Women have lots of options for birth control. There's the pill, patch, contraceptive sponge, diaphragm, Depo-Provera shot, NuvaRing vaginal ring, and intrauterine devices, or IUDs. For men, there are still just two effective methods: a condom or vasectomy.
But the reason isn’t because men aren’t willing to use different methods. Research and development for male contraceptives has been slow, and the field is littered with abandoned and unfinished efforts. Investigators working on male contraceptive drugs say there are two major challenges to bringing these products to the market. For one, blocking the production of millions of sperm per day in men versus preventing the release of one egg per month in women is just more complicated, biologically speaking. Secondly, there’s little funding available for clinical trials of these drugs.
Most recently, a study published in October and backed by the World Health Organization showed that a hormonal birth control injection for men effectively prevented pregnancy in their female partners. But the trial was stopped in 2012 on the recommendation of an outside panel noting one participant’s suicide and serious side effects in others, including depression.
Douglas Colvard, co-author of the study and deputy director of programs at the nonprofit scientific research institute Conrad, says the results were discouraging. The hormonal drug—a combination of progestogen and testosterone—will not be moving forward in clinical trials because Conrad and the WHO have no more funding available to retest another formulation, says Colvard.
Hormonal birth control for men, which is intended to suppress sperm formation, is the most widely studied form of a male contraceptive drug and has been investigated for the past four decades. One notable trial in 1,045 Chinese men testing a different injectable hormonal contraceptive was found to effectively and reversibly suppress sperm production. But the company that manufactured the drug, Zhejiang Xian Ju Pharmaceutical, never pursued further testing or regulatory approval for the injectable.
“To some extent, why we haven’t seen involvement with pharma companies is that they’ve been disappointed in the past with failed products that have focused primarily on hormonal efforts,” says Aaron Hamlin, executive director of the Male Contraception Initiative, an advocacy group based in Washington, D.C. For example, German pharmaceutical company Schering and Netherlands-based company Organon partnered in 2002 to develop a hormonal male birth control pill, but that effort was dropped just a few years later.
Gunda Georg, professor and head of the department of medicinal chemistry at the University of Minnesota, says she is not “not at all hopeful” that hormonal contraceptives for men will make their way to the market given the number of abandoned efforts and potential side effects. Instead, Georg’s lab is studying a non-hormonal male contraceptive option, an investigational drug called gamendazole that stunts the development of sperm. The immature sperm fragments are reabsorbed into the testis, the male organ that produce sperm, and never make it to the semen.
In rats, the compound was highly effective and reversible. Georg is planning more studies in monkeys in the hopes of advancing the drug into trials in people.
Another non-hormonal contraceptive method, Vasalgel, could be tested in people as soon as 2017. Developed by the Parsemus Foundation, the polymer gel is injected into the vas deferens, the tube that carries sperm to the penis. The gel is similar to an approach being studied in India called RISUG, or reversible inhibition of sperm under guidance. RISUG is in phase III clinical trials in India, but the study has been struggling to enroll enough participants.
Elaine Lissner, director and founder of the Parsemus Foundation, says Vasalgel has been effective at stopping sperm production in rabbits, monkeys, baboons, and dogs. But in larger animals, researchers have had trouble reversing its effects, so Lissner says more studies need to be done.
Researchers are working on non-hormonal pills, too. A team at Kings College London is studying phenoxybenzamine, which is currently used to treat high blood pressure, as a male contraceptive method. Dubbed the “clean sheets pill,” it’s a fast-acting drug meant to produce a semen-free orgasm. So far, it’s only been tested in animals.
In Indonesia, scientists are testing pills synthesized from a shrub called gendarussa in hundreds of men in clinical trials. Gendarussa is thought to work by disrupting an enzyme in the sperm head, weakening its ability to penetrate the ovum. It's in phase III trials in Indonesia, but investigators would need to repeat clinical trials in the U.S. to get approval from the U.S. Food and Drug Administration.
And James Bradner, of Harvard Medical School and the Dana-Farber Cancer Institute, discovered a compound called JQ1 that acts as an inhibitor to sperm production and mobility. Injections of the compound given to mice stopped sperm production drastically, and when stopped, sperm count in the mice returned to normal. Bradner and his team believe a pill version could eventually be developed for the same results.
What these investigational drugs need to advance to human trials is funding. Lissner says it’s easier to get a $100,000 grant from the National Institutes of Health than it is to raise millions of dollars to conduct later stage clinical trials. NIH spent $424 million in 2015 on this area, but much of that goes to research in female contraception and reproduction.
Meanwhile, Colvard’s study published in October on the failed male hormonal injection has faced a backlash because of the trial’s termination. He says the response “obviously speaks to the need for additional funding” for male contraception efforts.