APOE-ɛ4 Carrier Status and Donepezil Response in Patients with Alzheimer's Disease.

BACKGROUND: Previous studies have investigated associations between apolipoprotein E (APOE)-ɛ4 allele status and acetylcholinesterase inhibitor treatment response in patients with Alzheimer's disease. The ability to draw definitive conclusions regarding the effect of APOE-ɛ4 genotype on treatment response has been hindered by inconsistent results among studies and methodological limitations that restrict interpretation of study findings. OBJECTIVE: To determine whether APOE-ɛ4 carrier status influences the magnitude of change in 13-item Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog) score associated with acetylcholinesterase inhibitor treatment (i.e., donepezil). METHODS: Analyses were performed using pooled data from the donepezil and placebo treatment arms of three consecutive, similarly designed, 12-week, multi-national, randomized clinical studies that enrolled patients with mild-to-moderate Alzheimer's disease. Correlations between APOE-ɛ4 carrier status and ADAS-cog scores were evaluated using analysis of covariance. RESULTS: No appreciable interaction between donepezil response and APOE-ɛ4 carrier status or copy number was detected. Both carriers and non-carriers of APOE-ɛ4 who received donepezil experienced significant improvements from baseline in ADAS-cog score versus placebo (p <  0.05). Change from baseline to final observation in the donepezil treatment group was - 2.95 for APOE-ɛ4 carriers and - 4.09 for non-carriers (p = 0.23). In contrast, non-carriers of APOE-ɛ4 in the placebo treatment group exhibited a greater improvement from baseline versus carriers (-2.38 versus - 0.60, p = 0.05). CONCLUSION: Within this population, APOE genotype had no statistically significant effect on cognitive response to donepezil treatment; however, APOE-ɛ4 allele status was associated with a difference in the magnitude of the change in ADAS-cog of placebo-treated patients.

Smoking cessation pharmacogenetics: analysis of varenicline and bupropion in placebo-controlled clinical trials.

Despite effective therapies for smoking cessation, most smokers find quitting difficult and most successful quitters relapse. Considerable evidence supports a genetic risk for nicotine dependence; however, less is known about the pharmacogenetics of smoking cessation. In the first pharmacogenetic investigation of the efficacy of varenicline and bupropion, we examined whether genes important in the pharmacodynamics and pharmacokinetics of these drugs and nicotine predict medication efficacy and adverse events. Subjects participated in randomized, double-blind, placebo-controlled smoking cessation clinical trials, comparing varenicline, a nicotinic acetylcholine receptor (nAChR) partial agonist, with bupropion, a norepinephrine/dopamine reuptake inhibitor, and placebo. Primary analysis included 1175 smokers of European ancestry, and 785 single nucleotide polymorphisms from 24 genes, representing 254 linkage disequilibrium (LD) bins (genes included nAChR subunits, additional varenicline-specific genes, and genes involved in nicotine or bupropion metabolism). For varenicline, continuous abstinence (weeks 9-12) was associated with multiple nAChR subunit genes (including CHRNB2, CHRNA5, and CHRNA4) (OR=1.76; 95% CI: 1.23-2.52) (p<0.005); for bupropion, abstinence was associated with CYP2B6 (OR=1.78; 95% CI: 1.27-2.50) (p<0.001). Incidence of nausea was associated with several nAChR subunit genes (OR=0.50; 95% CI: 0.36-0.70) (p<0.0001) and time to relapse after quitting was associated with HTR3B (HR=1.97; 95% CI: 1.45-2.68) (p<0.0001). These data provide evidence for multiple genetic loci contributing to smoking cessation and therapeutic response. Different loci are associated with varenicline vs bupropion response, suggesting that additional research may identify clinically useful markers to guide treatment decisions.

PDE4B polymorphisms and decreased PDE4B expression are associated with schizophrenia.

Schizophrenia has a complex genetic underpinning and variations in a number of candidate genes have been identified that confer risk of developing the disorder. We report in the present studies that several single nucleotide polymorphisms (SNPs) and a two-SNP haplotype in PDE4B are associated with an increased incidence of schizophrenia in two large populations of Caucasian and African American patients. The SNPs in PDE4B associated with schizophrenia occur in intronic sequences in the vicinity of a critical splice junction that gives rise to the expression of PDE4B isoforms with distinct regulation and function. We also observed specific decreases in phosphodiesterase 4B (PDE4B) isoforms in brain tissue obtained postmortem from patients diagnosed with schizophrenia and bipolar disorder. PDE4B metabolically inactivates the second messenger cAMP to regulate intracellular signaling in neurons throughout the brain. Thus, the present observations suggest that dysregulation of intracellular signaling mediated by PDE4B is a significant factor in the cause and expression, respectively, of schizophrenia and bipolar disorder and that targeting PDE4B-regulated signaling pathways may yield new therapies to treat the totality of these disorders.