Researchers Are Testing a New Stem Cell Therapy in the Hopes of Saving Millions from Blindness
Of all the infirmities of old age, failing sight is among the cruelest. It can mean the end not only of independence, but of a whole spectrum of joys—from gazing at a sunset or a grandchild's face to reading a novel or watching TV.
The Phase 1 trial will likely run through 2022, followed by a larger Phase 2 trial that could last another two or three years.
The leading cause of vision loss in people over 55 is age-related macular degeneration, or AMD, which afflicts an estimated 11 million Americans. As photoreceptors in the macula (the central part of the retina) die off, patients experience increasingly severe blurring, dimming, distortions, and blank spots in one or both eyes.
The disorder comes in two varieties, "wet" and "dry," both driven by a complex interaction of genetic, environmental, and lifestyle factors. It begins when deposits of cellular debris accumulate beneath the retinal pigment epithelium (RPE)—a layer of cells that nourish and remove waste products from the photoreceptors above them. In wet AMD, this process triggers the growth of abnormal, leaky blood vessels that damage the photoreceptors. In dry AMD, which accounts for 80 to 90 percent of cases, RPE cells atrophy, causing photoreceptors to wither away. Wet AMD can be controlled in about a quarter of patients, usually by injections of medication into the eye. For dry AMD, no effective remedy exists.
Stem Cells: Promise and Perils
Over the past decade, stem cell therapy has been widely touted as a potential treatment for AMD. The idea is to augment a patient's ailing RPE cells with healthy ones grown in the lab. A few small clinical trials have shown promising results. In a study published in 2018, for example, a University of Southern California team cultivated RPE tissue from embryonic stem cells on a plastic matrix and transplanted it into the retinas of four patients with advanced dry AMD. Because the trial was designed to test safety rather than efficacy, lead researcher Amir Kashani told a reporter, "we didn't expect that replacing RPE cells would return a significant amount of vision." Yet acuity improved substantially in one recipient, and the others regained their lost ability to focus on an object.
Therapies based on embryonic stem cells, however, have two serious drawbacks: Using fetal cell lines raises ethical issues, and such treatments require the patient to take immunosuppressant drugs (which can cause health problems of their own) to prevent rejection. That's why some experts favor a different approach—one based on induced pluripotent stem cells (iPSCs). Such cells, first produced in 2006, are made by returning adult cells to an undifferentiated state, and then using chemicals to reprogram them as desired. Treatments grown from a patient's own tissues could sidestep both hurdles associated with embryonic cells.
At least hypothetically. Today, the only stem cell therapies approved by the U.S. Food and Drug Administration (FDA) are umbilical cord-derived products for various blood and immune disorders. Although scientists are probing the use of embryonic stem cells or iPSCs for conditions ranging from diabetes to Parkinson's disease, such applications remain experimental—or fraudulent, as a growing number of patients treated at unlicensed "stem cell clinics" have painfully learned. (Some have gone blind after receiving bogus AMD therapies at those facilities.)
Last December, researchers at the National Eye Institute in Bethesda, Maryland, began enrolling patients with dry AMD in the country's first clinical trial using tissue grown from the patients' own stem cells. Led by biologist Kapil Bharti, the team intends to implant custom-made RPE cells in 12 recipients. If the effort pans out, it could someday save the sight of countless oldsters.
That, however, is what's technically referred to as a very big "if."
The First Steps
Bharti's trial is not the first in the world to use patient-derived iPSCs to treat age-related macular degeneration. In 2013, Japanese researchers implanted such cells into the eyes of a 77-year-old woman with wet AMD; after a year, her vision had stabilized, and she no longer needed injections to keep abnormal blood vessels from forming. A second patient was scheduled for surgery—but the procedure was canceled after the lab-grown RPE cells showed signs of worrisome mutations. That incident illustrates one potential problem with using stem cells: Under some circumstances, the cells or the tissue they form could turn cancerous.
"The knowledge and expertise we're gaining can be applied to many other iPSC-based therapies."
Bharti and his colleagues have gone to great lengths to avoid such outcomes. "Our process is significantly different," he told me in a phone interview. His team begins with patients' blood stem cells, which appear to be more genomically stable than the skin cells that the Japanese group used. After converting the blood cells to RPE stem cells, his team cultures them in a single layer on a biodegradable scaffold, which helps them grow in an orderly manner. "We think this material gives us a big advantage," Bharti says. The team uses a machine-learning algorithm to identify optimal cell structure and ensure quality control.
