It seems a little unfair these testosterone implants, because of the side effects: more energy, losing weight and building muscle mass. Don’t you think?
Dr. Amory: It is beneficial. It is unfair. You bring up a good point about side effects. I mean people often ask me why we need a male pill. We have got very effective female contraception. Well, one of the reasons is the side effects that the female contraceptives cause. Some of them are annoyances and some of them can be quite serious. As you know, sometimes women using contraceptives will get blood clots and then they can’t use contraceptives. If you are in a couple where the woman has a reason not to use a contraceptive, the availability of a male contraceptive would be quite helpful.
Would there be any other risks to blocking vitamin A?
Dr. Amory: There are a couple of tissues we are looking at very carefully. The first is the eye of course. We would not want to affect vision. Fortunately, the step that we are blocking seems to be below the step where vitamin A is needed in the eyes. So we think that the eye should be fine. And then the other is the liver. So, in early versions of the compound that we are using caused some fat accumulation in the liver which long term could be harmful. We are hoping that our newer compounds will show less of those effects.
Now, the man we are talking to next, Michael?
What is Mike Leaman, doing right now?
Dr. Amory: Mike has been on probably 5 or 6 of our contraceptive trials over the last 15 years. So, just so you understand, the hormonal contraceptive trials, those are actually in clinical testing. We have done several of those trials and Mike has participated in those trials. What that entails for a man is, he usually comes in, we make sure he is healthy, and that it is unlikely that he is going to be harmed by participation in the study; then he gets either injections or gels of testosterone plus or minus a progestin over a period of about 6 months and then comes in monthly and we check his sperm counts and we watch them suppress to zero and then after 6 months of treatment. We will remove the treatment and watch the sperm counts come back up; just to assure that it works and that it is reversible. You might ask why is this not on the market? Well the problem with this approach is that it only works in about 80 to 90% of men.
Why does it not work on all?
Dr. Amory: We don’t know. So that has been the real bugaboo with this field. For the last 30 years a subset of men suppress their sperm counts, but not all the way to zero. Men make about 1000 sperm a second. So you really want to get the sperm count pretty much down to zero to ensure that they are effectively contraceptive. Women make one egg a month and I think for some reasons it has been easier to suppress the production of an egg a month than it is to suppress sperm production which is such as robust phenomenon.
The blocking the vitamin A is not in clinical trial yet?
Dr. Amory: We are testing. We are developing new drugs. We are testing them in mice and if we have a promising compound in mice, hopefully, we will be able to take it to humans, probably in the next 3 to 5 years.
You are testing in mice?
Dr. Amory: Oh, we use C-57 black 6 mice.
How temporary is it?
Dr. Amory: So the kinetics of this takes about 72 days from a sperm to go from its stem cell state to its mature state where it is ready to fertilize an egg. When you start one of these drugs, you are actually not contracted for about 2 to 3 months. It turns out, then you take the drug and then when you stop it, it takes about 2 to 3 months actually for you to become fertile again. So, there is a delay in the onset and a delay in the offset of this. It is really not for the person who is looking for contraception for a single encounter. It really is best viewed as something that somebody in a couple would use, probably a stable monogamous relationship, because of course none of these things will protect against sexually transmitted infections.
FOR MORE INFORMATION, PLEASE CONTACT:
John K. Amory, MD, MPH
University of Washington