O57 Specific Sulfonamide Inhibitors of CA IX are able to Image Hypoxia Response and Enhance the in vivo Therapeutic Effect of Conventional Cancer Treatments Ludwig Dubois 1 , Natasja G. Lieuwes1, Anne

Thiry1,2, Jean-Michel Dogné2, Claudiu T. Supuran3, Bradly G. Wouters1,4, Bernard Masereel2, Philippe Lambin1 1 Maastricht Radiation Oncology (MaastRO) Lab, GROW – School for Oncology and Developmental Biology, University Maastricht, Maastricht, The Netherlands, 2 Department of Pharmacy, Drug Design and Discovery Center, FUNDP, University of Namur, Namur, Belgium, 3 Laboratory of Bioinorganic this website Chemistry, Università degli Studi di Firenze, Florence, Italy, 4 Ontario Cancer Institute/Princess Margaret CYT387 nmr Hospital, University Health Network, Toronto, ON, Canada Background and Purpose: Hypoxia is an important micro-environmental parameter that influences tumor progression and treatment efficacy. The hypoxia target carbonic anhydrase IX (CA IX) is associated with poor prognosis and therapy resistance and is an important regulator of tumor pH. Several studies suggest it may INCB28060 be a potential imaging and therapeutic target. Recently, sulfonamide inhibitors (CAI) that bind and inhibit CA IX only during hypoxia have been developed. The aim of this study was to investigate the in vivo CAI binding properties using fluorescent

imaging and the possible therapeutic gain of combining specific CAI with irradiation. Material and Methods: NMRI-nu mice were inoculated subcutaneously into the lateral flank with HT-29 colorectal carcinoma cells. Non-invasive imaging was performed at several time pheromone points after CAI#1 (fluorescein-thioureido-homosulfanilamide) injection with our without modifying the tumor oxygen concentration levels. Tumor growth and potential treatment toxicity was monitored after injection of CAI#2 (indanesulfonamide) combined with irradiation (single tumor dose 10 Gy). Results: In vivo fluorescence imaging revealed for the first time specific CAI#1 accumulation (P = 0.008 compared with controls) in delineated tumor areas dependent on the oxygen concentration.

Treatment of animals with CAI#2 alone resulted in a significant growth delay (P = 0.024). Single irradiation treatment also demonstrated an increased specific doubling time evaluated at 4 times the starting tumor volume (P < 0.001). The specific doubling time was further increased by combining CAI#2 with irradiation (P = 0.016). No significant toxicity was observed, neither for the single, neither for the combined treatment schedules. Conclusions: These in vivo results confirm previous data showing that in vitro CAI binding occurs only under hypoxia. Furthermore, CAI as a single treatment is able to significantly reduce tumor growth, which was further enhanced by combining with irradiation, promising for further clinical testing.