It takes about six months for a patch of iPSCs to become viable RPE cells. When they're ready, a surgeon uses a specially-designed tool to insert the tiny structure into the retina. Within days, the scaffold melts away, enabling the transplanted RPE cells to integrate fully into their new environment. Bharti's team initially tested their method on rats and pigs with eye damage mimicking AMD. The study, published in January 2019 in Science Translational Medicine, found that at ten weeks, the implanted RPE cells continued to function normally and protected neighboring photoreceptors from further deterioration. No trace of mutagenesis appeared.
Encouraged by these results, Bharti began recruiting human subjects. The Phase 1 trial will likely run through 2022, followed by a larger Phase 2 trial that could last another two or three years. FDA approval would require an even larger Phase 3 trial, with a decision expected sometime between 2025 and 2028—that is, if nothing untoward happens before then. One unknown (among many) is whether implanted cells can thrive indefinitely under the biochemically hostile conditions of an eye with AMD.
"Most people don't have a sense of just how long it takes to get something like this to work, and how many failures—even disasters—there are along the way," says Marco Zarbin, professor and chair of Ophthalmology and visual science at Rutgers New Jersey Medical School and co-editor of the book Cell-Based Therapy for Degenerative Retinal Diseases. "The first kidney transplant was done in 1933. But the first successful kidney transplant was in 1954. That gives you a sense of the time frame. We're really taking the very first steps in this direction."
Looking Ahead
Even if Bharti's method proves safe and effective, there's the question of its practicality. "My sense is that using induced pluripotent stem cells to treat the patient from whom they're derived is a very expensive undertaking," Zarbin observes. "So you'd have to have a very dramatic clinical benefit to justify that cost."
Bharti concedes that the price of iPSC therapy is likely to be high, given that each "dose" is formulated for a single individual, requires months to manufacture, and must be administered via microsurgery. Still, he expects economies of scale and production to emerge with time. "We're working on automating several steps of the process," he explains. "When that kicks in, a technician will be able to make products for 10 or 20 people at once, so the cost will drop proportionately."
Meanwhile, other researchers are pressing ahead with therapies for AMD using embryonic stem cells, which could be mass-produced to treat any patient who needs them. But should that approach eventually win FDA approval, Bharti believes there will still be room for a technique that requires neither fetal cell lines nor immunosuppression.
And not only for eye ailments. "The knowledge and expertise we're gaining can be applied to many other iPSC-based therapies," says the scientist, who is currently consulting with several companies that are developing such treatments. "I'm hopeful that we can leverage these approaches for a wide range of applications, whether it's for vision or across the body."
NEI launches iPS cell therapy trial for dry AMD
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The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
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Here are the promising studies covered in this week's Friday Five:
- A pill to prevent lung cancer?
- Ancient wisdom about Neti pots could pay off for Covid
- Breakthrough for precision medicine and obesity
- How to refreeze the north and south poles
- The connection between taking multivitamin pills and brain health
New Options Are Emerging in the Search for Better Birth Control
About decade ago, Elizabeth Summers' options for birth control suddenly narrowed. Doctors diagnosed her with Factor V Leiden, a rare genetic disorder, after discovering blood clots in her lungs. The condition increases the risk of clotting, so physicians told Summers to stay away from the pill and other hormone-laden contraceptives. "Modern medicine has generally failed to provide me with an effective and convenient option," she says.
But new birth control options are emerging for women like Summers. These alternatives promise to provide more choices to women who can't ingest hormones or don't want to suffer their unpleasant side effects.
These new products have their own pros and cons. Still, doctors are welcoming new contraceptives following a long drought in innovation. "It's been a long time since we've had something new in the world of contraception," says Heather Irobunda, an obstetrician and gynecologist at NYC Health and Hospitals.
On social media, Irobunda often fields questions about one of these new options, a lubricating gel called Phexxi. San Diego-based Evofem, the company behind Phexxi, has been advertising the product on Hulu and Instagram after the gel was approved by the Food and Drug Administration in May 2020. The company's trendy ads target women who feel like condoms diminish the mood, but who also don't want to mess with an IUD or hormones.
Here's how it works: Phexxi is inserted via a tampon-like device up to an hour before sex. The gel regulates vaginal pH — essentially, the acidity levels — in a range that's inhospitable to sperm. It sounds a lot like spermicide, which is also placed in the vagina prior to sex to prevent pregnancy. But spermicide can damage the vagina's cell walls, which can increase the risk of contracting sexually transmitted diseases.
"Not only is innovation needed, but women want a non-hormonal option."
Phexxi isn't without side effects either. The most common one is vaginal burning, according to a late-stage trial. It's also possible to develop a urinary tract infection while using the product. That same study found that during typical use, Phexxi is about 86 percent effective at preventing pregnancy. The efficacy rate is comparable to condoms but lower than birth control pills (91 percent) and significantly lower than an IUD (99 percent).
