New Study Paves Way for Treating Second Eye in Gene Therapy Clinical Trial

All 12 participants in the gene therapy clinical trial for Leber congenital amaurosis (LCA) at the Children’s Hospital of Philadelphia (CHOP) have been so delighted with the vision restoration from treatment to one eye, they have been anxiously awaiting the go-ahead to have their second eye treated. Thanks to results from a Foundation-funded lab study in large animals, that will likely happen soon.

Drs. Al Maguire, Katherine High, and Jean Bennett, lead investigators on the CHOP trial team, recently conducted a large animal study confirming that treatment of a second eye with gene therapy is both safe and effective. The research team noted that the immune response in the second eye — one of the key outcomes to be monitored and analyzed — was minimal. Results of the study are being presented to the FDA to gain final approval for the potential treatment of the second eye in CHOP clinical trial participants.

Dr. Bennett notes, “Each one of our clinical trial subjects has asked if their second (previously best-seeing) eye can be treated with gene therapy as their initially treated eye is now their best-seeing eye. The results from our animal study show that administration to the second eye is safe and can result in efficacy that is stable. So far, what we have seen in large animals has been predictive in humans.”

“This is great news,” says Dr. Stephen Rose, chief research officer, Foundation Fighting Blindness. “Safety in human studies is paramount. For this clinical trial, we needed to confirm that there was no detrimental immune response with a second treatment.”

Thanks to this study’s results which provide a better understanding of the therapy’s immunological effects, people who were initially excluded from the original trial due to an immune response to the treatment may be eligible to participate. The study revealed that the immune response did not affect the health of the eye nor did it impact the effectiveness of the treatment.

Results of the study were published in the March 3, 2010 online version of the journal Science Translational Medicine.

The first person in the CHOP gene therapy clinical trial was treated in October 2007. All 12 participants in the CHOP study have demonstrated significant and stable vision restoration. The youngest participant is now nine-years old and was able to put away his white cane after treatment.