Thursday, May 15, 2008

Kid Time for LCA gene transfer?

(...continued from previous posts).  The promising results, and the surge of expectation they generated, will be used by the investigators and many advocates for the blind to defend pursuing the remainder of the study in children.  After all, children stand a better chance of benefiting, because their retinas have not yet degenerated.

Traditionally, bioethicists have frowned on pursuing studies in children that could otherwise be done in adults, because children are unable to provide valid consent.  Given that the primary objective of the study is safety, and that a sample size of 3 (or, combining the two studies, 6) and a follow-up of less than a year is minimally meaningful in terms of projecting safety, many bioethicists would question the prudence of continuing the study in pediatric populations.

The third volunteer in the Moorfield study was not an adult.  A report in Science magazine (2 May 2008) indicates that the Philadelphia team will test the agent next in an eight-year-old.
(photo credit: kiddocone 1998


IJGr said...

Since this experimental treatment was initially performed in dogs carrying a similar genetic condition, is it there any data showing results in young animals versus adult ones. This would help answering the question as how a growing body adapts to the transfering of this particular gene versus a non-growing (adult) body.
It will not resolve the ethical question about having children undergoing such type of treatment but it could give some idea about the expected outcome. Protocols in pre-clinical studies should be designed to support further steps in clinical studies, is it this case?

Jonathan Kimmelman said...

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You raise an important point. As I said in a previous posting, in this case the preclinical data were about as good as you'll ever find. The Philadelphia researchers indeed performed their preclinical studies in puppies. This is critical for reasons of both efficacy as well as safety. The latter was widely discussed when lympho-proliferative disorders were reported in children participating in X-SCID gene transfer studies: the vast majority of preclinical studies were performed in adult mice, but there is reason to believe that age might affect the genotoxicity and immunotoxicity of gene transfer agents (for example, pediatric tissues undergo more cell devisions and thus can accumulate more genetic "hits").