HLA-DQB1 6672G>C (rs113332494) is associated with clozapine-induced neutropenia and agranulocytosis in individuals of European ancestry.

The atypical antipsychotic clozapine is the only effective medication for treatment-resistant schizophrenia. However, it can also induce serious adverse drug reactions, including agranulocytosis and neutropenia. The mechanism by which it does so is largely unknown, but there is evidence for contributing genetic factors. Several studies identified HLA-DQB1 variants and especially a polymorphism located in HLA-DQB1 (6672G>C, rs113332494) as associated with clozapine-induced agranulocytosis and neutropenia. We analysed the risk allele distribution of SNP rs113332494 in a sample of 1396 controls and 178 neutropenia cases of which 60 developed agranulocytosis. Absolute neutrophil counts of 500/mm3 and 1500/mm3 were used for defining agranulocytosis and neutropenia cases, respectively. We also performed association analyses and analysed local ancestry patterns in individuals of European ancestry, seeking replication and extension of earlier findings. HLA-DQB1 (6672G>C, rs113332494) was associated with neutropenia (OR = 6.20, P = 2.20E-06) and agranulocytosis (OR = 10.49, P = 1.83E-06) in individuals of European ancestry. The association signal strengthened after including local ancestry estimates (neutropenia: OR = 10.38, P = 6.05E-08; agranulocytosis: OR = 16.31, P = 1.39E-06), with effect sizes being considerably larger for agranulocytosis. Using local ancestry estimates for prediction, the sensitivity of rs113332494 increased from 11.28 to 55.64% for neutropenia and from 16.67 to 53.70% for agranulocytosis. Our study further strengthens the evidence implicating HLA-DQB1 in agranulocytosis and neutropenia, suggesting components of the immune system as contributing to this serious adverse drug reaction. Using local ancestry estimates might help in identifying risk variants and improve prediction of haematological adverse effects.

Establishing the Cause of Anemia in a Premature Newborn Infant.

The three major causes of anemia in neonates are blood loss, decreased red blood cell production, and increased degradation of erythrocytes. Establishing the cause of anemia in a neonate born prematurely can be challenging. Clinically, fetomaternal hemorrhage (FMH) can be difficult to diagnose-the condition often presents only after the manifestation of severe fetal anemia. FMH can be confirmed by determining the fetal hemoglobin F fraction in the mother, which is traditionally performed using the Kleihauer-Betke test (KBT). Herein, we present a case study of a newborn baby boy of Dutch ethnicity with massive FMH and negative KBT result. The KBT result appeared to be false-negative due to AO antagonism. However, the results of an additional marker alpha-fetoprotein (AFP) test confirmed the diagnosis of massive FMH. Therefore, measuring AFP in maternal blood can be helpful in confirming FMH in unexplained anemia of the neonate.

Aberrant CYP2D6 metabolizer phenotypes do not show increased frequency in patients undergoing ECT after antidepressant therapy.

We investigated the accumulation of aberrant CYP2D6 genotypes and predicted metabolizer phenotypes (ultrarapid metabolizer, intermediate metabolizer and poor metabolizer) potentially affecting the antidepressant treatment response in depressive patients indicated for electroconvulsive therapy (ECT) compared with patients with a single episode of depression. Seventy-six Dutch White patients with unipolar or bipolar treatment-resistant depression who underwent ECT were genotyped using the Amplichip CYP450 Test for CYP2D6. Two hundred and eight patients with a single episode of unipolar or bipolar depression were used as controls. No difference was observed in the prevalence of CYP2D6 phenotypes (poor metabolizer, intermediate metabolizer, extensive metabolizer and ultrarapid metabolizer) between the ECT and the control patients (5.3, 38.7, 56.0 and 0.0% vs. 6.4, 51.0, 42.6 and 0.0%, respectively). The types of depression (odds ratio = 0.33, P = 0.018) and age (odds ratio = 1.55 for a 10-year increase, P < 0.001), but not CYP2D6 phenotype or activity score were associated with the response to antidepressant treatment. In conclusion, preemptive genotyping for CYP2D6 currently appears to have no clinical implications in treatment-resistant depressive patients indicated for ECT.

