Novel drug transporter substrates identification: An innovative approach based on metabolomic profiling, in silico ligand screening and biological validation.

Solute carrier (SLC) transport proteins are fundamental for the translocation of endogenous compounds and drugs across membranes, thus playing a critical role in disease susceptibility and drug response. Because only a limited number of transporter substrates are currently known, the function of a large number of SLC transporters is elusive. Here, we describe the proof-of-concept of a novel strategy to identify SLC transporter substrates exemplarily for the proton-coupled peptide transporter (PEPT) 2 (SLC15A2) and multidrug and toxin extrusion (MATE) 1 transporter (SLC47A1), which are important renal transporters of drug reabsorption and excretion, respectively. By combining metabolomic profiling of mice with genetically-disrupted transporters, in silico ligand screening and in vitro transport studies for experimental validation, we identified nucleobases and nucleoside-derived anticancer and antiviral agents (flucytosine, cytarabine, gemcitabine, capecitabine) as novel drug substrates of the MATE1 transporter. Our data confirms the successful applicability of this new approach for the identification of transporter substrates in general, which may prove particularly relevant in drug research.

Impact of very early introduction of everolimus on liver regeneration after partial liver transplantation in rats.

BACKGROUND/PURPOSE: This experimental study in rats aimed to investigate the impact of very early introduction (within 3 h) of everolimus (EVR) + reduced-tacrolimus (TAC) after partial liver transplantation (LT) on liver regeneration, rejection, and survival. METHODS: Based on appropriate dose of EVR + reduced-TAC in 70% hepatectomy (Experiment 1), allogeneic 30% partial LT (Experiment 2) and whole LT (Experiment 3) were performed. RESULTS: After partial LT in EVR + reduced-TAC therapy, restoration of liver graft weight (to that of the whole liver) was delayed compared with standard dose TAC monotherapy (standard-TAC) on day 3 (59.3% vs. 72.9%; p < .001) and 14 (88.1% vs. 95.5%; p = .01). Survival was 75%, which was not as high as the value of 100% observed for standard-TAC, because neither infection nor rejection could be prevented. By contrast, survival after whole LT was 100% as neither infection nor rejection occurred. CONCLUSIONS: The very early introduction of EVR + reduced-TAC after partial LT delayed liver regeneration, and made it difficult to manage the dose required to suppress both infection and rejection. On the other hand, EVR + reduced-TAC could be introduced safely very early after whole LT.

Therapeutic Drug Monitoring and Dosage Adjustments of Immunosuppressive Drugs When Combined With Nirmatrelvir/Ritonavir in Patients With COVID-19.

ABSTRACT: Nirmatrelvir/ritonavir (Paxlovid) consists of a peptidomimetic inhibitor (nirmatrelvir) of the SARS-CoV-2 main protease and a pharmacokinetic enhancer (ritonavir). It is approved for the treatment of mild-to-moderate COVID-19. This combination of nirmatrelvir and ritonavir can mediate significant and complex drug-drug interactions (DDIs), primarily due to the ritonavir component. Indeed, ritonavir inhibits the metabolism of nirmatrelvir through cytochrome P450 3A (CYP3A) leading to higher plasma concentrations and a longer half-life of nirmatrelvir. Coadministration of nirmatrelvir/ritonavir with immunosuppressive drugs (ISDs) is particularly challenging given the major involvement of CYP3A in the metabolism of most of these drugs and their narrow therapeutic ranges. Exposure of ISDs will be drastically increased through the potent ritonavir-mediated inhibition of CYP3A, resulting in an increased risk of adverse drug reactions. Although a decrease in the dosage of ISDs can prevent toxicity, an inappropriate dosage regimen may also result in insufficient exposure and a risk of rejection. Here, we provide some general recommendations for therapeutic drug monitoring of ISDs and dosing recommendations when coadministered with nirmatrelvir/ritonavir. Particularly, tacrolimus should be discontinued, or patients should be given a microdose on day 1, whereas cyclosporine dosage should be reduced to 20% of the initial dosage during the antiviral treatment. Dosages of mammalian target of rapamycin inhibitors (m-TORis) should also be adjusted while dosages of mycophenolic acid and corticosteroids are expected to be less impacted.

