Vasopharm BIOTECH is developing 4-aminotetrahydrobiopterin (ronopterin, VAS 203), a nitric oxide synthase inhibitor, for the treatment of traumatic brain injury. Ronopterin is an allosteric nitric oxide (NO) synthase inhibitor interacting with the tetrahydrobiopterinbinding site of the enzyme. Pre-clinical, proof-of-principle studies using controlled cortical impact showed that VAS203 had significant and positive effects on elevated intracranial pressure (ICP), which contributes to the deleterious consequences of TBI, as well as on neurological outcome measured with behavioural tests. By targeting both cerebral blood vessels and cerebral tissue in a region-specific manner VAS203 represents a completely novel pharmacological approach to TBI that can be administrated in addition to best standard of care. Ronopterin is currently in development for the treatment of traumatic brain injury.In the phase III clinical trial, ronopterin is administered as a 17 mg/kg intravenous infusion over 48 hours (daily dose of 8.5 mg/kg).