Building aGlobal Leader in

Orphan Oncology

May 2017

Euronext ParisNasdaq Copenhagen

Ticker ONXEO

2

Important Information

This presentation has been prepared for information and background purposes only and the information contained herein (unless otherwise indicated)has been solely provided by Onxeo (the “Company”). This presentation does not constitute an offer of securities, a prospectus or an offeringmemorandum in whole or in part, and does not contain comprehensive or complete information about the Company, which can be found elsewhere asdescribed below.The information and opinions contained in this document have not been subject to independent verification and are qualified in their entirety by thebusiness, financial and other information that the Company is required to publish in accordance with the rules, regulations and practices applicable tocompanies listed on Euronext Paris, including in particular the risk factors and other information in the Company’s Document de référence (RegistrationDocument) registered by the French Autorité des marchés financiers (Financial Markets Authority) (the “AMF”) on April 29, 2016 under no. D.16-0452,and available in both French and English language versions on the Company’s website, and in any other periodic report, all of which are available free ofcharge on the Company’s website (www.onxeo.com) (the “Exchange Information”).All information (including on markets) not separately sourced is based, in whole or in part, on internal Company data and estimates, and is provided asof the date of this presentation only, and is subject to change without notice.No representation, warranty or undertaking, express or implied, is made by the Company or any other person as to the accuracy, completeness orappropriateness of the information and opinions contained in this document. The Company, its subsidiaries, its advisors and representatives accept noresponsibility for and shall not, under any circumstance, be held liable for any loss or damage that may arise from the use of this document or theinformation or opinions contained in it. In particular, this document contains information on the use of the Company’s products and its competitiveposition. This information has been drawn from various sources or from the Company’s own estimates which may not be accurate and thus no relianceshould be placed on such information. Any prospective investors must make their own investigation and assessments and consult with their ownadvisers concerning any evaluation of the Company and its prospects, and this document, or any part of it, may not form the basis of or be relied on inconnection with any investment decision.All statements in this presentation other than statements of historical fact are or may be deemed to be forward-looking statements. These forwardlooking statements can be identified by the use of forward looking terminology, including the terms “development”, “estimates”, “expects”, “intends”,“may”, “planned”, “will”, “milestones”, “move to”, “on track”, “potential”, “targeting”, “time to market”, “value”, or other variations or comparableterminology, or by discussions of strategy, plans, objectives, goals, future events or intentions. These forward-looking statements relate to theCompany's future prospects, developments, marketing strategy and funding, as well as the Company’s technology, and are based on financial and non-financial information, including projections as to the future regulatory situation and other information and assumptions. They are subject to variousrisks and uncertainties, including those described in the Exchange Information.Forward-looking statements are not guarantees of future performance and the Company’s actual financial position, results and cash flow, regulatorysituation, as well as the trends in the sector in which the Company operates, may differ materially from those reflected in the forward-lookingstatements. The Company does not undertake any obligation to update any forward-looking statements or any other information in this presentation.

May 2017

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A publicly-traded biotech company specialized in orphan oncology

Developing innovative drugs to address unmet medical needs in Oncology

Based in Paris, Copenhagen and New York; listed on Euronext (Paris) and Nasdaq (Copenhagen)

A solid, diversified and well-balanced pipeline

Livatag®: Currently in Phase III for Hepatocellular Carcinoma (HCC)

Beleodaq®: Marketed in the US by Spectrum for 2nd line Peripheral T-Cell Lymphoma (PTCL)

AsiDNA™: 1st-in-class DNA Repair Signal Interfering with compelling Phase I data

…with significant sales potential

Livatag®: Potential Sales € 800 M (1)

Beleodaq®: Market Size from € 7.9 B in 2016 to € 19.3 B in 2025 (2)

AsiDNA™: Market Size to exceed € 2.1 B by 2025 just for the first pre-identified indication(3)

... and potentially value-creating near & mid-term milestones

Solid cash position to support currently planned operations until early 2018

Investment Thesis

(1) Internal estimate for HCC 1st line and 2nd line indications(2) Source GlobalData &Navigant for NSCLC +SCCHN+ PTCL indications(3) SourceGlobaData for TNBC indication

May 2017

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Onxeo’s laser-focused strategy

Crafting a solid and diversified orphan oncology pipeline

Capitalizing on preferred regulatory pathways (ODD, Fast Track…)

Currently 3 products with 3 different technologies

Balancing the development risk with products at diverse clinical stages (Ph. I to Ph. III)

Securing breakthrough technologies & products through focused M&A strategy:

Topotarget acquisition in 2014

DNA Therapeutics acquisition in 2016

Bring innovation to orphan oncology patients

Create shareholder value througha proven business model

Proven ability to identify and integrate promising pre-clinical technologies / products

