National Institute for Health and Clinical Excellence (NICE)
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NICE draft guidance extends recommendation for sapropterin to pregnant women and people aged up to 22 years with rare inherited metabolic condition phenylketonuria

NICE recently (20 August 2021) issued final draft guidance which now recommends sapropterin (also called Kuvan and made by BioMarin) as an option for treating phenylketonuria (PKU) in pregnant women until they give birth as well as for treating the condition in people until they turn 22.

Usually diagnosed in children, PKU is a rare, inherited, chronic and life-long metabolic condition. It is caused by the deficiency of an enzyme which breaks down phenylalanine, a compound which occurs naturally in protein-rich foods such as milk, eggs and meat. Phenylalanine in high concentrations is toxic to the central nervous system.

Current treatment for PKU is a lifetime adherence to a severely protein-restricted diet which cuts out most natural proteins (such as meat, fish, eggs, cheese, pulses, seeds, flour, bread and pasta), together with dietary supplementation. The aim of treatment with sapropterin is to reduce blood phenylalanine levels and relax the protein-restricted diet as much as possible.

Following public consultation on NICE’s previous draft guidance which recommended sapropterin for children up to 18 years old, the committee agreed that PKU is a particular concern if poorly controlled during pregnancy because it can cause severe congenital defects in unborn children. Currently, only pregnant women with PKU who aren’t able to control their condition through diet alone are able to access sapropterin on the NHS. This new recommendation could allow women to have sapropterin earlier in their pregnancy with potentially better outcomes for their unborn children.

The committee also acknowledged that sapropterin could prevent long-term irreversible brain damage in children, because childhood is most critical period for brain development.

In a further change from the earlier draft guidance, sapropterin is now also recommended for people aged from 18 until they turn 22. The committee felt people would benefit if treatment with sapropterin could be continued for as long as possible during final brain development and transition into adulthood. However, sapropterin is only cost effective in this group if they continue to take sapropterin at the dose they were having when they were under 18.   

There are currently around 2,000 people with PKU in NHS care in England. 

For adults the committee took into account other benefits from sapropterin because of fewer symptoms related to raised phenylalanine levels and not having to follow the protein-restricted diet as strictly. However, weight-based dosing of sapropterin means the costs are higher for adults. This, together with uncertainties about the extent to which it reduces reliance on a protein-restricted diet and the fact that there is no evidence to suggest a corresponding increase in benefits to offset these higher costs, means the cost-effectiveness estimates are substantially higher for adults aged 22 and above than NICE considers an acceptable use of NHS resources.

Meindert Boysen, deputy chief executive and director of the Centre for Health Technology Assessment at NICE, recently said:

“Although we’re pleased to now be able to recommend sapropterin for people up to 22 years of age and pregnant women, it’s disappointing not to have been able to extend the recommendation to all adults. Even when considering some additional potential benefits of sapropterin in this group, the price of the drug was too high to allow it to be considered an acceptable use of NHS resources. The committee were aware that generic products could be available in the near future and hoped these would be priced to allow access to this drug for all adults with PKU.”


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