Negative predictive value of IL28B, SLC28A2, and CYP27B1 SNPs and low RBV plasma exposure for therapeutic response to PEG/IFN-RBV treatment

Pharmacogenetic determinants of tenofovir diphosphate and lamivudine triphosphate concentrations in people with HIV/HBV coinfection

The nucleos(t)ide analogs require phosphorylation to the pharmacologically active anabolites in cells. We investigated the hypothesis that single-nucleotide polymorphisms (SNPs) in genes that encode transporters and phosphodiesterase (PDE) enzymes involved in tenofovir (TFV), disoproxil fumarate (TDF), and lamivudine (3TC) disposition will be associated with concentrations of their phosphate anabolites and virologic response. Individuals with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) coinfection receiving TDF/3TC-containing antiretroviral therapy were enrolled. Steady-state TFV diphosphate (TFV-DP) and 3TC triphosphate (3TC-TP) concentrations in peripheral blood mononuclear cells (PBMCs) and dried blood spot samples were quantified. The relationship between genetic variants and TFV-DP and 3TC-TP concentrations as well as with virologic response were examined using multivariable linear regression. Of the 136 participants (median age 43 years; 63% females), 6.6% had HBV non-suppression, and 7.4% had HIV non-suppression. The multidrug resistance protein 2 (encoded by ABCC2 rs2273697) SNP was associated with 3TC-TP concentrations in PBMCs. The human organic anion transporter-1 (encoded by SLC28A2) rs11854484 SNP was associated with HIV non-suppression, and when evaluated together with SNPs with marginal associations (ABCC2 rs717620 and PDE1C rs30561), participants with two or three variants compared to those with none of these variants had an adjusted odds ratio of 48.3 (confidence interval, 4.3-547.8) for HIV non-suppression. None of the SNPs were associated with HBV non-suppression. Our study identified ABCC2 SNP to be associated with 3TC-TP concentrations in PBMCs. Also, a combination of genetic variants of drug transporters and PDE was associated with HIV non-suppression.

Pharmacogenetics of the anti-HCV drug sofosbuvir: a preliminary study

Background

Sofosbuvir is a potent nucleotide HCV NS5B polymerase inhibitor that is also a P-glycoprotein (encoded by the ABCB1 gene) and breast cancer resistance protein (encoded by the ABCG2 gene) substrate. Concerning previous anti-HCV therapies, pharmacogenetics had a significant impact, particularly considering the association of interleukin28B polymorphisms with dual-therapy (ribavirin + pegylated IFN) outcomes.

Objectives

In this work, we investigated the association between sofosbuvir and its prevalent metabolite (GS-331007) plasma concentrations at 1 month of therapy and genetic variants (SNPs) in genes encoding transporters and nuclear factors (ABCB1, ABCG2 and HNF4α) related to sofosbuvir transport.

Patients and methods

Allelic discrimination was performed through real-time PCR, whereas plasma concentrations were evaluated through liquid chromatography. One hundred and thirteen patients were enrolled.

Results

Sofosbuvir concentrations were below the limit of quantification since the drug was converted into its GS-331007 metabolite. ABCB1 2677 G>T (P = 0.044) and HNF4α 975 C>G (P = 0.049) SNPs were associated with GS-331007 metabolite plasma concentrations. In linear multivariate analysis, liver stiffness, insulin resistance, baseline haemoglobin and haematocrit and SNPs in the ABCB1 gene (3435 CT/TT and 1236 TT genotypes) were significant predictors of GS-331007 concentrations. Furthermore, we performed sub-analyses considering the anti-HCV concomitant drug and HCV genotype, identifying specific polymorphisms associated with GS-331007 plasma concentrations: ABCB1 3435 C>T and HNF4α975 C>G in patients treated with daclatasvir, ABCB1 2677 G>T with ledipasvir and ABCB1 3435 C>T, ABCB1 2677 G>T, ABCG2 421 C>A and ABCG2 1194 + 928 C>A with ribavirin.

Conclusions

In this study we suggested sofosbuvir GS-331007 metabolite plasma levels were affected by variants in the ABCB1 and HNFα genes.

Influence of ABCB11 and HNF4α genes on daclatasvir plasma concentration: preliminary pharmacogenetic data from the Kineti-C study

Background

Daclatasvir is an inhibitor of HCV non-structural 5A protein and is a P-glycoprotein substrate. Pharmacogenetics has had a great impact on previous anti-HCV therapies, particularly considering the association of IL-28B polymorphisms with dual therapy outcome.

Objectives

We investigated the association between daclatasvir plasma concentrations at 2 weeks and 1 month of therapy and genetic variants (SNPs) in genes encoding transporters and nuclear factors (ABCB1, ABCB11 and HNF4α).

Patients and methods

Allelic discrimination was achieved through real-time PCR, whereas plasma concentrations were evaluated through LC-MS/MS.

