There is no cure for sensorineural hearing loss, the type that most of us with aging ears suffer from. At least not yet. But as I’ve written about in earlier posts, a pioneering treatment may be on the way. It’s called CGF166. It’s the only gene therapy for hearing loss now undergoing human trials in the U.S. and early reports are promising. Here’s a progress report.
First, a little background. The cause of most sensorineural hearing loss is fairly straightforward. As we get older we lose hair cells, the tiny vibration detectors in the cochlea, and as we lose hair cells we lose hearing. We are born with about 30,000 of them and we all lose them at different rates because of noise induced damage, ototoxic drugs, or genes that make you predisposed towards early age-related hearing loss.
Once they are gone they do not grow back. But CGF166 appears to be able to trigger the regeneration of hair cells.
It uses a gene know as Atoh1 which causes hair cells in mammals to grow in the embryo stage, and then shuts off. With CGF166, Atoh1 is added to a harmless virus which binds to cells in the cochlea and tells them to begin growing hair cells again.
It’s worked for mice and monkeys. Now Novartis is conducting trials to see if it also works for humans. These are what’s called Phase 1/2 trials in which the priority is safety and determining it it works. The trials are being conducted at three centres: Johns Hopkins in Baltimore, University of Kansas in Kansas City and Columbia University in New York.
I spoke with Dr. Lawrence Lustig who is conducting the Columbia trials, and he generously gave me an update on the progress.
The first patient received CFG166 in 2014 and they had planned on a total of 45 patients. But so far only 11 people have undergone treatment. For Dr. Lustig and his colleagues that is a disappointingly low number. I asked him why.
“One of the issues that we’re confronting in terms of trying to find patients who are candidates is the very restrictive criteria that we’re using for inclusion. Basically everybody who is a candidate is also a cochlear implant candidate. You have to have that level of hearing loss. But if it’s too severe then you’re no longer candidate either. So you have to be within a window of severity.
Number two, you can’t have certain rare genetic conditions (such as Usher Syndrome) for your hearing loss.
And number three, most people who have hearing loss at that level have already received a cochlear implant.”
These restrictive criteria may be loosened if CGF166 enters wide clinical use but, for now, as Dr. Lustig points out, “The FDA is being appropriately cautionary because this is the first time anyone’s ever done a gene therapy study.”
He also reports that so far none of the patients has had any major problems.
The procedure involves going down the ear canal and detaching the tympanic membrane (ear drum) to reach the cochlea. A laser is used to create a hole in the cochlea to deliver the CGF166. Remarkably, it only takes 30 minutes and the patient is sent home the same day.
The results so far are promising. “There have been a couple patients with hearing improvement, so we are definitely encouraged.”
Assuming that all goes well, when could CGF166 be approved for wider use?
“I would say it’s going to be at least a couple of years. We have to do a Phase 3 study yet. We’re hoping to add additional centres just to aid with the recruitment because patients are hard to find, and that will speed things up.”
Fingers crossed. If you think you might be candidate for the trial, go to the U.S. National Institutes of Health site: CGF166 clinical trials.
As well, you can contact Novartis directly: Novartis CGF166 trials.
For the record, I didn’t qualify. My hearing is still too good.