Since their inception in the 1950s, birth control pills have granted freedom and control to heterosexual couples. Yet the responsibilities – and unpleasant side effects – of non-barrier contraceptives (i.e. not a condom or diaphragm) have fallen upon the female half of the population. But soon, the frustrating wait for a proven male birth control product could have a poetic payoff.
A team of biochemists from the University of Minnesota and University of Kansas Medical Center has created a potential drug agent that appears safe and effective in rats. Rather bizarrely, the compound is a deadly toxin that was traditionally used by African warriors to make poison arrows.
Naturally produced by several species of African flowering plant, ouabain belongs to a class of chemicals known as cardiac glycosides. These compounds interfere with the ion pumps (protein-based channels through cell membranes) in cardiac muscle cells that move sodium ions out and potassium ions in. The increased internal sodium causes muscle cells (fibers) to release stored calcium ions, ultimately altering how muscles contract. Other cardiac glycosides, such as digitals, have been used for centuries to heal rather than hunt.
A slightly different type of sodium-potassium pump is present only in mammalian sperm cells and is essential for creating the wriggling movement of the sperm’s tail-like flagella. In a study published online in the Journal of Medical Chemistry, the researchers were able to modify the ouabain molecule to target only this version of the ion-pumping protein, and initial experiments on rats found that the new compound successfully immobilized sperm.
When sperm can’t move, they can’t travel into the fallopian tubes to fertilize an egg.
However, to make a good contraceptive, the method used to incapacitate sperm must also be reversible. Promisingly, the ouabain derivative checks that box too. The researchers stated that the contraceptive effect “should be reversible because [the protein] is only found on mature sperm cells. That means sperm cells produced after stopping treatment with the ouabain derivative shouldn’t be affected.”
And unlike past drug candidates that relied on hormones, the compound produced no harmful side effects (again, in rats). The importance of creating non-hormone male birth control options can’t be overstated. Effective hormonal medications have actually been around for decades, but men have dropped out of clinical trials and pharmaceutical companies have failed to show interest in bringing them to market – all because of unpleasant side effects (cue millions of women screaming internally).
In 2008, a large study in China demonstrated that an injectable testosterone precursor effectively suppressed sperm production in healthy male subjects. When receiving a monthly injection, the cumulative contraceptive success rate was 95.2 percent – a higher protection rate than every form of medical birth control except for implants and intrauterine devices (and vasectomy and tubal ligation, of course). Yet the drug developer never pursued further testing (more screams).
The Midwestern team’s paper represents a very early step in drug development that will need to be followed by years of additional research, with a great deal of financial investment, before a product could become available. Happily, another candidate is closer on the horizon: an injectable long-term contraceptive called Vasalgel, a gel polymer placed in the vas deferens, is slated for human testing this year.
Womankind must try to avoid resorting to methods that include the original poison arrows in the interim.