UPDATE: Sangamo Highlights Encouraging Preliminary Anti-Viral HIV Data during Treatment Interruption in Ongoing SB-728-T Phase 2 Trials

Sangamo BioSciences, Inc. SGMO announced today the presentation of new clinical data from its program to develop a ZFP Therapeutic^® for HIV/AIDS.  The data, which demonstrate that SB-728-T treatment results in a reduction in the HIV reservoir in HIV-infected subjects, are being presented at the 16^th Annual Meeting of the American Society of Gene and Cell Therapy (ASGCT).  The meeting is being held in Salt Lake City from May 15-18, 2013. HIV-infected subjects enrolled in Sangamo's ongoing SB-728-902 clinical trial (Cohorts 1-3) received a single infusion of SB-728-T which resulted in a durable increase in total CD4 T-cells driven by increased ZFN-modified CD4 central memory T-cells.  The extent of exposure of subjects to circulating zinc finger nuclease (ZFN) CCR5 protected CD4 T cells correlated with a long term decrease in the peripheral blood mononuclear cell (PBMC) HIV reservoir as measured by proviral DNA.  In addition, two of four evaluable subjects in Cohort 5 of this study showed a decrease of greater than one log in their viral load during a sixteen week treatment interruption (TI) with one of the subjects achieving a transiently undetectable viral load during the TI period. In subjects in which viral load decreased, a measureable anti-HIV response was observed, specifically a multi-functional response of CD8 T-cells to elements of HIV core proteins.  Summary of Clinical Data SB-728-0902 Cohorts 1-3 in Immunologic Non-Responders (INR) o Treatment of HIV subjects with a single infusion of SB-728-T leads to long term increases in CD4 counts (up to 3 years in some subjects). o Long-term increases in CD4 counts correlate with increased CD4 central memory and increased ZFN CCR5 protected central memory T-cells. o The extent of long-term exposure to circulating ZFN-CCR5 protected CD4 cells correlates with long-term decreases in the PBMC HIV reservoir.  SB-728-0902 Cohort 5 (CCR5 delta-32 Heterozygotes)  o Post SB-728-T infusion, a 16-week ART TI can lead to viral load reduction from initial peak. o Two out of four subjects showed reduction in viral load during TI o One subject achieved transient undetectable viral load during TI o The best viral load reduction responses are seen in subjects with CD8 T-cell HIV gag immune responses that are polyfunctional (expression of multiple cytokines) and the highest levels of bi-allelic modification of the CCR5 gene. SB-728-1101 Immunologic Responders with Cytoxan Conditioning  o Accrual and treatment in progress with ten subjects infused to date. o Analysis of numbers of modified SB-728-T cells and viral load during TI is in progress. Viral load decreases correlate with highest levels of estimated biallelic CCR5 modification o Decreases in viral load from peak to the end of TI correlated with mean circulating bi-allelic ZFN CCR5 protected CD4 cells during the TI for all patients to date who fully completed TI per protocol in SB-728-Penn, 902 Cohort 5(CCR5 delta-32 Heterozygotes) and 1101 studies.