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CHICAGO -- A no-scalpel vasectomy passed a preliminary clinical test, achieving near-100% azoospermia within 2 weeks and maintaining the status to day 30 in the first men to undergo the procedure.

Following injection of an occlusive nonhormonal hydrogel into the vas, sperm concentration decreased by as much as 99.98% by day 14 in the first six men who underwent the procedure. After 30 days, sperm concentration had decreased by 99.9%-100% in five of the six men. No serious adverse events (AEs) occurred.

Designed to maintain azoospermia for more than a year, the hydrogel dissolves spontaneously. In animal studies, the ADAM implantation procedure blocked sperm passage through the vas for up to 2 years, reported Nathan Lawrentschuk, MD, of Epworth Freemasons and Royal Melbourne hospitals in Australia, during the American Urological Association annual meeting.

"The available data have shown a favorable profile for the implantable hydrogel and suggest that the primary endpoint of the trial [safety] will be met," said Lawrentschuk. "All procedures to date have been successful. Patients have experienced mild and moderate adverse events, primarily related to the procedure, not the implant, all of which resolve quickly. Azoospermia has been observed in all patients with 30 days of biogel implantation, even with the lowest dose of biogel."

Enrollment in the trial continues, and additional sites across Australia are being recruited to accelerate the trial process. Long-term plans include expansion of clinical evaluation beyond Australia, he added.

Implantation occurs as an outpatient procedure, using local anesthetic, and requiring about 30 minutes to complete. During the procedure, the hydrogel is injected directly into the vas via cannulation, without need for an incision. The Virginia-based manufacturer, Contraline, has developed an injector that connects to the cannula and automatically delivers a specified dose of the gel.

Lawrentschuk reported initial results from a first-in-human trial that eventually will include 30 healthy men, ages 25-65, with normal semen parameters. Participants agreed to use an alternative form of contraceptive and had to be willing to accept the unknown risk of pregnancy during the study duration. Sperm concentration was assessed at baseline, day 14, and day 30. Follow-up will continue for up to 3 years.

The first seven patients to undergo implantation had a mean age of 37.7. None of the patients withdrew from the study.

The most commonly reported AEs were scrotal bruising and discomfort, swelling around the surgical site and testicular pain. All but a few AEs were mild and the rest were moderate. AEs resolved in an average of 4.6 days, and all AEs had resolved by day 14. In response to a question from the audience, Lawrentschuk said no scarring or obstructive problems occurred during animal studies with follow-up for as long as 2 years.

One patient was excluded from analysis because of a protocol violation. Day 14 sperm concentration assessments showed that three of the six men had achieved azoospermia (99.8%-99.98% reduction from baseline), and the remaining three had achieved azoospermia by day 30 (99.91-99.99% reduction from baseline).

During a discussion that followed the presentation, Lawrentschuk said the procedure causes substantially less pain than a conventional vasectomy. He manages postprocedure discomfort with acetaminophen.

The hydrogel implantation gives men the opportunity to take control of contraception, and initial reaction has been encouraging, as reflected in the number of men who have inquired about enrolling in the clinical trial, said Lawrentschuk.

"Whenever we open up a trial for recruitment, we have thousands of men wanting to be in the trial because they all want to be in charge of their own contraception," he said. "They want to be the ones making the choice."

In response to another question, Lawrentschuk acknowledged that investigators are not absolutely sure when the hydrogel will dissolve. The implantation remained effective for 2 years in animals before dissolving. Whether that will apply to men will be determined during long-term follow-up in the clinical trials.

When the gel does dissolve, men should be able to repeat the procedure if they want, he added.

This story has been updated to reflect that Lawrentschuk's son has not undergone the hydrogel procedure.

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