Sunday, April 27, 2008

Gene Therapy for Blindness (Update)

Back in May of last year I posted this, which linked to this BBC News story about Robert Johnson who underwent the first ever gene therapy for a sight disorder.

The "online first" section of the NEJM has the encouraging results of two preliminary clinical trials for gene therapy for retinal degeneration. Here is an excerpt from the NEJM editorial:

In both these studies, patients had severe vision loss secondary to Leber's congenital amaurosis that was documented by visual acuity and ERG, as well as by microperimetry, which measures retinal sensitivity at precise locations (carried out by Bainbridge et al.), and pupillary light reflex, measured by pupillometry (carried out by Maguire et al.). Bainbridge et al. showed no change in patients' visual acuity, whereas all three patients in the study by Maguire et al. found a gain in visual acuity. Visual acuity is a subjective measure, and since the patients could not be masked in either study, there is certainly a possibility of placebo effect for this outcome measure. Furthermore, measurement of visual acuity at such low levels of acuity is not reliable. The fact that three patients in the study by Maguire et al. showed improvement and the three patients in the study by Bainbridge et al. did not show improvement is of uncertain significance. With additional subjects and longer follow-up, this outcome may prove more informative, particularly if continued safety justifies the inclusion of patients with better baseline visual function.

As this Telegraph article notes, unfortunately the treatment was not successful for Mr Johnson. But he is quoted as saying: "For the team, I am thrilled that their hard work and dedication has paid off, with promising results in one patient allowing them to continue with this important trial,". The one patient was 18-year-old Steven Howarth, whose life has been transformed by the treatment. Here is a sample from the Telegraph story:

"Before the operation I used to rush home from college when it started to get dark because I was worried about getting around," he said.

"Now I can take my time and stay later at college if I need to, for band rehearsals and things like that."

His father, Tommy, said the change was "incredible".

"He's doing things now that he just couldn't do before," he said. "It's completely transformed the life he leads."

The teenager, of Westhoughton, near Bolton, said his eyes felt like sandpaper after the operation and he could not see anything.

"But it got much better after a week," he said. "Now my sight is definitely better when it's getting dark. It's a small change, but it makes a big difference to me."

Forbes also has an in-depth report on the two studies here.

What does gene therapy for vision involve? See this video.