Develop products into clinical up to inflexion points, attractive for partnering by Pharmaceutical key players

May 2017

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Onxeo’s key differentiating features

The product opportunities

A rich product pipeline generating multiple near / mid-term catalysts:

Candidates range from preclinical to advanced clinical stages (Phase III)

New ASiDNA™, 1st in-class Signal Interfering DNA (SiDNA) repair platform in clinic

New oral form under development for Beleodaq®

Innovative compounds totalling > several € B sales potential

Global reach and in-depth experience

3 products already approved by FDA and/or EMA

Unparalleled skills from preclinical & CMC to Phase II / Proof of Concept

A Board of Directors and Executive Team with deep US expertise – A network of prominent Scientific Advisors

May 2017

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Management team

International team of 50+ employees with deep expertise in strategy, finance and drug development, from preclinical to registration

Judith Greciet, CEO(formerly Pharmacia, Wyeth, Eisai)

Françoise Bono, CSO(Sanofi, Evotec)

Olivier de Beaumont, CMO(Stallergenes Greer, Quintiles, Aventis)

Nicolas Fellman, CFO(Pfizer, Ernst & Young)

Philippe Maitre, EVP US, Corp. Dev(Aventis, PPD, mAbRx)

Experienced and International Leadership Team

Board of directors

Joseph Zakrzewski, Chairman

Judith Greciet, CEO

Financière de la Montagne (represented by Nicolas Trebouta)

Elvira Sanz

Danièle Guyot-Caparros

Christine Garnier

Thomas Hofstaetter

Jean-Pierre Kinet

Jean-Pierre Bizzari

May 2017

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A diversified and well-balanced portfolio in orphan oncology

May 2017

Livatag® Update

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Livatag® mechanism of action optimal for liver cancer

Nanoparticle formulation of doxorubicin

Proprietary Transdrug™ nanotechnology platform

Nanoformulation designed to evade tumor cell resistance mediated by Multi Drug Resistance (MDR) efflux pumps

– Up to 12-fold increased exposure to liver tumor cells compared to doxorubicin

Mechanism of action

Absorption to the cell surface

Release of doxorubicin close to the cell membrane as ion pair doxo/PEBCA(*)

Ion pair protects doxorubicin - reduced drug efflux through MDR-related protein

Increased nuclear delivery of free doxorubicin with subsequent cytotoxic effect

(*) PEBCA polymer = Poly-Ethyl-Butyl-CyanoacrylateMay 2017

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Designed to confirm promising Phase II efficacy results

n=28 Patients with unresectable HCC

Multicenter, controlled and randomized trial; up to 3 injections per week over 4 weeks

Median survival of 31.7 months vs. 15 months for patients on TACE (p < 0.05)

Acute respiratory adverse events leading to study termination and change of administration scheme in phase III

Phase III Study to assess efficacy (OS) and safety of Livatag® (20 and 30mg/m² - slow IV) vs Best Standard of Care after failure or intolerance to sorafenib

A favorable safety profile confirmed by Data Safety Monitoring Board (DSMB) reviews

9 consecutive DSMB reviews: positive recommendations to continue study w/o modification

No apparent pulmonary toxicity after close to 1000 infusions, no unexpected AE.

Livatag® “ReLive” Phase III Pivotal Study on track to confirm efficacy

May 2017

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Livatag: ReLive Phase III Study - design

PHASE III

Randomized, comparative, 3 arms

390 patients (>= 18 years old)

11 countriesEU, US, MENA

70 active centers

6-hour IV infusion -20 mg/m²

n =130Best standard of care

n =130 <4 weeks>

n =130

< 4 weeks>

Preliminary resultsoverall survival

after 285 events

6-hour IV infusion - 30 mg/m²

< 4 weeks> < 4 weeks>< 4 weeks> … up to progression

< 4 weeks> < 4 weeks>< 4 weeks>

End of randomization

Jan, 2017Mid-17

TARGET POPULATION

2nd line or more advanced HCC having progressed or intolerant to sorafenib, stage BCLC B or C with a Child-Pugh score from A5 to B7

ENDPOINTSPrimary endpoint: Overall Survival

Secondary endpoints: Progression Free Survival, Objective Response Rate, Optimal dose, Safety, PK, Predictive factors of safety and efficacy, Quality of life

… up to progression

May 2017

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In the large but under-served HCC market

Only one product approved (Sorafenib) in first line HCC

Estimated incidence of 120,000 eligible patients (US + Europe); 480,000 patients WW

Sales estimates around €220m for 2nd line in Europe/US

Livatag full potential sales (WW - HCC all lines) estimated around €800m(1)