The Influence of the CYP3A4*22 Polymorphism and CYP2D6 Polymorphisms on Serum Concentrations of Aripiprazole, Haloperidol, Pimozide, and Risperidone in Psychiatric Patients.

INTRODUCTION: Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of greater than 50% of the prescribed drugs. Recently, the CYP3A4*22 allele was reported to be associated with lower CYP3A4 expression and activity. Quetiapine, an antipsychotic metabolized by only CYP3A4, displayed higher serum levels in CYP3A4*22 carriers. Aripiprazole, haloperidol, pimozide, and risperidone are antipsychotics that are metabolized by CYP3A4 and CYP2D6. We investigated to which degree the CYP3A4*22 single-nucleotide polymorphism affects serum concentrations of patients receiving these drugs and compared this with the influence of CYP2D6 polymorphisms. METHODS: Eight hundred thirty-four adult patients were included in this study, of whom 130 used aripiprazole, 312 used haloperidol, 86 used pimozide, and 396 used risperidone. Serum levels of the drug and, if available, their active metabolites were collected as well as information on dose. Patients were genotyped for CYP3A4*22 using restriction fragment length polymorphism analysis. Genotyping for CYP2D6 was done with allele-specific polymerase chain reaction. RESULTS: No differences were found in serum (dose-corrected) concentrations of the antipsychotics between CYP3A4*22 wild-type and carrier groups. In contrast, CYP2D6 genotype did affect dose-corrected concentrations of the antipsychotics: for example, median dose-corrected concentrations were 56%, 86%, and 400% higher in predicted poor metabolizers versus extensive metabolizers for aripiprazole (P = 0.004), haloperidol (P > 0.001), and risperidone (P < 0.001), respectively, although a multiple regression analysis showed that only 4% to 17% of the variation in these concentrations could be explained by CYP2D6 status. CONCLUSIONS: Heterozygous presence of CYP3A4*22 does not increase serum levels of antipsychotics metabolized by both CYP3A4 and CYP2D6, whereas CYP2D6 polymorphisms do affect serum levels to a limited extent.

The influence of the CYP3A4*22 polymorphism on serum concentration of quetiapine in psychiatric patients.

BACKGROUND: Besides dietary, hormonal, or pathological factors, mutations in cytochrome P450 enzymes are thought to be responsible for the interindividual differences in serum concentrations of cytochrome P450 (CYP450)-dependent drugs. Cytochrome P450 3A4 (CYP3A4) is involved in the metabolism of greater than 50% of the prescribed drugs. Recently, a new single-nucleotide polymorphism (SNP) was found (CYP3A4*22), which results in a decreased enzyme activity, in contrast to the other known SNPs in CYP3A4. We investigated to which degree the CYP3A4*22 SNP affects serum concentrations of patients receiving quetiapine, a drug exclusively metabolized by CYP3A4. METHODS: Two hundred thirty-eight adult patients receiving quetiapine were included in this study, based on availability of DNA, serum quetiapine levels, and information on dose. Patients were genotyped for CYP3A4*22 using allele-specific polymerase chain reaction, and, as a control, restriction fragment length polymorphism analysis. RESULTS: Carriers of the CYP3A4*22 allele (*1/*22 and *22/*22, n = 31) had 2.5-fold higher serum levels of quetiapine than did wild-type patients (n = 207; P = 0.03) when using a comparable dose (median, 300 mg/d for both wild-type and carriers; P = 0.67). The dose-corrected serum concentration (C/D) was 67% higher in carriers than in wild-type patients (P = 0.01). The number of patients who achieved serum levels above the therapeutic range (>500 µg/L) was also higher in *22-allele carriers (16.1% vs 2.9%; P = 0.007). CONCLUSION: Being a carrier of the CYP3A4*22 allele increases the serum concentration of quetiapine at comparable doses.

