Dosing strategies for de novo once-daily extended release tacrolimus in kidney transplant recipients based on CYP3A5 genotype

BACKGROUND Tacrolimus extended-release tablets have been Food and Drug Administrationapproved for use in the de novo kidney transplant population.Dosing requirements often vary for tacrolimus based on several factors including variation in metabolism based on CYP3A5 expression.Patients who express CYP3A5 often require higher dosing of immediate-release tacrolimus,but this has not been established for tacrolimus extended-release tablets in the de novo setting.AIM To obtain target trough concentrations of extended-release tacrolimus in de novo kidney transplant recipients according to CYP3A5 genotype.METHODS Single-arm,prospective,single-center,open-label,observational study(ClinicalTrials.gov:NCT037-13645).Life cycle pharma tacrolimus(LCPT)orally once daily at a starting dose of 0.13 mg/kg/day based on actual body weight.If weight is more than 120%of ideal body weight,an adjusted body weight was used.LCPT dose was adjusted to maintain tacrolimus trough concentrations of 8-10 ng/mL.Pharmacogenetic analysis of CYP3A5 genotype was performed at study conclusion.RESULTS Mean time to therapeutic tacrolimus trough concentration was longer in CYP3A5 intermediate and extensive metabolizers vs CYP3A5 non-expressers(6 d vs 13.5 d vs 4.5 d;P=0.025).Mean tacrolimus doses and weight-based doses to achieve therapeutic concentration were higher in CYP3A5 intermediate and extensive metabolizers vs CYP3A5 non-expressers(16 mg vs 16 mg vs 12 mg;P=0.010)(0.20 mg/kg vs 0.19 mg/kg vs 0.13 mg/kg;P=0.018).CYP3A5 extensive metabolizers experienced lower mean tacrolimus trough concentrations throughout the study period compared to CYP3A5 intermediate metabolizers and non-expressers(7.98 ng/mL vs 9.18 ng/mL vs 10.78 ng/mL;P=00.008).No differences were identified with regards to kidney graft function at 30-d post-transplant.Serious adverse events were reported for 13(36%)patients.CONCLUSION Expression of CYP3A5 leads to higher starting doses and incremental dosage titration of extended-release tacrolimus to achieve target trough concentrations.We suggest a higher starting dose of 0.2 mg/kg/d for CYP3A5 expressers.

Disruption of NAD^+ binding site in glyceraldehyde 3-phosphate dehydrogenase affects its intranuclear interactions

AIM:To characterize phosphorylation of human glyceraldehyde 3-phosphate dehydrogenase(GAPDH),and mobility of GAPDH in cancer cells treated with chemotherapeutic agents. METHODS:We used proteomics analysis to detect and characterize phosphorylation sites within human GAPDH. Site-specific mutagenesis and alanine scanning was then performed to evaluate functional significance of phosphorylation sites in the GAPDH polypeptide chain. Enzymatic properties of mutated GAPDH variants were assessed using kinetic studies. Intranuclear dynamics parameters(diffusion coefficient and the immobile fraction) were estimated using fluorescence recovery after photobleaching(FRAP) experiments and confocal microscopy. Molecular modeling experiments were performed to estimate the effects of mutations on NAD+ cofactor binding.RESULTS:Using MALDI-TOF analysis,we identified novel phosphorylation sites within the NAD+ binding center of GAPDH at Y94,S98,and T99. Using polyclonal antibody specific to phospho-T99-containing peptide within GAPDH,we demonstrated accumulation of phospho-T99-GAPDH inthe nuclear fractions of A549,HCT116,and SW48 cancer cel s after cytotoxic stress. We performed site-mutagenesis,and estimated enzymatic properties,intranuclear distribution,and intranuclear mobility of GAPDH mutated variants. Site-mutagenesis at positions S98 and T99 in the NAD+ binding center reduced enzymatic activity of GAPDH due to decreased affinity to NAD+(Km = 741 ± 257 μmol/L in T99 I vs 57 ± 11.1 μmol/L in wild type GAPDH. Molecular modeling experiments revealed the effect of mutations on NAD+ binding with GAPDH. FRAP(fluorescence recovery after photo bleaching) analysis showed that mutations in NAD+ binding center of GAPDH abrogated its intranuclear interactions. CONCLUSION:Our results suggest an important functional role of phosphorylated amino acids in the NAD+ binding center in GAPDH interactions with its intranuclear partners.