BACKGROUND OF THE INVENTION

As described in a commentary on pages 192-194 of the Journal of the American Veterinary Medicine Association (JAVMA) , Vol. 197, No. 2 (July 15, 1990), the population growth of unwanted pets represents a significant problem in the United States.

The problem of pet overpopulation in the United States reflects a similar problem with feral dogs and cats in developing and third world nations. As the JAVMA article describes, there are surgical methods for sterilizing dogs, cats, and other pets, but these methods are too expensive to be widely used at effective levels and have associated risks (e.g., anesthesia, infection and hemorrhage). Various products for non-surgical sterilization are currently under investigation, as indicated in the July 15, 1990 article, but none have proven to be entirely satisfactory.

Also, Stagg et al. U.S. Patent No. 4,356,189 discloses the sterilization of male animals by injection

of a weak acid such as lactic acid, or a weak base, into the spermatic cords. A product based on this invention was licensed for cattle by the Food and Drug Administration/Center for Veterinary Medicine, and was being evaluated for dogs, but the license was withdrawn in August of 1990 due to evidence of non-efficacy as a result of variability in administration of the drug. Additionally, this drug was not efficacious in dogs. Another product under development, zinc tannate, has shown promise in laboratory tests with rodents and rabbits. However, this product has yet to be tested in species intended for treatment, namely, dogs and cats. This agent is not intended for use in food production animals. See U.S. Patent Nos. 4,156,427 and 4,339,438.

Methods used for castration of livestock present different types of problems. The procedures are performed by non-veterinarians, and are traumatic on the animals, causing a high incidence of infection, poor growth, hemorrhage and death.

For example, about two percent of the hogs which are castrated every year develop severe disease or die from castration-associated infection. Others are sickened for a period of weeks, which causes their growth to temporarily slow. The actual number of hogs that become sick or die yearly in the United States from castration-associated infection is believed to be on the order of two million. Also, because of undetectable

abscesses caused by these infections, a large portion of the carcasses or parts of carcasses from hogs which do reach slaughter cannot be used for meat. Accordingly, there is a major need in both the field of food animal production, and in the field of pets, for an effective way to castrate animals in a manner that is safe and non-injurious to the animal, while being inexpensive as well. In accordance with this invention an enzymic preparation is used for castration, providing reliable, effective results at low cost, and with little or no pain to the animal. Furthermore, the properly used enzyme system of this invention appears to be safe to the animal so that, for example, millions of hogs can be saved over a period of a very few years by simply using the invention of this application rather than conventional castration. It is expected that similar savings will be found in other kinds of farm animals. The use of this invention is so simple that it can be used on pets in a widespread manner for the reliable control of pet populations.

Also by this invention, enzyme preparations can be used to destroy tumor tissue (malignant or non- malignant), typically in encapsulated tumors.

DESCRIPTION OF THE INVENTION

This invention relates to a method of chemically castrating male animals, which method comprises injecting into both testes or into both spermatic cords a castratingly effective amount of a protease enzyme preparation which is typically substantially free of collagenase activity. The phrase "substantially free of collagenase activity" identifies protease enzymes that either preferentially attack non-collagen proteins, or which are largely inactive to collagen. Thus the testes may be injected, to cause substantial protease activity within the testes, while the collagen outer tunic of the testes remains intact to essentially localize and contain the enzyme within the testes. It is understood that small amounts of collagenase activity may be present in the enzyme, as long as the enzyme used, under the conditions of use, does not effectively break down the outer collagen membrane of the testes to permit substantial and toxic release of the enzyme into the body of the animal.

Chymopapain has been found to be particularly useful for the purpose of castration because, while the chymopapain attacks membrane proteins in the reproductive (sperm producing) cell layer in the testes to collapse the associated structures therein and to

sterilize the animal, the non-cellular collagen connective tissue and outer tunic is not strongly attacked by chymopapain. Thus, the collagen outer tunic stays intact, having the effect of isolating the enzyme in the testes. It is of course desirable to isolate the enzyme in the testes, restricting free chymopapain or other enzyme to the testes, or target site. A spontaneous localization of the chymopapain typically takes place in the testes, so that damage outside of the testes does not have to occur when this invention is properly used.

