Choroideremia (CHM), a rare degenerative retinal disorder that currently has no approved treatment, may be responsive to genetic manipulation. In a study in JAMA Ophthalmology, researchers reported patients who were given a functional version of the CHM gene (via an adeno-associated virus vector) had stable or improved visual acuity following treatment.

The Phase II clinical trial enrolled six male patients with CHM who received the retinal therapy injection in one eye. The study’s primary endpoint was change in best-corrected visual acuity (BCVA) based on the Early Treatment Diabetic Retinopathy Study chart from baseline to 24 months in the treated eye vs. the control eye. Secondary endpoints included microperimetry variables, change in fundus autofluorescence and SD-OCT tomographic evaluations.

At baseline, the patients’ mean BCVA score was 60.3 (approximately 20/63 Snellen equivalent) in the study eyes and 69.3 (approximately 20/40 Snellen equivalent) in the control eyes. At 24 months, the study reported the BCVA change was 3.7 in the treated eyes and zero in the control eyes. Additionally, investigators reported a mean change in retinal sensitivity of 10.3dB in the treated eyes and 9.7dB in the control eyes,

The investigators noted a total of 28 adverse events, including conjunctival hyperemia and foreign body sensation; all were consistent with the procedure and none were regarded as severe.

While gene therapy was associated with maintained or improved visual acuity, the study noted the difference was not statistically significant compared with the control group.

Continued investigations could help define the efficacy and safety of gene therapy for CHM, the researchers said in their study.

Fischer MD, Ochakovski GA, Beier B, et al. Efficacy and safety of retinal gene therapy using adeno-associated virus vector for patients with choroideremia: a randomized clinical trial. JAMA Ophthalmol. August 29, 2019. [Epub ahead of print].