Researchers Are Testing a New Stem Cell Therapy in the Hopes of Saving Millions from Blindness
NIH researchers in Kapil Bharti's lab work toward the development of induced pluripotent stem cells to treat dry age-related macular degeneration.
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
Vaccine passports, if required by businesses and universities, may give people a false sense of security, one expert cautions.
Vaccines are one of the greatest public health accomplishments of all time. For centuries, public health has relied on vaccinations to prevent and control disease outbreaks for a plethora of infectious scourges, with our crowning achievement being the successful eradication of smallpox.
The purpose of vaccine documentation is to provide proof of an individual's protection from either becoming infected or transmitting a vaccine-preventable disease. Vouching for these protections requires a firm knowledge about the epidemiology of the disease, as well as scientific knowledge concerning the efficacy of the vaccine. The vaccines we currently require be documented have met these tests; the vaccine for COVID-19 has not yet been proven to do so.
Let's acknowledge that the term "vaccine passport" is a poor choice of words. Passports are a legal travel document created by nations and governed by law for identification of the bearer to control entry and exit from nation states. They often serve as legal forms of identification and as a record of international travel. They are generally very sophisticated documents that have been created in a secure manner and may include a range of electronic and, in some cases, biometric measures such as fingerprints to ensure the holder is indeed who they say they are. Vaccine passports are medical documents used to document the vaccination status of an individual. They do not undergo the same level of administrative scrutiny and cannot be used to verify that the presenter is indeed the vaccinated individual. Some companies do have electronic methods to address concerns about verification; however, most people currently have paper records that can be easily falsified.
"Vaccine passports" as currently proposed risk giving people a false sense of security.
Successful disease control from vaccination programs relies on the ability to vaccinate at a level that prevents large-scale disease spread and the ability to rapidly identify the presence of disease outbreaks. It requires reliable, safe, and effective vaccines that are easily delivered in clinical and nonclinical settings. Keeping vaccination information as a part of the medical record, and even having a separate specialized vaccine record for personal use, is a time-honored tradition.
Keeping a vaccination record provides a method to keep track of the many shots one receives and serves as a visual reminder to help ensure the appropriate vaccine shot schedule is maintained for vaccines requiring multiple doses. The vaccine record, when combined with vaccine safety monitoring systems, serves as a mechanism to track adverse events to monitor and ensure the safety of vaccines as a consumer product. The record also serves as the official record of vaccination when required for administrative or legally prescribed purposes.
"Vaccine passports" as currently proposed risk giving people a false sense of security. In the case of the COVID-19 vaccines currently approved for use, many of the essential questions remain unanswered. While we do know the current three vaccines are highly protective against severe disease and death, and there is some evidence that these vaccinations do reduce infections and virus transmission of SARS-CoV-2, we do not yet know the full degree to which this occurs.
For example, we know there have been some cases of people that have been infected in close proximity to getting their full vaccination and rare cases of breakthrough reinfections. A breakthrough infection in a restaurant is a challenge for contact tracing, but an outbreak from a movie theater exposure or a baseball game could spark a major outbreak at our current level of vaccination. Current CDC guidance recommends continued mask wearing in order to address these concerns.
We also do not yet know how long the protections will last and if or when a booster or revaccination is required. In effect, it is too soon to know. Should an annual booster shot be required, then a vaccine passport would require annual updating, a process more frequent than renewal of a driver's license.
We also know that the current SARS-CoV-2 virus is mutating briskly. While the current approved vaccines have remained effective overall, there is evidence of some degree of degradation in vaccine effectiveness against some of the circulating strains. We also have sparse data on many of the other emerging strains of concern because we have not had the surveillance capacity in the U.S. to gain an adequate sense of how the virus is changing to fully align vaccine effectiveness with viral capabilities.
The risk of people misusing these "passports" is troubling. The potential for using these documents for hiring, firing or job limitation is a serious concern. Unvaccinated workers are at risk of this form of discrimination even from well-meaning employers or supervisors. Health insurers are prohibited by the Affordable Care Act from discriminating based on preexisting conditions, but they could probably charge a higher premium for unvaccinated individuals. There also is a risk of stigmatizing individuals who are not vaccinated or have left their vaccine documentation at home. Another concern: the opportunity to discriminate based on race, gender, sexual orientation, or religion, using one's vaccination status as an excuse.
These "passports" are being discussed as a "ticket verification" for entry to many activities, including dining at restaurants, flying domestically and/or internationally, going to movie theaters and sporting events, etc. These are all activities we already are doing at reduced levels and for which wearing a mask, hand hygiene and physical distancing are effective disease control practices. COVID-19 vaccines are indeed the measure that will make the ability to totally reopen our society complete, but we are not there yet. Documentation of one's COVID-19 vaccine status may be useful in selected situations in the future. That remains to be seen.
Finally, inadequate vaccine supply and disparities in vaccine delivery have created enormous challenges in providing equal access to vaccination. Also, the amount of misinformation, disinformation, and lingering vaccine hesitancy continue to limit the speed at which we will reach the level of vaccination of the population that would make this documentation meaningful. The requirement for "vaccine passports" is already alienating people who are opposed to vaccinations for a variety of reasons, paradoxically risking reduced vaccine uptake. This politicization of the vaccination effort is of concern. There are indeed people who, due to medical contraindications or legal exemptions, will not be vaccinated, and we do not yet have a national framework on how to address this.
