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GnRH ANTAGONIST NAL-GLU PLUS TESTOSTERONE PRODUCES REVERSIBLE MALE INFERTILITY, RESEARCHER REPORTS; MALE CONTRACEPTIVE VACCINE IN PHASE I TRIALS

Executive Summary

The gonadotropin releasing hormone (GnRH) antagonist Nal-Glu given in combination with low dose testosterone induced reversible infertility in seven of eight men, researcher Spyros Pavlou, Beth Israel Hospital, reported at a Feb. 26-28 conference on contraceptive research sponsored by the National Institute of Child Health and Human Development, the Center for Population Research and the Rockefeller Center. Pavlou said the GnRH antagonist effectively suppressed serum levels of follicle stimulating hormone (FSH), leuteinizing hormone (LH) and testosterone in all eight men tested. He reported that azoospermia, the absence of sperm in the semen, was achieved in seven of eight men and that residual sperm in the eighth man showed no motility or viability. "None of the men complained of decreases in potency," Pavlou stated, and "no other side effects were seen, other than local reaction at the injection site." Sperm counts of the study participants returned to normal within 14 weeks after discontinuation of Nal-Glu treatment. The study results were presented at the Endocrine Society's annual meeting last June in Washington, D.C. and published in the December 1991 issue of the Journal of Clinical Endocrinology and Metabolism. Pavlou said further studies, using long-acting formulations of potent GnRH antagonists and testosterone, "should refine this regimen into a practical and effective male contraceptive." Pavlou and his colleagues also examined Nal-Glu's effects on serum lipids. Total cholesterol and low-density lipoprotein (LDL) levels showed no significant change. However, high-density lipoprotein (HDL) levels increased by 26% within two weeks after Nal-Glu administration and remained elevated throughout treatment but returned to baseline 12 to 14 weeks after treatment was discontinued. The Population Council recently launched a Phase I study of a male contraceptive vaccine that involves immunization against LHRH (leuteinizing-hormone releasing hormone), the conference was told. The immunocontraceptive vaccine is the first to enter clinicals in the U.S. and the council is negotiating with several pharmaceutical companies. The LHRH vaccine is being tested in four men with prostatic carcinoma. An additional eight to 10 men are to be included in the trial. A separate clinical trial with the vaccine is underway in India. Immunization with vaccine introduces synthesis of LHRH antibody, which causes suppression of LH and follicle stimulating hormone (FSH), which, in turn, suppress testosterone and sperm production. In animal studies, the vaccine completely suppressed sperm production and was totally reversible, The Population Council said. The vaccine will eventually be used in combination with androgen. The Council has developed a synthetic androgen, called MENT, that is 10 times as potent as testosterone and plans to use MENT as a one-year implant in conjunction with the LHRH vaccine and in conjunction with a single implant similar to Norplant that delivers LHRH analog. Wyeth-Ayerst's Norplant, a female contraceptive developed by The Population Council, delivers levonorgestrel for up to five years through rods implanted under the arm skin. A female contraceptive vaccine against HCG (human chorionic gonadotropin) has been tested in Phase I clinicals in India, Australia, Chile, Finland and the Dominican Republic, The Population Council reported. The Council, the World Health Organization, and the Indian Institute of Immunology have immunized over 110 women. Phase II trials with the vaccine are underway in India. The vaccine may act after fertilization and could thus be considered an abortifacient. Female contraceptive vaccines made from sperm protein are currently being tested in animals. Last year, John Herr, University of Virginia, began testing a vaccine made from the sperm protein SP-10 in baboons. The vaccine is expected to produce SP-10 antibodies that bind to proteins on the surface of the sperm and prevent fertilization. Ortho recently agreed to fund the UVA contraceptive vaccine research ("The Pink Sheet" Jan. 27, T&G-6). Paul Primakoff, University of Connecticut, has tested a vaccine using the sperm protein PH-20 and found it to be effective as a contraceptive in both male and female guinea pigs.
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