The Gift of Sound

For the first 11 years of his life, Aissam Dam knew only silence. But that changed last year, after Aissam, who was born Deaf, became the first person to undergo a groundbreaking medical procedure. Now he can hear almost perfectly from his right ear, where the treatment was tested. When asked what it’s like to be able to hear, Aissam said through a sign-language interpreter: “There’s no sound I don’t like. They’re all good!”

For his first 11 years of life, Aissam Dam knew only silence. But that changed last year. Aissam became the first person to have a groundbreaking medical procedure. He was born Deaf, but now he can hear almost perfectly from his right ear. That’s where the treatment was tested. Aissam was asked what it’s like to hear. He said through a sign-language interpreter, “There’s no sound I don’t like. They’re all good!”

Aissam, who is now 12, grew up in a poor region of Morocco, a country in North Africa. There were no teachers trained to educate a person who was Deaf, so Aissam couldn’t go to school and never learned to speak. To communicate with his family, Aissam created his own version of sign language. Then, last year, his family moved to Spain, where he learned Spanish sign language, allowing him to interact with more people. A hearing specialist examined Aissam. Afterward, the doctor gave him incredible news: He was eligible for a clinical trial, or experimental study, that could allow him to hear. But to take part, Aissam would have to travel to the United States.

On October 4, 2023, doctors at the Children’s Hospital of Philadelphia in Pennsylvania performed a pioneering gene therapy procedure on Aissam. Doctors inserted a working gene, or unit of hereditary information, into cells in Aissam’s right ear to cure his hearing loss. The treatment had never been attempted before, and doctors weren’t sure how well it would work. Thankfully, it succeeded beyond their expectations! In the year since, several more children with the same type of deafness have taken part in the experiment—with similar successful results. “It’s very rewarding to be able to do this miraculous type of treatment,” says Dr. John Germiller, who performed Aissam’s procedure.

Aissam is now 12. He grew up in a poor area of Morocco, a country in North Africa. There, no teachers were trained to educate a Deaf person. So Aissam couldn’t go to school and never learned to speak. To communicate with his family, Aissam made up his own sign language. Last year, his family moved to Spain. He learned Spanish sign language and could communicate with more people. A hearing specialist examined Aissam. Then the doctor gave him wonderful news. He qualified for a clinical trial, or experimental study. It could allow him to hear. But to take part, Aissam would have to travel to the United States.

On October 4, 2023, Aissam was at the Children’s Hospital of Philadelphia in Pennsylvania. Doctors performed a new gene therapy procedure on him. They used a working gene, or unit of hereditary information. Doctors inserted the gene into cells in Aissam’s right ear to cure his hearing loss. No one had ever tried the treatment before. Doctors didn’t know how well it would work. But it was even more successful than they expected! A year has passed, and several more children have taken part in the experiment. They had the same type of deafness, and they had similar successful results. Dr. John Germiller performed Aissam’s procedure. “It’s very rewarding to be able to do this miraculous type of treatment,” he says.

Fortunately, though, only patients with otoferlin deafness who had never had a cochlear implant, like Aissam, or those with an implant for only one ear, could take part in the gene therapy study. This is because scientists wanted to assess the results of the gene therapy on its own. Even though gene therapy shows a lot of promise for those with otoferlin deafness, Germiller says that cochlear implants are still a powerful tool to help patients with many different types of hearing loss.

But not all patients with otoferlin deafness could take part in the gene therapy study. It was for those who never had a cochlear implant, like Aissam. It also included those with an implant for only one ear. That way, scientists could see the results of the gene therapy alone. Gene therapy shows a lot of promise for those with otoferlin deafness. But Germiller says that cochlear implants are still a powerful tool. They help patients with many different types of hearing loss.  

Scientists discovered the genetic mutation that causes otoferlin deafness in 1999 and quickly began looking for a treatment. Around the same time, researchers had begun studying the use of gene therapies to cure inherited conditions—those caused by a mutated gene passed to a child from a parent. These include everything from cancer and blood disorders to blindness and deafness.