Vaccine passports are not the solution for reopening our society — a robust vaccination program is. The requirement to document one's vaccination status for COVID-19 may one day have its place. For now, it is an idea whose time has not yet come.
Editor's Note: This op/ed is part of a "Big Question" series on the ethics of vaccine passports. Read the flip side argument here.
A digital health passport required by businesses and universities could help us get back to normal more quickly, one expert argues.
"Vaccine passports" are a system that requires proof of a COVID-19 vaccination as a condition of engaging in activities that pose a risk of transmitted SARS-CoV-2. Digital Health Passes (DHPs) are typically a smartphone application with a code that verifies whether someone has been vaccinated.
Vaccine passports could very much be in our future. Many businesses are implementing or planning to require proof of vaccination as a condition of returning to the workplace. Colleges and universities have announced vaccine requirements for students, staff, and faculty. It may not be long before the private sector requires a vaccination card or image to attend an entertainment or sporting event, to travel, or even to dine or shop indoors, at least in some venues.
But it's unlikely the federal government or the states will launch DHPs, at least not in the near-term. President Biden announced the White House has no intention of requiring proof of vaccination. While no state has mandated DHPs, New York is piloting its Excelsior Pass on a voluntary basis, partnering with IBM. Other nations are not so hesitant. Israel's "Green Pass" has gotten the nation back to normal in record time. And various countries and regions are planning DHPs, including the European Union and the United Kingdom. Foreign airlines are likely to require proof of vaccination as a condition of flying internationally.
DHPs could emerge as a way to get us back to normal more quickly, but are they ethical? Let's start with the law. The US Equal Opportunity Commission (EEOC) has specifically said that employers have the legal right to require proof of vaccination as a condition of returning to work. Colleges and universities already require several vaccines for students living in dorms. Hospitals and nursing homes often mandate influenza vaccinations. And, of course, all states require childhood vaccinations for school attendance. Vaccine passports are lawful but are they ethical? The short answer is "yes" but only if we ensure no one is left behind.
Vaccine passports "don't force anyone to be vaccinated against his or her will. They simply say to individuals that if you choose not to be vaccinated, you can't work or recreate in public spaces that risk transmission of the virus."
Why are vaccine passports ethical? Vaccines are a miracle of modern science, but they have become a political symbol, and a significant part of the population doesn't want to get a jab. The rare cases of blood clots associated with the Johnson & Johnson and AstraZeneca vaccines have only created more distrust.
Most opposition to vaccine passports hinges on the claim that they infringe personal autonomy and liberty. But this argument misses the point. Of course, every competent adult has the right to make decisions that affect his or her own health and safety. But no one has a right to infringe on the rights of others, such as by exposing them to a potentially serious or deadly infectious disease. An individual can't claim the right to attend a crowded event mask-less and unvaccinated. This was once accepted across the political spectrum. Conservative economists called it an "externality," that is a person has no right to harm others. The U.S. has lost the tradition of the common good. We have become so focused on our own individual rights that we forget about our ethical obligations to our neighbors and to our community.
In fact, DHPs actually don't force anyone to be vaccinated against his or her will. They simply say to individuals that if you choose not to be vaccinated, you can't work or recreate in public spaces that risk transmission of the virus.
DHPs also don't infringe on privacy. Again, everyone has the choice whether to show proof of vaccination. It isn't required. Moreover, DHPs may actually protect privacy because all they do is show whether or not you have been vaccinated. They don't disclose any other personal medical information. All of us actually have already had to show proof of vaccination as a condition of going to school. Thus, DHPs are well established in the United States.
But there is one ethical argument against DHPs that I find to be powerful, and that is equity. If we require proof of vaccination while doses are scarce, we will give the already privileged even more privilege. And that would be unconscionable. Thus, DHPs should not be implemented until everyone who wants a vaccine is able to get a vaccine. Equity isn't a side issue. It needs to be front and center.
As of today, all adults in the U.S. are eligible to get vaccinated, and President Biden has pledged that by the end of May there will be enough doses to vaccinate the entire U.S. population. It is a realistic promise. Once vaccines become plentiful, everyone should get their shot. All Food and Drug Administration authorized vaccines are highly safe and effective, even the Johnson & Johnson vaccine that the FDA has just put on pause.
Businesses have an economic incentive to require proof of vaccination. Very few of us would feel comfortable returning to our jobs, shops, theaters, or restaurants unless we feel safe. Businesses understand the duty to create safer places for work, recreation, and commerce.
One question has dominated national conversation since the pandemic began. "When will we get back to normal?" There is a deep human yearning to hug family and friends, see our work colleagues, recreate, and be entertained. One day we will have defeated this wily virus and get back to normal. But vaccine passports can help us get back to the things we love faster and more safely. As long as we don't leave anyone behind, using this miracle of modern science to make our lives better is both lawful and ethical.
Editor's Note: This op/ed is part of a "Big Question" series on the ethics of vaccine passports. Read the flip-side argument here.