The future of non-hormonal birth control: Antibodies can stop sperm in their tracks
Unwanted pregnancy can now be added to the list of preventions that antibodies may be fighting in the near future. For decades, really since the 1980s, engineered monoclonal antibodies have been knocking out invading germs — preventing everything from cancer to COVID. Sperm, which have some of the same properties as germs, may be next.
Not only is there an unmet need on the market for alternatives to hormonal contraceptives, the genesis for the original research was personal for the then 22-year-old scientist who led it. Her findings were used to launch a company that could, within the decade, bring a new kind of contraceptive to the marketplace.
It’s Suruchi Shrestha’s research — published in Science Translational Medicine in August 2021 and conducted as part of her dissertation while she was a graduate student at the University of North Carolina at Chapel Hill — that could change the future of contraception for many women worldwide. According to a Guttmacher Institute report, in the U.S. alone, there were 46 million sexually active women of reproductive age (15–49) who did not want to get pregnant in 2018. With the overturning of Roe v. Wade last year, Shrestha’s research could, indeed, be life changing for millions of American women and their families.
Now a scientist with NextVivo, Shrestha is not directly involved in the development of the contraceptive that is based on her research. But, back in 2016 when she was going through her own problems with hormonal contraceptives, she “was very personally invested” in her research project, Shrestha says. She was coping with a long list of negative effects from an implanted hormonal IUD. According to the Mayo Clinic, those can include severe pelvic pain, headaches, acute acne, breast tenderness, irregular bleeding and mood swings. After a year, she had the IUD removed, but it took another full year before all the side effects finally subsided; she also watched her sister suffer the “same tribulations” after trying a hormonal IUD, she says.
For contraceptive use either daily or monthly, Shrestha says, “You want the antibody to be very potent and also cheap.” That was her goal when she launched her study.
Shrestha unshelved antibody research that had been sitting idle for decades. It was in the late 80s that scientists in Japan first tried to develop anti-sperm antibodies for contraceptive use. But, 35 years ago, “Antibody production had not been streamlined as it is now, so antibodies were very expensive,” Shrestha explains. So, they shifted away from birth control, opting to focus on developing antibodies for vaccines.
Over the course of the last three decades, different teams of researchers have been working to make the antibody more effective, bringing the cost down, though it’s still expensive, according to Shrestha. For contraceptive use either daily or monthly, she says, “You want the antibody to be very potent and also cheap.” That was her goal when she launched her study.
The problem with contraceptives for women, Shrestha says, is that all but a few of them are hormone-based or have other negative side effects. In fact, some studies and reports show that millions of women risk unintended pregnancy because of medical contraindications with hormone-based contraceptives or to avoid the risks and side effects. While there are about a dozen contraceptive choices for women, there are two for men: the condom, considered 98% effective if used correctly, and vasectomy, 99% effective. Neither of these choices are hormone-based.
On the non-hormonal side for women, there is the diaphragm which is considered only 87 percent effective. It works better with the addition of spermicides — Nonoxynol-9, or N-9 — however, they are detergents; they not only kill the sperm, they also erode the vaginal epithelium. And, there’s the non-hormonal IUD which is 99% effective. However, the IUD needs to be inserted by a medical professional, and it has a number of negative side effects, including painful cramping at a higher frequency and extremely heavy or “abnormal” and unpredictable menstrual flows.
The hormonal version of the IUD, also considered 99% effective, is the one Shrestha used which caused her two years of pain. Of course, there’s the pill, which needs to be taken daily, and the birth control ring which is worn 24/7. Both cause side effects similar to the other hormonal contraceptives on the market. The ring is considered 93% effective mostly because of user error; the pill is considered 99% effective if taken correctly.
“That’s where we saw this opening or gap for women. We want a safe, non-hormonal contraceptive,” Shrestha says. Compounding the lack of good choices, is poor access to quality sex education and family planning information, according to the non-profit Urban Institute. A focus group survey suggested that the sex education women received “often lacked substance, leaving them feeling unprepared to make smart decisions about their sexual health and safety,” wrote the authors of the Urban Institute report. In fact, nearly half (45%, or 2.8 million) of the pregnancies that occur each year in the US are unintended, reports the Guttmacher Institute. Globally the numbers are similar. According to a new report by the United Nations, each year there are 121 million unintended pregnancies, worldwide.