Results

Fifty-two patients were analysed, all enrolled in the Kineti-C study. HNF4α 975 C > G polymorphism was found to be associated with the daclatasvir plasma concentrations at 2 weeks (P = 0.009) and 1 month of therapy (P = 0.006). Linear regression analysis suggested that, at 2 weeks of therapy, age, baseline BMI and haematocrit were significant predictors of daclatasvir concentrations, whereas at 1 month of therapy ABCB111131 CC and HNF4α CG/GG genotypes were significant predictors of daclatasvir concentrations.

Conclusions

These are the first and preliminary results from our clinical study focusing on daclatasvir pharmacogenetics, showing that this approach could have a role in the era of new anti-HCV therapies.

Vitamin D pathway genetic variants are able to influence sofosbuvir and its main metabolite pharmacokinetics in HCV mono-infected patients

Vitamin D levels and genetic variants were associated with drug outcome/toxicity and concentrations. The plasma exposure of GS-331007, the main sofosbuvir metabolite, has been related to SVR. We evaluated the impact of polymorphisms in genes (CYP27B1, CYP24A1, VDBP and VDR) related to vitamin D pathway on sofosbuvir and GS-331007 plasma levels in HCV mono-infected patients at one month of treatment. Polymorphisms were investigated through real-time PCR; drug plasma quantification was performed through a UHPLC-MS/MS method. GS-331007 levels were associated with CYP24A1rs2248359 and VDRCdx2 variants in all the analyzed patients and linear regression analysis showed that sex, body mass index, HCV genotype, baseline estimated glomerular filtration rate, VDRCdx2AG/GG and CYP27B1-1260TT genotypes significantly predict concentrations. We performed sub-analyses considering the HCV genotype and the concomitant drug, identifying polymorphisms associated with GS-331007 concentrations. This is the first study focusing on vitamin D pathway gene variants and DAAs concentrations, but further studies are required.

Impact of vitamin D receptor and binding protein gene polymorphisms in clinical and laboratory data of HCV patients: Cross sectional study

Potential relationship of vitamin D, vitamin D receptor (VDR), and vitamin D binding protein (DBP) have been suggested in the pathophysiology of hepatitis C virus (HCV) infection. The aim of this observational study is to determine vitamin D levels, and VDR and DBP genetic polymorphism according demographic and laboratory data in chronic HCV patients (CHC).A total of 148 CHC patients gave serum samples for testing 25-hydroxyvitamin D (25 (OH)D) level by immunochemiluminometric assay (<20 ng/mL defined as deficient) and donated blood samples to allelic discrimination analysis using TaqMan assays. Analyzed single nucleotide polymorphisms (SNPs) were: VDR-rs7975232 (ApaI) C>A, rs731236 A>G (TaqI), rs1544410 C>T (BsmI), rs10735810 T>C (FokI) and carrier globulin/binding protein (GC)-rs4588 and rs7041 and the haplotype bAt [CCA]. Hepatic fibrosis was assessed using Fib-4 and Forns index.Eighty-two (54.40%) patients demonstrated deficiency of vitamin D and this was associated to AST (P = .019 [CI: 1.003-1.034]), total cholesterol (P = .038 [CI: 1.004-1.164]), fibrosis grade (P < .001 [CI: 0.000-0.844]), and FokI (P = .028) allele T presence. Association was found between VDR polymorphism and fibrosis (BsmI andTaqI), triglycerides (TaqI), and HDL (FokI). DBP polymorphism was associated to HCV genotype (GC rs7041), previous HCV treatment, and GGT (GC rs4588).In conclusion, low frequency of vitamin D deficiency was found, but VDR polymorphisms were frequently associated to fibrosis grade suggesting that they could be used as disease evaluation markers to understand the mechanisms underlying the virus-host interaction.

Vitamin D pathway gene polymorphisms and hepatocellular carcinoma in chronic hepatitis C-affected patients treated with new drugs

PURPOSE

Since HCV infection may lead to hepatocellular carcinoma (HCC) and vitamin D (deficiency) is related to cancer, we investigated if SNPs in genes involved in vitamin D pathway could predict HCV-related HCC presence in patients treated with new anti-HCV drugs.

METHODS

Patients with chronic hepatitis C and treated with direct-acting antivirals were enrolled. SNPs in VDR, CYP27B1, CYP24A1 and GC genes were assessed through real-time PCR. 258 patients were analyzed.

RESULTS

HCC was present in six patients, all taking sofosbuvir, all males and five/six had cirrhosis. HCV-RNA log levels at baseline were statistically different between patients with and without HCC. VDR FokI T > C SNP resulted associated with HCC: all the CC patients were free from HCC. An association between HCC presence and undetectable HCV-RNA at 1 month of therapy was suggested; cirrhosis was related to HCC. HCC risk factors were age, ribavirin administration, IL28Brs12979860CC and previous treatments; VDR FokICC, sex and insulin resistance were protective factors.

CONCLUSIONS

These data highlighted vitamin D pathway gene SNPs and HCC relationship in the Italian population; further studies are required.