Other examples of protease enzymes which are candidates for use in injecting the testes or tumors include serine proteinases such as chymotrypsin, trypsin, or sutilains; or cysteine proteinases such as papain, fucin, or bromelin. Additionally, enzymes which promote tissue diffusion, such as hyaluronidase, may be used in conjunction with the above enzymes. Thus, animals may be sterilized by single injections into the testes. Also, sterilization may be effected by an injection into the spermatic cords to collapse the epididymis and/or the vas deferens, having an effect rather like of a vasectomy. The animal in this manner retains more male characteristics, but is sterilized. Also, there is a possibility of reversal of the sterilization procedure if the enzyme has been applied only to the epididymis and/or vas deferens.

The enzyme may be applied to any desired animal, particularly mammals of very young age, such as dogs, cats, hogs, sheep, goats, cattle, horses, and the like. Many types of proteases from microbial, plant or animal organs are known to possess an enzyme activity which would be more highly destructive to loosely arrayed cell membrane proteins versus densely arrayed connective tissue matrices commonly known as collagen. The enzyme preparation of this invention may be conventionally buffered at a pH of about 7.2 to 8.2. Biocompatible buffers such as phosphate, imidazole, tris (hydroxy methyl) aminomethane or the like may be used. Typically, the pain of the injection to the animal is greatly reduced by maintaining the pH of an enzyme preparation similar to the tissues of the body. Additionally, or alternatively, the enzyme preparation may comprise an effective concentration of a local anesthetic such as lidocaine, carbocaine, buipivacaine or the like. Specifically, the enzyme preparation may contain about 0.1 to 4 weight percent of such local anesthetic in order to provide an effective dosage thereof.

The enzyme preparation of this invention may comprise a chymopapain activity-stabilizing amount of ethylenediamine tetraacetic acid (EDTA) and/or cysteine, both of which serve as enzyme preservatives and activators. For example, cysteine hydrochloride may be

present in a chymopapain enzyme preparation at a concentration of about 0.1 to 5000 millimoles per liter. EDTA may be present in about a concentration of 0.01-40 millimoles per liter, although for both of these materials other concentrations may be used where appropriate.

Other sulfhydryl containing enzyme stabilizing agents such as glutathione, methionine, or other known substances may act as equivalents to cysteine.

Other chelating agents such as disodium versenateor inositol hexaphosphate may also stabilize chymopapain enzyme activity.

Additionally, the enzyme preparation may include a fluorescent marker material in an effective concentration to be detectible in the urine of the animal, in the event that the enzyme preparation escapes from the region of the testes or a tumor. This serves as an indicator that some enzyme escape has taken place, so that the animal or patient may be observed. For example, guinacrine hydrochloride in a concentration of about 0.2 to 20 mg. per ml. of enzyme preparation may be used. Preferably, about 0.5 mg. per ml. of quinacrine hydrochloride may be used. Additionally, other non- toxic fluorescent markers may be used for the same purpose.

Additionally, the enzyme preparation of this invention may contain a vasoconstrictor in sufficient

concentration to cause constriction of precapiUary arterioles in the testes upon injection of the enzyme preparation therein, to further inhibit migration of the enzyme from the testes or a tumor. Typically, a vasoconstrictor such as epinephrine may be present in the enzyme preparation in a concentration of about 0.0005 to 0.1 percent by weight. Because of such vaso constriction, it may be possible to use enzymes that are stronger in collagenase activity than chymopapain.

It may be desired to inject at least a portion of the enzyme preparation into the epididymis of the testes. This procedure hastens sterilization by attacking the most mature sperm cells. Chymopapain-rich enzyme preparations are well- known and commercially available. Typically, ultrapure chymopapain preparations are not necessary for use in this invention, but may be used if desired. It is important that bacterial endotoxin levels be kept to non pyrogenic levels. The presence of other enzymes and the like does not necessarily render the invention ineffective as long as side effects from the enzyme activity and/or impurities are minimal.

The effective dose of the enzyme preparation depends of course on the type of animal or patient and the size of the testes or tumor. The particular dosage in terms of enzyme activity to be used in any individual

situation can be easily determined by simple experimentation using known testing methods.

