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Forward-Looking Statements

This presentation contains forward-looking statements, including statements related to Seattle Genetics’

corporate priorities, financial guidance and anticipated upcoming activities, potential regulatory approvals of

ADCETRIS in additional indications, the initiation of future clinical trials and data availability from ongoing

clinical trials and the timing thereof, the therapeutic and commercial potential of ADCETRIS and Seattle

Genetics’ product candidates, and other statements that refer to Seattle Genetics’ expectations and projections

or other characterizations of future events or circumstances. The results or events predicted in these

statements may differ materially from actual future results or events. Factors that may cause such differences

include risks related to Seattle Genetics’ ability to effectively commercialize ADCETRIS and the uncertainty of

future financial results, risks related to adverse or inconclusive clinical trial results and the uncertain and time-

consuming regulatory approval process, risks inherent in the research and development of pharmaceutical

drugs and the failure by Seattle Genetics to secure and maintain collaborations. More information about these

and other risks and uncertainties faced by Seattle Genetics is contained under the heading “Risk Factors” in the

company’s quarterly report on Form 10-Q for the quarter ended March 31, 2015 filed with the Securities and

Exchange Commission. Seattle Genetics disclaims any intention or obligation to update or revise any forward-

looking statements, whether as a result of new information, future events or otherwise.

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Corporate Priorities

Building ADCETRIS® into a Potential Major Global Brand

Approved for two indications in >55 countries; multiple guidelines listings

>30 ongoing clinical trials in broad array of CD30+ malignancies

Four phase 3 trials (AETHERA, ALCANZA, ECHELON-1, ECHELON-2)

Advancing Our Pipeline

7 clinical-stage programs, including 6 antibody-drug conjugates (ADCs) and 1 immuno-oncology agent

Goal to advance ~2 new programs into clinical development per year

Enhancing Our Leadership Position in ADCs

>20 ADCs in clinical trials utilize SGEN technology

Advancing ADC technology through innovative antibody engineering techniques, novel linkers and highly-potent drug chemotypes

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• ADCs harness the specificity of antibodies and the potency of cytotoxic agents

ADCs

TUMORCELL

ADCs Are An Integral Part of Cancer TherapyImproving patient outcomes with targeted therapies

Kinase Inhibitors

Target outside

of cell

Target signaling

pathways inside of cell

IMMUNECELL

Checkpoint

Inhibitors

CAR-T

Tumor

Vaccines

Activate immune cells

mAbs

• Combinations of these novel modalities are the future of treatment in oncology

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ADCs

TUMORCELL

Robust Product Pipeline

IMMUNECELL

SGEN is advancing multiple programs in clinical trials and

preclinical development for a broad array of hematologic

malignancies and solid tumors

• ADCETRIS

• SGN-CD33A

• SGN-CD19A

• SGN-LIV1A

• SGN-CD70A

• ASG-22ME

• ASG-15ME

• SEA-CD40

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ADCETRIS® (Brentuximab Vedotin) is an Expanding Global Brand

• ADC targeting CD30

• Approved in >55 countries for relapsed Hodgkin lymphoma (HL)

and systemic anaplastic large cell lymphoma (sALCL)

• SGEN has commercial rights in U.S. and Canada

• Collaboration with Takeda for ROW

• Broad global development plan

for potential additional indications in

earlier lines of therapy and

other CD30+ malignancies

• NCCN guidelines and compendia

listings in CD30+ PTCL,

CD30+ DLBCL, CTCL and HL

post-ASCT maintenance

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Broad Clinical Evidence of ADCETRIS Activity

Therapy N Setting ORR CR

Single-agent 102 Relapsed HL 75% 34%

Single-agent 58 Relapsed ALCL 86% 59%

Single-agent 48 Relapsed CTCL 73% 35%

Single-agent 48 Relapsed CD30+ DLBCL 44% 17%

Single-agent 34 Relapsed CD30+ PTCL 41% 24%

Single-agent 27 Frontline HL 60+ 93% 70%

A + AVD 26 Frontline HL 96% 96%

A + CHP 26 Frontline CD30+ MTCL 100% 88%

A + bendamustine 48 Second-line HL 96% 83%

A + RCHOP 51 Frontline DLBCL 80% 67%

A + dacarbazine 14 Frontline HL 60+ 93% 29%

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The ADCETRIS Opportunity

YTD

2014

ADCETRIS

approved in

U.S.

