Jefferies Global Healthcare Conference June 3, 2014

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Special Note Regarding Forward-Looking Statements This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this presentation that do not relate to matters of historical fact should be considered forward-looking statements, including statements regarding our expectations regarding the approval of products; expectations regarding development programs, trials, studies, approvals and commercialization; the sufficiency of financial resources; expected future cash balance and liquidity; expectations regarding in-license initiatives, collaborations and partnerships; and expectations regarding the Company’s plans and opportunities.

These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our limited operating history and expectations of losses for the foreseeable future; our lack of commercial sales; our failure to obtain any necessary additional financing; our substantial dependence on the success of certain of our lead product candidates, AT-001, AT-002, AT-003, AT-004, AT-005, AT-006, AT-007 and AT-008; our inability to identify, license, develop and commercialize additional product candidates; our inability to obtain regulatory approval for our existing or future product candidates; the lack of commercial success of our current or future product candidates; uncertainties regarding the outcomes of studies regarding our products; our inability to realize all of the anticipated benefits of our acquisitions of Vet Therapeutics and Okapi Sciences; effects of competition; our failure to attract and keep senior management and key scientific personnel; our complete reliance on third-party manufacturers and third parties to conduct all our target animal studies and certain other development efforts; our lack of a sales organization; our significant costs of operating as a public company; our lack of effective internal control over financial reporting; changes in distribution channels for pet therapeutics; consolidation of our customers; impacts of generic products; unanticipated safety or efficacy concerns; our limited patents and patent rights; our failure to comply with our intellectual property license obligations; our infringement of third party patents and challenges to our patents or rights; our failure to comply with regulatory requirements; our failure to report adverse medical events related to our products; legislative or regulatory changes; the volatility of our stock price; our status as an “emerging growth company,” as defined in the JOBS Act; the potential for dilution if we sell shares of our common stock in future financings; the significant control over our business by our principal stockholders and management; the potential that a significant portion of our total outstanding shares could be sold into the market in the near future; effects of anti-takeover provisions in our charter documents and under Delaware law; and our intention not to pay dividends. These and other important factors discussed under the caption "Risk Factors" in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission, or SEC, on March 26, 2014, along with our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this presentation. Any such forward-looking statements represent management's estimates as of the date of this presentation. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this presentation.

Safe Harbor Statement

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Investment Highlights

Large, growing market

De-risked drug development

Private-pay

Portfolio approach

Scalable and capital-efficient

Pure-play, first mover

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Source: APPA.

Our Market

Large and growing

– 2014E U.S. pet spend of $59B

Insensitive to recent recessions

68% of U.S. households

– 96M cats

– 83M dogs

Medicalization drives growth

– Historically, limited innovation

– Pet therapeutics underrepresented

U.S. Pet Owners Spend ($Billions)

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The Evolution of Pet Ownership

“Snoopy Generation” “Brian Generation”

Pets are family whose medical needs merit quality care

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A Favorable Comparison

Multiple Species Steps Direct to Species

~$1.3B ~$10M

~10 Years ~5 Years

Third Party Payer Private Pay

Generic Pressure Innovator Brand Loyalty

Difficult & Indirect Accessible & Direct

Pets Humans

De

velo

pm

en

t C

om

me

rcia

l

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Product Development at the FDA YR1 YR2 YR3 YR4 YR5 YR6 YR7 YR8 YR9 YR10 YR11 YR12 YR13

Pet

s H

um

ans

Proof of Concept in Lab Animals

Animal Toxicology SAR Chemistry, Selection of Lead

Animal pK

In vitro Toxicology

Chemistry Optimization

IND Filing

Human Clinical Studies

Phase I

Phase II

Final Formulation

Phase III

NDA

Proof of Concept in Dogs/Cats

pK in Dogs/Cats

API and Formulation Development

Dose Selection

Probe Safety in Dogs/Cats

Final Formulation

Field Studies

NADA EU Approval

De-Risking

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FDA and USDA Timelines FDA Center for Veterinary Medicine

Proof of Concept

INAD

Chemistry, Mfg. & Controls (CMC)

