Deferasirox Associated to Liver Failure and Death in a Sickle Cell Anemia Patient Homozygous for the -1774delG Polymorphism in the ABCC2 Gene Encoding Multidrug Resistance Protein 2 (MRP2)

Introduction: Regular blood transfusions may result in hemochromatosis, leading to damage of various organs. Deferasirox exhibits good efficacy as iron chelation therapy, however changes in liver parameters may occur, as well as, despite being rare, more serious complications such as liver failure. Multidrug resistance protein 2 (MRP2) is a member of the ATP-binding cassette (ABC) transporter family of membrane proteins encoded by the ABCC2 gene and is expressed in the canalicular part of the hepatocyte. MRP2 acts in the biliary transport of several endogenous compounds and many drugs, including Deferasirox. Thus, genetic polymorphisms related to the ABCC2 gene, which encodes the MRP2 protein, may influence individual susceptibility to hepatotoxicity related to Deferasirox.

Methods: Two functional genetic variants, rs369192412 (-1774delG) and rs717620 (-24C> T), of the ABCC2 gene, were studied using the DNA sequencing technique in 31 genomic DNA samples from patients with iron overload who were currently using or had previously used Deferasirox. The sequencing results were compared to clinical data related to the presence or absence of hepatotoxicity during the use of this drug.

Results: Of all patients studied, 9 (29%) of them developed hepatotoxicity based on elevation of AST and/or ALT >5 X ULN or elevation of bilirubins >3 X ULN, which occurred in an average of 239 (14-983) days after initiation of treatment. From the 9 (29%) patients with hepatotoxicity, only 2 (22.2%) of them had the polymorphism -24C> T in only one allele, and the remaining 7 (77.8%) patients did not (OR = 0.77, 95% CI = 0.06 to 5.91, p = 1). Despite no association was detected between the -17774delG polymorphism and hepatotoxicity (OR = lower, 95% CI = 0.06 to bottom, p = 0.29), this polymorphism was present in homozygosis in 1 patient with sickle cell anemia, who, coincidently, had fulminant hepatitis leading to death, with no other causes for liver toxicity and despite all introduced therapies.

Conclusions: Our study showed no correlation between ABCC2 polymorphisms (-24C> T, -1774delG) and hepatotoxicity to Deferasirox, however, the rs369192412 (-1774delG) polymorphism was present in homozygosis in the only patient who died due to fulminant hepatitis secondary to the drug. This data may indicate a possible influence of the presence of this polymorphism in the severity of liver damage related to Deferasirox.