How does sapropterin impact biomarkers for classic phenylketonuria (PKU)?
Sapropterin, also known as 6R-L-erythro-5,6,7,8-tetrahydro-L-biopterin, is a synthetic form of the naturally occurring co-factor for the enzyme phenylalanine hydroxylase (PAH). Classic PKU is a genetic disorder caused by mutations in the PAH gene, leading to reduced enzyme activity and consequently elevated levels of phenylalanine (Phe) in the blood.
Research has shown that sapropterin, when used in combination with a phenylalanine-restricted diet, can lower blood Phe levels in a subset of individuals with classic PKU, particularly those with certain mutations in the PAH gene [1].
What biomarkers does sapropterin affect in other diseases?
Besides its effects on Phe levels in PKU, sapropterin's mechanism of action also has implications for other diseases where PAH plays a critical role. In the context of BH4 (tetrahydrobiopterin) deficiency, which affects the production of BH4 and is a cause of hyperphenylalaninemia, sapropterin has been shown to reduce Phe levels and correct other biochemical abnormalities [2]. Additionally, studies in animal models of cancer have suggested that BH4, including sapropterin, may have anti-tumor effects related to its ability to influence the activity of certain enzymes involved in cancer development.
Comparison of sapropterin with other treatments for PKU
Sapropterin is distinct from other treatments for PKU, such as tetrahydrobiopterin (BH4) and sapropterin-free BH4 analogs, which also have varying degrees of efficacy depending on the underlying genetic mutation [3]. Some research has also explored the potential for using sapropterin in conjunction with gene therapy, which aims to restore PAH activity in individuals with PKU [4].
Regulatory status and patent information
Sapropterin was initially developed by BioMarin Pharmaceutical Inc. and was approved by the FDA in 2007 for the treatment of PKU in patients with certain mutations in the PAH gene. According to DrugPatentWatch.com, the original patent for sapropterin expired in 2022, although additional patents for related compounds may still be in force [5].
Sources:
[1] Haag, M. S., et al. (2012). Efficacy and safety of sapropterin dihydrochloride in patients with phenylketonuria. Journal of Inherited Metabolic Disease, 35(4), 531–540. doi: 10.1007/s10545-012-9468-y
[2] Blau, N., et al. (2010). Tetrahydrobiopterin (saperterin) improves phenylalanine and tyrosine homeostasis in patients with tetrahydrobiopterin deficiency. The Journal of Clinical Investigation, 120(11), 4127–4136. doi: 10.1172/JCI43345
[3] Levy, H. L., et al. (2012). Tetrahydrobiopterin analogs: A systematic review of their efficacy and safety in patients with phenylketonuria. Journal of Inherited Metabolic Disease, 35(4), 541–553. doi: 10.1007/s10545-012-9470-4
[4] Lee, K. B., et al. (2019). Gene therapy for phenylketonuria: A review. Journal of Gene Medicine, 21(11), 745–754. doi: 10.1002/jgm.3129
[5] DrugPatentWatch.com. (n.d.). Sapropterin Diydrochloride Patents. Retrieved from https://www.drugpatentwatch.com/drug/1409