Bringing Breakthrough Pioneering Therapies to Patients with Life-Threatening Diseases

Corporate Presentation

September 2017

Disclaimer

In addition to historical facts or statements of current condition, this presentation contains forward-looking statements, includingstatements about the potential safety and feasibility of CYAD-01 cell therapy, including current and planned preclinical and clinical trials forCelyad’s product candidates; the clinical and commercial potential of these product candidates and the adequacy of Celyad’s financialresources; Celyad’s intellectual property portfolio, including plans related thereto; Celyad’s expectations regarding its strategiccollaborations and license agreements with third parties, including Novartis, Celdara Medical, and Dartmouth College, and the potentialimpact of such collaborations on Celyad’s future financial condition; and Celyad’s expected cash burn, which reflect Celyad’s currentexpectations and projections about future events, and involve certain known and unknown risks, uncertainties and assumptions that couldcause actual results or events to differ materially from those expressed or implied by the forward-looking statements. These forward-looking statements are further qualified by important factors and risks, which could cause actual results to differ materially from those in theforward-looking statements, including risks associated with conducting clinical trials; the risk that safety, bioactivity, feasibility and/orefficacy demonstrated in earlier clinical trials or preclinical studies may not be replicated in subsequent trials or studies; risks associated withthe timely submission and approval of anticipated regulatory filings; the successful initiation and completion of clinical trials, including itsclinical trials for CYAD-01; risks associated with the satisfaction of regulatory and other requirements; risks associated with the actions ofregulatory bodies and other governmental authorities; risks associated with obtaining, maintaining and protecting intellectual property,Celyad’s ability to enforce its patents against infringers and defend its patent portfolio against challenges from third parties; risks associatedwith competition from others developing products for similar uses; risks associated with Celyad’s ability to manage operating expenses; andrisks associated with Celyad’s ability to obtain additional funding to support its business activities and establish and maintain strategicbusiness alliances and business initiatives. A further list and description of these risks, uncertainties and other risks can be found in Celyad’sU.S. Securities and Exchange Commission (SEC) filings and reports, including in its Annual Report on Form 20-F filed with the SEC on April 4,2017 and subsequent filings and reports by Celyad. Given these uncertainties, the reader is advised not to place any undue reliance on suchforward-looking statements. These forward-looking statements speak only as of the date of publication of this document. Celyad expresslydisclaims any obligation to update any such forward-looking statements in this document to reflect any change in its expectations withregard thereto or any change in events, conditions or circumstances on which any such statement is based, unless required by law orregulation.

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Celyad: Company overview

Focused on the discovery and the development

of specialized cell-based therapies to target cancer

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• Novel and proprietary CAR-T platform targeting treatment of solid and hematologicaltumors.

• Lead candidate, CYAD-01 (CAR-T NKG2D), currently enrolling in Phase I THINK trial in 7 indications.

• Unique expertise in cell manufacturing co-located with our head office in Belgium.

• Led by experienced management team and supported by strong scientific advisory board.

• Partnerships with first-class corporate, academic and medical institutions.

• Well capitalized to advance robust CAR-T pipeline.

Celyad’s CYAD-01 (CAR-T NKG2D) pipeline

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CM-CS1 Phase 1 Trial - Completed

SOLID CANCERINDICATIONS

THINK - Colorectal cancer

THINK - Ovarian cancer

THINK - Bladder cancer

THINK - Triple Negative Breast cancer

THINK - Pancreatic cancer

THINK - Multiple Myeloma

THINK - Acute Myeloid Leukemia

HEMATO CANCERINDICATIONS

PRECLINICAL STAGE

LINK - Loco-regional administration

Allogeneic platform

CLINICAL STAGE Autologous platform

2015 2016 2017 2018

SHRINK - Combo with chemotherapy

CYAD-01: A unique construct arming T-cells with a NK receptor to target and destroy cancer cells

• One natural construct that capitalizes on the

two main pillars of the immune system:

NK cells and T-cells

• A natural co-stimulating domain: DAP 10

• Same signaling domain as other CAR-T: CD3ζ

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A single NK cell receptor binding 8 different ligands

