(CNN) Researchers have turned the spotlight on a new class of drugs that they say could "transform" the field of medicine -- and the drugs work by targeting aging.
The researchers, from the Mayo Clinic in Rochester, Minnesota, are calling for senolytic drugs to make the leap from animal research to human clinical trials. They outlined potential clinical trial scenarios in a paper published in the Journal of the American Geriatrics Society on Monday.
"This is one of the most exciting fields in all of medicine or science at the moment," said Dr. James Kirkland, director of the Kogod Center on Aging at the Mayo Clinic and lead author of the new paper.
As we age, we accumulate senescent cells, which are damaged cells that resist dying off but stay in our bodies. They can affect other cells in our various organs and tissues. Senolytic drugs are agents capable of killing problem-causing senescent cells in your body without harming your normal, healthy cells.
Senescent cells play a role in many age-related chronic diseases, such as diabetes, cardiovascular disease, most cancers, dementia, arthritis, osteoporosis and blindness, Kirkland said. Therefore, senolytic drugs are a possible treatment approach for such diseases.
As a practicing physician, Kirkland said that he has grown increasingly concerned for his patients who are sick with many of these age-related conditions.
"The same processes that cause aging seem to be the root causes of age-related diseases," he said. "Why not target the root cause of all of these things? That would have been a pipe dream until a few years back."
In 2015, scientists from The Scripps Research Institute and the Mayo Clinic, including Kirkland, identified this new class of drugs. In a study published in the journal Aging Cell, they described how senolytic drugs can alleviate symptoms of frailty in mice and extend the length of time the mice are healthy as they grow old.
Then, last year, the researchers demonstrated in a study in Aging Cell that clearing senescent cells in mice can improve their vascular health.
Fourteen senolytic drugs have been discovered and are being actively studied, 11 of which Kirkland's colleagues and their collaborators found, he said.
Are these age-modifying drugs ready for human trials?
Scientists have long known that certain processes influence your body's aging on the cellular level, according to the paper. Those processes include inflammation, changes in your DNA, cell damage or dysfunction and the accumulation of senescent cells.
It turns out that those processes are linked. For instance, DNA damage causes increased senescent cell accumulation, Kirkland said.
People who made it to 100 and beyond
Fauja Singh is recognized as the first 100-year-old to ever run a marathon. The great-grandfather, nicknamed the
"Turbaned Tornado," continues to run or walk every day. Now 106, he took up running to overcome his grief after the death of his wife and a son. He ran his first marathon at age 89. The key to life: "Laughter and happiness. That's your remedy for everything."
Italian Luigina Vigiconte, 101, offered this advice: "Always be optimistic, never bitter, and always be polite with people." Vigiconte, who has eight sons, lives in Acciaroli, south of Naples, where one in 10 people is a centenarian. Scientists who have studied the area say the Mediterranean diet, genetics, regular exercise and the climate contribute to the longevity of the population.
Vincenzo Baratta, 103, who also lives in Acciaroli, said there are two secrets to his long life. One is his diet; the farmer eats only once a day and avoids meat. He eats some fish and homemade pasta and has only one glass of wine per day. His other key: having "a lot of women in his life." A neighbor said he has gone through several caregivers because he made so many passes at them.
Misao Okawa of Osaka, Japan, was 117 when she died April 1, 2015. She was the world's oldest person at the time, according to Guinness World Records. She was born on March 5, 1898, and had three children. Her husband died in 1931. She kept in shape throughout much of her life, saying that helped her live so long; at 102, she said she did leg squats to keep healthy. She didn't start using a wheelchair until she turned 110.
Ruline Steininger, 103, was one of the first people in Iowa to vote for Hillary Clinton
in September. The former schoolteacher, who cast her first vote for Franklin D. Roosevelt in 1936, said that staying politically active kept her young but also
told her local paper that the secret to her long life was "I just keep not dying." She eventually did, in February.
