Enfuvirtide Cerebrospinal Fluid (CSF) Pharmacokinetics and Potential use in Defining CSF HIV-1 Origin

Background Enfuvirtide is a potent inhibitor of systemic HIV-1 replication, but its penetration into the human central nervous system (CNS) has not been analysed. Here, we define cerebrospinal fluid (CSF) enfuvirtide pharmacokinetics and present a case illustrating the use of enfuvirtide as a probe to trace the origins of CSF HIV-1 quasispecies. Methods Enfuvirtide CSF pharmacokinetics were assessed in 18 CSF and plasma sample pairs from four HIV-1-infected individuals. Enfuvirtide levels were measured by liquid chromatography tandem mass spectrometry using known standards and controls that included spiked CSF samples from untreated, HIV-negative individuals. A segment of the gp41 coding region encompassing the heptad repeat HR-1 and HR-2 domains was amplified from selected CSF and plasma samples and independent clones sequenced to assess resistance-associated mutations. Results CSF and plasma samples obtained between 2 and 20 h after enfuvirtide injection showed plasma concentrations similar to previous reports (mean 3.687 SD ±1.828 mg/ml) with prolonged decay. By contrast, enfuvirtide in all CSF samples was below the assay detection limit of 0.025 mg/ml. In one individual, who developed a transient increase in CSF HIV-1 RNA, seven of seven CSF and plasma clones had identical enfuvirtide resistance-associated V38A mutations, suggesting that the CSF quasispecies derived from that of blood. Conclusions Enfuvirtide penetration into CSF is negligible; thus, in clinical settings, where direct CNS drug exposure is crucial, this drug Is not likely to directly contribute to the local therapeutic effect. Enfuvirtide can be used as a tool to dissect the origin of the CNS virus.