The early work on antibodies as a contraceptive had been inspired by women with infertility. It turns out that 9 to 12 percent of women who are treated for infertility have antibodies that develop naturally and work against sperm. Shrestha was encouraged that the antibodies were specific to the target — sperm — and therefore “very safe to use in women.” She aimed to make the antibodies more stable, more effective and less expensive so they could be more easily manufactured.
Since antibodies tend to stick to things that you tell them to stick to, the idea was, basically, to engineer antibodies to stick to sperm so they would stop swimming. Shrestha and her colleagues took the binding arm of an antibody that they’d isolated from an infertile woman. Then, targeting a unique surface antigen present on human sperm, they engineered a panel of antibodies with as many as six to 10 binding arms — “almost like tongs with prongs on the tongs, that bind the sperm,” explains Shrestha. “We decided to add those grabbers on top of it, behind it. So it went from having two prongs to almost 10. And the whole goal was to have so many arms binding the sperm that it clumps it” into a “dollop,” explains Shrestha, who earned a patent on her research.
Suruchi Shrestha works in the lab with a colleague. In 2016, her research on antibodies for birth control was inspired by her own experience with side effects from an implanted hormonal IUD.
UNC - Chapel Hill
The sperm stays right where it met the antibody, never reaching the egg for fertilization. Eventually, and naturally, “Our vaginal system will just flush it out,” Shrestha explains.
“She showed in her early studies that [she] definitely got the sperm immotile, so they didn't move. And that was a really promising start,” says Jasmine Edelstein, a scientist with an expertise in antibody engineering who was not involved in this research. Shrestha’s team at UNC reproduced the effect in the sheep, notes Edelstein, who works at the startup Be Biopharma. In fact, Shrestha’s anti-sperm antibodies that caused the sperm to agglutinate, or clump together, were 99.9% effective when delivered topically to the sheep’s reproductive tracts.
Going forward, Shrestha thinks the ideal approach would be delivering the antibodies through a vaginal ring. “We want to use it at the source of the spark,” Shrestha says, as opposed to less direct methods, such as taking a pill. The ring would dissolve after one month, she explains, “and then you get another one.”
Engineered to have a long shelf life, the anti-sperm antibody ring could be purchased without a prescription, and women could insert it themselves, without a doctor. “That's our hope, so that it is accessible,” Shrestha says. “Anybody can just go and grab it and not worry about pregnancy or unintended pregnancy.”
Her patented research has been licensed by several biotech companies for clinical trials. A number of Shrestha’s co-authors, including her lab advisor, Sam Lai, have launched a company, Mucommune, to continue developing the contraceptives based on these antibodies.
And, results from a small clinical trial run by researchers at Boston University Chobanian & Avedisian School of Medicine show that a dissolvable vaginal film with antibodies was safe when tested on healthy women of reproductive age. That same group of researchers last year received a $7.2 million grant from the National Institute of Health for further research on monoclonal antibody-based contraceptives, which have also been shown to block transmission of viruses, like HIV.
“As the costs come down, this becomes a more realistic option potentially for women,” says Edelstein. “The impact could be tremendous.”
This article was first published by Leaps.org in December, 2022. It has been lightly edited with updates for timeliness.
In 1962, the world was a remarkably different place: Neil Armstrong had yet to take his first steps on the lunar surface, John F. Kennedy was serving as president of the United States, and the Beatles were still a few years away from superstardom, having just recorded their first single.
The word “measles” was also a household name. Measles, which still exists in parts of the world today, is a highly contagious viral infection that typically causes fever, cough, muscle pain, fatigue, and a distinctive red rash. Measles was so pervasive around the world in 1962 that most children had gotten sick with it before the age of fifteen—but even though it was common, it was far from harmless. Measles killed around 400 to 500 people per year in the United States, and approximately 2.6 million people each year worldwide. Countless others suffered severe complications from measles, such as permanent blindness.