Company will initiate Licensing discussions after Phase III results

Exploration of Livatag full potential for HCC …… and beyond HCC (other solid tumors)

Targeting HCC 1st-line in combination with TKI’s

For other type of tumors:

– Preclinical combination studies with cytotoxics, targeted therapies and immunotherapies ongoing

– Supra-additive efficacy already demonstrated in combination with immuno-oncology agents in HCC and pancreas models

Livatag ®, a potential blockbuster

(1) internal estimateMay 2017

belinostat / Beleodaq®Update

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Beleodaq® (IV belinostat) approved as 2nd line treatment for PTCL

Peripheral T-cell lymphoma (PTCL) (1)

Subtype of non-Hodgkin’s lymphoma (NHL) which affects T-cells

Worldwide incidence = 38,000 to 58,000 cases (10-15% of NHL cases) / 17,000 to 27,000 incident cases in key pharmaceutical markets (US + EU28 + Japan + China)

FDA conditional approval in 2nd line PTCL following successful Phase II (Belief Study: n = 129)(2)

25.8 % ORR (CR&PR) - Median DoR of 13.6 months by IWG criteria (to disease progression)

Low incidence of Grade 3-4 hematologic toxicities (thrombocytopenia 7%; neutropenia 6.2%; anemia 10.9%)

Phase I Bel-CHOP combination performed to assess MTD and safety profile (n=23) in 1st Line PTCL

Belinostat MTD is 1000mg/m2 days 1-5 every 3 weeks + CHOP = approved doses

ORR 86%; CR 67% (CR CHOP ~50%), PR 19%

Phase III synopsis in PTCL 1st line under preparation with Spectrum Pharma

(1) International Peripheral T-Cell and Natural Killer/T-Cell Lymphoma Study , (J Clin Oncol 26 :4124-4130) and GLOBOCAN 2012, IARC data.

(2) Lee et al (FDA approval) Clin. Cancer Res. March 2015.May 2017

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belinostat (Beleodaq®), an HDAC inhibitor dedicated to improve immune response against solid tumors

A dedicated-target product profile

belinostat is an HDAC class 1 inhibitor with an HDAC6 component

Oral formulation of belinostat displays good bioavailability, very good tolerance and short half-life compatible with combination with immune check point therapies

An anticipated broad potential mechanism of action on tumor immune response

Strong potential for combination with anti-cancer immunotherapies

First positive data in immuno-competent mouse syngeneic model of Beleodaq® + CTLA4 Ab

May 2017

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belinostat / Beleodaq®: Build value potential beyond PTCL

Expand PTCL beyond the US (Europe – South America - ….)

Today’s sales limited to US Market (Last 12-month sales around $14.0M)

Expansion to South America through licensing agreement with Pint Pharma

Patient early access programs under consideration for Europe (PTCL)

Development of an oral formulation of Beleodaq® to expand product potential in particular for combination with immune checkpoint therapies

An important step providing opportunities for new indications & extended patent protection

Exploratory preclinical research program in combination with Immuno-Oncology agents

Follow-up studies ongoing to assess combination interest in various tumors, to enter clinic by year-end

Full market potential (IV and Oral forms combined): from € 7.9 B in 2016 to € 19.3 B in 2025 (1)

(1) Source GlobalData and Navigant for NSCLC +SCCHN+ PTCL indications

May 2017

AsiDNATM

An Innovative Concept Leadingto a First-in-Class Product

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AsiDNATM concept: leading tumor cells to death through the blinding of the DNA repair system

1

2

3Multiple DNA repair pathways are activated in cancer cells via the recruitment of several enzymes allowing them to repair efficiently damaged DNA and escape cell death

AsiDNA mimics DNA breaks into the cells and activates DNA damage signaling enzymes, thus inducing a “false” damage signal that prevents the repair enzymes from being recruited at the site where they should act to repair the damage on the tumor cell’s chromosomes

Cancer cells are no longer able to continue dividing with damaged DNA, resulting in cell death

Why DNA repair inhibition?• Many cancer treatments rely on DNA damaging agents

• Tumor cells survive genotoxic treatment by repairing DNA damage

• DNA repair is a main mechanism of resistance to radiotherapy and chemotherapy for advanced stagetumors (exposition to DNA damage and replication accidents that need to be repaired)

May 2017

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5’

3’

3’

5’

1. Quanz M, et al. PLoS ONE. 2009 4(7), doi: 10.1371/journal.pone.0006298 2. Berthault N, et al. Cancer Gene Therapy (2011), 1-12, doi: 10.1038/cgt.2011.3

AsiDNA™ - A first-in-class molecule

Double-stranded 32 bp DNA is tethered with a loop to prevent disassociation1

Phosphorothioate substitutions at the 5’ and 3’ ends to prevent degradation1

Efficient nuclear uptake of the DNA is mediated via a covalently linked cholesterol molecule2

