Investors' and Big Pharmas' hitherto frosty view of gene-based medicines may be starting to thaw, at least in places, warmed by clinical progress and a smattering of deals. Is there any real potential in this market? Until the first FDA approval, no-one's expecting any real heat. But there are companies which are enjoying limited success in the early stages, whose experience most likely reflects where at least the near-term potential of gene-based medicines lie.