Treatment with PEG-IFN and ribavirin in patients with chronic hepatitis C, low grade of hepatic fibrosis, genotype 1 and 4 and favorable IFNL3 genotype: A pharmacogenetic prospective study

The new direct-acting antivirals agents (DAAs) rapidly changed the treatment approach in chronic hepatitis C (CHC); however, the interferon (IFN)-free therapies availability is currently different in some countries, due to higher costs of these drugs. Naïve treated patients, who are not eligible for IFN-free therapies, could be selected for standard dual treatment with pegylated (PEG)-IFN and ribavirin (RBV), through IFN lambda 3 gene polymorphisms and fibrosis stage evaluation. Inclusion criteria were: naïve treated CHC patients with GT1 or GT4, without major contraindication to PEG-IFN or RBV, with fibrosis stage F0-F2 and IFNL3 rs8099917/rs12979860 TT/CC genotypes. 65 patients were included in the study. Overall SVR was observed in 50 patients (76.9%); SVR rates among different genotypes were as follows: 15 with GT1a (71.4%), 27 with GT1b (79.4%) and 8 for GT4 (80%). The RBV cutoff at 2weeks of 1800ng/mL, predictor of RVR, was determined (p=0.003; sensibility=60.4%, specificity=88.2%, positive predictive value=88.9%, negative predictive value=100%). In multivariate analysis, factors significantly associated with treatment failure were living alone condition (OR=4.302; 95%IC=1.254-16.257; p=0.034) and RBV plasma level <1800ng/mL at 2weeks (OR=4.970; 95%IC=1.405-17.565; p=0.009). Considering a pharmacogenetic-guided approach, dual therapy with PEG-IFN and RBV can be considered a reliable option for patients ineligible for IFN-free treatments, who are motivated and well informed about all the aspects related to PEG-IFN administration.

Association of vitamin D pathway SNPs and clinical response to interferon in a cohort of HBeAg-negative patients

AIM

Vitamin D modulates biological processes; an influence of vitamin D levels and genetic variants was identified concerning hepatitis B virus infection. We evaluated the role of some SNPs of vitamin D pathway genes in some clinical features of hepatitis B affected patients treated with pegylated interferon.

METHODS

We investigated SNPs in IL-28B, CYP27B1, CYP27A1, CYP24A1, VDBP and VDR genes, through real-time PCR.

RESULTS

 VDRApaI SNP was associated to viral load and HBsAg presence at different timings. In logistic regression analyses, VDRApaI AA genotype predicted baseline viral load >6 Log IU/ml (marker of nonresponse), and both virological and biochemical responses.

CONCLUSION

Pharmacogenetic data could help physicians in the prediction of patients with higher probability to achieve a good response.

Pharmacogenetics of ribavirin-induced anemia in HCV patients

Dual therapy (pegylated interferon plus ribavirin) was considered the standard of care for hepatitis C virus (HCV) treatment until 2011, when the first-wave direct-acting antivirals were added to this regimen for HCV genotype-1 patients to increase the sustained virological response rate. The second-wave direct-acting antivirals entered the clinical use also in some ribavirin (RBV)- and/or interferon-free combinations. Nevertheless, since some of the new therapeutic regimens also include RBV and its use results still associated with hemolytic anemia, this requires countermeasures to be prevented. These include the identification of several host predictive factors involved in RBV absorption, distribution, metabolism, elimination and many others that might influence this toxic effect. For this reason, we provided an overview of the potential role of pharmacogenomics in predisposing RBV-treated HCV patients to anemia.

VDR gene polymorphisms impact on anemia at 2 weeks of anti-HCV therapy: a possible mechanism for early RBV-induced anemia

OBJECTIVES

Vitamin D receptors (VDR) bind calcitriol and modulate several physiological systems through genomic and nongenomic pathways. Calcitriol stimulates store-operated channels Ca²⁺ influx by translocation of the caveolar VDR to the plasma membrane. Intracellular Ca²⁺ levels in erythrocytes control biophysical properties and an increase in its concentration can deregulate membrane composition, cell volume, glycolytic enzymes regulation, redox state, and cell clearance.We evaluated the role of single nucleotide polymorphisms in ITPA, CYP27B1, CYP24A1, and VDR genes in the prediction of ribavirin-induced anemia in HCV-1/2/3/4 patients at 2 and 4 weeks of treatment.

PATIENTS AND METHODS

Two hundred and twenty-five patients treated with ribavirin and pegylated interferon-α were genotyped by real-time PCR.

RESULTS

BMI at baseline more than 30 kg/m² [P=0.013, odds ratio (OR): 10.95, 95% confidence interval (CI): 1.66-74.21], alanine aminotransferase at baseline more than 37 IU/l (P=0.020, OR: 0.26, 95% CI: 0.09-0.81), and the VDR BsmI AA profile (P=0.003, OR: 5.09, 95% CI: 1.72-15.05) were anemia-predictive factors at 2 weeks of therapy. At week 4, the ITPA rs6051702 AC/CC profile (P=0.001, OR: 0.19, 95% CI: 0.07-0.51) was the only factor that could predict this side effect.

CONCLUSION

The BsmI AA genotype is a predictive factor of 2-week anemia and it could be related to a VDR-enhanced activity, and thus an increased calcium influx, resulting in the deregulation of the Ca²⁺-dependent signaling, which can lead to erythrocytes hemolysis. This rapid mechanism could be responsible for the development of early anemia.These results indicate for the first time the strong, significant, and independent role of VDR in the early development of ribavirin-induced anemia and confirm the ITPA function in the prediction of anemia at week 4.

