From The Scientist: "After 20 years of high-profile failure, gene therapy is finally well on its way to clinical approval. The concept is simple: if a mutated gene is causing a problem, replace or supplement it with a new, accurate copy. In theory, such a strategy could not just treat, but cure countless human genetic diseases. In practice, however, developing safe and effective gene therapies has not been easy. Even when identifying a disorder's genetic basis is fairly straightforward, finding the appropriate delivery vector to target the diseased tissues in the body, while avoiding unintended consequences, has challenged would-be gene therapists for more than 20 years. But more and more researchers are convinced that the technique is on the brink of becoming a common medical practice. ... In the last year alone, he says, major breakthroughs have been published for the use of gene therapy in patients with hemophilia, solid tumors, and leukemia, not to mention the dozens of trials yielding positive results for gene therapies to treat various types of blindness. ... It's just remarkable. These decades of work are suddenly really paying off. ... The history of medicine says every new technology starts with a great idea and then requires hard work and optimization. And I think that's exactly what's happened with gene therapy. Hurdles were identified - and there's always hurdles once you get into a complex human disease situation - and they've been addressed. ... The concepts aren't that much different than they were early on, but the tools are much better. Now [gene therapy] is actually fulfilling the promise that people said it would have."