Effect of Itraconazole and Its Metabolite Hydroxyitraconazole on the Blood Concentrations of Cyclosporine and Tacrolimus in Lung Transplant Recipients.

Invasive Aspergillus infection is a major factor for poor prognosis in patients receiving lung transplantation (LT). An antifungal agent, itraconazole (ITCZ), that has antimicrobial activity against Aspergillus species, is used as a prophylactic agent against Aspergillus infection after LT. ITCZ and its metabolite, hydroxyitraconazole (OH-ITCZ), potently inhibit CYP3A and P-glycoprotein that metabolize or excrete calcineurin inhibitors (CNIs), which are the first-line immunosuppressants used after LT; thus, concomitant use of ITCZ and CNIs could induce an increase in the blood concentration of CNIs. However, no criteria for dose reduction of CNIs upon concomitant use with ITCZ in LT recipients have been defined. In this study, the effect of ITCZ and OH-ITCZ on the blood concentrations of two CNIs, tacrolimus and cyclosporine, after LT were retrospectively evaluated. A total of 39 patients who received LT were evaluated. Effects of ITCZ and OH-ITCZ on the concentration/dosage (C/D) ratio of tacrolimus and cyclosporine were analyzed using linear mixed-effects models. The plasma concentrations of OH-ITCZ were about 2.5-fold higher than those of ITCZ. Moreover, there was a significant correlation between the plasma concentrations of ITCZ and OH-ITCZ. Based on parameters obtained in the linear regression analysis, the C/D ratios of cyclosporine and tacrolimus increase by an average of 2.25- and 2.70-fold, respectively, when the total plasma concentration of ITCZ plus OH-ITCZ is 1000 ng/mL. In conclusion, the plasma levels of ITCZ and OH-ITCZ could be key factors in drawing up the criterion for dose reduction of CNIs.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology.

ABSTRACT: When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.

Establishment of an experimental rat model of tacrolimus-induced kidney injury accompanied by interstitial fibrosis.

Nephrotoxicity is the major adverse reaction to tacrolimus; however, the underlying mechanisms remain to be fully elucidated. Although several tacrolimus-induced nephrotoxicity animal models have been reported, most renal injury rat models contain factors other than tacrolimus. Here, we report the development of a new nephrotoxicity with interstitial fibrosis rat model induced by tacrolimus administration. Thirty Wistar rats were randomly divided into four groups: sham-operated (Sham), vehicle-treated ischemia reperfusion (I/R) injury (IRI), tacrolimus treated (TAC) and tacrolimus treated I/R injury (TAC + IRI). Rats subjected to IR injury and treated with tacrolimus for 2 weeks showed higher serum creatinine (Scr), blood urea nitrogen (BUN), serum magnesium (Mg) and serum potassium (K), indicating decreased renal function. In addition, tacrolimus treatment combined with IR injury increased histological injury (tubular vacuolation, glomerulosclerosis and interstitial fibrosis), as well as α-smooth muscle actin (α-SMA), transforming growth factor-ß (TGF-ß), and kidney injury molecule-1 (KIM-1) expression in the renal cortex. In summary, we have developed a tacrolimus-induced kidney injury rat model with interstitial fibrosis within 2 weeks by creating conditions mimicking renal transplantation via tacrolimus administration following ischemia-reperfusion.

Continuous monitoring of neutrophils to lymphocytes ratio for estimating the onset, severity, and subsequent prognosis of immune related adverse events.

Immune checkpoint inhibitors (ICIs) play a central role in various cancers. ICIs can cause immune-related adverse events (irAEs). As severe irAEs can be life-threatening, biomarkers for estimating irAE onset are crucial. The neutrophils-to-lymphocytes ratio (NLR) reflects the systemic immune condition and known as a prognostic marker in ICI treatment. Our study evaluated if the NLR corresponded with irAEs, and its feasibility as a biomarker for irAE onset. We retrospectively analyzed 275 cancer patients treated with anti-PD-1 monotherapy. We observed 166 irAEs in 121 patients. The NLR was significantly elevated during irAEs. Patients experiencing interstitial pneumonitis showed NLR elevation 4 weeks before initial symptoms and diagnosis. Analyzing receiver operating characteristics curves revealed that elevated NLR distinguished subsequent pneumonitis severity with high accuracy (AUC 0.93, sensitivity 88.9%, specificity 88.2%, cut-off 2.37, p = 0.0004). After a severe irAE occurred, two NLR trends were observed. Patients who showed a prompt reduction in elevated NLRs had favorable progression-free survival (hazard ratio 0.32, 95% CI 0.10-1.01, p = 0.0140) and overall survival (hazard ratio 0.23, 95% CI 0.06-0.86, p = 0.0057) compared to the patients who maintained elevated NLRs. These findings suggest that continuous monitoring of NLR trends may predict irAE onset and severity and subsequent prognosis.

