a little pill for men

I don't think the asymmetry is as big as you may believe. Men that are not in a long term stable relationships also have good reasons to have such a birth control option.

Since men are required to assist with child rearing, via pair bonding or through financial assistance, it makes sense that men also have options beyond condoms. I can think plenty of scenarios where the men would leap at the chance to use such a pill, assuming no sexual performance side effects. Consider the female partner who secretly wants a child, or a philandering male (think Wilt Chamberlain).

On the other hand, some guys might, for the sake of their own peace of mind, want to ensure that the women they slept with didn't get pregnant...

I recently read "From the Lab into the World", a collection of essays by Carl Djerassi. He talks about both the technical and social issues surrounding a potential male birth control pill in several of the essays in that book.

One of the essays specifically about male fertility control was written in 1970. The book was published in 1994. He's quite pessimistic in 1970 about the long development and deployment times for a male pill, and his update notes from 1993 are no more optimistic - he consistently talks about no such pill becoming available in the foreseeable future, across 23 years of reflection.

As for the male demand and trust issues - for the first, I'm certain significant demand does exist (I'm one, I can think of many others). For the second, if the woman in this hypothetical relationship does not fully trust the man when he says he's taking the pill, she does have other options to fall back on, like the long-available female pill, for example. I don't think that asymmetry will be a major factor influencing public acceptance of a male pill - concerns (legitimate or otherwise) about the effects on male performance and sensation will probably swamp any such effect.

I disagree.
There is a strong asymmetry in both information and trust in the male and female pill, socially.
Since the principal burden of pregnancy falls on women, any woman wanting to avoid pregnancy is unlikely to trust claims of males, except for the relatively rare situation of a stable trusting relationship, where neither partner is seeking to have children.
In most other situations the woman will have to take her own contraceptive precautions, or insist on overt barrier contraception.
There are mirror situations of trust, like the "woman trying to trap the man into pregnancy", but those are rarer.
This still leaves a market for the male pill, and quite a substantial one, but not as attractive to the pharmacy developers.
For drugs with high development costs due to need for large clinical trials, and very high liability risk, development is only done if the potential market is very large.
So male pills don't happen, not because the biochemistry is too hard, but because working out the clinical details is not worth while for the industry. And the reasons why are mostly socially driven.

The "niche" of customers in stable long-term relationships is pretty damn big, you know. The existing birth control methods available for such couples fail a large number of them right now, too. Barrier methods can be cumbersome, messy, expensive, and typically have comparatively high failure rates. Some women can't take hormonal birth control because it causes unbearable mood swings. Others find that hormonal birth control kills their libido. I know multiple couples who are using natural family planning because all the alternatives they've tried have been worse for them for some reason.

Many women cynically wonder if the loss of libido and depression they've experienced on birth control pills are the sort of side effects that are considered unacceptable in a male version.

Which is not to say that birth control pills haven't been a valuable, incredibly valuable option for many, many, many women. They just aren't as perfect and magic as people seem to think.

i the relatively rare situation of a stable trusting relationship, where neither partner is seeking to have children.

Most marriages fall in this category for a substantial span of their existence, even if the couple intends to have children eventually. Timing is everything.

Yup. Believe me, I know.
But "pretty big" may not be "big enough" for a pharma exec contemplating probability of class action lawsuits and phase III costs.
Please note that I am not a pharma exec - I am a likely customer!

The side effect asymmetry is there also. Loss of libido would be cause for total market failure for a male contraceptive, even if relatively low in incidence.
Which is mildly ironic, since it would significantly increase the effectiveness of the product.

I'm glad to see that they were testing an implant + injections delivery system, rather than a daily pill. I wouldn't trust any birth control method that relied on my husband remembering to take a pill every single day at the same time.

I've found that just about any little pill can be effective for male birth control, depending on where you stick it.

I asked my wife her opinion. She basically echoed Liz's opinion. She wouldn't trust me to take the pills on a consistent basis. And I have to agree with her. When it came down to it, if my hormones were raging, I must wonder if I would bend the truth (of not being consistent with the pill) in order to have sex. I would like to think not, as I am quite honest, but hormones are unfortunately quite influential.

So perhaps you are correct about the asymmetry.

Yeah, I think I am correct about the asymmetry.
It is not fair.

The implant+injection delivery is what seems to have crashed the development, sounds like marketing decided it was not marketable in sufficient numbers.

As I mentioned, the most effective male contraceptive would correlate with erectile issues, and there are lots of ways to induce such disfunctionality, but most have poor market potential...

Women are no less forgetful or distracted than men. If there really is good reason to distrust men taking a pill every day (and remember, lots of men have medical conditions like hypertension that already entrusts them with a daily pill) then women are not to be fully trusted either. So the best course may simply be for both partners to take a pill - if one forgets, or the prevention fails for some reason, then the other has it covered.

And yes, I'd prefer a daily pill over an injection or implant.

"presumably not as complicated as managing female fertility..."

Not a safe presumption. In the female, the challenge is to reliably derail ONE ovum per month, somewhere in a reasonably well-known schedule of discrete steps -- a "small batch" process. In the male, you need to derail millions of spermatozoa, appearing and maturing in a "continuous flow" process.

And the mechanism for the latter has to be essentially all-or-nothing: a candidate drug may disable 99.97% of spermatozoa, but it MUST not yield even .03% damaged survivors which might lead to birth defects.

I fully agree that social and psychological factors, some of them indefensible, have played a part in the absence to date of a male pill. But that doesn't mean there aren't some inherent difficulties as well.

I didn't read all the comments, but I thought I'd put my two cents in anyway. Maybe I'm dating a lot of lousy guys, but if a guy told me he was on a pill, I'd make him wear a condom anyway. Why? STDs, my friends.

Furthermore, I also use the female birth control pill not only as a back-up in case the condom breaks, but also because of all the wonderful side effects, ie, hormone balancing and acne fighting.

So, I guess, what's the point of the guy taking a pill too?

Lastly, even though I'd rather be the one taking the pill, it does seem a bit unfair that women have to be burdened with more of the cost of birth control than men. You know, birth control pills aren't cheap.