Blood Sirolimus Concentrations Research Articles

Therapeutic Drug Monitoring for Sirolimus in Children with Vascular Anomalies: What Can We Learn from a Retrospective Study.

Objectives: Sirolimus (SRL), a mammalian target of rapamycin inhibitor, has been widely used to treat patients with vascular anomalies (VAs). The objectives of this study were to summarize the routine blood SRL monitoring data for VAs children, to investigate the factors contributing to the variable blood SRL concentrations and to evaluate the efficacy and safety of SRL therapy. Methods: VAs patients with routine blood SRL monitoring from July 2017 to April 2022 at the Department of Burns and Plastic Surgery, Children's Hospital of Nanjing Medical University were retrospectively collected. Clinical data were obtained from the hospital information system. Results: In total, 67 children (35 females) were enrolled. The therapeutic drug monitoring data showed that the range of measured blood trough concentrations (Ctrough) was 3.6-46.8 ng/mL. At the initial measurements, only 33% of patients were in the target concentration range (10-15 ng/mL). But this proportion became 54% at the last measurements. The whole blood-Ctrough-to-daily dose (Ctrough/Dose) ratio was significantly associated with age and body weight (BW). The patients' laboratory results did not change significantly after SRL treatment. Although the incidence of adverse events was relatively high (44.8%), most of them were mild and tolerable. 70.3% patients had total responses to SRL, whereas 29.7% children exhibited stable disease or progressive disease. No significant differences were found in Ctrough between the total response group and non-response group. Conclusions: This retrospective study revealed a high variability in SRL blood concentrations in Chinese children with VAs. Of note, pediatric patients with older age and a higher BW had a lower Ctrough/Dose ratio. It is a concern whether the range of 10-15 ng/mL is feasible for Chinese children based only on our study. Further studies recruiting more patients are required to redefine the target reference range for children with VAs.

Preventative treatment of tuberous sclerosis complex with sirolimus: Phase I safety and efficacy results.

Tuberous sclerosis complex (TSC) results from overactivity of the mechanistic target of rapamycin (mTOR). Sirolimus and everolimus are mTOR inhibitors that treat most facets of TSC but are understudied in infants. We sought to understand the safety and potential efficacy of preventative sirolimus in infants with TSC. We conducted a phase 1 clinical trial of sirolimus, treating five patients until 12 months of age. Enrolled infants had to be younger than 6 months of age with no history of seizures and no clinical indication for sirolimus treatment. Adverse events (AEs), tolerability, and blood concentrations of sirolimus measured by tandem mass spectrometry were tracked through 12 months of age, and clinical outcomes (seizure characteristics and developmental profiles) were tracked through 24 months of age. There were 92 AEs, with 34 possibly, probably, or definitely related to treatment. Of those, only two were grade 3 (both elevated lipids) and all AEs were resolved by the age of 24 months. During the trial, 94% of blood sirolimus trough levels were in the target range (5-15 ng/mL). Treatment was well tolerated, with less than 8% of doses held because of an AE (241 of 2941). Of the five patients, three developed seizures (but were well controlled on medications) at 24 months of age. Of the five patients, four had normal cognitive development for age. One was diagnosed with possible autism spectrum disorder. These results suggest that sirolimus is both safe and well tolerated by infants with TSC in the first year of life. Additionally, the preliminary work suggests a favorable efficacy profile compared with previous TSC cohorts not exposed to early sirolimus treatment. Results support sirolimus being studied as preventive treatment in TSC, which is now underway in a prospective phase 2 clinical trial (TSC-STEPS).

Effect of sirolimus on insulin dynamics in horses.

