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Press Release
Sangamo Presents New Clinical Data at CROI 2012 Demonstrating Persistent Positive Effects of ZFN Therapeutic for "Functional Cure" of HIV/AIDS
Data Highlight Positive Effects of SB-728-T on Immune System and Viral Load Reduction and Further Validate Strategy of Ongoing Phase 2 Trials

March 8, 2012

Richmond, Calif. -- Sangamo BioSciences, Inc. (Nasdaq: SGMO) announced that new data from its program to develop a 'functional cure' for HIV/AIDS were described in two presentations at the 19th Conference on Retroviruses and Opportunistic Infections (CROI), held in Seattle from March 5 to March 8, 2012.

"These data differentiate SB-728-T from other novel therapies as a feasible approach to controlling HIV/AIDS," said Ronald Mitsuyasu, M.D., Professor of Medicine, David Geffen School of Medicine at UCLA and a principal investigator in Sangamo's SB-728-T studies. "The results suggest that SB-728-T has a positive effect on immune health of HIV-infected patients and this effect is persistent for over a year in some subjects. Most importantly, SB-728-T treatment provides HIV-resistant T-cells that are capable of mounting an immune response to an inflammatory event in lymphoid tissues and has yielded encouraging effects on HIV viral load when antiretroviral drugs are withdrawn during a treatment interruption."

"These data add to our understanding of the positive viral load changes in SB-728-T-treated subjects, and suggest that an early cytokine burst may initiate the dramatic and prolonged increase in CD4 counts observed following SB-728-T treatment," said Dale Ando, M.D., Sangamo's vice president of therapeutic development and chief medical officer. "They also confirm that SB-728-T meets key requirements for our strategy for a 'functional cure' for HIV, by demonstrating durable engraftment and prolonged trafficking and dynamic immunological responsiveness in the gut mucosa. Together, these data further validate our strategy for the continued development of this ZFP Therapeutic as a 'functional cure' for HIV in two ongoing Phase 2 clinical trials designed to extend the observation of a statistically significant correlation between levels of bi-allelic modification of CD4 T cells and viral load reductions during treatment interruptions in HIV infection. The first study builds on the approximate doubling of bi-allelic engraftment that can be achieved in CCR5 delta-32 heterozygotes and seeks to confirm the occurrence of aviremia during treatment interruption as observed in one such patient in our Phase 1 program. The other clinical trial will examine the ability of a lymphopenic preconditioning regimen to enhance bi-allelic engraftment, and reduce viral load during treatment interruption, in non-CCR5-mutated HIV subjects."


Clinical Trial Data Summary

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Abstract # 155 "Induction of Acquired CCR5 Deficiency with Zinc Finger Nuclease (ZFN) Modified Autologous CD4 T-cells (SB-728-T) Correlates with Increases in CD4 Count and Effects on Viral Load (VL) in HIV-infected Subjects" -- Thursday, March 8, 2012

21 HIV-infected subjects were enrolled in Phase 1 clinical studies at the University of Pennsylvania and in California (SB-728-902) and received a single dose of SB-728-T (5 to 30 billion cells). All subjects were taking highly active antiretroviral therapy (HAART) and had stably controlled undetectable levels of HIV in their blood. Subjects were classified into two groups based on their CD4+ T-cell counts: one group of 15 subjects, with CD4+ T-cell counts below 500 cells/ ul designated Immune Non-Responders (INR), and a second group of six subjects with CD4+ T-cell counts of greater than 450 cells/ ul designated Immune Responders (IR). One month after SB-728-T treatment, six subjects in the INR group enrolled in the University of Pennsylvania study underwent a 12-week treatment interruption (TI) of their HAART.

The studies evaluated safety and tolerability, changes in CD4+ T-cell counts and the ratio of CD4+ to CD8+ T-cells as well as persistence of SB-728-T in the blood and trafficking of these ZFN-modified cells into gut-associated lymph tissue. In addition, viral DNA and changes in viral load (VL), as measured by HIV-RNA, were measured during the TI in the six INR subjects.