Phexxi – which comes in a pack of 12 – represents a tiny but growing part of the birth control market. Pharmacies dispensed more than 14,800 packs from April through June this year, a 65 percent increase over the previous quarter, according to data from Evofem.
"We've been able to demonstrate that not only is innovation needed, but women want a non-hormonal option," says Saundra Pelletier, Evofem's CEO.
Beyond contraception, the company is carrying out late-stage tests to gauge Phexxi's effectiveness at preventing the sexually transmitted infections chlamydia and gonorrhea.
Phexxi is inserted via a tampon-like device up to an hour before sex.
Phexxi
A New Pill
The first birth control pill arrived in 1960, combining the hormones estrogen and progestin to stop sperm from joining with an egg, giving women control over their fertility. Subsequent formulations sought to ease side effects, by way of lower amounts of estrogen. But some women still experience headaches and nausea – or more serious complications like blood clots. On social media, women noted that birth control pills are much more likely to cause blood clots than Johnson & Johnson's COVID-19 vaccine that was briefly paused to evaluate the risk of clots in women under age 50. What will it take, they wondered, for safer birth control?
Mithra Pharmaceuticals of Belgium sought to create a gentler pill. In April 2021, the FDA approved Mithra's Nextstellis, which includes a naturally occurring estrogen, the first new estrogen in the U.S. in 50 years. Nextstellis selectively acts on tissues lining the uterus, while other birth control pills have a broader target.
A Phase 3 trial showed a 98 percent efficacy rate. Andrew London, an obstetrician and gynecologist, who practices at several Maryland hospitals, says the results are in line with some other birth control pills. But, he added, early studies indicate that Nextstellis has a lower risk of blood clotting, along with other potential benefits, which additional clinical testing must confirm.
"It's not going to be worse than any other pill. We're hoping it's going to be significantly better," says London.
The estrogen in Nexstellis, called estetrol, was skipped over by the pharmaceutical industry after its discovery in the 1960s. Estetrol circulates between the mother and fetus during pregnancy. Decades later, researchers took a new look, after figuring out how to synthesize estetrol in a lab, as well as produce estetrol from plants.
"That allowed us to really start to investigate the properties and do all this stuff you have to do for any new drug," says Michele Gordon, vice president of marketing in women's health at Mayne Pharma, which licensed Nextstellis.
Bonnie Douglas, who followed the development of Nextstellis as part of a search for better birth control, recently switched to the product. "So far, it's much more tolerable," says Douglas. Previously, the Midwesterner was so desperate to find a contraceptive with fewer side effects that she turned to an online pharmacy to obtain a different birth control pill that had been approved in Canada but not in the U.S.
Contraceptive Access
Even if a contraceptive lands FDA approval, access poses a barrier. Getting insurers to cover new contraceptives can be difficult. For the uninsured, state and federal programs can help, and companies should keep prices in a reasonable range, while offering assistance programs. So says Kelly Blanchard, president of the nonprofit Ibis Reproductive Health. "For innovation to have impact, you want to reach as many folks as possible," she says.
In addition, companies developing new contraceptives have struggled to attract venture capital. That's changing, though.
In 2015, Sabrina Johnson founded DARÉ Bioscience around the idea of women's health. She estimated the company would be fully funded in six months, based on her track record in biotech and the demand for novel products.
But it's been difficult to get male investors interested in backing new contraceptives. It took Johnson two and a half years to raise the needed funds, via a reverse merger that took the company public. "There was so much education that was necessary," Johnson says, adding: "The landscape has changed considerably."
Johnson says she would like to think DARÉ had something to do with the shift, along with companies like Organon, a spinout of pharma company Merck that's focused on reproductive health. In surveying the fertility landscape, DARÉ saw limited non-hormonal options. On-demand options – like condoms – can detract from the moment. Copper IUDs must be inserted by a doctor and removed if a woman wants to return to fertility, and this method can have onerous side effects.
So, DARÉ created Ovaprene, a hormone-free device that's designed to be inserted into the vagina monthly by the user. The mesh product acts as a barrier, while releasing a chemical that immobilizes sperm. In an early study, the company reported that Ovaprene prevented almost all sperm from entering the cervical canal. The results, DARÉ believes, indicate high efficacy. Should Ovaprene eventually win regulatory approval, drug giant Bayer will handle commercializing the device.
Other new forms of birth control in development are further out, and that's assuming they perform well in clinical trials. Among them: a once-a-month birth control pill, along with a male version of the birth control pill. The latter is often brought up among women who say it's high time that men take a more proactive role in birth control.
For Summers, her search for a safe and convenient birth control continues. She tried Phexxi, which caused irritation. Still, she's excited that a non-hormonal option now exists. "I'm sure it will work for others," she says.
This article was first published by Leaps.org on August 31, 2021.