Clinical pharmacology of tenofovir clearance: a pharmacokinetic/pharmacogenetic study on plasma and urines

The HIV virus and hepatitis B virus nucleotide reverse transcriptase inhibitor tenofovir has been associated with proximal tubular toxicity; the latter was found to be predicted by plasma concentrations and with single-nucleotide polymorphisms in transporters-encoding genes. A cross-sectional analysis in adult HIV-positive patients with estimated creatinine clearance >60 ml min^-1 was performed. Twelve-hour plasma and urinary tenofovir concentrations and single-nucleotide polymorphisms in several transporter-encoding genes were analysed. In 289 patients 12-h tenofovir plasma, urinary and urinary to plasma ratios were 69 ng ml^-1 (interquartile range 51.5-95), 24.3 mg ml^-1 (14.3-37.7) and 384 (209-560). At multivariate analysis estimated creatinine clearance, protease inhibitors co-administration and SLC28A2 CT/TT genotypes were independently associated with plasma tenofovir exposure; ABCC10 GA/AA genotypes and protease inhibitor co-administration were independently associated with the urinary to plasma tenofovir ratio. Tenofovir clearance was associated with genetic polymorphisms in host genes and with co-administered drugs: if confirmed by ongoing studies these data may inform treatment tailoring and/or dose reductions.

UPLC-MS/MS method with automated on-line SPE for the isomer-specific quantification of the first-generation anti-HCV protease inhibitors in peripheral blood mononuclear cells

HCV infection affects over 170 million people worldwide. The current standard for treatment of genotype 1 infection is the association of the first generation protease inhibitors boceprevir or telaprevir to ribavirin and peginterferon α. Although the response rate has been improved with these new drugs, some pharmacokinetic/pharmacodinamic issues emerged in the past years. To date, some analytical methods are available for the quantification of these drugs in plasma; however, the real active concentrations of the two drugs are those in hepatocytes. Being the withdrawal of hepatocytes too invasive, in this work we aimed to develop and validate a chromatographic method coupled with tandem mass spectrometry capable of quantifying boceprevir and telaprevir isomers in peripheral blood mononuclear cells, used as an "in-vivo" cellular model of compartmentalization. The method used an on-line solid phase extraction protocol based on the new OSM(®) platform and was fully validated following FDA guidelines. This method showed mean intra- and inter-day inaccuracy and imprecision both lower than 15%, high and stable recovery and contained matrix effect, with a run time of 6min, comprehensive of SPE extraction. The method was then applied on 35 real samples from patients treated with boceprevir or telaprevir, with good analytical performances, thus assessing its eligibility for a possible future routine use. Peculiar pharmacokinetic data have been observed, suggesting the usefulness of investigating intracellular pharmacokinetics of these drugs. Further studies will be required to test the correlation of intracellular concentrations with effectiveness and toxicity of triple therapy.

Role of IL28B genotyping in patients with hepatitis C virus-associated mixed cryoglobulinemia and response to PEG-IFN and ribavirin treatment

The role of interleukin (IL) 28B in the treatment of chronic hepatitis C (CHC) has recently been examined in many studies, while a possible relationship between IL28B and the presence of mixed cryoglobulinemia (MC) remains to be clarified. In this study, we analyzed the influence of IL28B rs8099917/rs12979860 on the presence of MC and the role in treatment with PEG-IFN. We retrospectively examined 541 patients affected by CHC who were treated with pegylated interferon (PEG-IFN) and ribavirin from 2003 to 2012. We included all treatment-naïve patients without other viral co-infections or major contraindications to the PEG-IFN and ribavirin standard of care. One hundred seventy-five patients (32.3 %) had MC; 49 of these (33.3 %) had symptomatic MC. The IL28B rs8099917/rs12979860 TT/CC genotype was the most frequent in MC-positive patients with sustained virological response (SVR) (p < 0.001), while the TG/TC genotype was most frequent in non-SVR (p < 0.001). The TT/CC genotype was found to be the main positive predictive factor of MC in HCV patients (OR = 11.914; IQR = 7.092-18.776; p < 0.001); HCV genotype 2/3 was the strongest positive predictive factor of SVR (OR = 10.448; IQR = 8.352-21.561; p < 0.001); IL28B rs8099917/rs12979860 TT/CC was a better predictive factor than rs12979860 CC alone (OR = 9.829 vs. 2.663). Negative predictive factors were Metavir score F3-F4 (OR = 0.625; IQR = 0.416-0.779; p = 0.008), insulin-resistance (OR = 0.315; IQR = 0.224-0.585; p < 0.001) and presence of symptoms (OR = 0.716; IQR = 0.492-0.855; p < 0.001). IL28B rs8099917/rs12979860 is useful in the treatment of MC-positive HCV patients with PEG-IFN and ribavirin; the TT/CC genotype is associated with SVR, the TG/TC with non-SVR; TT/CC is also predictive of MC in HCV patients.

