The idea of a male contraceptive pill has been around almost as long as the female one. When Enovid was approved in 1960 for contraception, it presumably occurred to at least a few researchers that if you could suppress ovulation with a pill, you might also be able to suppress spermatogenesis with one. The basic endocrinology was the same. The feedback loops were analogous.
What followed was sixty-odd years of finding out why it was not, in practice, the same problem at all.
The fundamental obstacle to an oral male contraceptive has always been pharmacokinetic. Testosterone, when taken orally, is absorbed through the gut and passes through the liver before reaching systemic circulation — a process called first-pass hepatic metabolism. The liver metabolizes testosterone so efficiently that very little intact hormone makes it to the bloodstream. What does make it causes hepatic stress at the doses needed. Oral testosterone was essentially impractical as a contraceptive for most of the twentieth century.
The workaround for hypogonadism therapy has been testosterone undecanoate — a fatty acid ester that is absorbed via the lymphatic system, partially bypassing the liver. But oral testosterone undecanoate requires careful dosing with meals (specifically fatty meals), has inconsistent bioavailability, and the doses needed for HPT axis suppression are high. It is better than plain testosterone, but not ideal.
Enter dimethandrolone undecanoate. DMAU, for those who prefer not to say the full name at any speed.
What DMAU Is
Dimethandrolone undecanoate is a synthetic 19-norandrogen developed by the National Institutes of Health and the University of Washington. Its key pharmacological feature is that dimethandrolone (DMA) — the active drug after the undecanoate ester is cleaved in the body — has potent activity at both the androgen receptor and the progesterone receptor.
This dual activity is the important innovation. Most testosterone-based contraceptive regimens require two drugs: a testosterone compound to maintain androgenic function (muscle, bone, sexual function, mood) and a separate progestogen to enhance HPT axis suppression. DMAU does both in one molecule. It suppresses gonadotropins via both androgen and progesterone receptor pathways simultaneously, which theoretically allows better suppression with a single oral agent.
The compound was initially characterized by Bhangla J. Attardi and colleagues at the National Institutes of Health in the early 2000s. Animal studies in rats showed complete suppression of spermatogenesis, reversibility upon cessation, and — crucially — maintenance of normal bone mineral density in castrated animals. This last finding mattered because some earlier synthetic androgens had adverse bone effects at contraceptive doses.
Phase I: Safety and Pharmacokinetics
A Phase I dose-escalation study in healthy men was completed around 2014–2015. This study established short-term safety and tolerability of single oral doses of DMAU across dose levels. The pharmacokinetics were more favorable than standard testosterone — DMAU was absorbed efficiently when taken with food, achieved meaningful systemic concentrations, and produced measurable suppression of LH and FSH.
The single-dose tolerability data were clean: no serious adverse events, acceptable side effect profile, and reversible hormonal suppression.
A subsequent 28-day multi-dose pharmacokinetics study — published in 2018 in the Journal of Clinical Endocrinology and Metabolism (Thirumalai et al.) — enrolled 100 healthy men randomized to DMAU at varying doses (0 mg, 100 mg, 200 mg, or 400 mg taken once daily with food) for 28 days. The results were more than encouraging.
At the 400 mg dose, 89% of men showed suppression of testosterone to castrate-equivalent levels or near-castrate levels. LH and FSH were suppressed to below detectable limits in most men. No serious adverse events occurred. The most commonly reported side effects were weight gain (modest) and decreased HDL cholesterol.
The reduction in HDL — the so-called “good” cholesterol — deserves a note. Most androgenic hormones have some negative effect on HDL, and this is a cardiovascular risk marker worth monitoring. The magnitude of the reduction in the DMAU Phase I/II data was statistically significant but modest in absolute terms. Whether it translates to meaningful cardiovascular risk over long-term use cannot be determined from 28-day data.
Phase II: The Longer Look
Phase II data extended the observation period and added suppression of sperm production as a measurable outcome. A Phase IIa study published in 2019 in the Journal of Clinical Endocrinology and Metabolism (Thirumalai et al., 2019) tested DMAU in a larger cohort over 28 days with spermatogenesis as a secondary endpoint. The study confirmed:
- Dose-dependent suppression of LH, FSH, and testosterone.
- At the highest doses, suppression of testosterone to levels consistent with what you would expect to suppress spermatogenesis.
- Tolerability that was consistent with the Phase I data — weight gain and HDL reduction as the primary concerns.
Because spermatogenesis takes approximately 70–74 days to complete (the full cycle of sperm development from stem cell to mature sperm), a 28-day study cannot directly measure contraceptive adequacy of sperm suppression. The 28-day studies were hormonal suppression studies — proving that DMAU can shut down the endocrine drivers of sperm production — rather than efficacy studies showing actual sperm count reduction to contraceptive levels.
To demonstrate that, you need a study of at least 3–4 months. As of 2025, Phase III trials of DMAU have not been reported in the published literature.
Why It Is Still Not in a Pharmacy
DMAU Phase II data are, by the standards of drug development, promising. An oral agent, single drug, once daily, good hormonal suppression, acceptable short-term tolerability. This is closer to “the male pill” than anything previously described.
And yet.
Phase III trials are expensive. A Phase III contraceptive efficacy trial — large enough to demonstrate real-world pregnancy prevention, long enough to capture long-term safety signals including cardiovascular events and potential fertility-recovery outcomes — costs on the order of hundreds of millions of dollars. It requires regulatory agreement on endpoints, manufacturing scale-up, years of enrollment and follow-up, and a pharmaceutical company willing to bet that the market exists and is profitable.
DMAU is an NIH/academic project. It has no large pharmaceutical company behind it. The NIH has funded it through Phase II. The National Institute of Child Health and Human Development (NICHD), which funds the majority of male contraception research through its Contraceptive Discovery and Development branch, does not have the budget to run large Phase III trials independently. Without industry co-investment, Phase III does not happen on any predictable timeline.
The underlying commercial problem is not that no man would take a male pill — surveys consistently show that 55–60% of men express interest in hormonal contraception. The problem is that pharmaceutical companies have modeled the market and concluded that the regulatory pathway is unclear, the liability exposure (if men develop cardiovascular or other long-term adverse effects) is high, and the revenue opportunity does not justify the development cost. Female contraceptives have decades of established infrastructure, physician familiarity, and reimbursement pathways. Male contraceptives have none of those things.
DMAU is not dead. It is in the slow-motion purgatory of “promising Phase II results awaiting Phase III investment.” In pharmaceutical development, that purgatory can last indefinitely.
What DMAU Represents
The significance of DMAU in this story is not just the compound itself. It is what it proves is possible: an oral, single-agent, once-daily male contraceptive is pharmacologically achievable. The biology is not the obstacle. The route to phase III and beyond runs straight through the economics and risk tolerance of pharmaceutical development.
When people say “the male pill is almost here,” they usually mean something like DMAU. And they are, in a narrow technical sense, right. The molecule exists. The Phase II data are good. The pill is almost here the way a bridge is almost built when you have the blueprints, the engineering team, and the materials, but the construction company has declined to pick up shovels until someone guarantees them against loss.
Next up: Post 4 — The NES/T Gel: A 2023 Phase IIb trial of a combination transdermal gel applied by both partners showed it works for suppression. The obstacles are now almost entirely non-biological.
