PreKUnil Tablets: Let's Be Cautious

By Virginia Schuett, Editor, National PKU News

From the Winter 2002 issue of National PKU News

Throughout the history of PKU a constant theme among families and professionals has been "hope"-- hope that someday there will be a way to stop the diet safely or to make it easier to manage. In the early 1970's, hope took the form of "wishful thinking" when many clinicians allowed even very young children to stop the diet. The idea was that by early school age, the brain would be sufficiently developed so that it was no longer subject to insult by high blood phe levels. There was no scientific evidence that this was true. It took years to determine that the idea was incorrect, as ultimately documented by a large research project called the National Collaborative Study of Children Treated for PKU (directed by Dr. Richard Koch). We learned, in a very painful way, that the brain continues to be vulnerable to high blood phe levels well beyond early childhood (and probably forever). Sadly, many of the children who went off-diet during this era had their lives permanently altered by "wishful thinking."

It is with this history in mind that I am especially cautious about any change in PKU therapy. As a parent, or as an on-diet teen or adult, I'm sure that you want to be equally cautious about alternative therapies and change from the traditional PKU treatment that has proven so effective.

Thus, in my opinion, there is no clear answer to this issue's provocative headline question: Can a pill partially replace the PKU diet? We can remain hopeful that one day the answer will be yes, in some cases. But the information we have on the PreKUnil supplement regimen is far from complete. I believe that we need to have much more extensive scientific evidence that the pills are not only effective but also safe. To date we have studies of limited duration, with small numbers of patients, without published papers in peer-reviewed journals. In my view, the process of evaluating the effect of LNAA supplements on brain phe levels and cognitive functioning is at a very early stage.

I do not mean to denigrate the work of my colleagues in Denmark. Their research, combined with that being done by Dr. Koch and others, is very interesting and a beginning. But we need to explore the LNAA supplement idea much more thoroughly and completely and on a larger scale before we come to conclusions.

If the U.S. FDA reviews the pills as a "nutritional supplement" (which is likely) rather than using the more stringent criteria for reviewing them as a drug, they will only look at safety, not effectiveness. Therefore, if the pills are approved under this kind of review, it does not mean that they will necessarily be effective for the purpose they are designed. Nor does FDA approval mean the pill regimen is comparable to traditional strict diet in long-term outcome on a variety of measures.

Even if this therapy cannot partially replace the diet, it is possible that LNAA supplements will eventually prove to be beneficial as a facet of traditional treatment, for example, incorporating more LNAAs into the formula. Perhaps additional LNAAs would prevent brain phe spikes when blood phe levels fluctuate.

I am keeping an open mind about PreKUnil tablets/LNAA supplements, but I do want us to be as cautious as we need to be about any new therapy. May we not let wishful thinking supercede scientifically rigorous studies.