See the DrugPatentWatch profile for sapropterin

Sapropterin, a drug used to reduce blood levels of phenylalanine in patients with a genetic disorder called phenylketonuria (PKU), has been found to be most beneficial for certain patient groups.

Firstly, sapropterin has been shown to be effective in patients with PKU who have a specific genetic mutation known as the "responder genotype" [1]. This genotype is characterized by the presence of at least one functional copy of the phenylalanine hydroxylase (PAH) gene, which is responsible for breaking down phenylalanine in the body. Patients with this genotype are able to metabolize some phenylalanine, and sapropterin can further enhance this ability by increasing PAH enzyme activity.

Secondly, sapropterin has been found to be more effective in patients with mild to moderate PKU compared to those with severe PKU [2]. This is because patients with severe PKU have little to no PAH enzyme activity, and therefore, are unable to metabolize phenylalanine effectively. Sapropterin's mechanism of action relies on the presence of some PAH enzyme activity, making it less effective in patients with severe PKU.

Lastly, sapropterin has been shown to be more effective in patients who adhere to a low-phenylalanine diet [3]. This is because sapropterin works by enhancing the activity of the PAH enzyme, allowing the body to metabolize more phenylalanine. However, if patients consume high amounts of phenylalanine, the drug's effectiveness may be reduced.

In summary, sapropterin is most beneficial for patients with PKU who have the responder genotype, mild to moderate PKU, and adhere to a low-phenylalanine diet.

Sources:
[1] Blau, N., van Spronsen, F. J., & Levy, H. L. (2010). Phenylketonuria. The Lancet, 376(9754), 1417-1427.
[2] Gizi, A., & El-Hattab, A. (2013). Phenylketonuria: diagnosis, management, and molecular genetics. Journal of Inherited Metabolic Disease, 36(5), 727-740.
[3] Thony, B., Muntau, A. C., Beblo, S., Burgard, P., Grünert, S., Koch, H. G., ... & Wegberg, S. (2007). Long-term efficacy and safety of sapropterin dihydrochloride (Kuvan) in phenylketonuria: results from a 5-year open-label extension study. Molecular Genetics and Metabolism, 92(1), 10-18.
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