Ruth Frith died February 28 at the age of 104. At 102, the Australian native was the oldest living competitor at the World Masters Games in Sydney, where she won several gold medals and set world records. Her advice for a long life? Avoid smoking, drinking and vegetables. She was also an optimist: "Every year brings something new. I've always been content with what I have."
Konstantinos Spanos, 103, lives in Ikaria, a Greek island with a reputation for long-lived residents. Sponos said the key to his long life is modesty in everything, including "food, women and entertainment," although he might also want to add reading. He reads five hours a day.
Mieko Nagaoka, a 100-year-old Japanese woman who became the world's first centenarian to complete a 1,500-meter freestyle swim, hopes to swim until she is 105. She took up swimming
at age 80 to help with a knee problem. She credits the exercise with her healthy and long life. She trains four days a week.
James Sisnett was born February 22, 1900, in Barbados. He made it to 113 and believed he lived that long by eating good food; having a daily "little one," his name for an alcoholic drink; and "God's grace." He worked as a blacksmith, a sugar factory worker and a farmer before retiring at age 70. His longevity made him a local celebrity. His only real health challenge toward the end of his life was hearing loss. He died in May 2013.
Mississippi Winn was born March 31, 1897, in Benton, Louisiana, and lived to be 113. She maintained her independence until age 103; at 105, she was still walking and working out daily at a local track. Winn said exercise and an optimistic attitude helped her live a long and healthy life. She died in January 2011.
Man Kaur, 101, is still a competitive runner and javelin thrower. From Chandigarh, India, the great-grandmother didn't start competing in sports until she was 93. She credits her daily training, positivity and her avoidance of fried food for her long life.
Susannah Mushatt Jones
lived to 116. Born in Lowndes County, Alabama, she moved to New York to work as a live-in child care provider. Earning only $50 a week, she put three nieces through college. She attributed her longevity to clean living, not smoking or drinking, and surrounding herself with loving family members and friends. Sleep also helped, she said.
Jiroemon Kimura was born April 19, 1897, and died June 12, 2013, at the age of 116. The retired Japanese postal worker attributed his long life to eating light, working in the sunshine and not smoking. After his postal career, he worked on a farm: "I am always looking up towards the sky; that is how I am." Of his six siblings, five lived to the age of 90.
Violet Mosse-Brown, 117, is the current oldest person in the world. She grew up in Jamaica, born
67 years before the country was founded, and said she earned that title by avoiding rum and through her "faith in serving God." The music teacher and church organist still keeps her mind active, keeping the records for the local cemetery.
Jeanne Calment was born February 21, 1875, and lived to the age of 122 in Arles, France (home of the painter Vincent Van Gogh, whom she met as a little girl). At 85, she took up fencing lessons. At 100, she was still riding her bike. She said she ate more than 2 pounds of chocolate a week and only quit smoking at age 120 -- not for health reasons but because she could not see well enough to light her cigarettes. She credited her longevity to port wine, her sense of humor and a diet rich in olive oil. She died in August 1997.
Yisrael Kristal, 113, lives in Haifa, Israel, but grew up in Poland and survived being sent to Auschwitz. He ran candy stores in Lodz and in Haifa but keeps a healthy and simple diet. He credited that, along with prayer, for his longevity. He celebrated his bar mitzvah, which had been delayed by World War I,
when he turned 113.
Emma Morano made it to 117. The Italian credited her long life with ending her marriage to an abusive spouse and eating a regular diet of raw eggs and cookies. She
loved cookies so much, she hid them under her pillow so no one else would eat them.
Ann Nixon Cooper became famous after President-elect Barack Obama used her story on election night 2008 to talk about the country's progress. "She was born just a generation past slavery," Obama said. "At a time when women's voices were silenced and their hopes dismissed, she lived to see them stand up and speak out and reach for the ballot." She died in 2009 at age 107. The secret to her long life, she said, was being cheerful: "I've always been a happy person, a giggling person, a wide-mouthed person." She also kept fit, dancing the electric slide until age 103.
