1. ¹Department of Pharmacy, University of Southern California, Los Angeles, California, USA
2. ²The National Institute of Transplantation, Los Angeles, California, USA
3. ³Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
4. ⁴Department of Pediatrics, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
5. ⁵Department of Surgery, University of Southern California, Los Angeles, California, USA

Correspondence: GJ Burckart, (burckart@usc.edu)

Received 29 April 2007; Accepted 4 July 2007; Published online 12 September 2007.

Abstract

Inosine 5'-monophosphate dehydrogenase 1 (IMPDH1) catalyzes the rate-limiting step of the de novo pathway for purine synthesis and is a major target of the immunosuppressive drug mycophenolic acid (MPA). Few variants of the IMPDH1 gene have been reported. The objective of this study was to identify and characterize IMPDH1 variants to determine whether genetic variation contributes to differences in MPA response and toxicity in transplant patients. Seventeen genetic variants were identified in the IMPDH1 gene with allele frequencies ranging from 0.2 to 42.7% . In this study, 191 kidney transplant patients who received mycophenolate mofetil were genotyped for IMPDH1. Two single-nucleotide polymorphisms, rs2278293 and rs2278294, were significantly associated with the incidence of biopsy-proven acute rejection in the first year post-transplantation. Future studies of the multifactorial nature of acute rejection must consider IMPDH1 polymorphisms in MPA-treated patients.