Inhibitory effects of vandetanib on creatinine transport via renal organic cation transporter OCT2.

Vandetanib (ZD6474, Zactima®, Caprelsa®) is a newly developed dual tyrosine kinase inhibitor of vascular endothelial growth factor and epidermal growth factor receptor. Recently, several reports have indicated the interaction of vandetanib with tyrosine kinase inhibitors and transporters. However, these characteristics of vandetanib remain unclear. We examined the interaction of vandetanib with the human organic cation transporter 2 (hOCT2) stably expressed in human embryonic kidney (HEK) 293 cells. The specific uptake of vandetanib was not observed in hOCT2-expressing HEK293 cells. Vandetanib inhibited the uptake of creatinine mediated by hOCT2 in a dose-dependent manner. The IC50 value for vandetanib inhibition of creatinine uptake by hOCT2 was 3.7 ± 1.0 µM (average ± SE of three separate experiments). The IC50 value of cimetidine and trimethoprim for hOCT2 were 100 ± 13.5 and 52.1 ± 8.0 µM, respectively. Vandetanib showed markedly higher affinity for hOCT2 than cimetidine and trimethoprim. These results suggest that hOCT2 may play a crucial role in elevating the serum creatinine levels, as well as increasing the risk of renal impairment during vandetanib administration.

Association of lenvatinib plasma concentration with clinical efficacy and adverse events in patients with hepatocellular carcinoma.

PURPOSE: This study aimed to examine the association between the trough plasma concentration of lenvatinib with the objective response rate (ORR) and adverse events in patients with hepatocellular carcinoma (HCC). METHODS: Twenty-one patients with HCC who received lenvatinib were enrolled. We examined the median trough concentration (Ctrough median) of plasma lenvatinib until the first clinical response evaluation. The receiver-operating characteristic curve was drawn to show the discrimination potential of the Ctrough median for the ORR, using the modified Response Evaluation Criteria in Solid Tumors. Adverse events were graded based on the Common Terminology Criteria for Adverse Events (ver. 5.0). RESULTS: The Ctrough median values in the complete response and partial response group were significantly higher than those in the stable disease and progressive disease groups. The ORR was significantly higher in the high-Ctrough median group (≥ 42.68 ng/mL) than in the low-Ctrough median group (< 42.68 ng/mL) (80.0% vs. 18.2%; p = 0.0089). Although there was no difference in the occurrence of most adverse events between the high- and low-Ctrough median groups, the occurrence of any grade anorexia (100.0% vs. 45.5%; p = 0.0124) and grade 3 serious hypertension (70.0% vs. 18.2%; p = 0.0300) was significantly higher in the high-Ctrough median group than in the low-Ctrough median group. Multivariate analysis showed that high-Ctrough median was significantly associated with ORR development (odds ratio, 15.00; 95% confidence interval, 1.63-138.16; p = 0.0168). CONCLUSION: Maintaining Ctrough median above 42.68 ng/mL was crucial for achieving the ORR in patients with HCC.

Effects of Concomitant Administration of Vonoprazan Fumarate on the Tacrolimus Blood Concentration in Kidney Transplant Recipients.