First full year

U.S. sales;

approved in

EU

Global sales

>$250M

Continued

global

expansion;

global sales

nearing

$400M

2011 2012 2013 2014 2015 2016 – 2018

Continued data generation in

HL, DLBCL and other CD30+ NHL

Phase 3

Frontline HL

ECHELON-1

~

Phase 3

Frontline

MTCL

ECHELON-2

Phase 3

CTCL

ALCANZAPhase 3

AETHERA

sBLA

ADCETRIS has the opportunity

to be the foundation of care for

CD30-positive malignancies

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AETHERA Demonstrates Strong PFS Improvement

• Consolidation therapy generally well tolerated; overall safety profile consistent with current

prescribing information

• Interim OS analysis did not show a significant difference between treatment arms

o Small number of events

o Most placebo patients received ADCETRIS after progression

• Supplemental BLA filed with Priority Review; PDUFA date August 18, 2015

• Manuscript published in The Lancet; March 2015

PFS per Independent Review PFS per Investigator

HR 0.57; p=0.001

2-year PFS rate 63%HR 0.50; p=0.001

2-year PFS rate 65%

ADCETRIS

Placebo

ADCETRIS

Placebo

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Additional ADCETRIS Phase 3 Trials

Trial

Number of

Patients

Primary

Endpoint

ALCANZARelapsed CTCL

(vs. physician choice

methotrexate or

bexarotene)

124

ORR lasting

at least 4

months

• Two investigator-sponsored trials in relapsed

CTCL reported ~70% response rates

• Expect to complete enrollment in 2015; data

anticipated in 2016

ECHELON-1Frontline HL

(A+AVD vs. ABVD)

1,240 PFS• Seeking to redefine frontline therapy by

integrating ADCETRIS

• Expect to complete enrollment in

ECHELON-1 in 2015 and in ECHELON-2 in

2016; data from both trials expected 2017-2018

ECHELON-2Frontline MTCL

(A+CHP vs. CHOP)

450 PFS

Global trials being conducted under SPA agreements

with FDA and scientific advice from EMA

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Redefining Frontline HL and MTCL

• Expected CR rate in advanced HL:70-80% with ABVD

• Expected rate of pulmonary toxicity with ABVD alone: up to 25%

• Expected 3-year FFS in advanced HL: ~75%

Phase 1 A+AVD (N=26)

Complete remission 96%

Pulmonary toxicity (any event) 0%

3-year failure-free survival 92%

3-year overall survival 100%

3-year follow up data presented at ASH 2014

• Expected CR rate in MTCL:39-53% with CHOP

• Expected 5-year OS in MTCL: 12-49%

Phase 1 A+CHP (N=26)

Complete remission 88%

2-year progression-free survival 54%

2-year overall survival 80%

2-year follow up data presented at ESMO 2014

Frontline Advanced Hodgkin Lymphoma

Frontline Mature T-cell Lymphoma

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Higher single-agent activity and longer

median PFS in CD30+ patients

• CD30 positive: ORR 44%, median PFS 17

weeks (n=49)

• CD30 undetectable: ORR 31%, median PFS

6.3 weeks (n=42)

ADCETRIS Opportunity in Diffuse Large B-cell Lymphoma (DLBCL)

Plan to initiate randomized phase 2

trial of Rituxan and bendamustine

+/- ADCETRIS for R/R CD30+

DLBCL later in 2015

Frontline DLBCLRelapsed / Refractory DLBCL

Encouraging activity of A+RCHOP in

intermediate-high / high-risk patients

• ORR 80%, with 67% CRs (n=51)

• Higher CR rate and longer durability in

CD30+ patients

Cohort opened to evaluate

ADCETRIS plus RCHP in CD30

positive frontline DLBCL patients

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Clinical Trial Collaboration to Combine ADCETRIS with Opdivo (PD-1 Checkpoint Inhibitor)

• Goal: continue to establish ADCETRIS as foundation of care in

CD30+ malignancies, while also evaluating novel combinations that

may improve clinical outcomes for patients

• Clinical trial collaboration with Bristol-Myers Squibb to evaluate

combination of ADCETRIS and Opdivo (nivolumab)

• Two trials planned to begin in 2015

o Relapsed Hodgkin lymphoma

o Relapsed CD30+ non-Hodgkin lymphoma, including DLBCL

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Diverse Clinical-Stage PipelineSix ADCs and one immuno-oncology agent

Preclinical Phase 1 Phase 2 Pivotal / Phase 3

SGN-CD33A Relapsed AML

Frontline AML (single agent, combinations)

SGN-CD19A Relapsed DLBCL (R-ICE +/- SGN-CD19A): Phase 2 planned

Relapsed ALL, NHL

SGN-LIV1A Relapsed breast cancer

SGN-CD70A Relapsed NHL, renal cell carcinoma

ASG-22ME Relapsed solid tumors

ASG-15ME Relapsed bladder cancer

SEA-CD40 Relapsed solid tumors

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Promising Early Data with SGN-CD33A inAcute Myeloid Leukemia