Safety

Effectiveness

Labeling, FOI Summary, Other

Administrative NADA

Year 5Year 1 Year 2 Year 3 Year 4

USDA - Center for Veterinary Biologics

Proof of Concept

Manufacturing

File for Product License

Preclinical

Field Safety and Efficacy

Conditional Product License*

Extended Field Safety and Efficacy Study

Full Product License* Conditional l i censes granted under specia l ci rcumstances

Year 5Year 1 Year 2 Year 3 Year 4

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Alignment with the Veterinarian

Annual Exams 17%

Diagnostics 17%

Surgery 17% Non-Invasive

Procedures 9%

Pet Food Sales 4%

Heartworm Product Sales

6%

Flea-Tick Product Sales

6%

Vaccinations 15%

Source: DVM Newsmagazine’s State of the Profession Report 2012.

Innovation is valued and desired

Medicines are high margin to practice

Facing pressure from alternative channels

Other Pharma 9%

Practice Revenue Mix

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Building the Portfolio

Toxicology data are available

Effectiveness data are available

Manufacturing is scaled-up

Defined and conserved biology

Key Attributes

Unmet medical need

High incidence or prevalence

Known mechanism of action

Nuance in science

“Early de-risking”

Early De-Risking

Leveraging the investment in human therapeutics Pharmaceuticals Biologics US and OUS

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Our Pipeline

Proof of Concept Pilot Pivotal / Commercial

AT-001 Cat Osteoarthritis

AT-002 Cat Appetite Stimulant

AT-004 Dog B-Cell Lymphoma

AT-009 Dog Mast Cell

AT-003 Dog Post-operative Pain

AT-005 Dog T-Cell Lymphoma

AT-010 Dog Atopic Dermatitis

AT-003 Cat Post-operative Pain

AT-001 Dog Osteoarthritis

AT-011 Dog Canine Parvovirus

AT-007 Cat Feline Immunodeficiency Virus

AT-002 Dog Appetite Stimulant

AT-012 Cat Feline Calicivirus

AT-008 Dog Lymphoma

AT-006 Cat Feline Herpesvirus

AT-015 Cat Lymphoma

AT-014 Dog Osteosarcoma

Option 2 Beta

Option Gamma Atopic Dermatitis

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Animal Health Landscape

Total number of NADAs NADAs for dogs / cats Pet therapeutic NCEs*

2011 12 6 2

2012 11 6 0

2013 6 4 2

* NCE defined as new chemical entity not previously approved in humans or animals (excluding parasite drugs).

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Major News Flow 2014

Conditional license for AT-005

Initiate AT-002 Dog US pivotal field effectiveness study

Complete enrollment for full license AT-005

Full license for AT-004

Option program decisions

Commercial introduction

Initiate AT-003 Dog US pivotal field effectiveness study

Results of AT-001 Dog US pivotal field effectiveness study

Enroll AT-002 Dog US pivotal field effectiveness study

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Top Cancer Treatment States

Board Certified Veterinary Oncologists

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Lymphoma Opportunity

Conditional license granted from USDA for canine lymphoma products

Additional clinical trials being planned for canine lymphoma

During 2014, we will continue to build our internal commercial capabilities focused on developing the lymphoma market

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Robust Patent Portfolio Small Molecules

Focus on patent-protected innovation

Robust patent portfolio

22 granted & 5 pending US patents licensed

4 Antiviral patents licensed from KU Leuven

– 4 additional patent applications

Foreign counterparts filed in major markets

Human pharmaceutical patents

– Composition of matter

– Manufacturing

– Formulation

– Use

Pursuing additional pet therapeutic patents

Biologics

Speciesization of mAbs

– Counterparts in major markets (expiration 2029)

• Claims directed to heterochimeric mAb

• Covers all VX products

– Dependent claims directed to both CD52 & CD20 mAbs

– Divisional directed to methods of treatment, continuation directed to novel CD20 antigen

mAb Constant Domain Regions

‒ Counterparts in major markets (expiration 2030)

‒ Covers all VX products, including CD52 and CD20 mAbs

mAbs Directed to CD20 (at least 2031)

mAbs Directed to CD52 (at least 2031)

Unpublished applications directed to mAbs against other targets of interest

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Our Financial Profile

March 31, 2014 cash balance $79.9M for ongoing operations ₋ All acquisition contingent consideration have been paid