The association between CYP2D6 genotype and switching antipsychotic medication to clozapine.

PURPOSE: Genetic variation in the cytochrome P450 2D6 (CYP2D6) enzyme is responsible for interindividual differences in the metabolism of many antipsychotic drugs, but the clinical relevance of polymorphisms in CYP2D6 for response to antipsychotic treatment is relatively unknown. In the Netherlands, clozapine is prescribed only when patients are non-responsive to or intolerant of at least two different antipsychotics. The aim of our study was to determine the association of the CYP2D6 genotype with switching to clozapine, which served as a surrogate outcome marker for treatment response to antipsychotics. METHODS: CYP2D6 genotype was assessed in patients who had been switched to clozapine and compared with antipsychotic users whose treatment regimen included no more than two different antipsychotic drugs and no clozapine. We also performed the analysis in patients who only used CYP2D6-dependent antipsychotics. RESULTS: A total of 528 patients were included in the study (222 cases, 306 controls). No statistically significant differences were found in the distribution of the polymorphisms among the case and control groups, both in all patients and in only those patients using CYP2D6-dependent antipsychotics. However, a trend was observed, suggesting an inverse association between CYP2D6 genotype and the switch to clozapine. (9.5 vs. 5.1 % poor metabolisers and 1.3 vs. 2.6 % ultrarapid metabolisers in cases vs. controls, respectively). CONCLUSIONS: Although the results of our study suggest that the CYP2D6 phenotype is not a major determining factor for patients to be switched to clozapine treatment, larger studies are warranted with a focus on the clinical consequences of the CYP2D6 ultrarapid metaboliser and poor metaboliser phenotypes.

Treatment with high-dose simvastatin inhibits geranylgeranylation in AML blast cells in a subset of AML patients.

It is currently unknown whether the in vitro effects observed with statins in acute myeloid leukemia (AML) cells, including lowering of cholesterol, inhibition of isoprenylation, and sensitization to chemotherapy, also occur in vivo. Therefore, AML mononuclear cells (MNCs) were isolated from 12 patients before and after 7 days of high-dose (7.5-15 mg/kg/day) simvastatin treatment. Parallel mouse studies were performed to have, in addition to AML cells, access to liver tissue, a major target of statins. Serum cholesterol levels were lowered by simvastatin in all patients, however, only limited changes in the messenger RNA expression of cholesterol metabolism genes were seen in patient and mouse MNCs compared to murine liver cells. Still, two out of seven patients displayed an increased in vitro chemosensitivity of their AML cells upon simvastatin treatment. Gene set enrichment analysis on microarray data of AML patient cells and Western blot analysis for the isoprenylated proteins DnaJ and Rap1 on murine and AML patient MNCs demonstrated that in vivo simvastatin treatment resulted in inhibition of geranylgeranylation in murine MNCs and in a subset of patient AML MNCs. In summary, our data demonstrate that simvastatin treatment results in chemosensitization and inhibition of geranylgeranylation in AML cells of a subset of patients.

Combining simvastatin with the farnesyltransferase inhibitor tipifarnib results in an enhanced cytotoxic effect in a subset of primary CD34+ acute myeloid leukemia samples.