Vonoprazan fumarate (vonoprazan) is a new kind of acid suppressant with potent acid inhibitory effects. Therefore, it has been administered to kidney transplant recipients for treatment or prophylaxis of steroid ulcers, refractory peptic ulcers, and gastroesophageal reflux disease. Because tacrolimus, which is a well-established immunosuppressant for kidney transplantation, and vonoprazan share the CYP3A4 system for metabolism, drug interactions are anticipated upon simultaneous administration. We retrospectively analyzed 52 kidney transplant recipients who were converted from rabeprazole, which has a small effect on the tacrolimus trough blood concentration (C0), to vonoprazan between August 2016 and July 2019. We compared the tacrolimus C0/tacrolimus dose (C0/D) before and after conversion and serum liver enzymes, serum total bilirubin, and the estimated glomerular filtration rate (eGFR). As a result, mean tacrolimus C0/D before and after conversion was 1.98 ± 1.02 and 2.19 ± 1.15 (ng/mL)/(mg/d), respectively, (p < 0.001). Additionally, mean aspartate transaminase (AST) before and after conversion was 18.6 ± 4.2 and 19.6 ± 5.2 IU/L, respectively, (p = 0.037). Mean alanine transaminase (ALT) before and after conversion was 15.8 ± 5.5 and 17.6 ± 7.1 IU/L, respectively, (p = 0.007). Mean eGFR before and after conversion was 50.6 ± 14.4 and 51.4 ± 14.7 mL/min/1.73 m2, respectively (p = 0.021). Mean AST, ALT, and eGFR were slightly but significantly elevated within normal ranges after conversion. In conclusion, our study suggests that the mean tacrolimus C0/D was elevated significantly by converting from rabeprazole to vonoprazan, but it had little clinical significance. Vonoprazan can be administered safely to kidney transplant recipients receiving tacrolimus.

[Significant Changes Associated with the Transition from Outsourcing to In-hospital Therapeutic Drug Monitoring of Novel Antiepileptics].

For many of the novel antiepileptics, immunoassays, used for routine therapeutic drug monitoring (TDM), cannot be used. We could monitor eight novel antiepileptics using an LC/MS method since July 2017. The purpose of this study was to evaluate the significant changes associated with the transition from outsourcing to in-hospital monitoring of novel antiepileptics. The number of measurements of novel antiepileptics was significantly increased during the first (p<0.01) and second (p<0.001) years of in-hospital monitoring as compared to that one year prior to in-hospital monitoring which was outsourced. The proportion of measurements of novel antiepileptics to all antiepileptics was 19.7%, 31.1%, and 38.4% during outsourcing, and first, and second years of in-hospital monitoring, respectively. The measurement cost was significantly reduced during the first (p<0.001) and second (p<0.001) years of in-hospital monitoring as compared to that during outsourcing. In addition, the revenue from TDM of antiepileptic drugs was significantly increased during the first (p<0.05) and second (p<0.01) years of in-hospital monitoring as compared with that during outsourcing. In conclusion, the switch from outsourcing to in-hospital monitoring led to an increase in the number of orders, a reduction in the measurement-related expenses of novel antiepileptics, and an increase in the revenue from TDM of antiepileptic drugs, which could promote the proper use of novel antiepileptics through TDM.

CYP3A5 Genotype as a Potential Pharmacodynamic Biomarker for Tacrolimus Therapy in Ulcerative Colitis in Japanese Patients.

Tacrolimus has been used to induce remission in patients with steroid-refractory ulcerative colitis. It poses a problem of large individual differences in dosage necessary to attain target blood concentration and, often, this leads to drug inefficacy. We examined the difference in mRNA expression levels of ATP binding cassette transporter B1 (ABCB1) between inflamed and non-inflamed tissues, and the influence of CYP3A5 genotype on tacrolimus therapy. The mRNA expression of CYP3A4 in colonic mucosa and that of cytochrome p450 3A5 (CYP3A5) and ABCB1 in inflamed and non-inflamed areas were examined in 14 subjects. The mRNA expression levels of CYP3A5 were higher than that of CYP3A4. The mRNA expression of ABCB1 was lower in the inflamed than in the non-inflamed mucosa, despite that of CYP3A5 mRNA level being not significantly changed. Hence, the deterioration of the disease is related to the reduction of the barrier in the inflamed mucosa. The relationship between CYP3A5 genotype and blood concentration, dose, and concentration/dose (C/D) ratio of tacrolimus in 15 subjects was studied. The tacrolimus dose to maintain equivalent blood concentrations was lower in CYP3A5*3/*3 than in CYP3A5*1 carriers, and the C/D ratio was significantly higher in the latter. Thus, CYP3A5 polymorphism information played a role in determining the initial dose of tacrolimus. Furthermore, since the effect of tacrolimus appears earlier in CYP3A5*3/*3 than in CYP3A5*1/*1 and *1/*3, it seems necessary to change the evaluation time of therapeutic effect by CYP3A5 genotype. Additionally, the relationship between CYP3A5 genotype and C/D ratio of tacrolimus in colonic mucosa was investigated in 10 subjects. Tacrolimus concentration in the mucosa was two-fold higher in CYP3A5*3/*3 than in CYP3A5*1 carriers, although no significant difference in tacrolimus-blood levels was observed. Therefore, the local concentration of tacrolimus affected by CYP3A5 polymorphism might be related to its therapeutic effect.