For example, testes from dogs and cats can be removed surgically and preserved on ice for periods of hours. Enzyme preparations can then be injected into the testes, after which they are incubated in a sealed container at 32 to 37%C in a water bath. After four hours, the testes can be removed and the degree of tissue changed and/or amount of enzyme activity remaining can be assessed. By this testing method, untreated control testes demonstrate normal tissue structure and live sperm after four hours of incubation. Such testing may be used to show how much enzyme activity and by what method significant tissue changes which might lead to sterilization are produced. Following pilot testing in vitro, actual animal testing can be performed.

For example, piglets, which have testes about the size of small to medium size adult dogs, may be treated with a total of approximately 150 to 300 or 400 units of protease enzyme activity, into each testis, and other animals may typically be treated with proportional amounts of enzyme activity by injection into the testes, depending upon the mass of the testes. The enzyme units used here and below are well-known BAPNA units.

The chymopapain may be extracted from papaya latex according to the Boudart method, or in a manner

similar to that described especially pages 246 and 247 of an article entitled Chymopapain B by Donald K. Kuni itsu et al. from Methods in Enzy ology, Volume XIX, Proteolytic Enzymes, edited by Gertrude E. Perlmann et al. (1970) Academic Press. The purification method for the chymopapain is generally believed to be non- critical, being subject primarily to the constraints of enzyme activity and low toxicity so that the product is safe and effective. Safety and effectiveness are assured by frequent 0.22 micron (sterile) filtration and at least one 100,000 Dalton molecular filtration to remove endotoxins and other large molecules.

The enzyme preparation for parenteral use must be sterilized in a conventional manner, making use for example of technology similar to the chymopapain injectable product used for treatment of prolapsed spinal disks. See for example the article by Paul J. Garvin et al. entitled Chymopapain: A Pharmacologic and Toxicologic Evaluation in Experimental Animals, pages 204-223, "Clinical Orthopaedics" No. 42 (1965) J.B. Lippincott Company.

The enzyme preparation may be encapsulated in microspheres or microvesicles to promote slow release into the testes or tumor and containment in the testes or tumor, if desired, with the microcapsules or microvesicles being implanted therein.

Thus the enzyme preparation and the method of use thereof provides a significant improvement in, particularly, the enzyme castration of animals for ease of operation, low cost, and safety, so that a higher percentage of the animals avoid negative side effects from the process than in surgical castration.

Alternatively, the enzyme preparations discussed above may be injected into large, typically inoperable tumors of human patients and animals to destroy tumor cells, thus reducing the tumor size or even substantially eliminating the tumor. Thus, the metabolic burden of the tumor can be quickly and easily reduced, and in some cases the reduction of the mass of the tumor may render it more amenable to surgical removal.

Protease enzymes as described above may be used, with the desired added ingredients as also discussed above for the purposes described. The enzymes may or may not be substantially free of collagenase activity.

Such a process of debulking or destroying a tumor can be used in conjunction with other forms of cancer therapy such as hyperthermia, radiation, and/or chemotherapy to produce additive or synergistic effects greater than the effect of any agent alone.

The use of proteolytic enzymes to debulk cancer or other tumor tissue mass in accordance with this invention is relatively non-specific in its effects on

tumor cells, and is typically not resisted by different clones of tumor cells, such as are found in multidrug resistant cancers which have been shown to have variable resistances to hyperthermia, irradiation and/or chemotherapeutic agents. Thus, by this invention, resistant tumor cells can be destroyed in large numbers. By this invention reduction or debulking of a tumor tissue mass may be effected without surgery. Such reduction of tumor tissue mass is an important step in the local control of cancer, to reduce the drain on host body resources as well as other advantages. Preferably, a chymopapain-rich enzyme formulation is preferred for the reduction of tumors in accordance with this invention. Because chymopapain is inert to collagen particularly, tumors having a collagen outer coat are thus preferred for treatment in accordance with this invention. Additionally, the formulation, as previously described, may contain a vasoconstrictor in sufficient concentration to cause constriction of nearby precapiUary arterioles and other blood vessels, to limit the spread of the enzyme out of the tumor area. Additionally, the other ingredients described above may be present for their stated purposes as well. The enzyme may be administered in any appropriate way for local delivery to a tumor site or sites for example by needle, catheter, or other orthotopic,

parenteral administration, in appropriate, effective but substantially non-toxic doses.

The above disclosure, and the examples below, have been offered for illustrative purposes only, and are not intended to limit the scope of the invention of this application, which is as defined in the claims below.

