RESEARCH
Search for Antifertility Drugs Widens Many drug firms see nonsteroidal chemicals as potential route to cheaper oral contraceptives 144TH
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Medicinal Chemistry
These Nonsteroidal Chemicals Are Among Those Being Tested As Oral Antifertility Agents Implantation inhibitor
The push to uncover new antifertility agents is moving into high gear. Lat est find is a series of diphenyldihydronaphthalenes which show promising activity in experimental animals. Most active of the series is l-{2-[p( 3 , 4 - dihydro-6-methoxy-2-phenyl-lnaphthyl)phenoxy] ethyl } -pyrroli dine hydrochloride, called U-11100A by Upjohn. U-11100A is the most potent oral antifertility agent seen to date aside from estrogens, Upjohn's Dr. Daniel Lednicer, Dr. Gordon W. Duncan, and Stanley C. Lyster told the Symposium on Nonsteroidal Antifertility Agents. Preliminary clinical trials have been started. Also among nonsteroidal compounds are 2,4-dinitropyrroles substituted at C-l from Ortho Research Foundation, and some halogenated diamines from Sterling-Winthrop Research Institute. These chemicals inhibit sperm pro duction. Male rats given single doses of Ortho's l-(N,/V-diethylcarbamylmethyl ) -2,4-dinitropyrrole ( ORF1616) became sterile in about three weeks. The Winthrop chemicals have been tested on humans. Most potent is N,A7'-bis ( dichloracetyl ) -1,8-octanediamine (WIN-18446). This chemi cal reduces sperm counts in humans but also causes severe Antabuse-type reactions if the subject consumes al cohol, says Dr. Carl G. Heller of Pa cific Northwest Research Foundation, Seattle, Wash. Clinical tests have also been started with a derivative of dithiocarbamoylhy drazine : 1 -a-methylallylthiocarbamoyl- 2 -methylthiocarbamoylhydrazine (Ayerst-61122 and ICI-33828). This material inhibits ovulation. And Merrell's clomiphene (MRL-41), chemically l-[p- (^-diethylaminoethoxy ) phenyl] -1,2-diphenyl-2-chloroethylene, inhibits implantation in test ani60
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l-{ 2-Ip-(3,4-Dihydro-6-methoxy· 2-phenyl-l-naphthyI)phenoxy] ethyl }-pyrrolidine hydrochloride Upjohn U-11100A
Ovulation Inhibitor
l-a-Methylallylthiocarbamoyl· 2-methylthiocarbamoylhydrazine Ayerst-61122;ICI-33828
Antispermatogenlc agents, l-(N,NDiethylcarbamylmethyl)2,4-dinitropyrrole ORF-1616
0 11
mais. In humans, though, tests to date indicate clomiphene actually stimulates fertility. Steroidal antifertility agents are also quite effective. For example, Searle's ethynodiol diacetate ( 17-ethynyl-4-androstene-3,17-diol-3,17-diacetate) is now in widespread clinical trial.
N,N»-Bis(dichloroacetyl)-l,8octanediamine WIN 18446 Λ
Searle says this product is five times more potent than norethynodrel ( Searle's Enovid ). Another steroidal agent, Lilly's chlormadinone, 6-c h 1 ο r o-17-a-hydroxypregna-4,6-diene-3,20-dione ace tate, is being tested in "sequential therapy." This approach involves giv-
ing an estrogen alone for the first 15 days of the dosage cycle, followed by a combination of estrogen and chlormadinone for five days. The usual approach for steroidal agents involves taking a combination of progestin and estrogen for 20 days. Population Growth. Behind the effort to find antifertility drugs lies the much discussed population explosion. Present world population—some 3 billion— is about double that of 70 years ago. Forecasts call for this number to double within 40 years. Greatest growth is in poorer, less developed regions, with Latin America leading the way. Statistics show that Latin America's population growth is more than four times faster than that of northwestern Europe. Hope of slowing the population explosion through drugs got a boost in 1956 when synthetic oral progestins ( profertility agents ) proved capable of stopping ovulation. This touched off tests of 19-norsteroids as possible oral contraceptives. Out of such programs came products such as Sear le 's Enovid, Parke, Davis & Co/s Norlutin, and Ortho's Ortho-Novum. The P-D and Ortho products are being sold under license with Syntex, whose scientists synthesized the original compound. The three drugs are actually combinations of a 19-norsteroid with a small amount of a synthetic estrogen. Additional 19norsteroids are being sold outside of the U.S. While very effective—some clinicians claim 100%—these products have some shortcomings. Occasional side effects include nausea, midcycle bleeding, weight gain, and breast tenderness. Relatively high cost is also a big problem. And dosage cycles of 20 days offer an opportunity for missing a dose and possibly upsetting the result sought. Today, at least 14 drug companies have active programs searching for lower cost oral antifertility agents which have fewer side effects and can be taken less frequently. Searle's ethynodiol diacetate, active at much lower dosages than Enovid, could be cheaper with fewer side effects. And since Lilly's chlormadinone can be taken for only five days instead of 20, cost of treatment should be lower. Possibly all the steroidal contraceptives may lend themselves to the sequential therapy approach. There is some evidence that the 19-nor-
Steroidal Antifertility Agents Are Also Being Tested 17-ethynyl-4androstene-3,17diol-3,17-diacetate Searle'sethynodiol diacetate
