Most of us know someone affected by hearing loss, but we may not fully realize the hardships that lack of hearing can bring. Hearing loss can lead to isolation, frustration, and a debilitating ringing in the ears known as tinnitus. It is also closely correlated with dementia. 

The biotechnology company Frequency Therapeutics is seeking to reverse hearing loss — not with hearing aids or implants, but with a new kind of regenerative therapy. The company uses small molecules to program progenitor cells, a descendant of stem cells in the inner ear, to create the tiny hair cells that allow us to hear. 

Progenitor cells generate hair cells when humans are in utero, but they become dormant before birth and never again turn into more specialized cells such as the hair cells of the cochlea. Humans are born with about 15,000 hair cells in each cochlea. Such cells die over time and never regenerate. 

“Tissues throughout your body contain progenitor cells, so we see a huge range of applications,” says Frequency co-founder and Chief Scientific Officer Chris Loose Ph.D. “We believe this is the future of regenerative medicine.” 

In 2012, the research team was able to use small molecules to turn progenitor cells into thousands of hair cells in the lab. Harvard-MIT Health Sciences and Technology affiliate faculty member Jeff Karp says no one had ever produced such a large number of hair cells before. He still remembers looking at the results while visiting his family, including his father, who wears a hearing aid. 

“I looked at them and said, ‘I think we have a breakthrough,’” Karp says. “That’s the first and only time I’ve used that phrase.” 

About the Clinical Trial 

Hair cells die off when exposed to loud noises or drugs including certain chemotherapies and antibiotics. Frequency’s drug candidate is designed to be injected into the ear to regenerate these cells within the cochlea. In clinical trials, the company has already improved people’s hearing as measured by tests of speech perception — the ability to understand speech and recognize words. 

In Frequency’s first clinical study, the company saw statistically significant improvements in speech perception in some participants after a single injection, with some responses lasting nearly two years. 

The company has dosed more than 200 patients to date and has seen clinically meaningful improvements in speech perception in three separate clinical studies. Another study failed to show improvements in hearing compared to the placebo group, but the company attributes that result to flaws in the design of the trial. 

Now Frequency is recruiting for a 124-person trial from which preliminary results should be available early next year. 

The company’s founders hope to solve a problem that impacts more than 40 million people in the U.S. and hundreds of millions more around the world. 

“Hearing is such an important sense; it connects people to their community and cultivates a sense of identity,” says Karp. “I think the potential to restore hearing will have enormous impact on society.” 

The founders believe their approach — injecting small molecules into the inner ear to turn progenitor cells into more specialized cells — offers advantages over gene therapies, which may rely on extracting a patient’s cells, programming them in a lab, and then delivering them to the right area. 

“Tissues throughout your body contain progenitor cells, so we see a huge range of applications,” Loose says. “We believe this is the future of regenerative medicine.” 

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