Conclusions of Clemson et al. concerning Valproic Acid are premature
Dear Sir, With great interest we read the article of Clemson et al. about a new treatment for retinitis pigmentosa (RP). However, the authors' claim that their data suggest that valproic acid (VPA) may be an effective treatment for RP is unfounded and also regrettably misleading for the many desperate RP-patients. In fact, we are surprised that the editors of the BJO have published this study in its present form. Firstly, the design of the study as well as the medical ethical approval (approved in Massachusetts, but conducted in Florida) is obscure: why were the patients treated only for a very short time (2 to 6 months), while RP is a slowly progressive chronic condition? Why were only 7 patients treated and described as the results were as promising as the authors claimed? Why was the treatment stopped, as there were no or few side effects and what happened after the treatment was stopped? Secondly, the theoretical action of VPA on the dysfunctional photoreceptors is unsatisfactorily explained and no experimental data on retinal tissue are provided. Why was the treatment not tested on rats or mice with RP? In view of the limited life span of these animals, unequivocal data on the efficacy of VPA could have been provided. Thirdly, the authors announce their intention to start a controlled clinical trial with VPA, but no such trial has been registered yet at the Current Controlled Trials Register. For the RP-patients longing for treatment, this is very disappointing, to say the least.
Conflict of Interest: