A modified version of the virus that causes AIDS could be the unlikely saviour of a promising treatment for a host of deadly diseases

IN TECHNOLOGY, it is called the hype cycle: what initially seems a promising breakthrough leads to inflated expectations until it becomes clear that a great deal of time, money and effort will be needed to realise that promise. Disillusionment sets in until the first real successes are reported, and then the hype is on again.

So it has gone with gene therapy. When, in the late 1980s, the genes for debilitating inherited diseases began to be identified, many believed that cures were within reach, by replacing the faulty genes with working ones. But getting the right gene into the right place without doing more harm than good proved tricky. Now, 23 years after the first gene therapy trial for a rare immune disease called ADA-SCID, researchers finally have some successes to report (see "'Bubble kid' success puts gene therapy back on track").

Still, a major barrier remains: cost. The first gene therapy drug to be approved for clinical use, to treat a pancreatic disease, is also the world's most expensive drug. At the moment, the production of modified viruses the vectors used to shuttle genes into a person's cells is prohibitively expensive, meaning only a handful of those with the diseases in question can be treated.

Pharmaceutical companies may have the means and know-how to scale up production, but inherited genetic diseases are not common. So the industry has been reluctant to invest in treatments for them, preferring instead to channel cash towards bigger killers like cancer.

By a stroke of fortune, a promising form of cancer treatment relying on immunotherapy uses the same viral vector that gene therapists are working on to treat diseases like SCID: a modified version of the virus that causes HIV. Some 700 trials using this kind of safer vector are under way, treating a range of degenerative and immune disorders.

It may seem ironic that a virus that has killed so many holds the potential to yield a cure for a host of other deadly diseases, but such is scientific progress: it comes from unexpected places. That should give fresh grounds for the pharma industry to look again at gene therapy. With a bit of ingenuity and effort, gene therapy might finally live up to the hype.

Correction: When this article was first published on 30 October 2013, the strap and standfirst confused HIV and AIDS.

This article appeared in print under the headline "Live up to the hype"

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Gene therapy needs a hero to live up to the hype