Intracellular accumulation of boceprevir according to plasma concentrations and pharmacogenetics

Boceprevir (BOC) is a directly-acting antiviral agent for the treatment of hepatitis C virus genotype 1 (HCV-1) infection. It is a mixture of two stereoisomers, the inactive R and the active S isomers. No data have previously been published on BOC intracellular accumulation. In this study, BOC isomer concentrations in peripheral blood mononuclear cells (PBMCs) and plasma were determined. The influence of various single nucleotide polymorphisms (SNPs) on plasma and intracellular drug exposure at Week 4 of triple therapy were also evaluated. Plasma and intracellular BOC concentrations were determined at the end of the dosing interval (C(trough)) using a UPLC-MS/MS validated method. Allelic discrimination was performed through real-time PCR. Median plasma concentrations were 65.97 ng/mL for the S isomer and 36.31 ng/mL for the R isomer; the median S/R plasma concentration ratio was 1.66. The median PBMC concentration was 2285.88 ng/mL for the S isomer; the R isomer was undetectable within PBMCs. The median S isomer PBMC/plasma concentration ratio was 28.59. A significant positive correlation was found between plasma and PBMC S isomer concentrations. ABCB1 1236, SLC28A2 124 and IL28B rs12979860 SNPs were associated with the S isomer PBMC/plasma concentration ratio. In regression models, S isomer plasma levels and FokI polymorphism were able to predict S isomer intracellular exposure, whereas SNPs in AKR1, BCRP1 and SLC28A2 predicted the S isomer PBMC/plasma concentration ratio. No similar data regarding BOC pharmacogenetics and pharmacokinetics have been published previously. This study adds a novel and useful overview of the pharmacological properties of this drug.

Treatment optimization of naïve HCV-1 patients using IL28B, RVR and fibrosis stage

The treatment of patients with HCV genotype 1 is quickly changing. The clinician could optimize the selection of patients who may benefit from standard therapy with pegylated-interferon and ribavirin instead of more expensive new combinations with the directly acting antivirals. We retrospectively examined in our cohort of 232 patients with genotype 1 infection the role of interleukin 28B (both rs8099917 and rs12979860), fibrosis stage and rapid virological response. Global SVR in TT/CC patients was 88.3% (98% in F0-F1, 80% in F2-F3); in TT/TC was 68.2 (85% in F0-F1, 71.4% in F2-F3). Rapid virological response was related to rs12979860 CC genotype but is not useful to predict the virological response in TG/GG patients at rs8099917. The standard dual therapy may be successfully administered in all TT/CC and TT/TC patients without F4 fibrosis score. Conversely, patients with TG/CC or GG/CC genotypes should be treated with other therapeutic options.

Role of CYP27B1+2838 promoter polymorphism in the treatment of chronic hepatitis B HBeAg negative with PEG-interferon

In HBV-infected patients, the vitamin D deficiency has been related to chronic liver diseases, progression of hepatic fibrosis and poor response to the treatment. The CYP27B1 gene, which encodes the 1-α-hidroxylase and involved in the 1,25-dihydroxyvitamin D synthesis, was recently associated to type-1 diabetes, autoimmune disorders and treatment response in HCV. Then, we aimed to investigate the role of CYP27B1 polymorphisms in HBV treatment with PEG-IFN. We retrospectively enrolled 190 patients with chronic hepatitis B HBeAg negative treated for 48 weeks with PEG-IFN α-2a. We examined the role of rs4646536 CYP27B1 SNP (CYP27B1+2838) according to virological and serological response. Our results showed that the TT genotype of CYP27B1+2838 was significantly prevalent in patients with end-of-therapy virological response (37.6%) vs CT/CC (9.4%) (P < 0.001). Virological relapse was prevalent in patients with CT/CC genotype (12.6%) vs TT genotype (2.1%) (P < 0.001). TT genotype was also related to HBsAg loss (P = 0.004) and anti-HBs appearance (P = 0.002). In the multivariate analysis, the TT genotype resulted to be a good positive predictor of sustained virological response (OR = 5.632, IC = 1.938-16.368, P = 0.001) and serological response (OR = 6.161, IC = 1.856-20.457, P = 0.003). The CYP27B1+2838 polymorphism may be useful as pretreatment factor to selection of patients with higher probability of response to therapy.

Nucleoside transporter proteins as biomarkers of drug responsiveness and drug targets