To create a gene therapy to treat an inherited condition, scientists start with a healthy gene. It will function in place of the defective version. They insert the working gene into a viral vector. This harmless virus delivers the healthy gene to cells in the body with the problematic mutation. In Aissam’s case, that meant the hair cells in the inner ear. Once inside the cells, the new gene allows them to function normally (see How Gene Therapy Works).

The U.S. Food and Drug Administration (FDA) approved the first gene therapy in 2017 to treat a form of leukemia, a type of blood cancer. Today there are about 20 different FDA-approved gene therapies and hundreds more being studied, like the one to treat otoferlin deafness.

Scientists discovered the genetic mutation behind otoferlin deafness in 1999. Quickly, they began looking for a treatment. Around that time, researchers had begun studying gene therapies for inherited conditions. These occur when a parent passes a mutated gene to a child. They include everything from cancer and blood disorders to blindness and deafness. 

To create gene therapies for inherited conditions, scientists start with a healthy gene. It will work in place of the flawed gene. They insert the working gene into a viral vector. This is a harmless virus. It delivers the healthy gene to body cells with the harmful mutation. For Aissam, those were the hair cells in the inner ear. After the new gene is inside the cells, it allows them to work normally (see How Gene Therapy Works).

The U.S. Food and Drug Administration (FDA) approved the first gene therapy in 2017. It treats a form of leukemia, a type of blood cancer. Today there are about 20 different FDA-approved gene therapies. Hundreds more are being studied, like the one to treat otoferlin deafness.

In 2019, scientists first tested the gene therapy in mice with otoferlin deafness. “It completely restored the hearing in most of the mice,” says Germiller. Next, a biotechnology company formulated a liquid medicine containing harmless viral vectors carrying functioning otoferlin genes to be tested on people.

To deliver the experimental medicine, Germiller pioneered a surgical procedure to reach a tiny area within the ear’s cochlea, a coiled, fluid-filled structure where hair cells grow. He uses a small camera and microscope to see inside the ear. Then he carefully lifts the eardrum like a curtain to move deeper into the middle and inner ear. Once he reaches the cochlea, he makes two tiny incisions and injects the medicine inside. Viruses in the fluid then attach to the nonfunctioning hair cells to deliver healthy genes.

Scientists tested the gene therapy in mice with otoferlin deafness first. That was in 2019. “It completely restored the hearing in most of the mice,” says Germiller. Next, a biotechnology company created a liquid medicine to be tested on people. It contained harmless viral vectors that carried working otoferlin genes. 

Germiller developed a surgical procedure to deliver the experimental medicine. He needed to reach a tiny area inside the ear’s cochlea. Hair cells grow inside this coiled, fluid-filled structure. Germiller uses a small camera and microscope to see inside the ear. He carefully lifts the eardrum like a curtain. Then he can move deeper into the middle and inner ear. When he reaches the cochlea, he makes two tiny cuts and injects the medicine inside. Viruses in the medicine attach to the nonworking hair cells. Then the viruses deliver healthy genes.

The procedure was carried out in Aissam’s right ear. Just days later, he began to hear traffic noises. Two months later, the hearing in his ear was almost completely normal! Germiller says that these exciting findings give hope not just to patients with otoferlin deafness, but also to those affected by the many different genetic causes of hearing loss.

This trial is still ongoing and currently enrolling patients. Germiller says that after the study is complete, Aissam will likely be able to have his left ear treated with the same therapy. Through an interpreter, Aissam said that he can hear everything now—from electronic beeping noises to scissors clipping his hair. But the sounds he loves the most are people’s voices.

Aissam had the procedure in his right ear. Just days later, he began to hear traffic noises. Two months later, the hearing in his ear was almost completely normal! These exciting findings give hope not just to patients with otoferlin deafness, says Germiller. They may also help people with many different genetic causes of hearing loss.

This study is still going on. More patients are joining. After the study is complete, Aissam can likely have the same therapy for his left ear, says Germiller. Through an interpreter, Aissam said that he can hear everything now. He even hears electronic beeping noises and scissors clipping his hair. But people’s voices are the sounds he loves the most.