Rapidity and Severity of Hemoglobin Decreasing Associated with Erythrocyte Inosine Triphosphatase Activity and ATP Concentration during Chronic Hepatitis C Treatment

Pharmacogenomics with red cells: a model to study protein variants of drug transporter genes

The PharmacoScan pharmacogenomics platform screens for variation in genes that affect drug absorption, distribution, metabolism, elimination, immune adverse reactions and targets. Among the 1,191 genes tested on the platform, 12 genes are expressed in the red cell membrane: ABCC1, ABCC4, ABCC5, ABCG2, CFTR, SLC16A1, SLC19A1, SLC29A1, ATP7A, CYP4F3, EPHX1 and FLOT1. These genes represent 5 ATP-binding cassette proteins, 3 solute carrier proteins, 1 ATP transport protein and 3 genes associated with drug metabolism and adverse drug reactions. Only ABCG2 and SLC29A1 encode blood group systems, JR and AUG, respectively. We propose red cells as an ex vivo model system to study the effect of heritable variants in genes encoding the transport proteins on the pharmacokinetics of drugs. Altered pharmacodynamics in red cells could also cause adverse reactions, such as haemolysis, hitherto unexplained by other mechanisms.

Induction of inosine triphosphatase activity during ribavirin treatment for chronic hepatitis C

BACKGROUND

Ribavirin (RBV) is an antiviral agent and the primary component for chronic hepatitis C (CHC) therapy. Hemolytic anemia is limitation for RBV treatment. Inosine triphosphatase (ITPA) activity has been associated with severity of RBV-induced anemia. However, changes in ITPA activity during CHC therapy are unknown. The aim of this study was to measure the time-dependent change in ITPA activity over the RBV treatment.

METHODS

Forty-two patients with CHC were evaluated for ITPA activity over the course of RBV treatment.

RESULTS

The median value of ITPA activity at start of RBV treatment was 134.2 μmol/h/g hemoglobin (Hb; range, 26.3-251.0 μmol/h/g Hb). The ITPA activity values at 4, 8, and 12 weeks during RBV treatment were 143.2, 202.2, and 225.7 μmol/h/g Hb, respectively, and these ITPA values were significantly elevated compared with the start of treatment (p < 0.001). In patients with ITPA variants, patients with anemia (Hb < 10 g/dL) had greater elevated ITPA activities compared with patients without anemia at 12 weeks.

CONCLUSION

Our findings indicate that ITPA activities are elevated with RBV therapy, and this elevation may be a risk of anemia in late therapeutic phase in patients that began with low ITPA activity.