Tragedy hits home
Author Roald Dahl at his Buckinghamshire home with Olivia, daughter Chantal, and wife Patricia Neal in 1960.
Ben Martin / Getty Images
That year, British author Roald Dahl was beginning to make a name for himself, having just published his best-selling book James and the Giant Peach. Dahl, who would go on to write some of the most well-loved children’s books of the century, lived in southern England with his wife and three children. One day, Dahl and his wife, actress Patricia Neal, received word that there was an outbreak of measles at his daughters’ school.
While some parents quarantined their children, many others also considered measles a harmless childhood disease. Neal later recalled in her autobiography that a family member had advised her to “let the girls get measles,” thinking it would strengthen their immune systems and be “good for them.” Reluctantly, Dahl and Neal let their two school-aged children, Olivia and Chantal, continue school. Olivia, then aged seven, fell sick with the measles not long after that.
Neither Dahl nor Neal were terribly concerned about Olivia’s infection. Dahl would write later that it seemed to be taking its “usual course,” and the two would read and spend time together while Olivia rested. After a few days of fever and fatigue, Dahl wrote, Olivia seemed like she was “well on the road to recovery.”
But one afternoon, as the two sat on Olivia’s bed making animals out of pipe cleaners, Dahl noticed that Olivia’s “fingers and her mind were not working together.” When Dahl asked how she was feeling, Olivia replied, “I feel all sleepy.”
Within an hour, Dahl wrote, Olivia was unconscious. Within 12 hours, she was dead.
Olivia died of measles encephalitis, an inflammation of the brain caused by an infection. Approximately 1 in 1,000 people infected with measles develop encephalitis, and of those who develop it, between 10 and 20 percent will die.
Dahl was overcome with grief and wracked with guilt for being unable to prevent his daughter’s death. Mourning, Dahl threw himself into his writing and, in his spare time, spent hours lovingly constructing a rock garden on Olivia’s grave in a local churchyard.
After Olivia’s death, Dahl wrote sixteen novels and several collections of short stories, including Matilda, Fantastic Mr. Fox, and Willy Wonka and the Chocolate Factory, which garnered him worldwide acclaim. His most influential piece of writing, however, wasn’t written until 1986.
A father's plea
Roald Dahl and the open letter he wrote in 1986, encouraging parents to vaccinate their children against measles.
By 1986, measles was no longer the global health threat that it had been in the 1960s, thanks to a measles vaccine that became available just one year after Olivia had died. Still, in the United Kingdom alone, approximately 80,000 people every year were infected with measles. This bothered Dahl, especially since measles rates in the United States had dropped by 98 percent compared to pre-vaccine years. “Why do we have so much measles in Britain when the Americans have virtually gotten rid of it?,” Dahl was reported to have said.
So Dahl set out to prevent a tragedy like Olivia’s from happening again. With encouragement from several prominent public health activists, Dahl wrote an open letter addressed to parents in the UK. The letter recounted his daughter’s death from encephalitis and begged parents to protect their own children from measles:
“...there is today something that parents can do to make sure that this sort of tragedy does not happen to a child of theirs. They can insist that their child is immunised [sic] against measles. I was unable to do that for Olivia in 1962 because in those days a reliable measles vaccine had not been discovered. Today a good and safe vaccine is available to every family and all you have to do is to ask your doctor to administer it.”
Dahl went on to say that although many parents still viewed measles as a harmless illness, he knew from experience that it was not. Measles was capable of causing disability and death, Dahl wrote, whereas a child had a better chance of “choking on a chocolate bar” than developing any serious complication from the vaccine. Dahl ended his letter by saying how happy he knew Olivia would be “if only she could know that her death had helped to save a good deal of illness and death among other children.”
Dahl’s letter was published in early 1986 and distributed to local healthcare workers, schools, and to parents of children who were particularly at risk. As the letter circulated, vaccination rates continued to climb year after year.
