The Food and Drug Administration on Thursday approved a gene therapy that can cure a rare, inherited form of deafness. The treatment is the first to restore normal hearing in children who were born deaf.

The maker of the therapy, Regeneron, plans to provide it free to any child who needs it. “We wanted to make a statement,” Dr. George Yancopoulos, Regeneron’s chief scientific officer said on Thursday morning.

He explained that the company wants to be sure its treatment “would be able to reach its full potential and help as many people as possible.”

Some gene therapies for other diseases, priced in the millions of dollars, have had dismal sales.

The therapy called Otarmeni, is intended for children with otoferlin deafness, a rare form of hearing loss caused by a mutation in a single gene. The mutation destroys a protein in the inner ear that is needed to transmit sound to the brain.

Although otoferlin deafness accounts for just 2 percent to 8 percent of congenital hearing loss, the new treatment “is groundbreaking,” Dr. Dylan Chan, a pediatric otolaryngologist at the University of California, San Francisco, said.

He added, “This is the first time in history that there has been a medical therapy that has enabled deaf children to hear.”

Dr. Chan has been a paid adviser to Regeneron and to Eli Lilly, which is also developing a gene therapy for otoferlin deafness. He is also a principal investigator for Lilly’s clinical trial of the treatment.

Dr. Daniel Lee, the director of pediatric otology and neurotology at the Massachusetts Eye and Ear Infirmary, said he also viewed the therapy as groundbreaking. “We have now entered the era of biological treatment for inner ear hearing loss,” he said.

Dr. Lee is on the advisory board of a small biotech company, Skylark Bio, that is developing gene therapy for a different form of inherited deafness.

Until now, the only treatment for otoferlin deafness was a cochlear implant, an electronic device placed in the inner ear. The implants can restore sound but not normal hearing. And the sounds come through as robotic or tinny.

People with cochlear implants have difficulty in noisy environments. They do not hear high frequencies. And at night they have to recharge the batteries, leaving them deaf until the morning.

In addition to Regeneron and Lilly, two other companies, in China and in France, are also developing gene therapies for otoferlin deafness.

Dr. Eliot Shearer, a pediatric surgeon who specializes in hearing loss at Boston Children’s Hospital, said the otoferlin gene therapy is only the beginning of treatments for deafness. “There are over 150 known genetic causes of hearing loss, and thousands of mutations in those genes,” Dr. Shearer said. “Now that it is known that it’s possible to correct genetic hearing loss, new possibilities open up.”

Dr. Shearer is a principal investigator of both the Regeneron and Lilly otoferlin clinical trials.

To treat deafness with gene therapy, researchers had to solve a problem: getting the genes to the cochlea, a spiral shaped cavity almost at the center of the skull. The cochlea is filled with fluid and lined with 3,500 inner hair cells, each tuned to a specific pitch.

Sound vibrations ripple through the fluid, bending the microscopic hairs. When a hair cell bends, it fires. An electric signal travels along the auditory nerve to the brain, and the person hears the sound.

Researchers chose to focus on otoferlin deafness because its cause was straightforward. The otoferlin gene is expressed only in the hair cells of the inner ear. The inner ear structures, including the hair cells, are intact. So to allow patients to hear, doctors simply needed to deliver a working copy of the otoferlin gene.

Otolaryngologists had long thought that injecting a medicine into the inner ear would inevitably damage the delicate cells and membranes of the cochlea.

But children with otoferlin deafness are already unable to hear. Even if an attempt at gene therapy damaged their inner ears, they could still receive cochlear implants.

“It was the perfect target,” Dr. Chan said.

Kerri M., whose baby, Miles, had otoferlin deafness, said gene therapy “completely changed our lives.” She spoke on condition of anonymity because she wanted to protect her son’s diagnosis from appearing on the internet.

Dr. Shearer said Miles’s hearing loss was so profound that he could not hear a jet engine if it were next to him.

