Biotech & drug discovery · Contraception
YourChoice Therapeutics
A San Francisco company developing YCT-529, an oral non-hormonal male contraceptive licensed from the University of Minnesota. Its first-in-human safety study is finished and published. The study that will show whether the pill lowers sperm counts in men is still running.
Sixteen men in Nottingham
The first people to swallow YCT-529 were 16 healthy men between 32 and 59 years old, at a Phase 1 unit run by Quotient Sciences in Nottingham, England. Every one of them had already had a vasectomy. That was deliberate. If a drug designed to switch off sperm production turned out not to switch back on, these were the men least exposed to the consequence.
The first subject was enrolled on November 20, 2023. Two cohorts took single doses of 10, 30, 90 and 180 milligrams after fasting, against placebo. Eight men returned and took 30 milligrams after a high fat breakfast to test absorption. The planned top dose of 200 milligrams was cut to 180 to stay inside exposures the animal studies had cleared. The trial tracked heart rhythm, blood chemistry, four hormones, five inflammatory markers and a daily diary of mood and sexual desire. It did not measure sperm at all. Nobody in it could produce any.
Why the shelf is empty
For reversible contraception, men have condoms and withdrawal. Vasectomy is surgical, and reversal is neither cheap nor certain. The published failure rate for condoms in typical use is about 13 percent.
Most male candidates that got close worked by suppressing testosterone, and side effects stopped several of them. YCT-529 goes through vitamin A instead. Retinoic acid, a vitamin A metabolite, has to bind a nuclear receptor called RAR-alpha for sperm to develop and be released. Mice engineered without RAR-alpha are sterile and otherwise normal, and that sterility reverses. The link was first seen in the 1930s, when researchers deprived mice, rats and monkeys of vitamin A.
Two founders and a discarded plan
Nadja Mannowetz trained as a food engineer, took a PhD in biology, and became a sperm biologist in Polina Lishko’s laboratory at the University of California, Berkeley. Akash Bakshi studied biochemistry and cell biology, then worked in research commercialization, most recently in Berkeley’s licensing office. They founded the company in 2018 and went through Y Combinator.
The first product was not for men. In 2019 the National Institute of Child Health and Human Development awarded the company $224,998 for a project titled “Plant-derived molecular condom as an on-demand nonhormonal female contraceptive,” with Mannowetz as principal investigator. It is still the only federal award on record to the company itself.
Investors were not interested. The team had licensed a compound called niclosamide from the University of Minnesota, and when the pandemic arrived that molecule looked like an antiviral. They spun it out as ANA Therapeutics, which NeuroBo Pharmaceuticals acquired in 2020. Then they went back to contraception and picked the harder target.
A molecule out of Minnesota
YCT-529 was not invented at YourChoice. It came from the laboratory of Gunda Georg at the University of Minnesota College of Pharmacy, working with Debra Wolgemuth’s group at Columbia University. Georg has said the team designed and discarded roughly 400 molecules. YCT-529 was made in 2015 and its potential became clear in 2018. In a cell-based reporter assay it inhibits RAR-alpha with an IC50 of 6.8 nanomolar and does not inhibit the beta or gamma isoforms up to 3,750 nanomolar.
The university filed a patent application in 2021 and licensed the technology to YourChoice. The published application, US-2022-0388993-A1, dates to December 8, 2022, with Georg as an inventor and the Regents of the University of Minnesota as owner. YourChoice holds the exclusive license and Georg consults for the company, all declared in the trial paper.
In mice at 10 milligrams per kilogram per day for four weeks, the compound was 99 percent effective at preventing pregnancies, reversible within six weeks. In non-human primates sperm production fell within two weeks and counts recovered fully within 10 to 15 weeks. Rat and dog studies supporting the investigational new drug application reported a safety margin of 22 to 40 times.
The study that matters
The second trial, NCT06542237, started on September 11, 2024 at New Zealand Clinical Research in Auckland. It is open label, not placebo controlled, and escalates doses across repeat daily dosing for 28, 90 or 180 days. The registry lists an estimated enrollment of 88 and describes participants as men waiting for a vasectomy, plus men who have decided not to father children. Here sperm counts are the point. Georg set the bar in December 2025: a normal man produces 60 million to 600 million sperm in about four milliliters, and a contraceptive has to push that under one million per milliliter.
