Plasma pharmacokinetics and cerebrospinal fluid penetration of hypericin in nonhuman primates

Hypericin, a polycyclic aromatic dianthroquinone, is a natural pigment deri ved from the plant Hypericum perforatum (St John's Wort). The compound has been synthesized and shown to inhibit the growth of malignant glioma cell l ines in vitro via inhibition of protein kinase C. Oral hypericin has entere d clinical trials in adults with recurrent malignant glioma. Purpose: The p resent study was performed to characterize the plasma pharmacokinetics (PK) and cerebrospinal fluid (CSF) penetration of hypericin in nonhuman primate s. Methods: Hypericin was administered as an intravenous bolus dose of 2 mg /kg (n = 3) or 5 mg/kg (n = 1). Plasma and CSF (ventricular or lumbar) were sampled Frier to administration and at frequent intervals for up to 50 h a fter administration of the drug. Hypericin concentrations in plasma and CSI ; were determined using a specific reverse-phase HPLC assay. Results: Mean peak plasma concentration of hypericin following the 2 mg/kg dose was 142 /- 45 muM. Elimination of hypericin from plasma was biexponential, with an average alpha half-life of 2.8 +/- 0.3 h and average terminal half-life of 26 +/- 14 h. Conclusions: The 2 mg/kg dose in the nonhuman primate was suff icient to maintain plasma concentrations above 10 muM (the in vitro concent ration required for growth inhibition of human glioma cell lines) for up to 12 h. No hypericin was detected in the CSF of any animal (lower limit of d etection 0.1 muM); the CSF penetration is therefore less than 1%. A severe dose-limiting photosensitivity skin rash was seen at the 5 mg/kg dose level .