Pentosan polysulfate as a prophylactic and therapeutic agent against prion disease

Pentosan polysulfate (PPS) acts by imitating the physiological roles of the heparans. It binds to heparan binding sites on proteins and alters the physiological actions of these proteins. PPS acts as a prophylactic agent against infection with prions both in vivo and in vitro. Low concentrations (10 mg/ml) are needed extracellularly for this effect to be seen but, due to cellular uptake, it is believed that a much higher concentration is found intracellularly. The prophylactic effect of PPS is observed if the drug is administered to mice between 3 months before and approximately 30 days after the inoculation of the disease. After that point it is considered that the infection has entered the nervous system, and that the drug cannot penetrate the blood-brain barrier. The prophylaxis of humans with oral PPS and the current therapeutic activity of the drug when given by intracerebroventricular infusion to symptomatic, prion-infected animals are discussed.