What is proven, and what is still claimed
| Evidence | What the record shows | Source type |
|---|---|---|
| Phase 1a | NCT06094283, double-blind, placebo controlled, single ascending dose, 16 enrolled, completed Jun 18, 2024, one site. Published in Communications Medicine Jul 22, 2025: no effect on testosterone, FSH, LH or SHBG, no QTcF prolongation past the 10 millisecond threshold of regulatory concern, no change in mood or sexual desire, half-life 51 to 76 hours. Sperm was not assessed. | Public record |
| The one drug-related event | A participant in the 90 and 180 mg cohort had an asymptomatic cardiac arrhythmia on Holter monitoring, classified as possibly related to YCT-529 and cleared by a cardiologist. The paper’s plain language summary states that no adverse effects were noted. | Public record |
| Correction | An author correction published Sep 21, 2026 restored Gunda I. Georg as an author with her affiliation and fixed the author contributions and competing interests sections. | Public record |
| Current study, as registered | NCT06542237, open label dose escalation, 28, 90 or 180 day dosing, estimated enrollment 88, phases listed as Phase 1 and Phase 2, started Sep 11, 2024, estimated primary completion Jul 31, 2026, still listed as recruiting. | Public record |
| Current study, as announced | Company releases describe up to 50 volunteers aged 28 to 70 and 28 and 90 day dosing. The registry records 88 and a 180 day arm. The website states the program is in Phase 2 trials and a university release calls it phase 2a. | Differs from registry |
| Effect on sperm counts in men | STAT reported in February 2026, on the company’s word, that a reduction in sperm count had been observed. No results are posted to the registry and no efficacy paper has appeared. | Company-stated |
| Federal funding to the company | One award: NICHD 1R43HD097944-01, FY2019, $224,998, for the female candidate rather than YCT-529. No NSF award found. | Public record |
| Regulatory status | No FDA approval, clearance or marketing application on public record. The company labels YCT-529 investigational. | Public record |
Read plainly: the single-dose safety package is real, peer reviewed, and reassuring about the things that matter most for a contraceptive, above all hormones and mood. Everything about whether the pill works is unpublished. The one drug-related finding, a transient arrhythmia in one volunteer, is a small signal a larger study will either clear or not. And the gap between how the ongoing trial is registered and how it is described in press materials is wide enough that the registry is the document to read.
What to watch
- Sperm count data from NCT06542237. Estimated primary completion was July 31, 2026, and the registry still shows the study recruiting.
- Whether the registry entry is updated to match the enrollment and phase language used in company communications.
- A larger placebo controlled efficacy trial in men who are not vasectomized, and the capital to run it.
- Any new financing. The last announced round was the $15 million Series A in July 2022.
- Whether the non-hormonal female program, the one the 2019 federal grant paid for, is ever restarted.
In their words
“I’m just looking at sperm counts.”
Akash Bakshi, co-founder and CEO, Bloomberg, 2026 · Independent
“It was the same team, the same drug, just a different indication.”
Akash Bakshi on the COVID spinout outraising the contraceptive company, Fierce Biotech, 2024 · Independent
“We consciously chose to inhibit the vitamin A signaling pathway in the testis because nearly 100 years of research has validated this pathway and shows that infertility can be reversed easily.”
Gunda Georg, University of Minnesota, December 2023 · Company release
“In order to be effective, the sperm count has to be lower than one million per milliliter.”
Gunda Georg, University of Minnesota interview, December 2025 · Interview
“I think it would be overstating the data to say they know much about side effects yet.”
Stephanie Page, endocrinologist, University of Washington School of Medicine, to Scientific American, 2025 · Independent
“We are receiving emails from men all over the world asking to participate.”
Nadja Mannowetz, co-founder and chief science officer, to STAT, February 2026 · Independent
Related companies
Sources
- Public recordClinicalTrials.gov NCT06094283
- Public recordClinicalTrials.gov NCT06542237
- Public recordSafety and pharmacokinetics of the non-hormonal male contraceptive YCT-529
- Public recordAuthor Correction to the same paper
- Public recordTargeting the retinoid signaling pathway with YCT-529 in mice and primates
- Public recordFrom concept to the clinic: RAR alpha antagonist YCT-529
- Public recordNIH RePORTER 1R43HD097944-01, NICHD
- Public recordForm D, Portfolia 2025 YourChoice SPV LLC
- IndependentThe future of male birth control could be pills, gels and implants
- IndependentAs male birth control gets closer to reality, men are lining up for clinical trials
- IndependentMale birth control pill to stop sperm production passes safety test
- IndependentNo hormones, no problem: YourChoice’s male birth control is safe for men, so far
- IndependentBehind the scenes: creating a hormone-free male birth control pill
- IndependentClosing the contraceptive gap: non-hormonal male pill advances in clinical trials
- IndependentYourChoice Therapeutics banks $15M for male contraception
- CompanyYourChoice Therapeutics begins first-in-human trial
- CompanyYourChoice Therapeutics begins second human study
- CompanyYourChoice Therapeutics website
Profile researched and written by Healthcare Discovery. Last updated September 29, 2026.