Sirolimus, a mechanistic target of rapamycin inhibitor, suppresses insulin production in other species and has therapeutic potential for hyperinsulinemia in horses. Determine the pharmacokinetics (PKs) of sirolimus and evaluate its effect on insulin dynamics in healthy and insulin dysregulation (ID) horses. Eight Standardbred geldings. A PK study was performed followed by a placebo-controlled, randomized, crossover study. Blood sirolimus concentrations were measured by liquid chromatography-mass-spectrometry. PK indices were estimated by fitting a 2-compartment model using nonlinear least squares regression. An oral glucose test (OGT) was conducted before and 4, 24, 72, and 144 hours after administration of sirolimus or placebo. Effects of time, treatment and animal on blood glucose and insulin concentrations were analyzed using mixed-effects linear regression. Sirolimus was then administered to 4horses with dexamethasone-induced ID and an OGT was performed at baseline, after ID induction and after 7 days of treatment. Median (range) maximum sirolimus concentration was 277.0 (247.5-316.06) ng/mL at 5 (5-10) min and half-life was 3552 (3248-4767) min. Mean (range) oral bioavailability was 9.5 (6.8-12.4)%. Sirolimus had a significant effect on insulin concentration 24 hours after a single dose: median (interquartile range) insulin at 60 min (5.0 [3.7-7.0] μIU/mL) was 37 (-5 to 54)% less than placebo (8.7 [5.8-13.7] μIU/mL, P=.03); and at 120 min (10.2 [8.4-12.2] μIU/mL) was 28 (-15 to 53)% less than placebo (14.9 [8.4-24.8] μIU/mL, P=.02). There was minimal effect on glucose concentration. Insulin responses decreased toward baseline in ID horses after 7 days of treatment. Sirolimus decreased the insulinemic response to glucose and warrants further investigation.

Successful Treatment of Fibro-Adipose Vascular Anomaly with Sirolimus

BackgroundThe purpose of this study was to present our initial experience in using sirolimus therapy to treat fibro-adipose vascular anomaly (FAVA). MethodsWe retrospectively reviewed the medical records of eight patients with FAVA who were treated with sirolimus at our hospital between July 2017 and October 2020. ResultsSix girls (75%) and two boys (25%) were included in the cohort; the average age was 8 years (range, 1–13 years). Vascular tumors developed mainly on the extremities, including the forearm (n = 2; 25.0%), calf (n = 4; 50.0%), and thigh (n = 2; 25.0%). The predominant symptoms included swelling of the lesion (n = 8; 100%), pain (n = 7; 87.5%), contracture (n = 3; 37.5%), and phlebectasia (n = 3; 37.5%). Magnetic resonance imaging was the primary method used for FAVA diagnosis, and all patients underwent enhanced MRI. All lesions were heterogeneous with hyperintense T1 signals. The fat-suppressed T2-weighted images also revealed heterogeneous hyperintense masses, thus indicating fibrofatty infiltration. All eight patients received a sirolimus treatment regimen after FAVA diagnosis. One patient underwent tumor resection but experienced recurrence, whereas the other six patients underwent biopsy. Histological examination revealed that the lesions consisted of fibrofatty tissue with abnormal venous channels and anomalous lymphatic vascular components. Sirolimus softened the masses and caused tumor shrinkage within 5.25 ± 2.6 weeks (range, 2–10 weeks) after treatment initiation. The tumors also involuted rapidly and became stable within 7.75 ± 2.25 months after treatment initiation (range, 6–12 months). All seven patients experiencing pain reported relief within 3.8 ± 1.8 weeks (range, 2–7 weeks) after initiation of sirolimus therapy. Sirolimus alleviated but did not fully resolve the contracture in three patients. Remarkably, five patients exhibited a complete response, and three patients exhibited a partial response. At the time of the last follow-up, three patients had begun to gradually taper off sirolimus after 24 months of treatment and maintained a low blood sirolimus concentration. No serious adverse effects were observed during treatment. ConclusionFAVA is a complex vascular malformation that appears to respond well to sirolimus treatment. Thus, sirolimus may be an effective and safe treatment for FAVA. Level of evidenceLEVEL IV.

Comparison of LC-MS/MS and EMIT methods for the precise determination of blood sirolimus in children with vascular anomalies.

