Alyssa Berry: As Vasalgel emphasizes the reabsorption of sperm into the body, many men worry about a buildup or blockage of sperm in the vas deferens. Can you comment on whether this has been observed in your studies or rather, how likely it is to occur?
Elaine Lissner: It may be reassuring to men to be reminded that sperm in the vas deferens are resorbed by the body in other, more familiar situations—after vasectomy, or if a man doesn’t have sex or ejaculate for a while. In addition, it’s important to remember that most of the semen released by the body during ejaculation does not travel through the vas deferens and will therefore not be blocked by Vasalgel.
Upcoming clinical trials of Vasalgel will give definitive data on any side effects. Until then, we base expectations in part on vasectomy statistics, because in both cases the sperm cells produced by the testes cannot be released from the body via ejaculation. According to the American Urological Association, 1-2% of men who have had vasectomies experience chronic pain (although highly experienced doctors report much lower rates), such pain may be caused by a build-up of pressure from unreleased sperm cells and fluid.
Our current understanding of Vasalgel is that fluids can pass through the gel, but sperm cannot (the gel in a sense filters out the sperm). This will likely reduce the incidence of such back-pressure. In recently published rabbit studies, less damage was seen in the testicular and epididymal sperm production and storage areas than would be expected with vasectomy, a heartening result.
AB: Some men are worried about the risk of sterilization with Vasalgel. Based on your studies, can you comment on the likelihood of this risk?
EL: The ability to reverse the contraceptive effect is desired by many men seeking later reproductive potential, until Vasalgel is proven to be reliably reversible in men (by dissolving the gel and flushing it from the vas deferens), it must be considered an alternative to vasectomy.
Some men may also choose to freeze their sperm in conjunction with the procedure as an extra precaution. Initial clinical trials will enroll only men interested in a permanent contraceptive effect until reversibility of the contraceptive is proven in humans.
AB: Are studies being conducted that focus on the reversibility of Vasalgel? If so, does the data seem promising?
EL: Yes, preclinical studies focused on reversibility are promising, but not conclusive in larger animals. Preclinical testing of Vasalgel in a rabbit model resulted in rapid and durable efficacy of the contraceptive. Vasalgel was then flushed from the vas deferens with a sodium bicarbonate (baking soda) solution, which restored sperm flow.
However, in larger animals (baboons and dogs), reversing the contraceptive effect in a similar way has not yet been successful. Research is ongoing to clarify the issues and optimize the procedure, and additional preclinical studies will be conducted before testing reversal in humans.
AB: Perhaps the number one question asked by readers across the world pertains to the pain associated with Vasalgel injection. Where is the injection site? In humans, would you anticipate this procedure to require general anesthesia or a local anesthetic? Did any of the animal subjects display pain post-procedure?
EL: The procedure to place Vasalgel is in many respects similar to the no-scalpel vasectomy (NSV) procedure, which entails less pain and fewer side effects than traditional vasectomy. About 500,000 North American men already get vasectomies each year. In NSV, the tube-like structure that carries sperm from the epididymis out through the urethra (the vas deferens) is accessed at the scrotum through a small puncture in the skin.
However, for Vasalgel insertion, unlike vasectomy, once the vas deferens is accessed, it is not cut— the Vasalgel is simply injected inside. A local anesthetic is used to prevent pain during the procedure. Unlike for female sterilization, which is more invasive, general anesthesia is not needed.
Any post-procedure discomfort is expected to be minor and brief, similar to after the no-scalpel vasectomy procedure. Given that vasectomy makes up 10-20% of contraceptive use in countries where it has become popularized and is readily available, many men are clearly deciding that the short-term discomfort is worth it.
The vas deferens in other species is more difficult to access, requiring sedation and minor surgery, followed by pain medication. Thus, experience from human vasectomy is a better analog than the experience in this primate study. However, it was reassuring that in this primate study, side effects were comparable to, or less than, would be expected from vasectomy.
AB: Now that we have seen positive results from the rhesus monkey study, how soon do you anticipate human clinical trials to occur?
This year, we are working on production of the clinical material, extensive safety and stability testing required by the regulatory process, planning of the clinical trial, and finally applying for regulatory approval to conduct the first trial in humans. Fundraising for the social venture project will occur mid-year. If all goes well, we anticipate the first human clinical trial to start next year in 2018.
Thumbnail picture credit: Parsemus Foundation