Use of Mycophenolate Mofetil Suspension as Part of Induction Therapy After Living-Donor Liver Transplant.

OBJECTIVES: The aim of this study was to evaluate recipient safety, tolerability, and pharmacokinetics of mycophenolate mofetil suspension compared with mycophenolate mofetil capsules as part of induction therapy after living-donor liver transplant. MATERIALS AND METHODS: Between July 2017 and April 2019, we retrospectively enrolled 20 adult primary living-donor liver transplant recipients. Recipients were divided into 3 groups: group 1 received mycophenolate mofetil suspension of 3000 mg (n = 6), group 2 received 3000 mg mycophenolate mofetil via opened capsules (n = 8), and group 3 received mycophenolate mofetil suspension of 2000 mg (n = 6). Administration was started on postoperative day 1, with tacrolimus administered on postoperative day 2 or day 3. RESULTS: The values of area under the plasma concentration time curve for 0 to 12 hours were significantly higher in the 3000 mg/day mycophenolate mofetil suspension group than in the 2000 mg/day mycophenolate mofetil suspension group (P = .024) and in the 3000mg/day mycophenolate mofetil capsule group (P = .013). Significant positive correlations were shown between blood concentration at 8 hours after administration and the plasma concentration time curve for 0 to 12 hours (r2 = 0.96; P < .001) in patients in the suspension group. No patients required mycophenolate mofetil reduction because of leukopenia and diarrhea. Only 1 biopsy-proven acute cellular rejection was recognized in the mycophenolate mofetil suspension group (at 2000 mg/day). There were no significant differences in frequency of opportunistic infections among the 3 groups. CONCLUSIONS: Mycophenolate mofetil suspension is useful as part of immunosuppressive induction therapy after living-donor liver transplant because its concentration increases greater than that of mycophenolate mofetil capsules and because of the low risk of rejection and adverse events.

Influence of POR*28 Polymorphisms on CYP3A5*3-Associated Variations in Tacrolimus Blood Levels at an Early Stage after Liver Transplantation.

It is well known that the CYP3A5*3 polymorphism is an important marker that correlates with the tacrolimus dose requirement after organ transplantation. Recently, it has been revealed that the POR*28 polymorphism affects the pharmacokinetics of tacrolimus in renal transplant patients. In this study, we examined whether POR*28 as well as CYP3A5*3 polymorphism in Japanese recipients and donors would be another biomarker for the variation of tacrolimus blood levels in the recipients during the first month after living-donor liver transplantation. We enrolled 65 patients treated with tacrolimus, who underwent liver transplantation between July 2016 and January 2019. Genomic DNA was extracted from whole-blood samples, and genotyping was performed to examine the presence of CYP3A5*3 and POR*28 polymorphisms in the recipients and donors. The CYP3A5*3/*3 genotype (defective CYP3A5) of the recipient (standard partial regression coefficient [median C/D ratio of CYP3A5 expressor vs. CYP3A5 non-expressor, p value]: Pod 1-7, ß= -0.389 [1.76 vs. 2.73, p < 0.001]; Pod 8-14, ß = -0.345 [2.03 vs. 2.83, p < 0.001]; Pod 15-21, ß= -0.417 [1.75 vs. 2.94, p < 0.001]; Pod 22-28, ß = -0.627 [1.55 vs. 2.90, p < 0.001]) rather than donor (Pod 1-7, ß = n/a [1.88 vs. 2.76]; Pod 8-14, ß = n/a [1.99 vs. 2.93]; Pod 15-21, ß = -0.175 [1.91 vs. 2.94, p = 0.004]; Pod 22-28, ß = n/a [1.61 vs. 2.67]) significantly contributed to the increase in the concentration/dose (C/D) ratio of tacrolimus for at least one month after surgery. We found that the tacrolimus C/D ratio significantly decreased from the third week after transplantation when the recipient carried both CYP3A5*1 (functional CYP3A5) and POR*28 (n = 19 [29.2%], median C/D ratio [inter quartile range] = 1.58 [1.39-2.17]), compared with that in the recipients carrying CYP3A5*1 and POR*1/*1 (n = 8 [12.3%], median C/D ratio [inter quartile range] = 2.23 [2.05-3.06]) (p < 0.001). In conclusion, to our knowledge, this is the first report suggesting that the POR*28 polymorphism is another biomarker for the tacrolimus oral dosage after liver transplantation in patients carrying CYP3A5*1 rather than CYP3A5*3/*3.