Nucleoside and nucleobase analogs are currently used in the treatment of solid tumors, lymphoproliferative diseases, viral infections such as hepatitis and AIDS, and some inflammatory diseases such as Crohn. Two gene families are implicated in the uptake of nucleosides and nucleoside analogs into cells, SCL28 and SLC29. The former encodes hCNT1, hCNT2, and hCNT3 proteins. They translocate nucleosides in a Na⁺ coupled manner with high affinity and some substrate selectivity, being hCNT1 and hCNT2 pyrimidine- and purine-preferring, respectively, and hCNT3 a broad selectivity transporter. SLC29 genes encode four members, being hENT1 and hENT2 the only two which are unequivocally implicated in the translocation of nucleosides and nucleobases (the latter mostly via hENT2) at the cell plasma membrane. Some nucleoside-derived drugs can also interact with and be translocated by members of the SLC22 gene family, particularly hOCT and hOAT proteins. Inter-individual differences in transporter function and perhaps, more importantly, altered expression associated with the disease itself might modulate the transporter profile of target cells, thereby determining drug bioavailability and action. Drug transporter pharmacology has been periodically reviewed. Thus, with this contribution we aim at providing a state-of-the-art overview of the clinical evidence generated so far supporting the concept that these membrane proteins can indeed be biomarkers suitable for diagnosis and/or prognosis. Last but not least, some of these transporter proteins can also be envisaged as drug targets, as long as they can show “transceptor” functions, in some cases related to their role as modulators of extracellular adenosine levels, thereby providing a functional link between P1 receptors and transporters.

ABCB11 and ABCB1 gene polymorphisms impact on telaprevir pharmacokinetic at one month of therapy

In 2011 direct-acting antivirals, including telaprevir, have been developed to achieve a better antiviral effect. It was reported that telaprevir is a substrate of P-glycoprotein (ABCB1) and cytochrome P450 3A4. The aim of this retrospective study was the evaluation of the influence of some single nucleotide polymorphisms (SNPs) of genes (ABCB1, SLC28A2/3, SLC29A1) involved in TLV and RBV transport and their correlation with plasma TLV drug exposure at 1 month of therapy. We also investigated the association of a SNP in ABCB11 gene, whose role in TLV transport was not yet shown. Twenty-nine HCV-1 patients treated with telaprevir, ribavirin and pegylated-interferon-α were retrospectively analyzed; allelic discrimination was performed by real-time PCR. Telaprevir Ctrough levels were influenced by Metavir score (P=0.023), ABCB1 2677 G>T (P=0.006), ABCB1 1236 C>T (P=0.015) and ABCB11 1131 T>C (P=0.033) SNPs. Regarding ABCB1 3435 C>T, a not statistically significant trend in telaprevir plasma concentration was observed. Metavir score (P=0.002, OR -336; 95% CI -535;-138), ABCB1 2677 (P=0.020, OR 497; 95% CI 86; 910), ABCB11 1131 (P=0.002, OR 641; 95% CI 259;1023) and CNT2 -146 (P=0.006, OR -426; 95% CI -721;-132) were able to predict telaprevir plasma levels in the regression analysis. Other SNPs showed no association. This study reveals BSEP implication in telaprevir transport and confirms the involvement and influence of P-glycoprotein on telaprevir plasma levels. To date, no similar data concerning pharmacogenetics and pharmacokinetics were published, but further studies in different and bigger cohorts are needed.

Role of pharmacogenetic in ribavirin outcome prediction and pharmacokinetics in an Italian cohort of HCV-1 and 4 patients

Ribavirin is phosphorylated by adenosine kinase 1 (AK1) and cytosolic 5'-nucleotidase 2 and it is transported into cells by concentrative nucleoside transporters (CNT) 2/3, coded by SLC28A2/3 genes, and equilibrative nucleoside transporters (ENT) 1/2, coded by SLC29A1/2 genes. We evaluated the association of some polymorphisms of IL28B, SLC28A2/3, SLC29A1, ABCB1, NT5C2, AK1, HNF4α genes and ribavirin treatment outcome and pharmacokinetics after 4weeks of therapy, in a cohort of HCV-1/4 Italian patients. Allelic discrimination was performed by real-time PCR; plasma concentrations were determined at the end of dosing interval (Ctrough) using an HPLC-UV method. Non response was negatively predicted by cryoglobulinemia and IL28B_rs12980275 AA genotype and positively by Metavir score; Metavir score, insulin resistance and SLC28A2_rs1060896 CA/AA and HNF4α_rs1884613 CC genotypes were negative predictive factors of SVR, whereas HCV viral load at baseline and IL28B_rs12980275 AA and rs8099917 TT genotypes positively predicted this outcome; RVR was negatively predicted by insulin resistance and positively by cryoglobulinemia and IL28B_rs12980275 AA genotype; Metavir score and insulin resistance were able to negatively predict EVR, whereas cryoglobulinemia and IL28B_rs12980275 AA genotype positively predicted it; at last, virological relapse was negatively predicted by IL28B_rs8099917 TT and AK1_rs1109374 TT genotypes, insulin resistance was a positive predictor factor. Concerning ribavirin pharmacokinetics, SLC28A2_rs11854488 TT was related to lower Ctrough levels; conversely patients with TC profile of SLC28A3_rs10868138 and SLC29A1_rs760370 GG genotype had higher ribavirin levels. These results might contribute to the clarification of mechanisms causing the individuality in the response to ribavirin containing therapy.

Vitamin D pathway gene variants and HCV-2/3 therapy outcomes

BACKGROUND

The combination of ribavirin and pegylated interferon-α is considered the standard of care for HCV-2/3 genotypes. The immune system plays a key role in the achievement of a sustained virological response (SVR). Vitamin D seems to influence antiviral response in chronic hepatitis C and its pathway is controlled by polymorphic genes such as CYP27B1, CYP24A1 and VDR. In this study, we have investigated the correlation among the treatment outcomes and single nucleotide polymorphisms (SNPs) in the above-mentioned genes and IL28B genes.

