Secretin is a signaling peptide that stimulates the pancreas. It kicks in when food is consumed, causing the pancreas to secrete its mixture of digestive enzymes. Until 1996, not many people (outside of gastrointestinal specialists and researchers) had heard of it, or devoted much thought to it. But that year, an autistic boy from New Hampshire, Parker Beck, was given secretin to help diagnose some GI problems - and his autistic symptoms apparently improved.

Well, that touched off some interest, as you can imagine. There is no generally accepted therapy for autism; the demand for one is terribly acute. There was a complex patent scuffle involving the University of Maryland and the Beck family, and Mrs. Beck ended up listed (quite properly) as an inventor and (more unusually) the assignee of the rights to the resulting patent for secretin as a treatment for autism.. She licensed the patent to a small biotech, Repligen.

A secretin underground sprang up very quickly, as you'd expect. Parents were trying it all over the place, and anecdotal evidence was all over the place, too: it worked, it didn't work, it worked a bit, it started to work, it stopped working. Controlled clinical trials were the only thing that could sort out the confusion. (As a drug company scientist, you'd expect me to say that, but I say it because I'm a scientist, not because I work for a drug company.)

I should emphasize that secretin as an autism therapy is not at all a crazy idea. First off, just about anything that shows possible efficacy for a terrible untreated condition is worth a look. Second, many autistic patients show gastrointestinal abnormalities, for reasons that aren't clear at all. (Are they related to the cause of autism, or are they an effect of it? Or are they just a distant sideshow? No one knows.) And secretin is found inside the brain (like a dizzying array of other peptide hormones), so it could well be a player in brain development. There's constant crosstalk between the brain and the digestive system, since eating is a rather important physiological response. The systems involved are complex and only partially understood (just ask anyone who does research on obesity and eating disorders); all sorts of things are plausible.

But interesting hypotheses are fragile things. The early trials of secretin didn't look very promising, but those were small samples. Further trials didn't look very convincing, either. Repligen's multiple-dose Phase II trial didn't do much better. By this time, many practitioners were abandoning hope. There have been a number of possible therapies for untreatable conditions that have looked promising anecdotally, but didn't hold up to scrutiny, and secretin was looking like another addition to that sad list.

Repligen pressed ahead to Phase III trials, hoping that a larger number of patients would show enough of a statistical effect to gain FDA approval. The first of these results have come out, and that's what was making the headlines this week. This is the largest trial of secretin so far, and it appears, again, almost completely negative. There's a hint of efficacy among a subset of higher-functioning autistic patients, but any time you hear that kind of post facto reasoning you should stay in your seat. Statistical power starts evaporating when you so subset analysis - you actually need more convincing evidence when you slice and dice the data like that, not hints of something that might be happening. That sort of thing is almost always noise.

So, as best as can be determined, secretin is not a viable therapy for autism. There are still autistic patients who appear to have been helped by it, although by this time you have to wonder how many of these cases are just due to chance (and how many are due to understandable observer bias.) Autism is a very heterogeneous disease, though, which makes it still possible that in some cases secretin is helpful. But we don't know how to diagnose these - if anyone figures that out, a further clinical trial would certainly be warranted. For now, though, secretin does not seem to be of any general use.

But that probably won't be the end of the story. I expect that there will still be desperate parents who will try secretin. And there will probably be some who will believe that it's helped. And as long as there's a market, there will surely be people who will supply secretin, at a cost of many thousands of dollars a year, and whether it does any good or not isn't going to be a concern of theirs at all. A sad situation.