Donor CYP3A5 Gene Polymorphism Alone Cannot Predict Tacrolimus Intrarenal Concentration in Renal Transplant Recipients.

CYP3A5 gene polymorphism in recipients plays an important role in tacrolimus blood pharmacokinetics after renal transplantation. Even though CYP3A5 protein is expressed in renal tubular cells, little is known about the influence on the tacrolimus intrarenal exposure and hence graft outcome. The aim of our study was to investigate how the tacrolimus intrarenal concentration (Ctissue) could be predicted based on donor CYP3A5 gene polymorphism in renal transplant recipients. A total of 52 Japanese renal transplant patients receiving tacrolimus were enrolled in this study. Seventy-four renal biopsy specimens were obtained at 3 months and 1 year after transplantation to determine the donor CYP3A5 polymorphism and measure the Ctissue by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The tacrolimus Ctissue ranged from 52 to 399 pg/mg tissue (n = 74) and was weak but significantly correlated with tacrolimus trough concentration (C0) at 3 months after transplantation (Spearman, r = 0.3560, p = 0.0096). No significant relationship was observed between the donor CYP3A5 gene polymorphism and Ctissue or Ctissue/C0. These data showed that the tacrolimus systemic level has an impact on tacrolimus renal accumulation after renal transplantation. However, donor CYP3A5 gene polymorphism alone cannot be used to predict tacrolimus intrarenal exposure. This study may be valuable for exploring tacrolimus renal metabolism and toxicology mechanism in renal transplant recipients.

Effects of Diluent Volume and Administration Time on the Incidence of Anaphylaxis Following Docetaxel Therapy in Breast Cancer.

Hypersensitivity reactions, including anaphylaxis, are common side effects associated with docetaxel treatment in breast cancer patients. However, preventive measures have not yet been established. In this study, we retrospectively analyzed the risk factors for developing anaphylaxis in 182 female breast cancer patients treated with docetaxel. We found that 6.6% of all patients (n = 12) experienced anaphylaxis. Multivariate analyses indicated that concentration of docetaxel higher than 0.275 mg/m2/mL, docetaxel dose rate higher than 1.15 mg/m2/min, and white blood cell count less than 4290 cells/mL are risk factors for developing docetaxel-related anaphylaxis. In particular, concentrations of docetaxel or doses per administration time were associated with a high odds ratio (11.88 or 11.60) for docetaxel-related anaphylaxis. Moreover, patients receiving doses in 250 mL volume experienced anaphylaxis more frequently than those receiving doses in 500 mL (7.0 vs. 0.9%, p = 0.0236). Additionally, patients receiving treatments over 60 min tended to experience anaphylaxis more frequently than those who were treated over 90 min (6.7 vs. 1.1%, p = 0.0637). The present results indicate that high docetaxel concentrations, high dose rates, and low white blood cell counts are risk factors for developing docetaxel-related anaphylaxis, and administering docetaxel diluted in 500 mL over 90 min may limit docetaxel-induced hypersensitivity reactions.

Increasing Diluent Volume Decreases Bendamustine-Induced Venous Irritation without Reducing the Therapeutic Efficacy.