Sterilization Examples

Example 1

A complete formulation believed to optimally provide the advantages of this invention is a chymopapain rich enzyme solution having 150-250 units of enzyme activity per ml., a pH of 7.2 to 8.2, from 135 to 155 meq/L of sodium ion, from 135-155 meq/L of chloride ion, 1 millimole per liter of ethylenediamine tetraacetic acid, 10 millimoles per liter of cysteine HC1, 0.2 to 1 percent ( /V) of lidocaine HC1, 0.001 percent (W/V) epinephrine, 0.05 percent (W/V) of quinacrine HC1, and sterile water q.s..

Such an enzyme formulation may be injected into the testicles of any desired male mammal in the manner described above to achieve sterilization.

Alternatively, such an enzyme formulation may be injected into a preferably encapsulated tumor to cause

significant reduction of its mass through large-scale cell death.

Example 2

Four Duroc-cross, male piglets approximately nine weeks of age (weaned) were injected in the testicles with three doses of enzyme preparation. The doses selected were IX, 2X and 3X of a minimum clinical dose determined from in vitro studies. The piglets ranged from 10.0 to 16.0 kg in weight. The objective of the study was to demonstrate any changes in testicular tissue which would result from these enzyme doses. These piglets were anesthetized with ketamine HC1 and acepromazine maleate, and were given injections as follows:

Piglet No. Description of Dose

1R 180 units of enzyme activity in 1.0 ml. of volume (qs with saline) into each testis.

2R 150 units of enzyme activity in 1.0 ml. of volume (qs with saline) into each testis.

1L 180 units of enzyme activity in 1.0 ml. of volume (qs with saline) into each testis.

2L 270 units of enzyme activity in 1.0 ml. of volume into each testis. Injection doses were based upon estimates of the testicular sizes of the piglets, being approximately 3 to 4 grams in weight per testis. By calculation it was intended to administer approximately 30, 60 or 90 units

of enzyme activity per gram of testis to each testis. The total body doses of enzyme activity were 9 to 27 units of enzyme per kg of body weight. These amounts were well within known safety margins.

Treatment Results

The testes of all piglets became turgid upon injection, and remained in this condition for approximately 36 hours. Several of the animals also appeared to have cyanotic testes. The piglets all recovered uneventfully from anesthesia and showed no signs of sensitivity on palpation, anorexia, or abnormal gait. Food intake was normal for 45 days during which period the piglets averaged 0.45 to 0.60 pounds of gain per day. The piglets were turned out into a pasture where they were inadvertently exposed to two days of near freezing weather. All piglets developed pneumonia and were brought back to the barn for antibiotic treatment and care. Between September 18 and October 5, three piglets died. Necropsies on Piglets 2R and 1L confirmed death due to acute pneumonia. Changes in the testicular tissues included absence of the germinal layer of the seminiferous tubules. The third piglet which died was not autopsied. The remaining piglet has been allowed to grow to slaughter weight, for future testing.

Multiple (step) sections of Piglets 2R and 1L show a total absence of spermatogenesis. The seminiferous tubules were filled with a connective tissue lattice. This finding was considered unrelated to the animals' deaths due to acute pneumonia.

Results of this study suggest that doses of 30 to 90 units of enzyme activity can be administered safely to piglets and produce degeneration of the germinal layer of the seminiferous tubules, to produce sterility.

Example 3

Three groups of five rats each were injected with non-catalyzed suspensions of three different enzyme preparations. The left testis was used for test injections and the right testis received saline (control) injections. The objective of the study was to comparatively evaluate the action of enzyme with the action of a physiological solution.

Rats weighing 227 to 261 g were manually restrained and injected with the following enzyme preparations:

Group Description of Dose

A-l 162 units of papain in saline in 0.25 ml. volume (left testis) ; 0.25 ml. saline (right testis) A-2 163 units of chymopapain in saline in 0.25 ml. (left testis); 0.25 ml. saline (right testis).

A-3 500 units technical grade papain in 0.25 ml.

(left testis); 0.25 ml. saline (right testis).

The enzyme preparations were not catalyzed so that more of the basic effects of the proteins could be studied versus effects from the enzyme activity, or additives.