Net Loss for 1st Quarter 2014 was ($9.2M) or ($0.34)/per share – Includes full consolidation of Vet Therapeutics and Okapi Sciences

R&D investment will increase as a result of advancing our deep pipeline

Continue to identify non-dilutive sources of capital ‒ Partnering opportunities globally

‒ Out-licensing of non-core products

‒ Debt instruments

Sufficiently funded through 2015

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Investment Highlights

Large, growing market

De-risked drug development

Private-pay

Portfolio approach

Scalable and capital-efficient

Pure-play, first mover

Product Detail

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AT-001 for Osteoarthritis Pain

Medical Need

Established market (U.S. sales $260M, mostly NSAIDs for dogs)

Existing NSAID products have side effects and require monitoring

Safer product for pain and inflammation of osteoarthritis

Our Solution

EP4 receptor antagonist (a novel mechanism)

‒ Potential for significantly improved safety profile vs. Coxibs

Pilot field study completed in 2013

Pivotal field studies were initiated in 2014, with FDA approval expected in 2016

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AT-001 Biology

Phospholipids

Arachidonic Acid

Cyclooxygenase (COX)-2

PGE 2(House keeping)

TXA 2 PGI 2

NSAIDs

• GI mucosa

protection

• Platelet

aggregation

• Renal function

regulation

EP2 EP3

Cyclooxygenase (COX)-1

EP1

PGE 2(Inflammatory)

• Pain and Inflammation

EP4 ReceptorOther EP Receptors

COXIBsAT-001 EP4 Receptor

Antagonist

EP4 Receptor • Pain and Inflammation

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AT-002 for Inappetence

Medical Need

No currently approved product

Effective appetite stimulus to avoid feeding tubes and euthanasia

Seen in aging and chronic conditions

Our Solution

Mimics ghrelin (hunger hormone) to turn on appetite

Statistically significant results on increased appetite and weight gain in dog pilot study

Pivotal field study began in late 2013, with FDA approval expected in 2016

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AT-002 Biology

Brain

Pituitary gland

Stomach

Intestine

Ghrelin Ghrelin

Increases appetite

Promotes growth hormone secretion

Regulates energy metabolism

Stimulates production of lean body mass

AT-002 Ghrelin Agonist

Growth Hormone (GH)

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AT-003 for Post-Operative Pain

Medical Need

Pain increasingly recognized and treated

Need for long-acting, non-narcotic post-operative pain relief

Our Solution

Bupivacaine liposome injectable suspension

Pacira launched product for human use in early 2012

Pilot studies began in 2013, with NADA expected in 2016

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AT-003 Biology

Discrete chambers within a lipid matrix, each filled with bupivacaine liposome

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Pet Antibodies A proprietary platform