Sirolimus (SRL) is a mammalian target of rapamycin (mTOR) inhibitor. The whole blood concentration of SRL is routinely monitored to tailor dosage and prevent toxicity. Currently, the enzyme multiplied immunoassay technique (EMIT) is often applied to perform therapeutic drug monitoring (TDM) of SRL, but the cross-reactivity with various metabolites is of great concern. A more specific method is required, such as liquid chromatography–tandem mass spectrometry (LC-MS/MS). However, no study on the method comparison of the EMIT and LC-MS/MS for the measurement of whole blood SRL concentration in children with vascular anomalies has been reported. This study developed a simple and sensitive LC-MS/MS assay for the determination of SRL. Meanwhile, consistency between LC-MS/MS and the EMIT was evaluated by linear regression and Bland–Altman analysis. Whole blood samples were deproteinized with methanol for erythrocyte lysis, and the resulting solution was injected into the LC-MS/MS system using the positive electrospray ionization mode. The multiple reaction monitoring transitions of m/z 931.7 → 864.6 and m/z 934.7 → 864.6 were used for SRL and SRL-d3 as the internal standards, respectively. The analytes were separated on a C18 column with a gradient mobile phase (0.1 mM formic acid and 0.05 mM ammonium acetate in methanol/ultrapure water). Blood samples collected from children with vascular anomalies undergoing SRL therapy were tested by EMIT and by LC-MS/MS. The linear range of LC-MS/MS was 0.500–50.0 ng/ml and that of the EMIT was 3.50–30.0 ng/ml. A significant positive correlation between the two assays was established with a regression equation described as [ EMIT ] = 1.281 × [ LC−MS/MS ] + 2.450 (r = 0.8361). Bland–Altman plots showed a mean concentration overestimation of 4.7 ng/ml [95% CI: (−3.1, 12.6)] and a positive bias of 63.1% [95% CI: (−36.1, 162.3)] generated by the EMIT more than that of by LC-MS/MS. In conclusion, the two methods were closely correlated, indicating that switching between the two methods is feasible. Considering the overestimation nature of the EMIT assay, switching from the EMIT to the LC-MS/MS method deserves close attention and necessary re-evaluation for the target therapeutic reference range, may be required when methods are switched within the same clinical laboratory or results are compared between different laboratories.

Topical sirolimus solution for lingual microcystic lymphatic malformations in children and adults (TOPGUN): study protocol for a multicenter, randomized, assessor-blinded, controlled, stepped-wedge clinical trial

BackgroundLingual microcystic lymphatic malformations (LMLMs) are rare congenital vascular malformations presenting as clusters of cysts filled with lymph fluid or blood. Even small well-limited lesions can be responsible for a heavy burden, inducing pain, aesthetic prejudice, or oozing, bleeding, infections. The natural history of LMLMs is progressive worsening punctuated by acute flares. Therapeutic options include surgery, laser excision, and radiofrequency ablation but all are potentially detrimental and expose to local relapse. Therefore, the management frequently relies on a “watchful waiting” approach. In complicated LMLMs, treatment with oral sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, is often used. Topical applications of sirolimus on the buccal mucosae have been reported in other oral diseases with good tolerance and none to slight detectable blood sirolimus concentrations. We aim to evaluate the efficacy and safety of a 1 mg/mL sirolimus solution applied once daily on LMLM of any stage in children and adults after 4, 8, 12, 16, 20, and 24 weeks of treatment compared to usual care (no treatment).MethodsThis is a randomized, multicentric study using an individually randomized stepped-wedge design over 24 weeks to evaluate topical application of a 1 mg/mL sirolimus solution once daily, on LMLM, versus usual care (no treatment), the control condition. Participants begin with an observational period and later switch to the intervention at a randomized time (week 0, 4, 8, or 12). Visits occur every 4 weeks, either in the study center or by teleconsulting. The primary outcome will be the evaluation of global severity of the LMLM on monthly standardized photographs by 3 independent blinded experts using the physical global assessment (PGA) 0 to 5 scale. Secondary outcomes will include lesion size measurement and quality of life assessment, investigator, and patient-assessed global disease and specific symptoms (oozing, bleeding, sialorrhea, eating impairment, taste modification, aesthetic impairment, pain, and global discomfort) assessment. A biological monitoring will be performed including residual blood sirolimus concentration and usual laboratory parameters.DiscussionGiven the disappointing state of current treatment options in LMLMs, topical sirolimus could become firstline therapy in treating LMLMs if its efficacy and safety were to be demonstrated.Trial registrationClinicalTrials.gov NCT04128722. Registered on 24 September 2019.EudraCT: EUCTR2019-001530-33-FRSponsor (University Hospital Center of Tours – CHRU Tours): DR190041-TOPGUNFrench regulatory authorities: ID RCB: 2019-001530-33

Estimation of Blood Sirolimus Concentration Based on Tacrolimus Concentration/Dose Normalized by Body Weight Ratio in Lung Transplant Patients.

