use for the formulation.

Hyaluronic acid, particularly in the substantially pure hyalectin and hyalastine fractions, has, therefore, been shown to be an effective vehicle or excipient for use in combination with various drugs having ophthalmic utility or activity. Pharmaceutical compositions containing the HA fractions as the drug vehicle are particularly useful because the HA fractions exhibit a high level of tolerability to the eye and a high compatibility with the corneal epithelium.

Use of the HA fractions, moreover, provides a means for actually enhancing the in vivo biological activity of ophthalmic drugs. The use of the particular hyalectin and hyalastine HA fractions is further useful and important because these fractions, when administered in the eye, do not exhibit undesirable inflammatory side reactions.