Highly Efficient and Specific Multiplexed Gene Editing in T cells Using Enhanced Zinc-Finger Nucleases (ZFNs) Enables Strategic Engineering of Allogeneic T Cell Immunotherapies

Sumiti JainMay 19th, 2018

This presentation contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private SecuritiesLitigation Reform Act of 1995, as amended. These forward-looking statements include, but are not limited to, the duration for whichexisting capital resources can provide for planned operations; the design of clinical trials and expected timing for release of data; theanticipated clinical development milestones and other potential value drivers in the future; the expected benefits of the collaboration withPfizer; the expected capability of Sangamo’s technologies; the ability of Sangamo to research and develop novel gene-based therapiesand the anticipated benefits of applying Sangamo’s ZFP technology platform to specific human diseases; anticipated benefits fromcorporate partnerships; and the potential of Sangamo’s genome editing technology to treat genetic diseases. Our actual results may differmaterially and adversely from those expressed in any forward-looking statements as a result of various factors and uncertainties. Factorsthat could cause actual results to differ include, but are not limited to, the dependence on the success of clinical trials of lead programs,the lengthy and uncertain regulatory approval process, uncertainties related to the timing of initiation and completion of clinical trials,whether clinical trial results will validate and support the safety and efficacy of Sangamo’s therapeutics, the ability to establish strategicpartnerships and our ability to control expenses and achieve our milestones that generate revenues under our agreements. Further, therecan be no assurance that the necessary regulatory approvals will be obtained or that Sangamo and its partners will be able to developcommercially viable gene-based therapeutics. Actual results may differ from those projected in forward-looking statements due to risksand uncertainties that exist in Sangamo’s operations and business environments. These risks and uncertainties are described more fullyin Sangamo’s Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q as filed with the Securities and Exchange Commission.Forward-looking statements contained in this presentation are based on our current expectations and are made as of the date hereof.Sangamo undertakes no duty to update such information except as required under applicable law.

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Forward Looking Statements

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Vision: Off-the-shelf allogeneic T-cell therapies

HLAs

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Toolkit to generate healthy donor allogeneic CAR T cells

TCR⍺β

CAR

Healthy Donor

Eliminate HLA Class I

Eliminate Endogenous TCR

CAR Expression

ZFN mRNATRAC Knockout

AAV6 DonorTargeted Insertion

of CD19 CAR into TRAC

ZFN mRNAβ2M Knockout

Prevent rejection

Prevent GvHD

Immune specificity

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The ZFN platform for genome editing

Efficiency | Ability to edit at the desired target nucleotide

Precision | Ability to target any desired nucleotide

Specificity | Ability to edit the targeted nucleotidewithout editing elsewhere in the genome

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ZFN Platform: Best-in-class gene editing

Innovation Result

New dimer architectures yield higher modification activity

Increase DNA editing efficiency to as high as 99.5%

Phosphate contact tuning via replacement of key residues

Off-target cleavage undetectable (>1000 fold reduction)Specificity

Precision

Efficiency

New linkers for configuring DNA-binding modules

300-fold increase in design options for targeting any given sequence

Precision

SpecificityEfficiency

Precision

SpecificityEfficiency

CGA----------------TTTTGCACTCGTGATAAGGGGGAAAAGAACACCCGCTCACCCGAGTCC--GGGCAATATTTTTGCACTCGTGATAAGGGGGAAACCCGCTCACC

CGAGT---TGGGCAATATTTTTGCACTCGTGATAAGGGAAGAACACCCGCTCACC ACC--------------GCAATATTTTTGCACTCGTGATAAGGGGGAAAACACCCGCTC

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Single-step multiplexed T cell editing

Activated T Cells Gene Editing

ZFN mRNA Electroporationβ2M and TRAC Knockout

AAV6 TransductionCD19 CAR

Insertion into TRAC

From Healthy Donor

Expand + Analyze

Phenotype(FACS)

Genotype(MiSeq)

ZFN-KO of TRAC achieves 95-99% loss of surface TCR

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CD3

97% CD3neg

TRAC-ZFN Treated T cells 97% CD3 KO

~1:1 CorrelationGenotype and Phenotype

Untreated control

% T

RAC

Inde

l

% CD3-neg

ZFN-KO of β2M consistently achieves >90% loss of class I HLA

9HLA Class I

91% HLAneg

β2M-ZFN Treated T Cells 91% HLA Class I KO

Untreated control

β2M-KO Achieves Functional Loss of HLA Class I Expression

⍺2 ⍺2

⍺3 β-microgloblin

Highly efficient double KO and GFP TI into TRAC

10GFP

GFP TI into TRAC91% GFP expression

91% GFPpos

TRAC + β2M double KO91% double neg

CD3

HLA

-AB

C

Unedited T cells Double KO T cells(TRAC/B2M)