PURPOSE: To show whether the inhibitory effects of the cholesterol synthesis inhibitor simvastatin on human CD34(+) acute myeloid leukemia (AML) cells can be further promoted by combining it with the farnesyltransferase inhibitor tipifarnib. EXPERIMENTAL DESIGN: Normal CD34(+), AML CD34(+), and CD34(-) sorted subfractions, and AML cell lines (TF-1 and KG1A) were exposed to simvastatin and tipifarnib. RESULTS: Both simvastatin and tipifarnib showed a cytotoxic effect on AML cell lines, which was additive when used in combination. In primary sorted CD34(+) AML cells, a heterogeneous response pattern was observed upon treatment with simvastatin when analyzing cell survival. A group of normal (n = 12) and abnormal (n = 10) responders were identified within the AML CD34(+) subfraction when compared with normal CD34(+) cells. This distinction was not observed within the AML CD34(-) cell fraction. When the CD34(+) AML cells were exposed to simvastatin and tipifarnib, a significant enhanced inhibitory effect was shown exclusively in the normal AML responder group, whereas the AML CD34(-) cell fractions all showed an enhanced inhibitory effect. The observed heterogeneity in AML responsiveness could not be explained by differences in effects on cholesterol metabolism genes or extracellular signal-regulated kinase phosphorylation in response to simvastatin and tipifarnib treatment. CONCLUSION: The results suggest that combined treatment with statins and farnesyltransferase inhibitors may be beneficial for a subset of AML patients that can be defined by studying the AML CD34(+) fraction.

Variability in responsiveness to lovastatin of the primitive CD34+ AML subfraction compared to normal CD34+ cells.

In the present study, we questioned whether the cholesterol synthesis inhibitor lovastatin potentiates the cytotoxicity of chemotherapeutic agents in the primitive CD34(+) subpopulation of acute myeloid leukemia (AML) cells. AML mononuclear cells (n = 17) were sorted in CD34(+) and CD34(-) fractions and compared to normal CD34(+/-) cells (n = 7). The percentage of surviving cells upon exposure to lovastatin (25-100 microM) and/or chemotherapeutics (cytarabin or daunorubicin) was determined with a luminescent cell viability assay. The results demonstrate that the primitive CD34(+) subpopulation of normal and AML cells displayed a higher sensitivity to lovastatin than the more mature CD34(-) subpopulation. The combination of lovastatin and chemotherapeutics resulted in a more pronounced inhibitory effect on both subpopulations. In contrast to the homogeneous results in normal CD34(+) cells, a distinct heterogeneity in lovastatin sensitivity was found in AML samples. Therefore, a group of normal (n = 11) and abnormal (n = 6) responders were identified based on a reduced or increased cell survival compared to normal CD34(+) cells. This distinction was not only observed in the CD34(+) AML subfraction but also in CD34(+)CD38(-)AML cells. In the abnormal responder group, 50% of patients presented with unfavorable cytogenetics and significant higher peripheral blast cell counts, which coincided with poor treatment results. In summary, the findings indicate that the primitive subfraction of CD34(+) AML cells is in the majority of cases affected by lovastatin treatment, which is potentiated when combined with chemotherapeutics. Heterogeneity of the response observed in AML patients allowed identification of a subgroup with poor prognosis.

Site-specific inhibition of glomerulonephritis progression by targeted delivery of dexamethasone to glomerular endothelium.

Glomerulonephritis represents a group of renal diseases with glomerular inflammation as a common pathologic finding. Because of the underlying immunologic character of these disorders, they are frequently treated with glucocorticoids and cytotoxic immunosuppressive agents. Although effective, use of these compounds has limitations as a result of toxicity and systemic side effects. In the current study, we tested the hypothesis that targeted delivery of dexamethasone (dexa) by immunoliposomes to activated glomerular endothelium decreases renal injury but prevents its systemic side effects. E-selectin was chosen as a target molecule based on its disease-specific expression on activated glomerular endothelium in a mouse anti-glomerular basement membrane glomerulonephritis. Site-selective delivery of Ab(Esel) liposome-encapsulated dexamethasone strongly reduced glomerular proinflammatory gene expression without affecting blood glucose levels, a severe side effect of administration of free dexamethasone. Dexa-Ab(Esel) liposomes reduced renal injury as shown by a reduction of blood urea nitrogen levels, decreased glomerular crescent formation, and down-regulation of disease-associated genes. Immunoliposomal drug delivery to glomerular endothelium presents a powerful new strategy for treatment of glomerulonephritis to sustain efficacy and prevent side effects of potent anti-inflammatory drugs.