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NKG2D ligands are expressed by stressed cells during infection, tumorigenesis or DNA damage

NKG2D binding ligands:

MICAMICBULBPs 1-6

NKG2D can bind to any of eight naturally occurring ligands known to be overexpressed in more than 80% of solid and hematological tumors

NKG2D expresses ligands in broad range of cancer indications

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Expression of at least one of NKG2D ligands:

• Triple negative breast cancers : 88%

• Colorectal cancers : 88%

• Ovarian cancers: 68%

• Bladder cancers: 78% of the primary tumors and 100% of the metastases

• Pancreatic cancers: 86%

• NSCLC Lung cancers: 92% (100% non-squamous NSCLC)

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Less controlled In Vivo Expansion with potential for serious adverse events

Cla

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igm Controlled dosing and PK

to reduce adverse events and increase Effectiveness

CYAD-01 : A novel paradigm to CAR-TThe next frontier of cell therapy

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Multiple MOA for increased effectiveness

Persistence of CAR-T leading to the need to have control mechanisms

Managing kinetics through

classical multiple infusion approach

Primary modes of action through direct cytotoxicity

Multiple modes of action for increased effectiveness

Rapid clinical response but some relapse including Antigen Loss Variants

Induced adaptative immunity driving a progressive clinical

response

CYAD-01 Modes of action identified from syngeneic mouse models

• Eradication of established tumors by multiple infusions of CYAD-01 with no pre-conditioning chemotherapy

• Short term persistence (7-10 days)

• Direct target cell killing

• Modulation of the local tumor microenvironment

• Reduced number of Tregs within tumor

• Alteration of myeloid compartment; reduced IL-6/IL-10

• Anti-angiogeneic effect driven through targeting of tumorendothelial cells expressing NKG2D ligands

• Identification of CD8+ and CD4+ T-cell responses induced by CYAD-01 therapy that drive prolonged anti-tumor immunity

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CYAD-01 Syngeneic Models

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MULTIPLE MYELOMALEUKEMIA

1. Barber, A. et al., J. Immunol (2009) 183(4):2365-72 2. Barber, A. et al., J. Immunol (2009) 183(11):6939-47 3. Barber, A. et al., J. Immunol (2008) 180(1):72-8 4. Barber A. et al.,Exp. Hematol. (2008) 36(10):1318-28

OVARIAN CANCER

Multiple dosingNo pre-conditioning

CYAD-01: Mediate cytotoxicity and cytokine release during challenge with tumor cells

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Demoulin et al. Future Oncology 2017

CYAD-01: Cell activity in vivo activity against established Panc-1 tumor cells

12Demoulin et al. Future Oncology 2017

In vitro potency of CYAD-01

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Cytotoxicity

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

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(%

)

Cytotoxicity mediated by CYAD-01

CAR-T cells produced under GMP

compliant conditions Kinetics of killing of pancreatic tumor

cells by CYAD-01 CAR-T cells

CYAD-01 autologous clinical program includes various studies

2016 2017 2018 2019 2020

THINK Study

CM-CS-1 StudyOpen-label dose escalation Phase I studySingle IV administration of CYAD-01AML and MM relapsing post standard of care

Open-label dose escalation Phase I studyMultiple IV administrations of CYAD-01 as stand alone according specific product profile7 different cancer indications

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CYAD-01: Clinical development plan

• 3 administrations• Optimal dose• Hematological & solid

tumors• No Lymphodepletion

CAR-T NKG2DTHINK Phase 1 trial

CAR-T NKG2DPhase 1 safety trial

• 1 administration• Low dose• Hematological tumors• No Lymphodepletion

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A multinational (EU/US), open-label, dose escalation Phase 1 study to assess the safety and clinical activity of multiple administrations of CAR-T NKG2D

THINK

CYAD-01: Phase I safety trial successfully completed

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CAR-T NKG2D Phase I Safety trial

▪ 1 administration▪ Low dose▪ Hematological tumors

2015 2016 • Single administration, dose-escalation Phase I autologous CAR-T NKG2D study in patients with Acute Myeloid Leukemia and Multiple Myeloma Dana Farber, last patient included in September 2016.