Post-Baseline Bone Marrow Blast Reduction

• Bone marrow blast clearance in 44% of evaluable

patients treated across all dose levels, including 21%

with CR/CRi

• 77% of patients treated at doses 40 mcg/kg or higher

had ≥50% blast reduction

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Acute Myeloid Leukemia Treatment Paradigm

Younger, Fit Unfit / Decline

Intensive Therapy

Frontline High-dose chemotherapy (“7+3”)

followed by consolidation

Hypomethylating agents or

low-dose chemotherapy

Relapsed/

Refractory

7+3 failures or treatment to

re-induce remission to enable

allogeneic transplant

Treatment determined by

performance status; best supportive

care common

• AML patient outcomes have not meaningfully changed in more than 30 years

• SGN-CD33A utilizes newest SGEN ADC technology (PBD dimer, EC-mAb)

• CD33 is expressed across AML regardless of subtype, cytogenetic abnormality

or underlying mutational heterogeneity

Phase 1b 7+3 combination;

single-agent maintenance,

consolidation

Phase 1 single-agent

and HMA combination

SGN-CD33A clinical trials

Phase 1 single-agentPhase 1 single-agent and

future trial opportunity

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SGN-CD19A is Active and Tolerable in R/R DLBCLNovel ADC Targeting CD19

Best % Change Per Patient in Index Lesions(doses ≥3 mg/kg)

• Marked single-agent activity

across multiple dose levels:

ORR 35%; CR rate 20%

• Combinations enabled by lack

of significant hematologic

toxicity or neuropathy

• Plan to initiate randomized

phase 2 trial in relapsed

DLBCL during 2015: R-ICE +/-

SGN-CD19A

Goal of planned combination trial is to increase

CR rate prior to autologous transplant

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Additional Clinical-Stage Programs Advancing

*Being developed in collaboration with Agensys, an affiliate of Astellas

Program Target Status

SGN-LIV1A LIV-1 • Phase 1 trial in relapsed metastatic breast cancer

SGN-CD70APBD-based ADC

CD70 • Phase 1 trial in relapsed NHL, metastatic renal cell carcinoma

ASG-22ME* Nectin-4 • Phase 1 trial in relapsed solid tumors, such as bladder, breast and lung cancers

ASG-15ME* SLITRK6 • Phase 1 trial in relapsed bladder cancer

SEA-CD40Immuno-oncology agent

CD40 • Phase 1 trial in relapsed solid tumors

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ADC Collaborations with Industry-Leading Companies

>$300M generated to date with potential for ~$4.5B in future milestones plus royalties

Collaborator Program Preclinical Phase 1 Phase 2 Pivotal/Phase 3

Glembatumumab vedotin (Anti-GPNMB) Breast cancer

Melanoma

Anti-CD79b (RG7596, DCDS4501A) Non-Hodgkin lymphoma

Anti-NaPi2b (RG7599, DNIB0600A) Ovarian, non-small cell lung cancer

Anti-STEAP1 (RG7450, DSTP3086S) Prostate cancer

RG7882 Ovarian, pancreatic cancer

RG7841 Solid tumors

Anti-PSMA ADC Prostate cancer

Anti-GCC ADC Advanced gastrointestinal malignancies

Anti-EGFR ADC Glioblastoma

Undisclosed ADC Cancer

Affiliate of Astellas

Anti-ENPP3 ADC Renal cell carcinoma

Anti-CD37 ADC Cancer

Anti-5T4 ADC Solid tumors

Anti-C4.4a ADC Solid tumors

Anti-FGFR2 ADC Cancer

Anti-BCMA ADC Multiple myeloma, hematologic malignancies

Anti-TF ADC Solid tumors (Opt-in at end of phase 1)

Others Several additional collaborator programs

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Strong Financial Position

1Q15 total revenues $82.2 million

ADCETRIS net sales $48.9 million

Collaboration revenue $22.2 million

Royalty revenue $11.1 million

Cash & investments as of March 31, 2015 $296.0 million

Debt None

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Anticipated Upcoming Activities

• Continue expanding ADCETRIS into earlier lines of therapy and other

CD30+ malignancies

o Obtain approval decision for ADCETRIS in the AETHERA setting

o Complete enrollment in ECHELON-1 and ALCANZA trials in 2015

and in ECHELON-2 in 2016

o Broaden clinical investigation in frontline and relapsed DLBCL

o Initiate combination trials with Opdivo (nivolumab) in HL and NHL

o Initiate exploratory trial in systemic lupus erythematosus

• Advance robust product pipeline

o Report emerging data on SGN-CD33A in AML and

discuss registration strategies

o Initiate phase 2 trial of SGN-CD19A in

second-line DLBCL

o Report data from pipeline programs