These studies demonstrated:

Abstract #433 "A Single Infusion of Zinc Finger Nuclease CCR5 Modified Autologous CD4 T Cells (SB-728-T) Increases CD4 Counts and Leads to Decrease in HIV Proviral Load in an Aviremic HIV-infected Subject" Wednesday, March 7, 2012

In one INR subject (01-104) who received a single dose of SB-728-T (10 billion cells) an inflammatory event unrelated to SB-728-T infusion was observed in the gut mucosa by histology and surface marker staining of mucosal inflammatory cells from 3 to 6 months after infusion. Subsequently, a greater than 1 log increase in SB-728-T was observed locally in the gut, preceding resolution of the inflammation.

This study demonstrated:

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"The data presented at CROI further support our fundamental rationale for SB-728-T and, importantly, the design of our ongoing Phase 2 clinical trials which will enable us to quickly maximize the impact of SB-728-T on viral load and the overall immune system of HIV-infected individuals," said Geoff Nichol, M.B., Ch.B., Sangamo's executive vice president of research and development. "Our ZFP technology provides a novel platform for the creation of transformational ZFP Therapeutics and we are focused on using it to develop curative therapies for HIV and multiple monogenic and rare diseases."

Webcasts of all the presentations at CROI 2012 can be accessed via the following link http://retroconference.org/static/webcasts/2012/.

About SB-728-T

SB-728-T is an autologous CD4 T-cell product in which the gene for CCR5, a co-receptor for HIV entry, is modified via ZFN-mediated genome editing to disrupt the CCR5 protein. T-cells with a disrupted CCR5 protein are resistant to infection by the most common strain of HIV.

About Sangamo

Sangamo BioSciences, Inc. is focused on research and development of novel DNA-binding proteins for therapeutic gene regulation and genome editing. It has ongoing Phase 2 and Phase 1/2 clinical trials to evaluate the safety and efficacy of a novel ZFP Therapeutic® for the treatment of HIV/AIDS. Sangamo's other therapeutic programs are focused on monogenic diseases, including hemophilia, hemoglobinopathies such as sickle cell anemia and beta-thalassemia, and a program in Parkinson's disease. Sangamo's core competencies enable the engineering of a class of DNA-binding proteins known as zinc finger DNA-binding proteins (ZFPs). Engineering of ZFPs that recognize a specific DNA sequence enables the creation of sequence-specific ZFP Nucleases (ZFNs) for gene modification and ZFP transcription factors (ZFP TFs) that can control gene expression and, consequently, cell function. Sangamo has entered into a strategic collaboration with Shire to develop therapeutics for hemophilia and other monogenic diseases and has established strategic partnerships with companies in non-therapeutic applications of its technology including Dow AgroSciences and Sigma-Aldrich Corporation. For more information about Sangamo, visit the company's website at www.sangamo.com

ZFP Therapeutic is a registered trademark of Sangamo BioSciences, Inc.

This press release may contain forward-looking statements based on Sangamo's current expectations. These forward-looking statements include, without limitation, references relating to research and development of novel ZFP TFs and ZFNs and therapeutic applications of Sangamo's ZFP technology platform for the treatment of HIV/AIDS, including a potential functional cure of HIV/AIDS, the expansion of clinical studies of SB-728-T in HIV-infected individuals and the initiation of additional preclinical and clinical studies of ZFN-gene modification. Actual results may differ materially from these forward-looking statements due to a number of factors, including uncertainties relating to the initiation and completion of stages of our clinical trials, whether the clinical trials will validate and support the tolerability and efficacy of ZFNs, technological challenges, Sangamo's ability to develop commercially viable products and technological developments by our competitors. For a more detailed discussion of these and other risks, please see Sangamo's SEC filings, including the risk factors described in its Annual Report on Form 10-K and its most recent Quarterly Report on Form 10-Q. Sangamo BioSciences, Inc. assumes no obligation to update the forward-looking information contained in this press release.




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