Therapeutic Hyaluronidases

Testicular hyaluronidase is the principal hyaluronidase used as a therapeutic agent. The enzyme has been extracted from both bovine and ovine testicular tissue and semen.

Homogenization followed by centrifugation and precipitation of the supernatant with ammonium sulfate is used to obtain a crude preparation. The enzyme has been further purified to homogeneity by ion-exchange (cation and anion), gel-filtration and affinity (heparin-Sepharose) chromatographies [140].

Bovine testicular hyaluronidase has been used in the cosmetic, pharmaceutical, and medical fields. However, the advent of bovine spongiform encephalitis halted commercial production of bovine hyaluronidase. Wydase from Wyeth was one of the most popular bovine preparations, but production of this product has now ceased. However, a new formulation called Vitrase, by ISTA Pharmaceuticals Inc., has recently gained FDA approval. This enzyme is derived from sheep testicular tissue and is formulated as a sterile lyophilized 6200 USP unit preparation with 5 mg of lactose, 1.92 mg of potassium phosphate dibasic, and 1.22 mg of potassium phosphate monobasic as excipients. The product can be reconstituted with sodium chloride injection, USP [150]. Attempts have been made to clone bovine testicular hyaluronidase in an effective expression system that will yield a correctly glycosylated and functional enzyme [151]. Newer preparations include recombinant human testicular enzyme (rHuPH 20), which has been developed by Halozyme Therapeutics. This enzyme has completed phase-3 trials and is indicated for use in in vitro fertilization (to break down the outer hyaluronan layer of the oocyte), and as a spreading factor for anesthesia. These products are being developed to offer safer and purer alternatives to the existing slaughterhouse-derived extracts that carry risks of pathogen contamination, immunogenicity, and toxicity [152].

Hyaluronidase exerts it therapeutic effect by making tissue more permeable to injected fluids, leading to increased speed of drug absorption. Preparations of bovine testicular hyal-uronidase have been applied therapeutically in the fields of orthopedics, ophthalmology, and internal medicine for many years with efficacy and safety. A common field of application is its addition to local anesthetic agents, especially ophthalmic anesthesia, to improve the rapidity of onset, dispersion, depth, and duration of the local anesthesia [153,154].

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