Preliminary data from the University of Pennsylvania-sponsored Phase I safety study of Sangamo‘s zinc finger nuclease (ZFN) based product, SB-728-T, for HIV/AIDS have shown exciting early results.

CD4+ T-cells are removed from the subject’s blood and treated with Sangamo’s ZFNs, which are designed to modify the DNA sequence encoding the CCR5 gene.

A single HIV-positive subject was treated with SB-728-T and, as part of the study, began a structured treatment interruption (STI) from his antiviral drug therapy four weeks after SB-728-T treatment.

12 weeks later, the STI ended and the subject resumed antiviral therapy. During the study, the subject’s CD4+ T-cell count, the number of circulating ZFN-modified cells and viral loads were measured periodically. In addition, rectal biopsies were taken prior to treatment and at the end of the STI period to monitor levels of CD4+ and ZFN-modified T-cells in the GALT.

During the monitoring period, the subject continued to demonstrate stable CD4+ T-cell counts and stable levels of ZFN-modified T-cells. In rectal biopsy samples taken at the end of the STI period, ZFN-modified cells were found in the GALT, suggesting that these cells circulate and traffic normally.

Sangamo’s vice-president of therapeutic development and chief medical officer Dale Ando said that preliminary results are very encouraging and recapitulate observations that the company has made in preclinical studies.

“Importantly, ZFN-modified cells expanded over the period that we monitored the subject and were well tolerated. As expected, the subject’s viral load increased during the STI. However, the kinetics of this subject’s viral rebound was delayed,” Ando said.