Chronic Administration of MRSI Agent IEPA Increases Tumor PH; Has Potential to Bias PH Measurement

Heather H. Cornnell¹, Ihor Luhach¹, Gary Martinez¹, Arig Ibrahim Hashim¹, Robert A. Gatenby², Robert J. Gillies¹

Measurement of pH using MRI has the potential to help aide in disease diagnosis and evaluation; notably in cancers, which have been shown to have an acidic microenvironment. In small animal models, IEPA (2-imidazole-1-yl-3-ethoxycarbonylpropionic acid) has been used as a MRSI agent to noninvasively map tumor pH. However, IEPA has a pKa of ~ 7 and we have recently shown that chronic oral administration of IEPA can inhibit spontaneous metastases. These results were accompanied by an increase in tumor and urine pH, which illustrates that IEPA has the potential to alter the pH of the tissue being measured by MRSI.