Accidental Discovery Could Lead to Male Birth Control Pill
WOODS HOLE, Mass. (AP) _ Researchers have stumbled onto a new drug that blocks the action of sperm in laboratory animals, a finding that could someday lead to a birth control pill for men.
The drug may be superior in some respects to other substances being investigated as possible male contraceptives, said Sheldon Segal, of the Marine Biological Laboratory in Woods Hole and the Rockefeller Foundation in New York.
In research conducted this summer at the Marine Biological Laboratory, Segal and colleagues including Mukesh Sahni and Samuel Koide of the Population Council in New York found that the drug blocked the fertilization of clam eggs by immobilizing sperm.
The clams, known scientifically as Spisula solidissima, the same variety used to make clam chowder, are useful for the study of fertilization because they produce large quantities of sperm and eggs and their sperm resemble human sperm, Segal said.
″Most of what we know about human sperm physiology has been learned here at Woods Hole from sea urchin and Spisula sperm,″ Segal said.
The new drug, designated Ph CL68A, was discovered accidentally when doctors noticed that a related drug commonly used to treat colitis, an inflammation of the large intestine, produced rare occurrences of infertility in men.
That attracted Segal’s attention. ″We are constantly searching for a contraceptive for males,″ he said. ″We don’t feel the contraceptive burden should fall exclusively on women.″
This summer, Segal and his colleagues tested the colitis drug - sulfasalazine - and several chemically similar drugs, including Ph CL68A.
They found that only Ph CL68A was effective at preventing fertilization.
Sulfasalazine did not block fertilization, which leaves its rare ability to produce infertility unexplained, Koide said.
Dr. Gerald Weissmann, director of rheumatology at New York University, noted that this side effect of sulfasalazine was very rare and reversible, and he said that patients who require the drug for treatment of colitis should not be frightened away from it. Sulfasalazine is also nearing approval for use in treating rheumatoid arthritis, Weissmann said.
Segal also has been studying the contraceptive properties of gossypol, a cottonseed extract that has been studied extensively in China as a potential male contraceptive.
In new studies this summer, Segal and Hiroshi Ueno of Rockefeller University determined that gossypol works by attacking the enzymes used by sperm to obtain energy and thus sustain movement.
Segal said that the two other principal candidates for male contraceptives are a drug called leutinizing hormone releasing hormone, or LHRH, and specially made antibodies directed against sperm.
The problem with LHRH, Segal said, is that it attacks both sperm and male hormones, and therefore interferes with the sex drive.
The notion of using antibodies to immobilize or inactivate sperm is an interesting one, Segal said, but very far from practical application.
Gossypol’s drawback is that it can lower potassium levels in the blood. A potential problem with Ph CL68A is that it is counteracted by proteins in blood, and thus might have to be given in high doses, said Koide.