Temporary sperm blocker yields exciting results in first-in-human trial

Injecting a degradable hydrogel into the vas deferens appears to be a feasible means of birth control for men, leading to sperm-free semen within only 30 days of implantation with a low potential for harm, according to the initial results of a first-in-human clinical trial presented at EAU 2023.

“So far, there has been no unanticipated significant [safety] problems. In fact, we have only observed relatively minor adverse events—the sort of things you commonly expect after having a vasectomy such as bruising and discomfort at the site, and these are generally resolved promptly,” reported principal investigator Dr Paul Anderson from Royal Melbourne Hospital in Melbourne, Australia.

Called ADAM system, the injectable hydrogel is biocompatible and designed to temporarily obstruct the vas deferens for more than a year. Once inside, the hydrogel thickens and prevents sperm from travelling through the vas deferens without affecting sensation or ejaculation. The blocked sperm, according to the developers, break down naturally and are absorbed by the body. [https://tinyurl.com/28rr8dkb]

At the end of its lifespan, the hydrogel spontaneously dissolves, Anderson pointed out. This makes ADAM a reversible form of male contraception.

“The ADAM implantation procedure utilizes a no-scalpel vasectomy approach to externalize the vas, and then the vas is cannulated with the hydrogel delivered through an injection device, which mixes the true components of the gel and delivers them in the prescribed amount into the vas deferens,” Anderson said.

The preliminary analysis included four men (mean age 36.3 years) who underwent intravasal implantation of 120 uL of ADAM. None of them experienced serious adverse events (AEs) within 3 weeks of the procedure. [EAU 2023, abstract A0681]

Most AEs were mild (63.6 percent) or moderate (66.4 percent) in severity and were related to the procedure but not the hydrogel itself. Aside from the scrotal bruising and discomfort noted earlier by Anderson, other AEs that occurred were swelling around the surgical site, unilateral and bilateral testicular pain, and discomfort from stitches (in the participant who underwent scalpel-based approach).

Anderson also stressed that postprocedure recovery in men who received intravasal injection of the hydrogel was similar to that in men who received vasectomy.

As for efficacy, sperm concentration decreased by an average of 99.5 percent from baseline at day 21, with three men reaching azoospermia. Postprocedure semen analyses at 14 days showed a mean volume of 1.9 mL, mean pH of 8.3, mean concentration of 1.1 M/mL, mean motility of 0.0 percent, and mean total motile sperm count of 0.5.

Additional data

“Based on the available data, a Data and Safety Monitoring Board (DSMB) has determined a favourable safety profile for the ADAM system, which suggests that the primary endpoint of the study will be met,” Anderson shared, adding that all procedures to date have been successful.

For the study, Anderson and colleagues are looking to enrol and conduct implantations in 25 healthy and fertile men who are otherwise suitable for a vasectomy, no longer desire biological children, and have normal semen parameters (≥15 million sperm/mL, ≥40 percent total motility). Importantly, the study candidates must be willing to attend eight follow-up visits and complete assessments (eg, regular semen sampling for 3 years), to use an alternative method of contraception, and to accept unknown risk of pregnancy during the study duration.

Currently, a total of seven patients have been enrolled and had the hydrogel implanted, and four of them have reached the 90-day follow-up to date. None of the seven patients have withdrawn from the study, Anderson said.

“Epworth Hospital has begun screening and enrolling participants for subsequent cohorts, and additional sites across Australia are being activated to further accelerate the study,” he said.