ALTERATION OF RATE AND CHARACTER OF HAIR GROWTH

This invention relates to a method and composition for altering the rate and character of mammalian hair growth particularly androgen- 5 stimulated hair growth, by topical application to the skin of a composition containing an inhibitor of the enzyme L-asparagine synthetase.

It has previously been proposed that the rate of hair growth, as well as the character of

10 hair can be modified by topical application of inhibitors of certain enzymes such as inhibitors of 5-cι-reductase or ornithine decarboxylase, or such antiandrogens as androgen receptor binding agents, as described in U.S. Patent Νos. 4,720,489 and

15 4,885,289. Moreover, it has been theorized that certain other enzymes, including gamma glutamyl transpeptidase, are involved in various stages of hair follicle formation or of hair growth, but the relation between the various enzymes and the

20 reactions which they control, as well as their effect upon each other and upon hair growth, has not been fully understood, as appears from Richards et al., Cancer Research, Vol. 42, 4143-4152 (1982) and DeYoung et al. Cancer Research, Vol. 38, 3697-

25 3701 (1978); and Chase, Physiol. Zool. Vol 24, 1-8

^• (1951).

In the present invention it has been found that the rate and character of mammalian

SUBSTITUTESHEET

(including human) hair growth, particularly androgen-stimulated hair growth, can be modified by topical application to the skin of a composition containing an organic inhibitor of the enzyme L- asparagine synthetase. Inorganic inhibitors such as zinc chloride are undesirable because they tend to be irritants. The present invention includes a cosmetic process of reducing the rate and altering the character of mammalian hair growth which comprises the step of applying to skin a composition containing an organic inhibitor of L- asparagine synthetase.

Among the known organic inhibitors of the enzyme L-asparagine synthetase which can be used in the present invention are: guanidinosuccinic acid; oxaloacetic acid; L-cysteinesulfinic acid; diethyl aminomalonate; dipeptides containing L-aspartic acid (L-aspartylglycine, L-aspartyl-L-leucine, L- aspartyl-L-phenylalanine, L-aspartyl-L-proline, L- _$ -aspartyl-L-serine and L-α-aspartyl-L-valine); N-o-nitrophenylsulfenyl-L-aspartic acid; N-o- nitrophenylsulfenyl-L-glutamine; S-adenosyl-L- methionine; L-homoserine-3-adenylate; palmitic acid; lauric acid; and ethacrynic acid. Of these, guanidinosuccinic acid, ethacrynic acid, oxaloacetic acid, L-cysteinesulfinic acid and diethyl aminomalonate are preferred.

The composition contains, in addition to the inhibitor, a non-toxic dermatologically acceptable vehicle or carrier which is adapted to be spread upon the skin. The concentration of the inhibitor in the composition may be varied over a wide range, either in the form of a solution or dispersion, containing from 0.1 to 30% by weight of the inhibitor, preferably 2 to 15%, and the composition may be applied at a dosage rate of 10 to 25 mg/cm ² of skin. That is, the dosage of

inhibitor itself is from 10 to 7,500 μg per square centimeter of skin. Penetration enhancers may also be present in the composition, including alcohol, acetone, propylene glycol, polyethylene glycol, dimethyl sulfoxide, 2-pyrrolidone, N-methyl-2- pyrrolidone, surfactants, azone, and the like, preferably in an amount effective to cause at least 10% inhibition of hair growth when the composition is applied to the skin adjacent the hair. The maximum amount of composition effectively applied is limited by the rate at which the inhibitor penetrates the skin.

The following specific examples are intended to illustrate more clearly the nature of the present invention without acting as a limitation upon its scope. Example 1

A vehicle or carrier was prepared having the following composition: Component Percent concentration bv weight

Water 68%

Ethanol 16%

Propylene Glycol 5%

Dipropylene Glycol 5% Benzyl Alcohol 4%

Propylene Carbonate 2%

To separate portions of the vehicle were added amounts of four different inhibitors of L- asparagine synthetase as shown in Table 1 and the pH was adjusted with sodium hydroxide to achieve complete dissolution.