Treatment Results

The enzyme treated animals showed no signs of toxicity acutely or after 25 days. Testes treated with enzyme preparations showed variable enlargement followed by shrinkage when the testes were palpated. Control testes were considered normal in size and texture. Histopathological evaluation of testes for all animals showed fibrosis and scarring of the treated testis and normal spermatic genesis in the untreated testis for all animals among the three enzyme treated groups.

It was concluded that even though enzyme activity was not maximized by catalytic additives, the action on the testis was of a type which could cause sterility (i.e., cessation of spermatogenesis). Catalyzed enzyme would of course exhibit greater enzyme activity.

Tumor Reduction Examples

Example 4

Formulations of chymopapain solutions were prepared at pH 7.2 - 8.2 having varying enzyme activities in the range of 5 to 70 enzyme activity units per ml.. The solution contained 135-155 milliequivalents per liter of sodium chloride, 1.0 millimole per liter of EDTA, 10 millimoles per liter of Cysteine hydrochloride, 1 percent (W/V) of lidocaine hydrochloride and 0.002 percent (W/V) epinephrine.

Example 4a

Twenty-five male C3H/HeJ mice were injected with about 2 x 10° FSall (fibrosarcoma cells) in the right rear leg to cause 5-6 millimeter diameter tumors to appear in seven days. On the seventh day after tumor implant, each mouse was injected in the tumor with 0.02 ml of one of the chymopapain enzyme solutions of Example 4, minus the lidocaine ingredient, or, as a control, a corresponding epinephrine solution without the enzyme. All tumors were observed to turn pale upon injection as a result of the presence of the epinephrine.

The animals were observed daily for changes in the tumor site and for signs of toxicity. On the following day after injection of the enzyme, the tumors were remeasured for size. Results are found in Table 1 below.

Table 1

Tumor Changes and Toxic Signs From Chymopapain and Control Injections in Tumor Bearing Mice.

4 20 Units/ml 5 3 Tumors Reduced in Enzyme Size, 2 Tumors Grew

5 40 Units/ml 5 3 Tumors

Enzyme Disappeared,

1 Tumor Reduced to 3 mm, 1 Tumor Grew

The mice appeared to be subject to intense itching at the injection site for about 2 hours at all concentrations of the enzyme administered. Daily monitoring of tumors revealed the three tumors with substantial reduction in mass of test group 4 remained significantly smaller for eight days after enzyme injection, at which time their 6-8 millimeter diameters were less that the 10 millimeter average of test group

4 and the 10 to 13 millimeter average of test groups 1- 3. No serious toxic symptoms were observed in the mice apart from the transient intense itching.

This study shows that chymopapain injected in an effective quantity into a tumor can significantly reduce tumor mass (i.e. debulk the tumor) .

Example 4b.

Thirty male C3H/HeJ mice were injected with FSall fibrosarcoma tumor cells in the right flank area.

Tumors were allowed to grow to 7 to 8 mm in diameter on day eight (post injection) , and up to 13 mm in diameter on day nine.

On days eight or nine, tumors were in ected with approximately 0.03 ml of one of four enzyme preparations of Example 4 or a control vehicle, without enzyme. Lidocaine was present to decrease the intensity of post- injection itching observed with the previous tumor dissolution study of Example 4a. The study animals used in this study were monitored acutely for 24 to 48 hours. Results of the study are summarized below in Table 2. As before, the tumors became pale from the epinephrine.

Table 2

Tumor Changes and Toxic Signs From Chymopapain and Control Injections in Tumor Bearing Mice.

Test Number The Day

Grou Test Substance of Mice In ected Tumor Chan es

Acute monitoring revealed that all mice ate, drank and eliminated normally. No signs of acute toxicity other than mild itching were noted. The itching persisted for one or two hours. Also, some skin ulcers appeared from central massive destruction of the tumor. All tumors treated with Enzyme were noticeably reduced in mass (50 percent or greater) . Also, in 24 hours the tumors in most of the animals of groups 3, 4 and 5 had collapsed in the middle (i.e. cavitated) . While the tumors in these animals opened due to necrosis, resulting in some skin ulceration, the animals

continued to eat, drink and otherwise behave normally. No animal deaths occurred in any dosage range.

The results of this study confirmed the ability of protease enzyme to significantly debulk tumors, and for the presence of the Lidocaine to suppress bad side- effects by localizing the enzyme in the tumor.