Pet specific antibodies with 85%+ pet sequences

Pet Fc region

Most effective IgG sequence

Straightforward engineering with no shuffling

IP protected

Mouse Pet Specific

Highly specific ‒ Developed against pet targets

Non immunogenic ‒ Compatible with pet immune

system

Highly potent ‒ Engages pet immune system

Cost effective ‒ High yield production

heavy chain

light chain

VH

VL CH1

CH2

CH3

CL

Proprietary Platform Pet Specific Antibodies

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Oncology Is Target-Rich

Chemotherapy Human Cancer Use Pet Cancer Use

Cyclophosphamide Lymphomas MM, solid tumors

Doxorubicin Lymphomas MM, solid tumors

Vincristine Lymphomas MM, solid tumors

Prednisone Lymphomas MM, solid tumors

L-asparaginase Leukemia, Lymphoma

Carboplatin Solid Tumors

Cis-platinum Sarcoma, Carcinoma, Lymphoma

Mitoxantrone Breast cancer, AML, Lymphomas

Lomustine Brain/CNS, Lymphoma, Mast cell

Methotrexate Lymphomas Osteosarcoma

Antibody Human Cancer Use Pet Cancer Use

Rituxan (CD20) Non-Hodgkin's Lymphoma X

Avastin (VEGF) Solid Tumors X

Erbitux (EGFR) Solid Tumors X

Herceptin (HER2) Breast Cancer X

Campath (CD52) Chronic Lymphocytic Leukemia X

Mylotarg (CD33) Acute Myeloid Leukemia X

Zevalin (CD20) Follicular Lymphoma X

Bexxar (CD20) Non-Hodgkin's Lymphoma X

Vectibix (EGFR) Solid Tumors X

TheraCIM (EGFR) Solid Tumors X

Human Chemo Market

Currently no protein market Immunogenicity Lack of efficacy

Human drugs migrate unchanged into veterinary practice

Human Cancer Antibody Market

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Canine Lymphoma Ideal for first antibody therapy

A canine-specific antibody therapy could achieve in dogs what Rituxan has done for human lymphoma

Lymphoma is most common blood cancer in dogs - 6% of total dog cancer

Lymphoma is the most treated cancer - Chemotherapy is the current “standard of care”

- Approximately 300,000 dogs are diagnosed per year in the U.S.

- Treatment cost ranges between $2,500 and $10,000

Clinical manifestations are similar to humans

Lymphocyte targeting has proven efficacious in pets

Hemangiosarcoma

Sarcoma

Lymphoma

Mast Cell

Skin

Bone Other

RITUXAN-LIKE APPROACH FOR DOG LYMPHOMA

Incidence

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Medical Need

Chemo achieves short remissions and has a very high relapse rate

Chemo is harsh on pets and burdensome on owners

Need effective and safe therapy to maintain remission as long as possible

Our Solution

First-in-class product

Effective and safe B-cell depletion

Aid in the treatment of canine B-cell lymphoma

USDA conditional license granted; expect full license in 2014

Market Potential

Approximately 300,000 dogs are diagnosed per year in the U.S.

Canine lymphoma is treated with chemotherapy (like in humans)

Cost to pet owners of lymphoma treatment: ~$5,000

AT-004 Canine-specific antibody for B-cell lymphoma

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Medical Need

24% of all lymphoma is T cell lymphoma

Our Solution

First-in-class product

Effective and safe T-cell depletion

Aid in the treatment of canine T-cell lymphoma

Submitted for USDA product license; expect conditional license 2014

AT-005 Canine-specific antibody for T-cell lymphoma

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Feline Herpes is a common virus in cats

– 97% of cats exposed

– 4% with symptoms in US and EU

– Most prevalent ocular disease

Vaccinations are only option

– Not 100% effective

– Most cats unvaccinated

Similar to humans, virus not cured

AT-006 Feline Herpesvirus

Incidence

Calici

Herpes

FIV

FeLV

FIP

Parvo

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Treatment of herpetic ocular disease in cats caused by FHV-1 or FVR

Product can be used as a diagnostic as no diagnostic exists

Eyedrops are applied to affected eye

Product is a sterile solution

File for EU review in 2015

Expect U.S. marketing approval in 2017 or 2018

Exclusively licensed to Novartis Animal Health globally

AT-006 Feline Herpesvirus

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FIV is a serious viral disease in cats

– 2.5% incidence in the US

– Incidence is highly variable in Europe ranging from 2.1% to 12.5%

Clinical signs include chronic infections and weight loss, AIDS like symptoms and death

No currently approved antivirals for cats

AT-007 Feline Immunodeficiency Virus

Incidence

Calici

Herpes

FIV

FeLV

FIP

Parvo

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For the treatment of cats from 6 months of age infected with FIV; same product is active against FeLV (feline leukemia virus)

“Improvement of cat’s well-being and quality of life”

Treatment by injection with a sterile solution over the course of several weeks

Same compound family as Tenofovir, which was developed at KU Leuven

Expect U.S. marketing approval in 2017 or 2018

AT-007 Feline Immunodeficiency Virus

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Other Pipeline Products

Product Species Indication Development Status

AT-008 Dog Lymphoma Pivotal field study

AT-009 Dog Mast cell tumor Lead selection

AT-010 Dog Atopic dermatitis Lead selection

AT-011 Dog Parvovirus infections Lead selection

AT-012 Cat Calicivirus infections Lead selection

AT-014 Dog Osteosarcoma Pilot studies

AT-015 Cat Lymphoma Proof of concept