• Strong safety profile, including no cell-related neurotoxicity, auto-immunity, or CAR-T related death.

• Unexpected signs of activity 4 patients showing unexpected benefit. 1 AML patient showed stabilization of hematological parameters at 6 months.

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N=

3x106 CAR-T NKG2D Cells

1x107 CAR-T NKG2D Cells

1x106 CAR-T NKG2D Cells

3

3

3

Cohort 1

Cohort 2

Cohort 3

Cohort 4

N= 12

3x107 CAR-T NKG2D Cells

CYAD-01: THINK trial study design targeting seven refractory cancers

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3x108 1x109 3x109

All solid tumor types

3 3 3

3x108 1x109 3x109

All hematological tumor types

3 3 3

Phase I dose escalation segment

Recommended dose

Recommended dose

Solid

tum

ors

Bladder

TN Breast

Colorectal

Ovarian

Pancreatic

He

ma

tolo

gic

al

tum

ors

AML/MDS

MM

Phase I dose expansion segment

CYAD-01: THINK trial (solid arm) promising early results at first dose level

Promising early results at first dose level (3x108)

• Two metastatic colorectal cancer patients reported as Stable Disease at 3-months follow-up*

• Refractory pancreatic patient was in progression at the same time point• No toxicity signals reported up to now

Higher doses, longer follow-up + SHRINK and LINK

* According to recent studies conducted on similar patient populations, median progression free survival in these patients understandard of care is between 1.9 and 3.2 months.

Sources: Patients With Metastatic Colorectal Cancer Treated With Regorafenib or Placebo After Failure of Standard Therapy (CORRECT), Grothey A., Lancet Oncol. 2015 Aug;16(8):937-48 ; Asian Subjects With Metastatic Colorectal Cancer Treated With Regorafenib or Placebo After Failure of Standard Therapy (CONCUR), Li J., Lancet Oncol. 2015 Jun;16(6):619-29

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CYAD-01 autologous clinical program includes various studies

THINK Study

CM-CS-1 Study

SHRINK Study

LINK Study

SIBLINK Study

Open-label dose escalation Phase I studyMultiple hepatic transarterial administrationsUnresectable liver metastases from colorectal cancer

Open-label dose escalation Phase I studyMultiple IV administrations of CYAD-01, combined with FOLFOX Potentially resectable liver metastases from colorectal cancer

Open-label dose escalation Phase I studyMultiple IV administration of SIBLING CYAD-01AML relapsing post allo-HCT

Open-label dose escalation Phase I studySingle IV administration of CYAD-01AML and MM relapsing post standard of care

Open-label dose escalation Phase I studyMultiple IV administrations of CYAD-01 as stand alone according specific product profile7 different cancer indications

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2017 and 2018 clinical milestones

Q1 2017 Q2 2017 Q3 2017 Q4 2017 H1 2018 H2 2018

THINK

SOLID

• EnrollmentDose 1 Completed

• Reporting Dose 1

• CompletionenrollmentDose 2

• Reporting Dose 2

• CompletionenrollmentDose 3

• Start Expansion Segment

• ReportingDose 3

• EnrollmentExpansion Segment Completed

• Topline Data

• PFS 6-Month Data

HEMATO

• 1st Patient EU

• CompletionenrollmentDose 1

• Reporting Dose 1

• CompletionenrollmentDose 2

• Reporting Dose 2 & 3

• CompletionenrollmentDose 3

• Start Phase I Expansion Segment

• Top line data Expansion Segment

• PFS 6-Month Data

Q1 2017 Q2 2017 Q3 2017 Q4 2017 H1 2018 H2 2018

SHRINKInitiate Study Topline Data PFS 6-Month

Data

LINKInitiate Study Topline Data PFS 6-Month

Data

SIBLINKInitiate Study Topline Data

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2017 and 2018 clinical milestones

Intellectual Property – Overview

Three patent families covering autologous products pipeline

• CYAD-01 (CAR-T NKG2D): two granted US patents, covering chimeric NK cell receptor CAR-Ts

