Raltegravir for HAM/TSP

Objective: In this pilot study, we wish to determine the effects of Raltegravir, a clinically approved HIV-1 integrase inhibitor, on HTLV-1 proviral load (PVL) in patients with HTLV-1 associated myelopathy / tropical spastic paraparesis (HAM/TSP). We will also provide safety and tolerability information on Raltegravir use in this condition and examine the correlation of immune activation markers in HAM/TSP with the effects of Raltegravir on the PVL. Study population: HAM/TSP, a relentlessly progressive and disabling myelopathy, occurs in up to 3% of HTLV-1 infected subjects. It results from immune-mediated bystander damage of the neural tissues in association with an elevated PVL. In fact, a high PVL is considered to be the main risk factor for developing HAM/TSP as the risk of disease rises exponentially once the PVL exceeds 1 %. Currently there is no effective treatment for HAM/TSP. There is evidence that active HTLV-1 replication, through the retroviral life cycle with new virus integration, is occurring in vivo and contributes to the total HTLV-1 PVL in infected subjects. Recently it was shown that Raltegravir could inhibit cell-free and cell-to-cell transmission of HTLV-1 in vitro. Given the substantial clinical experience with its use in HIV-1 infection and particularly its excellent safety profile, this agent is an attractive therapeutic option for patients with HAM/TSP, either alone or in combination with immunomodulatory treatment. In this pilot study we wish to determine the effects of Raltegravir in vivo on HTLV-1 PVL and immune activation markers in patients with HAM/TSP. Design: In this 15 months single center, single arm, open label, baseline versus treatment pilot clinical trial, sixteen subjects with HAM/TSP will receive Raltegravir at 400mg by mouth twice daily in an initial 6 months treatment phase, followed by an additional 9 months post treatment phase. Outcome measures will be collected every 3 months for the duration of the study. Outcome measures: The primary outcome measure is HTLV-1 proviral load, which will be measured by quantitative PCR. Secondary outcome measures include safety and tolerability of Raltegravir, which will be assessed by clinical exam and standardized neurological disability scales as well as clinical laboratory studies. In addition, viral and immunologic outcome measures investigating the impact of Raltegravir on HTLV-1 biology and its effects on immune function will be measured including HTLV-1 proviral load in different lymphocyte populations, the number of long terminal repeat (LTR) circles and HTLV-1 mRNA expression levels in freshly isolated PBMC, assays of spontaneous lymphoproliferation and T-cell phenotype analysis.