25. A Dose Escalation Study of Cyclophophamide (CTX) to Enhance SB-728-T Engraftment

Background: CCR5 modified autologous CD4 cells (SB-728-T) are safe and increases total CD4 counts. The cells traffic to lymphoid tissues and have a selective survival advantage during ART treatment interruption (TI). Additional studies in CCR5 D32 heterozygote HIV subjects showed VL reductions during TI correlated with circulating bi-allelic CCR5-modified CD4 cells supporting the importance of maximizing engraftment. Low dose CTX has been successfully used to increase T cell engraftment. This study examines the effect of escalating doses of CTX on SB-728-T engraftment.Methods: A dose escalation study of IV CTX, with doses ranging from 100 mg/m2 to 2 g/m2 (n=3-6/cohort), administered 1-3 days prior to SB-728-T (>90% CD4