Russell DeKelver, PhD Sangamo BioSciences, Inc.

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1 ZFN-Mediated In Vivo Genome Editing Results in Supraphysiological Levels of Human Iduronate 2-Sulfatase and Phenotypic Correction in a Murine MPS II Model Russell DeKelver, PhD Sangamo BioSciences, Inc.

2 Disclosure Information WORLD Symposium TM 2016 (Russell DeKelver) I have the following financial relationships to disclose: Stockholder in: Sangamo BioSciences Employee of: Sangamo BioSciences I will not discuss off label use and/or investigational use in my presentation.

3 Systemic delivery of ZFP Therapeutics via AAV vectors for in vivo correction of monogenic disease ZFN Pair and Corrective Gene Packaged into adenoassociated viral vectors (AAV) One-time Peripheral IV Administration ZFN1 ZFN2 AAV Vectors ZFN1 ZFN2 hids AAV Traffics to Liver And Permanently Integrates Gene Homology Therapeutic Gene Homology Liver Cells Secrete Corrective Protein for Uptake in Secondary Tissues In Vivo Protein Replacement (e.g. human IDS)

4 Zinc Finger Nucleases (ZFNs) are specific molecular scissors ZFP2 5 T A C C C A A C G C G A A T T A T G G C G G C G T G C G C T T A A C G C A T G G G T 3 A T G G G T T G C G C T T A A T A C C G C C G C A C G C G A A T T G C G T A C C C A 3 5 Genomic DNA ZFP1 Nuclease Zinc Finger Protein 1 identifies and binds to DNA sequence Part of the ZFN that makes a cut in DNA/Gene (Nuclease) Zinc Finger Protein 2 identifies and binds to DNA sequence Our proprietary ZFN technology allows us to specifically target and modify any gene or DNA sequence in the human body.

5 Integration of corrective gene leads to permanent production of a missing enzyme ZFN2 5 T A C C C A A C G C G A A T T A T G G C G G C G T G C G C T T A A C G C A T G G G T 3 A T G G G T T G C G C T T A A T A C C G C C G C A C G C G A A T T G C G T A C C C A 3 5 Genomic DNA ZFN1 Nuclease domains 5 T A C C C A A C G C G A A T T A T G 3 A T G G G T T G C G C T T A A T A C C G C G C G T G C G C T T A A C G C A T G A C G C G A A T T G C G T A C G G T C C A 3 5 Permanent protein production 5 T A C CCAACGCGAAT T A T G 3 A T G G G T T G C G C T T A A T A C Therapeutic Gene of Choice T G C G C T T A A C G C A T G G G T A C G C G A A T T G C G T A C C C A 3 5 MPS I & II Gaucher Fabry Other Genes e.g. Factor 9, other LSDs

6 Targeted integration at the Albumin locus leads to high transgene expression Albumin (the most abundant blood plasma protein) has all properties of an ideal In vivo Protein Replacement Platform TM gene: Safe to co-opt a small percentage of Albumin Tissue specific and only produced in the liver Very highly expressed relative to protein replacement therapies > Normal Albumin levels in blood: mg/ml ; Synthesis rate from liver: ~ g /week

7 Targeted integration at the Albumin locus leads to high transgene expression Albumin (the most abundant blood plasma protein) has all properties of an ideal In vivo Protein Replacement Platform TM gene: Safe to co-opt a small percentage of Albumin Tissue specific and only produced in the liver Very highly expressed relative to protein replacement therapies > Normal Albumin levels in blood: mg/ml ; Synthesis rate from liver: ~ g /week Disease: MPS I (Hurler) MPS II (Hunter) Gaucher ERT Dose: (mg/week 75kg patient) % of Albumin production rate: 0.054% 0.047% 0.063% A very small fraction of natural Albumin synthesis is needed to drive therapeutic levels of replacement protein

8 ZFN-mediated integration of hids cdna at the Albumin locus results in secreted hids protein Liver Plasma & other tissues

9 4-month study to demonstrate ZFN-mediated correction of an MPS II mouse model AAV2/8 vectors ZFN1 hids ZFN2 ZFN+Donor (low, medium, high) Donor only Untreated MPS II mice 7-8 weeks old n = 8-13/group Study analysis a) hids protein expression in liver b) IDS enzyme activity in liver, plasma and secondary tissues c) GAG biomarker reduction d) Barnes Maze (learning & memory)

10 Human IDS is expressed in livers and secreted into plasma of treated mice Liver hids expression (4 months) Plasma IDS activity

11 Significant increase in IDS enzyme activity in all analyzed tissues of treated mice 4 months post-dosing IDS activity (nmol/hr/mg) * * * * * * Tissue IDS Activity # * # * * * Wild type, Untreated (n=10) MPS II, Untreated (n=10) MPS II, ZFN+Donor Low (n=5) MPS II, ZFN+Donor Mid (n=4) MPS II, ZFN+Donor High (n=10) MPS II, Donor Only (n=3) Muscle Brain Liver Spleen Kidney Lung Heart Muscle Brain 0 P-values: ZFN+Donor vs MPS II Untreated *p<0.01; # p<0.05

12 Significant GAG biomarker reduction in peripheral tissues of ZFN+Donor treated mice 4 months post-dosing GAG levels (µg GAGs/mg protein) Tissue GAG Levels Wild type, Untreated (n=10) MPS II, Untreated (n=10) MPS II, ZFN+Donor Low (n=5) MPS II, ZFN+Donor Mid (n=4) MPS II, ZFN+Donor High (n=10) MPS II, Donor Only (n=4) # 0 * * * * * # * Muscle Brain P-values: ZFN+Donor vs MPS II Untreated *p<0.01; # p<0.05

13 Thomas Wechsler 2015 Barnes Maze test setup Only one of the 40 platform holes is not blocked and allows the animal to hide from the light above ( escape hole ) Barnes Maze assesses the ability of the animal to learn and memorize the location of the escape hole Visual cues on the walls aid the animal The time to find the escape hole is measured on six consecutive days

14 Significant cognitive benefits observed in ZFN+Donor high dose group Barnes Maze L a te n c y to T a rg e t E s c a p e H o le (s e c ) * * Untreated ZFN+Donor high dose T e s t D a y P-values, p<0.05: * ZFN+Donor Compared to MPS II Untreated

15 Integration of human IDS at liver Albumin locus in MPS II mice led to: hids expression in liver, secretion into plasma, and uptake by secondary tissues Stable increased IDS activity and decreased GAG storage through 4 months following a single treatment Significant cognitive benefits at 4 months in the high dose group These data support the development of Sangamo s In Vivo Protein Replacement Platform TM for the potential single-dose treatment of lysosomal storage disease

16 Acknowledgments Sangamo BioSciences Thomas Wechsler Michelle Rohde Susan Tom Bob Radeke Hoang-Oanh Nguyen Scott Sproul Marshall Huston Annemarie Ledeboer Carolyn Gaspar Melanie Butler Amy Manning-Bog Kathleen Meyer Edward J. Rebar Michael C. Holmes Poster #80 MPS II Poster #229 MPS I - Li Ou R. Scott McIvor Chester Whitley Kanut Laoharawee Li Ou Kelly Podetz-Pedersen