Four groups (eight animals in each group) of male intact Golden Syrian hamsters were provided. These animals were considered acceptable models for human beard hair growth in that they display oval shaped flank organs, one on each side, each about 8 mm. in major diameter, which grow

SUBSTITUTESHEET

thick black and coarse hair similar to human beard hair. These organs produce hair in response to androgens in the hamster. The flank organs of each hamster were depilated by applying a thioglycolate- based chemical depilatory (Surgex) , and to one organ of each animal was applied 10μl of vehicle alone once a day, while to the other organ of each animal was applied an equal amount of vehicle containing inhibitor. After three weeks of such applications (five days a week) , the flank organs were shaved and the amount of recovered hair (hair mass) from each was weighed. The extent of reduction in hair growth by the inhibitor was expressed as the percent decrease in hair mass on the organ treated with inhibitor as compared to the organ treated with vehicle alone. As a control, one group of eight animals had both flank organs of each animal treated with vehicle alone. The results were as shown in Table 1 below.

Table 1

Tnh-ib-i-Hπn n*F Tfai*r Orr**h

Hamster Flank Orαan Tftir Tfore (va.) Treatment Amount pH Untreated Treated Percent ^g ∞ ^p _ Mean ά SP -tfean t SP Irti tipn

Cuitiul 7 1.92 + 0.19 1.81 ± 0.24

(vehicle) fire-mi flino- succinic acid 6% 7 1.48 + 0.09 0.64 ± 0.07 57.1%

Oxaloacetic acid 10% 3-4 1.44 + 0.18 0.77 ± 0.11 38.0% cysteine- sulfinic acid 6% 3-4 1.44 + 0.16 1.10 ± 0.19 25.5% Diethyl amino- malcnate 10% 3-4 1.53 ± 0.18 1.18 ± 0.18 23.3%

Example 2

Compositions were prepared containing 5%, 10%, and 20% respectively of guanidinosuccinic acid in the vehicle described in Example 1 above and applied as in that Example. The results were as shown in Table 2.

Table 2 Inhibition of Ha-i-r orut ^~ y bv Guanidinosuccinic Acid

^Tfaπwt "* ^oτ ' fhnk ^Q rαan Hair M^ ⁽ πa. ^'

Treatment Amount pH Untreated Treated Percent

Grou ^p _ ffi**m + ffp Tfr-?T t P -Inh b tion

Control 7 2.17 ± 0.24 1.78 ± 0.25 Guanidino¬ succinic acid 5% 7 1.52 ± 0.19 0.69 ± 0.14 52.6 ± 8.2

Guanidino¬ succinic acid 10% 7 1.86 + 0.18 0.72 ± 0.19 55.7 ± 15.1

Guanidino- S iinic acid 20% 7 1.83 ± 0.31 0.38 ± 0.12 80.1 ± 5.8

It was found that similar topical, treatments with a 10 and 20% solution of guanidinosuccinic acid (two treatments over a 24 hour period using groups of 10 animals) resulted in a respective 76 and 85% reduction of L-asparagine synthetase activity in the hamster hair follicles. Example 3

Compositions were prepared containing 10% and 20% by weight of ethacrynic acid respectively in the vehicle described in Example 1 above, and applied to hamster flank organs under the same conditions as described in Example 1 except that seven animals were in each group instead of eight. The results are shown in Table 3 below.

SUBSTITUTESHEET

Table ?

fry Ethacrynic tort

ft -ster Flanft prgqn ffijr my fir.)

Treatment Amount rfi Untreated Treated Percent

Grou ^p _ tfean t SP w^η + -^ ictύfejϋso

Oii ul 7 2.85 + 0.26 2.82 ± 0.32

Ethacrynic acid 10% 5 3.09 ± 0.27 1.82 ± 0.22 42%

Ethacrynic acid 20% 5 2.47 + 0.27 0.91 ± 0.10 63%

Similar results can be obtained using other organic inhibitors of L-asparagine synthetase.