Miles was given the Regeneron therapy on May 19, 2025, when he was 13 months old. At his last visit, his hearing was normal.

“We are so fortunate,” his mother said. “Our baby was born deaf, and now he can hear.”

Most children who received the gene therapy have had hearing restored, but not all have been as fortunate as Miles. So far, Dr. Chan said, about 80 percent of the patients who have been treated successfully in clinical trials were able to hear well without needing cochlear implants.

Most still needed a hearing aid, but about 30 percent of those who could hear after the treatment were like Miles — their hearing was in the normal range.

The next target for the scientists working on gene therapies to correct deafness is mutations in the GJB2 gene. It causes the most common form of congenital hearing loss in children and accounts for about 20 percent of cases.

Dr. Lee explained that the biology of GJB2 deafness is more complex than that of otoferlin, because cells in the cochlea are damaged. Otoferlin’s gene therapy, in contrast, is like fixing a broken wire — the cells are normal, they just can’t transmit a signal.

Dr. Lee said Skylark Bio hopes to start a gene therapy clinical trial this year for GJB2-related deafness in children 9 months old to 7 years old in the United States.

Dr. John Germiller, a pediatric otology surgeon at Children’s Hospital of Philadelphia and the University of Pennsylvania, predicted that the next frontier will be people with genes that cause progressive hearing loss, not necessarily babies.

Hearing loss and the loss of hair cells in the cochlea tend to occur together, he said. The goal will be to use gene therapy to save the hair cells that are remaining.

Dr. Germiller is a principal investigator for the Lilly otoferlin trial and treated the first patient in the United States two years ago.

Dr. Chan offered an even more ambitious hope for the future — the end of most forms of deafness.

“A lot of people are working on how to reprogram cells of the inner ear to rebuild themselves,” Dr. Chan said. The hope is to recreate the cochlea.

“That,” Dr. Chan added, is “the ultimate holy grail.”

Over four days and nearly 20 hours of testimony, under harsh questioning from Democrats, Health Secretary Robert F. Kennedy Jr. has repeatedly backed away from his longstanding criticism of the measles, mumps and rubella vaccine. On Wednesday, he made his strongest statement yet — albeit on behalf of his department and not himself.

“We promote the M.M.R.,” Mr. Kennedy told the Senate Finance Committee on Wednesday morning, referring to the combined vaccine for measles, mumps and rubella. “We have advised every child to get the M.M.R. That’s what we do.”

The comment stands in stark contrast to Mr. Kennedy’s past advice, and senators wondered aloud why he hasn’t told the public what he said on Capitol Hill this week. Last week, he conceded the measles vaccine is “safe and effective” for most people.

When measles broke out in Texas last year, Mr. Kennedy did not recommend vaccination; he said it should be “a personal choice.” Last year, asked if he would advise parents to vaccinate newborns, he said it was not up to him to provide medical advice. His advice, he said, was: “Do your own research.”

But even as he shifted on measles, Mr. Kennedy stuck by his longstanding assertion that improvements in hygiene and sanitation, and not vaccination, fueled the decline in deaths from infectious diseases during the 20th century.

“If you want to talk about what, why disease mortality has disappeared in the 20th century, it was not vaccines,” he said, testifying before the Senate health committee Wednesday afternoon.

As proof, Mr. Kennedy cited a study published in the journal Pediatrics in 2000. But he failed to note that the study also reported that vaccines introduced in the second half of the 20th century had “virtually eliminated” deaths from diseases including polio and measles. In 1999, the Centers for Disease Control and Prevention listed vaccination as one of “ten great public health achievements” of the 20th century.

After Mr. Kennedy made the assertion, Senator Bill Cassidy, the Republican chairman of the Senate health committee, asked about the author of the study; Mr. Kennedy gave him the author’s name. Later in the hearing, Mr. Cassidy produced the paper and told Mr. Kennedy he had taken it out of context.