The intravenous injection of bendamustine often induces venous irritation, which reduces patients' QOL. We previously reported that the dilution of the final volume of bendamustine from 250 to 500 mL significantly decreased the incidence of venous irritation. However, the influence of this change on the therapeutic efficacy of bendamustine remains unclear. Therefore, the aim of this study was to evaluate the efficacy and safety profiles of bendamustine at different dilutions of the final volume, comparing with the correspondences of previous studies. Thirty-four patients, who received a total of 161 courses of bendamustine and rituximab chemotherapy, were included in this study. The overall response rate of this regimen was 94.1% in this study, which was comparable to that reported in the BRB study (94.2%, a phase II study of bendamustine plus rituximab therapy in Japanese patients). Additionally, the median progression-free survival was not inferior to that reported in the BRB study. Bendamustine-induced venous irritation was observed in 17.6% of the patients during the first treatment cycle administered at a final volume of 500 mL, and was found to be lower than that observed in the control, where bendamustine was administered at a final volume of 250 mL (85.7%). These results suggest that diluting bendamustine to 500 mL, but not to 250 mL, reduces the incidence of venous irritation without a negative impact on its therapeutic efficacy; thus, this simple strategy may be beneficial to ensure efficacy and safety in patients receiving regimens including bendamustine.

Significance of Ethnic Factors in Immunosuppressive Therapy Management After Organ Transplantation.

Clinical outcomes after organ transplantation have greatly improved in the past 2 decades with the discovery and development of immunosuppressive drugs such as calcineurin inhibitors, antiproliferative agents, and mammalian target of rapamycin inhibitors. However, individualized dosage regimens have not yet been fully established for these drugs except for therapeutic drug monitoring-based dosage modification because of extensive interindividual variations in immunosuppressive drug pharmacokinetics. The variations in immunosuppressive drug pharmacokinetics are attributed to interindividual variations in the functional activity of cytochrome P450 enzymes, UDP-glucuronosyltransferases, and ATP-binding cassette subfamily B member 1 (known as P-glycoprotein or multidrug resistance 1) in the liver and small intestine. Some genetic variations have been found to be involved to at least some degree in pharmacokinetic variations in post-transplant immunosuppressive therapy. It is well known that the frequencies and effect size of minor alleles vary greatly between different races. Thus, ethnic considerations might provide useful information for optimizing individualized immunosuppressive therapy after organ transplantation. Here, we review ethnic factors affecting the pharmacokinetics of immunosuppressive drugs requiring therapeutic drug monitoring, including tacrolimus, cyclosporine, mycophenolate mofetil, sirolimus, and everolimus.

Comparison of 4 Commercial Immunoassays Used in Measuring the Concentration of Tacrolimus in Blood and Their Cross-Reactivity to Its Metabolites.

BACKGROUND: Therapeutic drug monitoring of tacrolimus is necessary for appropriate dose adjustment for a successful immunosuppressive therapy. Several commercial immunoassays are available for tacrolimus measurements. This study aimed at simultaneously evaluating the analytical performances of 4 such immunoassays, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a standard. For the first time, cross-reactivity to tacrolimus metabolites was assessed at concentrations frequently observed in clinical settings, as opposed to the higher concentrations tested by assay manufacturers. METHODS: An affinity column-mediated immunoassay (ACMIA), using upgraded flex reagents; released in 2015, a chemiluminescence immunoassay (CLIA), an electrochemiluminescence immunoassay (ECLIA), and a latex agglutination turbidimetric immunoassay (LTIA) were evaluated using frozen whole blood samples collected from transplantation patients. Cross-reactivities to 3 major tacrolimus metabolites (13-O-demethyl-tacrolimus [M-I], 31-O-demethyl-tacrolimus [M-II], and 15-O-demethyl-tacrolimus [M-III]) were evaluated. RESULTS: Each immunoassay correlated well with LC-MS/MS, and the Pearson's correlation coefficients (R) were 0.974, 0.977, 0.978, and 0.902 for ACMIA, CLIA, ECLIA, and LTIA, respectively. Using Bland-Altman difference plots to compare the immunoassays with LC-MS/MS, the calculated average biases were -6.73%, 6.07%, 7.46%, and 12.27% for ACMIA, CLIA, ECLIA, and LTIA, respectively. The cross-reactivities of ACMIA to the tacrolimus metabolites M-II and M-III were 81% and 78%, respectively, when blood was spiked at 2 ng/mL, and 94% and 68%, respectively, when it was spiked at 5 ng/mL. CONCLUSIONS: Each immunoassay was useful, but had its own characteristics. ACMIA cross-reactivities to M-II and M-III were much higher than the respective 18% and 15% reported on its package insert, suggesting that cross-reactivity should be examined at clinically relevant concentrations.