32 bp DNA duplex with a 5´-Chol-TEG & a non-nucleotidic loop - Protected from disassociation and degradation and designed for optimal cellular uptake

Cholesterol - Vector that promotes cellular uptake

Loop- Coupling Agent

Active 32 bp DNA duplex

AsiDNA – First lead of a new class of DNA repair inhibitors

Binds and activates DNA-PK and PARP signaling enzymes

Sequence not specific, chosen to be non-homologous

Genomic DNA length optimized

May 2017

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Synergistic effect of AsiDNA™ combined with various PARP inhibitors including oloparib(2)

Increased unrepaired DNA break sites, DNA damages and cell lethality in 21 different tumor cell lines including BRCA mutated

No lethality observed in healthy cells

Strong indication that drug resistance to the combination would be a very rare event

Preclinical in vivo efficacy of AsiDNA™ vs. PARP inhibitors in mouse triple negative breast cancer model(1) : potential as monotherapy in genetically unstable tumors

(1) Article under finalization: “ Predictive Biomarkers to AsiDNA”. (2) Jdey W, et al. Clin Can Res. 2016;22:DOI: 10.1158/1078-0432.CCR-16-1193.

AsiDNA™- Solid synergy in combination with PARP inhibitors

May 2017

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AsiDNA™- First clinical outcome and development strategy

DRIIM phase I (2015)(1)

23 metastatic melanoma patients, 12 centers in France

AsiDNA™ in combination with radiotherapy, (3 doses/week for 2 weeks, Intra-Tumoral admin.)

Good tolerance, strong immune tolerance and no evidence of inflammatory phenomena

ORR = 59%; CR = 30%; PR = 29% ( CR rate from low-dose radiotherapy alone less than 10% (Konefal et al, 1987; Olivier et al, 2007)

Strong evidence supporting activity by systemic administration

Preclinical animal models

Observations from DRIIM Phase I

Mechanistic and predictive biomarkers available to support clinical development

Next step to demonstrate potential when dosed via intravenous route

Phase I in mono and combination in preparation (2017)

Broad spectrum of potential indications. Market Size for TNBC from € 0.8 B in 2016 to

€2.1 B by 2025 (2)

(1) Le Tourneau C, et al. BJC. 2016;1-7; doi:10.1038/bjc.2016.120.(2): Source GlobalData

May 2017

IP & Financial Position

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Solid IP protection(*) for all products in the pipeline

Livatag®

Composition patent through 2019 with additional patents through 2032

New patent filing on composition potentially protecting Livatag® WW until 2036

Orphan status in both Europe and US; Fast Track designation in US

Beleodaq®

Drug substance patent until 2021, drug product patent until 2027 (2026 o/US)

Orphan status in both EU & US - accelerated FDA approval July 2014for 2nd line PTCL

AsiDNA™

Proprietary technology (Method of Use) patent until 2024

Drug product and related compounds protected until 2031

(*) Not including potential supplementary protection certificate (SPC) or patent term extension (PTE).

May 2017

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Shareholder structure and financial profile

Shareholder structure (as of Oct. 5, 2016)(1)

Key statistics(1):

Dual listing Paris/Copenhagen (ticker ONXEO)

47M shares outstanding

Market capitalization : ± €120M

3.9% of shares owned by BoD, Management & Staff (on a fully diluted basis excluding Financière de la Montagne)(2)

Cash position on 12/31/2016: €29,2M (incl. gross proceeds from Sept. 2016 private placement)

Cash to early 2018

(1) At closing of the €12.5M Capital Increase (2) 3.9% represents shares held by top management, board of directors (excluding Financière de la Montagne),

executive committee and shares resulting from stock options, free shares and warrants granted to Onxeo staff.

May 2017

Upcoming Milestones

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Significant near & mid-term newsflow

Livatag®

ReLive Phase III trial preliminary results

Beleodaq® Oral

Oral formulation preclinical results

mono

Beleodaq® Oral

Oral formulation preclinical results

combo

H1 2017 H2 2017

Beleodaq® Oral

Phase I/II initiation

AsiDNA™

Preclinical PoCof IV activity

AsiDNA™

Phase I Initiation (Systemic administration)

AsiDNA™

Phase I Results

H2 2018H1 2018

May 2017

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A differentiated biotech company in orphan oncology

A strong & diversified

product portfolioTargeting significant

unmet medical needs

Multi-billion market potential

A proactive, experienced global team

May 2017

Contacts:Judith Greciet – CEONicolas Fellmann – CFOTel: +33 1 45 58 76 00 - contact@onxeo.com

Company Information:www.onxeo.com