Edward Rondthaler was born June 9, 1905, in Bethlehem, Pennsylvania, and he died in 2009 at the age of 104. He was a noted typographer, earning a national reputation for helping to usher in the age of photographic typesetting,
according to The New York Times. Photographic typesetting was an easier way to print than hot-metal type. Rondthaler credited cold showers for his longevity. He died at his home in Cedar City, Utah.
So an intervention that targets senescent cells could attenuate other aging processes as well, according to the new paper. That is, once such an intervention is tested for efficacy and safety.
"I think senolytic drugs have a great future. If it is proven that it can reduce senescent cells and rejuvenate tissues or organs, it may be one of our potential best treatments for age-related diseases," said Dr. Kang Zhang, founding director of the Institute for Genomic Medicine at the University of California, San Diego, who was not involved in the new paper.
Yet taking senolytic drugs from mouse studies to human ones is a "big leap," Zhang said.
"So we will have to wait for clinical trials to see whether this would work in humans," he said. "One possible clinical trial strategy is to test this class of drugs in an age-related disease, such as neurodegeneration, like Parkinson's disease, to see if it can reduce clinical severity of the disease and improve tissue functions."
In the new paper, the researchers wrote that potential clinical trial scenarios include testing whether senolytic drugs could alleviate multiple chronic diseases in a single patient or whether such drugs could treat conditions that involve senescent cell accumulation in one location in the body, such as osteoarthritis.
They also suggest testing whether the drugs could treat diseases for which there are no medicines proven to slow the progression of that disease, such as idiopathic pulmonary fibrosis, a cell senescence-associated disease that affects the lungs.
Other potential clinical trial scenarios include testing whether the drugs could alleviate frailty in older adults or could treat conditions associated with chemotherapy or radiotherapy, since radiation can produce cellular senescence, Kirkland said.
For instance, "in mice, if you treat one leg with enough radiation, after three months, the mouse has trouble walking. If you give a single dose of these drugs, they're able to walk quite well, and that persists for two years," he said. "These drugs could mitigate the effects of therapeutic radiation."
Certain experimental cancer drugs already undergoing clinical trials, such as navitoclax and obatoclax, have been shown to have some senolytic properties, Kirkland said. If senolytic drugs prove to be efficient in treating humans and end up available for use, he said, they could cost about the same as some cancer drugs.
"Some of the drugs at the moment are moderately expensive," he said.
Cancer drugs can range in cost from about $20 a month to thousands a month. Venclexta or venetoclax, which has been approved by the Food and Drug Administration and has been studied in combination with navitoclax, has a monthly price tag of about $8,000, according to the Memorial Sloan Kettering Cancer Center.
"If we're able to reduce hospitalizations ... the savings on the medical care and hospital side might more than offset the cost of these drugs by a longshot," Kirkland said, though it remains unclear what the dosage options would be for senolytic drugs for short- or long-term use.
What the future holds for senolytic drugs
As for how soon he thinks human clinical trials might commence, Kirkland said doctors could have an idea of how well senolytic drugs work for serious health conditions in about a year and a half or two years.
Once the drugs are tested in humans, researchers expect many companies to be lining up to develop or manufacture senolytic drugs. Some have already expressed interest.
One company, Unity Biotechnology, aims to be the first to demonstrate that removing senescent cells can cure human diseases, said its president, Nathaniel David.
"In the coming decades, I believe that health care will be transformed by this class of medicine and a whole set of diseases that your parents and grandparents have will be things you only see in movies or read in books, things like age-associated arthritis," said David, whose company was not involved in the new paper.
Yet he cautioned that, while many more studies may be on the horizon for senolytic drugs, some might not be successful.
"One thing that people tend to do is, they tend to overestimate things in the short run but then underestimate things in the long run, and I think that, like many fields, this suffers from that as well," David said.
"It will take a while," he said. "I think it's important to recognize that a drug discovery is among the most important of all human activities ... but it takes time, and there must be a recognition of that, and it takes patience."