Regulatable promoters and gene therapy for Parkinson's disease: Is the only thing to fear, fear itself?

Gene therapy for Parkinson's disease has become a clinical reality with three different approaches currently being tested in patients. All three trials employ an adeno-associated virus with a type two serotype (AAV2). To date, no serious adverse events related to the injections of therapeutic vectors have been reported in any patient. This safety profile was predicted based upon, in some cases, exhaustive preclinical testing in both rodent and primate species. Still some argue that regulatable promoters are required so that expression of the transgene can be halted should untoward side effects arise. We argue that given the current empirical data base of AAV2, the lack of regulatable promoters that have been proven to be safe and effective, and the pressing clinical needs of PD patients, the mandatory use of regulatable vectors is not only unnecessary but, in some instances, misguided and potentially dangerous. This commentary will outline the issues related to the use of regulatable promoters for gene therapy for PD and express our opinion as to why mandating the use of such promoters might result in outcomes that are unsafe, unproductive, and counter to the progress of scientifically sound, clinical research.