6-chloro-17-a-hydroxypregna4,6-diene-3,20-dione acetate Lilly's chlormadinone
steroid factors in both Enovid and Ortho-Novum are metabolized to an estrogen, probably ethynyl estradiol. Should this prove to be the case, substitution of cheaper estrogens for the first 15 days of the dosage cycle could give much lower treatment costs and possibly fewer side effects. Several drug makers are becoming convinced that the nonsteroidal approach will yield the cheapest, safest, and most convenient antifertility drugs. Big areas of study by the drug firms include chemicals which block ovulation or developments of the ovum and chemicals which inhibit sperm formation. Single Dose Effective. Upjohn's diphenyldihydronaphthalenes came out of a long-term research program to find steroid antagonists. Prior to the use of dihydronaphthalênes, Upjohn scientists had noted antifertility activity in a series of 2,3-diphenylindenes. Laboratory animals fed 100microgram doses of these chemicals for four days immediately after mating failed to become pregnant. One of the most active of this series is 2-[p(6 - methoxy - 2 - phenylinden - 3- yl)phenoxy]triethylamine hydrochloride (U-11555A), Dr. Lednicer says. No antifertility activity has been seen in 2,3-diarylindenes which lack the basic ether group. However, Upjohn's U11555A is found to be unstable to oxygen and turns red on standing in air with a change in its ultraviolet absorption spectrum. Spurred by the activity found in 2,3diphenylindenes, Upjohn scientists synthesized a series of 1,2-diphenyl-
3,4-dihydronaphthalenes. These compounds are stable and are very potent antifertility agents in animals such as rats, guinea pigs, and rabbits, Dr. Duncan says. The most active compound of this series is Upjohn's U-11100A. Only a 5-microgram dose per day for four days following mating is needed to prevent pregnancy in rats. The natural estrogen, estrone, is active at four micrograms in the same test system, Dr. Lednicer notes. Also getting tests is 2-[p-(3,4-dihydro-6methoxy-2-phenyl-l-naphthyl) phenoxy]triethy lamine ( U-10520A). This compound is effective in rats at a dose of 50 micrograms per day for four days following mating. At higher doses—five to 10 times the minimum effective dose—both compounds prevent pregnancy in animals when administered to them on any one of four days following mating, or on the day before mating. Not Toxic. The dihydronaphthalenes are estrogen antagonists. They have no other significant hormonal activity at the therapeutic dose, Dr. Duncan says. They produce changes in the physiology of the Fallopian tube and the uterus. Possibly the changes produced in these organs inhibit development of the egg, he says. At any rate, eggs don't mature and no implants are found on the wall of the uterus in test animals. The drugs have no effect on the blastocyst itself. When given to animals later than four days after mating, normal pregnancies and normal offspring result. The new Upjohn agents enjoy a APRIL
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good therapeutic index, Dr. Duncan adds. Acute toxicity studies show that U-11100A has an LD 5 0 of 302 mg. per kilogram of body weight in rats. The LD 5 0 of U-10520A in rats is 547 mg. per kilogram. These values, plus other experience with test animals, in dicate that these compounds are not toxic at therapeutic doses, the Upjohn scientists say. Inhibit Ovulation. The dithiocarbamoylhydrazine derivatives were developed by Imperial Chemical In dustries. Ay erst Laboratories has the U.S. license. The compounds seem to act on the pituitary to prevent ovulation. This action apparently is much like that of the steroidal con traceptives. Early clinical tests indicate that doses of about 25 mg. per day don't inhibit ovulation in humans. Inhibi tion occurs when doses near 50 mg. per day are given for several days. At doses high enough to control ovula tion completely, some nausea and sedation have been detected. Cost also becomes a factor with the higher doses. Ortho's dinitropyrroles stop sperm production at the primary spermato cyte stage. In rats, a single dose of 500 mg. per kilogram of body weight produces sterility in 21 days. The animals remain sterile for about 28 days. Sterility can be maintained in definitely by repeating the dosage every four weeks. The rats become fertile again about 50 days after medi cation is stopped. Mode of action of the dinitropyrroles seems to be the same as that of Winthrop's bis(dichloroacetyl) di amines and some thiophenes and nitrofurans. The nitrofurans are known to produce sperm mutations. A serious drawback to antispermatogenic agents tested to date is the long time needed to produce sterility and also to recover fertility once medica tion is stopped. Perhaps the ultimate in antifertility agents would be a contraceptive vac cine. Several research programs are aimed at developing immunological methods of controlling conception. Spurring this approach is the fact that sperm antibodies are known to exist in both men and women. Success here could mean that specific vac cines, when injected, could block a reproductive process. Maintaining sterility would then become a matter of an occasional booster shot. But re search and testing remain to be done. 62
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Technique Profiles Thermal Decomposition Dynamic reflectance spectroscopy (DRS) follows decomposition of CoBr26H20 144TH
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Analytical Chemistry A thermal technique, dynamic reflec tance spectroscopy (DRS), for study ing solid coordination compounds has been developed by Dr. Wesley W. Wendlandt of Texas Technological College, Lubbock. Dr. Wendlandt has used the technique to study the thermal decomposition of CoBr 2 -6HoO. In the past, diffuse reflectance spec troscopy has been used mainly at ambient or low temperatures. In this technique, reflectance spectra are ob tained on powdered crystalline sam ples. The samples are either pure or diluted with a matrix substance. Spectra obtained by the technique show good correlation with solution absorption spectra and single crystal spectra. Diffuse reflectance spectroscopy can give useful information about un stable compounds whose single crys tal spectra would be difficult to ob tain. Also, the technique has po
tential in studying surface phenomena since the reflectance measures the surface layer. Recently, Dr. Wendlandt with Preston H. Franke, Jr., and James P. Smith (also of Texas Technological College) devised a high-temperature sample holder in which the reflectance spectra of solid samples could be de termined from ambient temperature to 500° C. [Anal Chem., 35, 105 (1963)]. In their technique, they use static temperatures—that is, the sample's temperature is held constant while the reflectance spectrum is scanned from 350 to 750 τημ. In DRS, the spectrophotometer is set on a wave length where a peak in the reflectance spectrum either in creases or decreases with temperature change. The sample reflectance is measured as a function of increasing sample temperature. Dr. Wendlandt's apparatus consists of a Bausch & Lomb Spectronic 505 spectrophotometer equipped with a standard diffuse reflectance attach ment. He measures the heated sample's reflectance at a fixed wave
Diffuse reflectance curves show thermal decomposition of CoBr 2 6H 2 0. curve maxima indicate new compound formation
Shifts in
Dynamic Reflectance Spectroscopy Curves Show Anhydrous CoBr2 Formation
begins to fall off at about 125° C. The peak in the 702-m/x. curve ap proaches a maximum at about 75° C , and then falls off rapidly with increas ing temperature. The curve at 430 m/x. has a horizontal portion, which shows the formation of the anhydrous salt, CoBr 2 , with increasing tempera ture. Dr. Wendlandt points out that there are several applications of DRS to other compounds: • Studying the thermal dissociation of colored salts and complexes. • Solid-state reactions in which a colored reactant or product is in volved.
Dynamic reflectance spectroscopy curves obtained by Dr. Wesley W. Wendlandt of Texas Technological College, Lubbock, show how the reflectance of a CoBr2 6H 2 0 sample at a fixed wave length varies with temperature. Horizontal portion of curve at 430 ητίμ. shows formation of anhydrous CoBr2
length with a time-rate accessory whose output is recorded on one channel of a Varian Model G-22 stripchart recorder. A chromel-alumel thermocouple detects the sample tem perature, which is recorded on the recorder's other channel. Using DRS, Dr. Wendlandt has studied mixtures containing about 30% C o B r 2 6 H 2 0 and 70% A1 2 0 3 , with A1 2 0 3 as the reference substance. He has obtained reflectance curves of CoBr 2 6 H 2 0 in alumina at constant temperatures from 25° to 250° C. He has also obtained DRS curves for CoBr 2 6 H 2 0 at 430, 542, and 702 τημ. At room temperature, the reflect ance curve of CoBr 2 -6H 2 0 has peak maxima at 550, 640, 665, 695, and 725 m/x., Dr. Wendlandt notes. When the sample is heated to 50° C , the peaks all increase in intensity. At 100° C , the 640-, 665-, 695-, and 725-m/A. peaks decrease while the 550-m/A. peak increases in intensity. The change in peak intensity with temperature is probably caused by formation of intermediate hydrates. The exact structures of these aren't known. The reflectance curves change little from 150° to 250° C , and show peak maxima at 640, 400, and a shoulder peak at 570 m/x. Dr. Wendlandt con cludes from this that the curve at 150° C. is that of the anhydrous CoBr 2 . Thermogravimetry of a CoBr 2 -6H 2 0 sample supports this con clusion; the anhydrous CoBr 2 weight level is attained at about 150° C. Dr. Wendlandt's DRS curves show
the formation and decomposition tem peratures for the intermediate hy drates and the anhydrous CoBr 2 . They show a very marked increase in peak intensity at 542 and 702 m/x. The curve peak in the 542-m/x. curve is at a maximum at about 100° C. and
• Determining thermochromic tran sition temperatures. • Possible kinetic studies of the for mation and decomposition of colored compounds. Unlike thermogravimetry and dif ferential thermal analysis, DRS can be used to monitor a single reaction at a time, Dr. Wendlandt points out. Thus it eliminates the effect of com peting reactions which occur simul taneously.
SPECTRUM. Dr. Wesley W. Wendlandt (right) and James P. Smith of Texas Tech nological College, Lubbock, examine diffuse reflectance spectrum of CoBr2 6H 2 0 APRIL
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