Thirty-one years after Dahl’s letter was published, and 55 years after Olivia’s death, the World Health Organization declared in 2017 that measles had officially been eradicated for the first time in the UK thanks to high rates of vaccination.
A small step back
As vaccination rates decline, measles is now making a strong comeback in the United States and elsewhere.
Today, vaccination rates for the measles are in decline, and countries like the UK and the US, who had once eradicated measles completely, are now seeing a comeback. The Centers for Disease Control and Prevention (CDC) recently reported that between December 1, 2023 and January 23, 2024, 23 cases of measles had been confirmed across multiple states. The majority of these cases, they reported, were among children and adolescents who had traveled internationally and had not yet been vaccinated even though they were eligible to do so.
Roald Dahl passed away in 1990, but fortunately, his writing continues to live on. While readers can explore fantastical worlds through his novels and short stories, they can also look back to a reality when tragic deaths like Olivia’s happened far too often. The difference is that today, thanks to modern science, we now have the tools to stop them.
Sarah Watts is a health and science writer based in Chicago.
On today’s episode of Making Sense of Science, I’m honored to be joined by Dr. Paul Song, a physician, oncologist, progressive activist and biotech chief medical officer. Through his company, NKGen Biotech, Dr. Song is leveraging the power of patients’ own immune systems by supercharging the body’s natural killer cells to make new treatments for Alzheimer’s and cancer.
Whereas other treatments for Alzheimer’s focus directly on reducing the build-up of proteins in the brain such as amyloid and tau in patients will mild cognitive impairment, NKGen is seeking to help patients that much of the rest of the medical community has written off as hopeless cases, those with late stage Alzheimer’s. And in small studies, NKGen has shown remarkable results, even improvement in the symptoms of people with these very progressed forms of Alzheimer’s, above and beyond slowing down the disease.
In the realm of cancer, Dr. Song is similarly setting his sights on another group of patients for whom treatment options are few and far between: people with solid tumors. Whereas some gradual progress has been made in treating blood cancers such as certain leukemias in past few decades, solid tumors have been even more of a challenge. But Dr. Song’s approach of using natural killer cells to treat solid tumors is promising. You may have heard of CAR-T, which uses genetic engineering to introduce cells into the body that have a particular function to help treat a disease. NKGen focuses on other means to enhance the 40 plus receptors of natural killer cells, making them more receptive and sensitive to picking out cancer cells.
Paul Y. Song, MD is currently CEO and Vice Chairman of NKGen Biotech. Dr. Song’s last clinical role was Asst. Professor at the Samuel Oschin Cancer Center at Cedars Sinai Medical Center.
Dr. Song served as the very first visiting fellow on healthcare policy in the California Department of Insurance in 2013.He is currently on the advisory board of the Pritzker School of Molecular Engineering at the University of Chicago and a board member of Mercy Corps, The Center for Health and Democracy, and Gideon’s Promise.
Dr. Song graduated with honors from the University of Chicago and received his MD from George Washington University. He completed his residency in radiation oncology at the University of Chicago where he served as Chief Resident and did a brachytherapy fellowship at the Institute Gustave Roussy in Villejuif, France. He was also awarded an ASTRO research fellowship in 1995 for his research in radiation inducible gene therapy.
With Dr. Song’s leadership, NKGen Biotech’s work on natural killer cells represents cutting-edge science leading to key findings and important pieces of the puzzle for treating two of humanity’s most intractable diseases.
- Paul Song LinkedIn
- NKGen Biotech on Twitter - @NKGenBiotech
- NKGen Website: https://nkgenbiotech.com/
- NKGen appoints Paul Song
- Patient Story: https://pix11.com/news/local-news/long-island/promising-new-treatment-for-advanced-alzheimers-patients/
- FDA Clearance: https://nkgenbiotech.com/nkgen-biotech-receives-ind-clearance-from-fda-for-snk02-allogeneic-natural-killer-cell-therapy-for-solid-tumors/Q3 earnings data: https://www.nasdaq.com/press-release/nkgen-biotech-inc.-reports-third-quarter-2023-financial-results-and-business