This past February, the National Institutes of Health (NIH) hosted a scientific review conference on Phenylketonuria to discuss the “state of the science and future research needs.” The event was free and open to the public, but even if you could not cover the cost of travel and accommodations, the two-day event was also broadcasted live via webcast. I managed to log-on during my lunch break and listened intently to a session on PKU and Pregnancy. To my surprise, much of the PKU and Pregnancy presentation focused on Sapropterin and its use during maternal PKU (Sapropterin is the generic name for Kuvan, the first prescription drug approved by the U.S. Food and Drug Administration to lower blood phe levels in PKU patients).
To be clear, Kuvan is not recommended for maternal PKU unless the benefits outweigh the risks. That is because when ranked on the FDA’s pregnancy classification of drugs, Sapropterin is considered a category C drug since it is still unclear whether Sapropterin crosses the human placenta.
Research presented at the NIH conference confirmed that in some rare instances, Sapropterin had been prescribed to pregnant PKU patients, but only when the woman could not achieve dietary control at the start of her pregnancy. As early as 2005, Sapropterin was the focus of a study led by medical pioneer and PKU advocate Dr. Richard Koch. The patient was responsive to Sapropterin and during her pregnancy, she continued the medication at 40, 60, and 100 mg per day in the first, second, and third trimesters. Used in combination with low-protein food, optimal phe levels were achieved without any nausea and vomiting. More importantly, the woman’s child was born normal. Four years later, another study conducted by one of the presenters, Dr. Gabriella Pridjian from Tulane Hayward Genetics Center, reported on another pregnant PKU patient who had difficulty tolerating low-phe protein supplements. She was instructed to divide the Sapropterin up twice daily and ultimately had a healthy baby delivered through c-section. Pridjian noted that there were plans to eventually formally test the baby (who was now three years old) for any intellectual or developmental issues.
In addition to these two case studies, the NIH panel reported that other pregnancies involving the use of Sapropterin were currently underway. In addition to concerns about whether Sapropterin harms a developing fetus, doctors admitted it was hard to determine if symptoms such as headache, rhinorrhea, vomiting, fever, abdominal pain, rashes or nasal congestion were a result of the prescription drug or simply associated with the pregnancy.
Even though the maker of Kuvan, BioMarin, does in fact encourage pregnant women who were exposed to Kuvan during their pregnancy to participate in ongoing studies about the drug’s effect, there are no plans for future controlled studies. Based on what little has been conducted, including the two case studies I’ve mentioned here, initial reports of using Sapropterin during pregnancy are encouraging. However, continued research on this matter is definitely a must, especially with concern to the long-term implications the drug might have on a PKU woman’s child.