METHODS

A total of 112 HCV-2/3 patients treated with interferon plus ribavirin were retrospectively studied; allelic discrimination was performed by real-time PCR.

RESULTS

CYP24A1rs2585428, IL28Brs12979860 and rs8099917 SNPs affected treatment failure and body mass index (BMI), Metavir score, IL28Brs8099917TT and CYP24A1rs2585428GG were the only factors able to predict it. SVR was predicted by Metavir score, HCV RNA at baseline and early virological response (EVR). IL28Brs12979860 SNP and HCV RNA were also related to rapid virological response. EVR was predicted by BMI, Metavir score and CYP24A1rs2585428 SNP. IL28Brs8099917TT and FokITT were relapse prediction factors.

CONCLUSIONS

In addition to non-genetic factors, SNPs in the vitamin D pathway seem to have a role in HCV-2/3 therapy outcomes. This study reveals the likely usefulness of pharmacogenetic-based ribavirin and interferon therapy to help identify patients for whom therapy could be successful or not, also considering new future expensive therapy options. To date, no similar data were published on these viral genotypes, but further studies in different and bigger cohorts are needed.

Ribavirin uptake into human hepatocyte HHL5 cells is enhanced by interferon-α via up-regulation of the human concentrative nucleoside transporter (hCNT2)

Ribavirin is a broad spectrum antiviral that increases the response rate in chronic hepatitis C patients when administered in combination with IFNα. Ribavirin is a purine nucleoside derivative, transported into hepatocytes by nucleoside transporters. hCNT2 is the best candidate to mediate ribavirin uptake into hepatocytes due to its high-affinity for purines and its capacity to concentrate its substrates intracellularly. The aim of this study was to determine whether hCNT2 function is under IFNα modulation. IFNα treatment of the nontransformed human hepatocyte-derived cell line HHL5 induced a rapid and transient increase in hCNT2 activity after cytokine addition. hCNT2 activity up-regulation was associated with increased ribavirin accumulation into cells. This increase was consistent with the translocation of hCNT2-containing vesicles to the plasma membrane via a mechanism requiring ERK 1/2 and ROCK activation and cytoskeleton integrity. Longer treatments with IFNα induced transcriptional activation of the hCNT2-encoding gene (SLC28A2), resulting in a sustained increase in hCNT2-related activity. These observations are proof of concept for at least one of the putative mechanisms underlying the synergistic responses induced by combination therapy with IFNα and ribavirin.

Identification of naïve HVC-4 patients who may be treated with pegylated-interferon and ribavirin according to IL28B polymorphisms

BACKGROUND

The current treatment of HCV-4 patients is dual therapy with PEG-IFN and ribavirin; however, new drugs against this genotype will be available within few months. Despite the evidenced good virological response in IFN-free regimens, the high cost of these new therapies will require patient selection. In our paper we propose the use of both rs8099917 and rs12979860 IL28-B polymorphisms, in order to identify potentially categories of SVR, null-responder and relapse and consequently to choose the dual therapy or novel approach.

METHODS

One hundred and sixty-nine patients with chronic hepatitis C and genotype 4 treated with pegylated interferon and ribavirin for 48weeks were retrospectively studied. All patients were genotyped for rs8099917 and rs12979860 interleukin-28B polymorphisms.

RESULTS

80 patients with SVR (88.8%) had the TT/CC or TT/TC (rs8099917/rs12979860) (p<0.001) genotypes; the null-responders (n=13), 9 (69.2%) showed the GG/TT allelic distribution (p<0.001); relapsers showed a prevalent distribution of the TG/TC genotype (83.3%) (p<0.001). The 6 (100%) breakthrough patients showed TT/TC genotype, while the partial responders patients did not show any particular IL-28B genetic profile. Genetic profiles different from TT/CC showed 94.9% negative predictive value for SVR, with 92.6% of sensitivity and 65.2% of specificity. Insulin-resistance, diabetes and liver fibrosis were not relevant in our multivariate analysis.

CONCLUSIONS

The combination of both rs8099917/rs12979860 polymorphisms is useful for early identification of SVR, null-responders and relapsers. This could be used to chose between standard dual therapy or novel approach with IFN-free regimens.

