ABT-526 and ABT-510, Antiangiogenic Thrombospondin-1 Peptides, Are Active in Dogs With Naturally Occurring Canine Cancers Including Soft Tissue Sarcomas Anthony Rusk 1, Jack Henkin 2, Evelyn McKeegan 2, Fortuna Haviv 2, Sandra Majest 2, and Chand Khanna Animal Clinical Investigation, LLC 1 and Abbott Laboratories 2

COOH I cell binding 11 1 heparin binding NH 2 - S I Procoll _ RGD binding EGF-like (trimer) I S S 33 Thrombospondin-1 Large multi-domain protein with multiple receptors Anti-angiogenic domain is 2nd type-1 repeat Drs. Noel Bouck, Olga Volpert, Jack Henkin Series of related TSP-1 peptides: ABT-526

ABT-526 Inhibits Mouse Corneal Neovascularization Vehicle ABT mg/kg/day ABT mg/kg/day (b-FGF micropellet)

Integration of a Comparative Approach Activity Toxicity Pharmacokinetics Pharmacodynamics Dose Regimen Schedule Biomarkers Responding Histologies Combination therapies Small Animal Preclinical Phase III Human Clinical Trials Tumor-Bearing Dog Studies Phase II Human Clinical Trials Phase I Human Clinical Trials Tumor-Bearing Dog Studies Non-Human Primate Beagle Dog New Cancer Drug

Companion Animal Cancer Models  Large outbred Animals  Strong Genetic similarities to Humans  Naturally Occurring cancers  Immune competant and syngeneic Relevant Tumor Histology/Genetics  Relevant Response Profiles to Conventional Chemotherapy  Tumor Heterogeneity  Metastasis Biology  Recurrence/Resistance Cancer IN Companion Animals  75 Million Companion Animals in the US  6 million pet dogs diagnosed with cancer each year  Pet owners seek advanced care for their pets Translational Opportunity TO PROVIDE OPPORTUNITIES TO INCLUDE NATURALLY OCCURRING CANCER MODELS IN THE STUDY OF CANCER BIOLOGY AND THERAPY

Thrombospondin-1 Peptides in Pet Dogs with Measurable Malignant Cancers Design: Open label single agent Eligibility:Histologically confirmed Measurable No concurrent cancer therapy Washout of 21 days Endpoints: Toxicity Pharmacokinetics (limited) Tumor Response Significant disease stabilization Objective response Khanna et al ASCO 2002 Predictions based on past Experience: Thalidomide Sedation at higher doses 12 cases treated No objective responses Disease stabilization 3 cases All cases measurable and advanced stage of disease

Dog #1-26: ABT mg BID, SC Dog #27-72: ABT mg/kg BID, SC Dog# 1-30: ABT mg BID, SC Dog# : ABT mg/kg QD or divided BID, SC TSP-1 Peptide Assignment, Dose, Schedule

Results: Accrual and Toxicity Animal Clinical Investigation, LLC: Cancer Network  Accrual Total: 242 Cases (2 years) Evaluable: 180 (68 sarcomas) *on therapy > 30 days  No Toxicity  Relevant population (Geriatric Dogs)  No arthritis  No delayed wound healing  No keratitis  Some dogs continue on therapy over 3 years

VEGF induced Endothelial Cell chemotaxis ABT-526 inhibited canine EC chemotaxis by greater than 60% at 100 nM concentrations. Serum Pharmacokinetics In Vitro Activity 100nM = 0.1 µg/mL Results: Pharmacokinetics / In Vitro Activity ABT-526 half-life = 48 min (range 33 to 60 min) ABT-510 half-life = 44 minutes (range 36 to 44 min) Pharmacokinetic profile stable after 1 month Detection limit 10 ng/ml

RESULTS: RESPONSES  Significant stable disease seen in 23/180 (13%) evaluable cases  Objective responses: 19/180 (11%) evaluable cases  Head and Neck Carcinoma  Mammary Carcinoma  NH lymphoma  Cutaneous lymphoma  Sarcoma (Objective responses seen in 9/68 (13%) dogs  Synovial Sarcoma  Hemangiosarcoma  Soft Tissue Sarcoma

Day 30 Day 60 Day 90 Response: Maxillary squamous cell carcinoma (T3N0M0) Day 270 Day 0

Metastatic Synovial Sarcoma (Agent: TSP-1) Day 0Day 30 Day 60

Predictors of Response??  Response to therapy could not be predicted based on:  Initial tumor burden  Stage of disease  Primary versus metastatic lesions  Past treatments  Notable responses:  Slow Progression: Progression rate that would allow > 30 days of treatment  Soft tissue sarcoma (No responses in 10 dogs with osteosarcoma)  Lymphoma  Radiation “field’ failures

# * * Assessment of Biomarkers of Drug Exposure/Response Circulating endothelial cells (CEC’s) and CEC subsets may predict exposure and response to TSP-1 * *

Thrombospondin-1 Peptides Ask appropriate questions…Listen to the Answers Antiangiogenic TSP-1 peptides are active against bulky and metastatic disease Antiangiogenic TSP-1 peptides require extended time on therapy Antiangiogenic TSP-1 peptides are active against NH-Lymphoma Most dogs do not respond to therapy Determinants of the responsive “patient” not known Resistance has been seen in 80% of dogs responding to antiangiogenic therapy The biology of antiangiogenic responses seen in measurable tumors may not predict responses against micrometastatic disease Combination of TSP-1 peptides with cytotoxic chemotherapy are complimentary Circulating endothelial cells may be a valuable predictor of response

Translational Trials with Antiangiogenic Thrombospondin-1 Peptides Pet dogs Open Label Single Agent Any Measurable Malignant Cancer >500 dogs Adult Phase I Trial Adult Phase II Trial Pediatric Trials Relapsed NH-Lymphoma Randomized Placebo Blinded Completed 105 cases Activity supported + CCNU Pet dogs Hemangiosarcoma Single agent adjuvant therapy Completed 30 case pilot No activity demonstrated Pet dogs Biomarker Validation -Circulating Endothelial Cells -Other Adult Phase II Trial Adult Phase III Trial High Grade NH-Lymphoma Newly diagnosed Soft tissue sarcoma (biomarker) Biology Trials Pet dogs TSP-1 + Radiation therapy -Head and Neck Carcinoma Combination with Chemotherapy

Ongoing Studies DOGS  Prospective study of antiangiogenic peptides of TSP-1 in dogs with measurable soft tissue sarcoma  Endpoints  Response (MRI confirmation)  Biomarkers of exposure and response (tumor, circulating cells, plasma) Goal: To define determinants of the response “patient” HUMAN  Over 400 cancer patients have been treated in Phase 1 and 2 trials with ABT-510  Signals of efficacy is seen in soft tissue sarcoma  Characteristics of responding patient are unknow

Acknowledgements Animal Clinical Investigation, LLC Jennifer Turner Kate Cadorette Tony Rusk Abbott Laboratories Inc Jack Henkin Evelyn McKeegan Rick Lesniewski