11/24/2011 01:09 EST | Updated 01/24/2012 05:12 EST

Do Stem Cells Really Offer a Miracle Cure?

Quarterback Peyton Manning has used it. So has New York Yankee pitcher Bartolo Colon. Ditto Texas Governor and presidential hopeful Rick Perry. You can get it to combat wrinkles and reverse the aging process. You can even get it to improve your sex life.

What is this miracle cure, this elixir of life? Stem cell therapy.

But does it actually work? I think not -- at least not yet.

A recent event underscores the cavernous gap between the well-publicized (and completely legitimate) promise of stem cell research and actual, efficacious, therapies. Last week, a California biotech company, Geron, decided to terminate a much-scrutinized and highly-anticipated stem cell clinical trial. This was a one-of-a-kind, first-in-the-world initiative that involved the injection of stem cells into the backs of patients with recent spinal cord injuries.

It is no surprise, then, that last week's decision generated both shock and anger. And for the patients hoping for a near-future cure, it was nothing less than heartbreaking.

Not only did the company decide to stop this particular trial, it decided to get out of the field of stem cell therapies altogether. So definitive was the decision that Geron gave back millions of public research dollars.

We need to be careful not to over-interpret the Geron pull out. This is one company and one trial. There are now a few other clinical experiments in the pipeline (emphasis on a few), such as one to treat a form of blindness. And we must remember that not all things that are called "stem cell therapies" are the same. Manning, for instance, reportedly received a type of adult stem cells, though there are few details on the exact nature of his treatment.

Still, the move by Geron provides an opportunity to reflect on the state of stem cell research today. A reality check.

First, ignore the hype. I believe there is little evidence that any of the often advertised stem cell therapies, embryonic or otherwise, work. Yes, there are a handful of decades-old treatments, such as the use of cord blood stem cells for some forms of cancer, which are clinically beneficial. But the list of proven treatments is short and does not include any for common diseases or injuries. (The International Society of Stem Cell Research has a terrific website that outlines what is available.)

Manning, Colon and Perry may have had a positive experience (the placebo effect is a powerful thing, after all), but, to date, I believe good clinical evidence simply does not exist.

Second, despite the hope of many, it isn't going to be easy to make money off stem cell research -- at least with a treatment that is scientifically legitimate, appropriately tested and approved by the relevant regulatory agencies (three characteristics missing from most of the stem cell therapies currently offered in clinics around the world). Economic growth has often been one of the ways that the huge public investment in stem cell research has been justified. Just a few weeks ago, for example, the UK government announced that it was committing millions in a stem cell research centre with the hope that it will help drive the UK economic recovery.

But the ability of emerging stem cell technologies to stimulate the economy and create jobs is far from certain. Indeed, economics is the explicit reason for the Geron pull out. The company press release stated that the decision was made after a strategic review of the costs, timelines and "clinical, manufacturing and regulatory complexities associated" with this kind of research. In other words, stem cell research is not, from the perspective of this company, worth it.

I don't mean to be a downer. In fact, I believe that stem cell research holds tremendous potential. I remain fully confident that, one day, therapies will emerge. But the inappropriate hype associated with this area hurts policy debates, leads to unmet expectations, and has the potential to mislead the public about the actual state of the science. The Geron story is a sober reminder that promise is not reality, even in a field as exciting as stem cell research.