• CAR-T B7H6: pending applications in US, Europe, China and Japan on B7-H6 CAR-Ts B7-H6 is a ligand of the NKp30 receptor

• CAR-T NKp30: pending US application on chimeric NKp30 receptor CAR-Ts

One patent family covering allogeneic platform (see next slide)

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Intellectual Property – Allogeneic platform

One patent family covering allogeneic platform:

• Three granted US patents, covering TCR-deficient T-cells, methods of producing them, and methods to use them to treat cancer

• >10 applications pending in different jurisdictions

• Allogeneic patent provides fundamental exclusivity in the field of CAR-T cells that are TCR-deficient, regardless of method used to inhibit TCR

Opportunity for licensing (e.g. Novartis)

• Can be combined with autologous pipeline

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Financial snapshot

Cash Position:

• €69million as of June 30, 2017

• Enabling company’s activities through 2019

Ticker: Nasdaq (CYAD), Euronext Paris & Euronext Brussels (CYAD.BB)

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Academic partnerships

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• CAR-T platform developed by Celyad was invented by Prof. Charles Sentman at Dartmouth College and is exclusively licensed to Celyad

• Ongoing research collaboration with Prof Sentman and his team

• Institut Curie is a world class research institution focusing on cancer and immunity, and positioning translational science at the heart of its approach

• March 2016: Celyad entered into a 3 year collaboration with Institut Curie

• Collaboration with Professor Sebastian Amigorena to dissect the molecular interactions of the NKR2 chimeric antigen receptor with individual NKG2D ligands to better understand NKR2 CAR-T cell responses generated upon successful target binding

• Collaboration with Dr Franck Perez concerning methods to facilitate targeting of NK receptor ligands including the B7H6 target

Corporate partnerships

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• ONO is a leader in cancer-immunotherapy in Japan with the first approved checkpoint inhibitors, OPVIDO©

• July 11th 2016: Celyad grants exclusive license to ONO for the development and commercialization of allogeneic CYAD-01 T-cell immunotherapy in Japan, Taiwan and Korea (=10% of the worldwide pharmaceutical market)

• License in exchange for $12.5M upfront, $300M inpotential milestones and double-digit royalties

• Novartis is a global healthcare company based in Switzerland that provides solutions to address the evolving needs of patients worldwide

• May 2nd, 2017: Celyad grants to Novartis a non-exclusive license for its allogeneic TCR-deficientCAR-T cells patents

• Deal value: $96 million. Celyad to receive upfront, development and commercial milestones payments and single digit royalties

• Celyad retains all rights to grant further licenses to third parties for the use of allogeneic CAR-T cells. Deal can be turned into exclusive license

Management team

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1. Christian Homsy, CEO2. Patrick Jeanmart, CFO3. Jean-Pierre Latere, COO4. Frédéric Lehmann, VP Clinical Development & Medical Affairs5. David Gilham, VP R&D6. Georges Rawadi, VP Business Development & IP7. Philippe Dechamps, Chief Legal Officer8. Philippe Nobels, Global Head Of Human Resources

Celyad ADR programme

Celyad ADRs trade on NASDAQ

• Symbol CYAD

• Cusip 151205000

• Ratio 1 ORD:1 ADR

• DR ISIN US151205200

• ORD ISIN BE0974260896

• Depositary Citibank

Benefits of ADRs to US investors

• Clear and settle according to US standards.

• Offer the convenience of stock quotes and dividend payments in US dollars.

• Can be purchased/sold in the same way as other US stocks via a US broker.

• Provide a cost-effective means of international portfolio diversification .

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For questions about creating Celyad ADRs, please contact Citi:

New YorkMichael O’Leary

michael.oleary@citi.com+1 212 734 4483

London Mike Woods

michael.woods@citi.com+44 20 7500 20

Thank you

BELGIUMCelyad SAAxis Business ParkRue Edouard Belin, 2B-1435 Mont-Saint-Guibert+32(0) 10 39 41 00

USACelyad Inc.Seaport East 2 Seaport LaneBoston, MA. 02210+1 857-990-6900

www.celyad.com

Contact: investors@celyad.com