What's the usual time frame for sapropterin's biomarker effects?

In PKU patients who are responsive to sapropterin (BH4):

- Early changes (biomarker: plasma phenylalanine, Phe) can appear quickly—often within 24–48 hours after starting or increasing the dose.
- More substantial reductions are usually seen over the first 1–2 weeks.
- A steady, full effect is typically reached by about 2–4 weeks; some patients may take up to 6 weeks.
- Clinically, a 1–2 week trial is often used to assess responsiveness: if there is no meaningful drop in Phe after that period at an adequate dose, the patient is likely a non‑responder.

If you want, I can tailor this to a specific dosing plan or lab target.