91%

AAV TI of CD19 CAR into TRAC yields functional CAR-T cells

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Protein-L/ CARE:T Ratio

% C

D19

+ K

562 Untreated

CD19 CARTRAC KO

CD19 CAR Double KO

0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5

0

2 0

4 0

6 0

8 0

1 0 077%CARpos

Specific Lysis of CD19+ K562 Cells4hrs; co-culture of CAR-T cells with K562wt and CD19+ K562

CAR TI into Double KO77% CARpos

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Improve specificity of ZFNs by varying phosphate contact

Arg phosphatecontact variant

DNA

zinc finger Fok domain

Fok domain

Lys phosphatecontact variant

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% Indels

ZFN Pair B2M (ON-Target) OFF-Target A # Architecture 4ug 1ug 0.5ug 4ug 1ug 0.5ug 1 parent 100.0 96.6 89.1 4.89 1.32 0.12 2 optimized 99.3 89.9 73.9 0.02 0.00 0.00 3 optimized 100.0 95.1 81.6 0.02 0.01 0.00 4 optimized 100.0 96.9 83.3 0.01 0.00 0.00 5 optimized 100.0 93.4 74.2 0.02 0.00 0.01

Optimized ZFN pairs exhibit highly efficient editing and improved specificity

Loss of off-target activity vs. parent

Optimized ZFNs targeting B2M exhibit no off-target activity

Determine if the optimized ZFN pairs exhibit off-target activity at new sites by performing an unbiased integration site analysisNext

Optimized ZFNs targeting B2M exhibit no off-target activity

Genome-wide unbiased oligonucleotide duplex integration analysis revealed NO off-target activity for the optimized ZFN pairs

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Verify off-target activity in T cells in an at-scale process which achieves clinically relevant editing efficienciesNext

Off-Target Site?

DSB

Integrated Donor

Donor

Sequence Reveals Candidate Off-Target Site

Adaptor

Genome

• Treat cells with ZFNs + donor oligo duplex

• Sequence genome segments adjacent to integrated donors

• Treat K562 or HepG2 cells with ZFNs• PCR-amplify candidate off-target sites• Assess for indels

Identify Candidate OTsOligo-Duplex End-Capture Assay

Confirm OTsDeep Sequencing forActual ZFN Activity

2

1

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Locus Integrant count

% Indels p-value if < 0.05ZFN-treated Control

On Target 3386 95.23 0.14

Highly efficient genome editing is critical for multiple gene modifications

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1 KO + 1 KO + 1 TI Compounded Efficiency

99% x 99% x 99% = 97%

90% x 90% x 90% = 73%

70% x 70% x 70% = 34%

50% x 50% x 50% = 13%

Very High

Medium

Low

High

Simultaneous multiplex editing efficiency: 3x ZFN KO + 1x TI

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76% of cells have all 4 edits

Potential ApplicationUniversal T cells with checkpoint gene knock-out

Single Step Editing

ZFN Knock-out1. TRAC (TCR)2. β2M (HLA-class I)3. CISH (checkpoint gene)

Targeted Insertion4. GFP (into TRAC)

T C R-

β 2 M-

C I S H-

G F P+

0

5 0

1 0 0

9 3 % 9 6 % 9 3 % 9 1 %

TRAC -

93% 96% 93% 91%

β2M - CISH - GFP +

% E

ditin

g

Acknowledgements

Genome EditingGary LeeLynn TruongNimisha GandhiAnthony Conway and TeamAndreas Reik and Team

TechnologyEdward RebarJeff Miller and TeamLei Zhang and TeamDeepak PatilBioinformatics

LeadershipSandy MacraeMichael Holmes

AAV Production Richard Surosky and Team

Slide Number 1Forward Looking StatementsVision: Off-the-shelf allogeneic T-cell therapiesToolkit to generate healthy donor allogeneic CAR T cellsThe ZFN platform for genome editingZFN Platform: Best-in-class gene editingSingle-step multiplexed T cell editingZFN-KO of TRAC achieves 95-99% loss of surface TCRZFN-KO of β2M consistently achieves >90% loss of class I HLAHighly efficient double KO and GFP TI into TRACAAV TI of CD19 CAR into TRAC yields functional CAR-T cellsSlide Number 12Slide Number 13Slide Number 14Slide Number 15Highly efficient genome editing is critical for multiple gene modificationsSimultaneous multiplex editing efficiency: 3x ZFN KO + 1x TISlide Number 18