Role of IL28-B polymorphisms in the treatment of chronic hepatitis B HBeAg-negative patients with peginterferon

Interleukin (IL)28-B polymorphism has been related to interferon response in the treatment of hepatitis C, but its role in chronic hepatitis B (CHB) therapy is still poorly understood. We aimed to investigate the effect of IL28-B polymorphisms in the treatment with pegylated-interferon (PEG-IFN) of patients with CHB. We retrospectively analyzed 190 patients with chronic hepatitis B e antigen (HBeAg) negative, genotype A (22%), B (12%), C (10%), D (33%), E (20%), treated with PEG-IFN alfa-2a for 48weeks; genotype analysis was performed for IL28-B polymorphisms rs12979860, rs8099917 and rs12980275 according to virological, serological and biochemical response. During 2years of follow-up 12 patients (6.3%) cleared hepatitis B surface antigen (HBsAg) with seroconversion, 40 (21%) obtained a negative viral load and 104 (54.7%) gained a biochemical response. We found a difference of distribution of rs12979860 CC genotype among different ethnicity (p=0.013). Rs12979860 CC genotype was significantly associated with serological and virological response (p<0.001); rs8099917 TT and rs12980275 AA genotypes were mostly related with virological response (p<0.001). In multivariate logistic analysis rs12979860 CC was predictive of virological response (OR=4.290; CI=1.589-11.580, p=0.004) and serological response (OR=10.129; CI=2.440-42.044; p<0.001). Rs8099917 TT was predictive only of virological response (OR=3.746, CI=1.235-11.355; p=0.020). The E genotype was a negative predictive factor of virological response (OR=0.057; CI=0.014-0.238; p<0.001). IL28-B polymorphisms are related to different response in the treatment of CHB HBeAg-negative with PEG-IFN, and the E genotype is a novel negative predictive factor.

Influence of low-density lipoprotein cholesterol on virological response to telaprevir-based triple therapy for chronic HCV genotype 1b infection

Elevated serum low-density lipoprotein cholesterol (LDL-C) level has been associated with sustained virological response (SVR) by chronic hepatitis C patients treated with pegylated-interferon (PEG-IFN) α and ribavirin (RBV). The aim of this study was to investigate the relation between the baseline LDL-C level and the treatment outcome from telaprevir (TVR)-based triple therapy. This prospective, multicenter study consisted of 241 treatment-experienced patients infected with HCV genotype 1b. All received 12 weeks of TVR in combination with 24 weeks of PEG-IFNα2b and RBV. The SVR rate was 81.3% (196 of 241) by intention-to-treat analysis. Higher LDL-C level was strongly associated with SVR (P=1.3×10⁻⁸). The area under the receiver operating characteristic curve for predicting SVR was 0.78 and the cutoff value for the LDL-C level at baseline was 95 mg/dL. In multivariable logistic regression analysis of predictors of SVR, LDL-C ≥95 mg/dL (odds ratio [OR] 3.60, P=0.0238), α-fetoprotein ≤5.0 ng/mL (OR 5.06, P=0.0060), prior relapse to PEG-IFNα and RBV (OR 5.71, P=0.0008), and rapid virological response (HCV RNA undetectable at week 4) (OR 5.52, P=0.0010) were extracted as independent predictors of SVR. For prior partial and null responders, the SVR rates of the groups with LDL-C ≥95 mg/dL were significantly higher than those of the <95 mg/dL groups with IL28B TG/GG and pretreatment platelet count <150×10⁹/L (both P<0.05). The baseline LDL-C level exerted a potent influence on the SVR of treatment-experienced patients treated with TVR-based triple therapy, especially for prior partial and null responders to PEG-IFNα and RBV.

Development and validation of a useful UPLC-MS/MS method for quantification of total and phosphorylated-ribavirin in peripheral blood mononuclear cells of HCV+ patients

The current standard-of-care therapy in HCV consists in ribavirin (RBV) plus pegylated-interferon-α 2a or 2b and, for HCV-1 infected patients, also directly acting antivirals (DAAs). Despite the increase in the number of patients who reach sustained virological response (SVR) for HCV-1, a great inter-individual variability in the response to therapy remains. Whether new drugs are available in combination with RBV and Peg-IFN for HCV-1, the treatment of the other viral genotypes remains the same: this issue highlights the lasting importance of RBV and Peg-IFN in anti-HCV treatment. Moreover, a strong limiting factor to the usefulness of anti-HCV treatment remains the occurrence of adverse events, first of all hemolytic anemia, which have increased with the addition of DAAs, but is mainly an RBV-dependent effect. For these reasons, the monitoring of RBV exposure in the various compartments should be important. Since the routinely determination of RBV in the target cells as the hepatocytes is impracticable for of its invasiveness, the quantification in easier to obtain cells could be a good choice. In this work, we developed and validated an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) assay method to quantify RBV concentrations in peripheral blood mononucleated cells (PBMCs). QCs were prepared with RBV and RBV-monophosphate (RMP). Each sample was divided into two aliquots, which undergone the same extraction procedure: one was treated with acid phosphatase to convert RBV phosphorylated metabolites into free RBV, the other one was not-treated. The extracts were analyzed with reverse-phase column with UPLC-MS/MS. Calibration curves fitted a least squares model (weighed 1/X) for ribavirin levels in a range from 0.1 ng to 200 ng (mean r(2)=0.9993). Accuracy, intra-day and inter-day precision of the methods were in accordance with FDA guidelines. Moreover, phosphorylated QCs were used to assess the correct determination of total RBV concentration. We tested this method by monitoring RBV concentrations in PBMCs from 20 HCV+ patients, receiving alpha interferon-plus RBV combination therapy. This method showed to be reliable, precise, accurate and suitable for evaluation of intracellular RBV concentrations.