Sirolimus and tacrolimus require accurate drug dosing based on their target blood levels to produce better clinical outcomes, specifically, the avoidance of drug-induced adverse effects and the maintenance of efficacy. However, because the ideal dose of sirolimus and the schedule for measuring its blood levels are unclear in lung transplant patients, an index is required for estimating sirolimus blood concentrations. The aim of this work is to study the correlation between the trough concentration/dose normalized by body weight (C0/D) ratios of sirolimus and tacrolimus in lung transplant patients. Thirteen lymphangiomyomatosis patients who underwent lung transplantation and were treated with sirolimus and tacrolimus from February 2015 to July 2018 were divided into 2 groups, one receiving twice-daily (TD, n = 6) and the other once-daily (OD, n = 7) tacrolimus formulations. The correlation between the C0/D ratio of sirolimus and patient background was evaluated using Spearman's rank correlation coefficient. Correlations between sirolimus and tacrolimus C0/D ratios or doses were analyzed by single regression analysis. Significant correlations were found between the C0/D ratios of sirolimus and tacrolimus. The regression equations from the initial data of TD and OD groups at steady state were y = 1.880x + 32.636 (adjusted R = 0.743, P = 0.017) and y = 1.684x + 38.816 (adjusted R = 0.919, P < 0.001), respectively. In addition, the regression equations from all data of TD and OD groups were y = 1.883x + 4.170 (adjusted R = 0.546, P < 0.001) and y = 1.950x + 43.188 (adjusted R = 0.898, P < 0.001), respectively. A significant correlation between the dosage of sirolimus and tacrolimus was observed only in the OD group, with relatively low accuracy. Blood sirolimus concentrations can be estimated using the C0/D ratio of tacrolimus, suggesting that the C0/D ratio of tacrolimus is an index of required sirolimus dosage and the frequency of blood sirolimus concentration measurements.

Abstract 348: ABI-009 (nab-Sirolimus) improves tumor accumulation and antitumor activity over oral mTOR inhibitors

Abstract Background: mTOR pathway has been implicated in cell survival and proliferation and is an attractive target for cancer therapy. ABI-009 (nab-sirolimus) is an injectable nanoparticle form of human albumin-bound sirolimus with a mean particle size of approximately 100 nm developed with a proprietary nanoparticle albumin-bound (nab®) technology. ABI-009 is currently in phase 1 and 2 clinical studies for the treatment of multiple cancer types, including bladder cancer, soft-tissue sarcomas, neuroendocrine tumors, colorectal cancer, glioblastoma, and various childhood cancers, and a registrational phase 2 study for malignant perivascular epithelioid cell carcinoma (PEComa). In nonclinical and clinical studies, ABI-009 demonstrated a PK profile distinct from oral mTOR inhibitors. This study compared the antitumor activity, tissue penetration, and pharmacodynamics of ABI-009 with equal doses of oral mTOR inhibitors at clinically relevant doses in a mouse tumor xenograft model. Methods: Athymic mice bearing subcutaneous UMUC3 bladder cancer xenografts were treated with saline, ABI-009 (IV, 7.5 mg/kg, 2x/wk), sirolimus and everolimus (PO, 3 mg/kg/day, 5 days/wk). Body weights, tumor measurements, and clinical signs were recorded 3x/wk for up to 5 wks. Tumor and blood sirolimus concentrations were also obtained (tumor: D1 1h and 24h, D4 1h, D7; blood: D4 1h, D7). Markers for mTOR pathway activation (pS6, p4EBP1) will also be analyzed. Results: Overall, all treatments were well tolerated with no significant body weight loss in any group. ABI-009 IV resulted in significantly higher sirolimus concentrations in the tumor compared with oral mTOR inhibitors at all time points tested. Tumor AUC with ABI-009 IV over 1 week were significantly higher vs equal weekly dose of oral sirolimus (43 fold) and everolimus (12 fold) (p &amp;lt; 0.0001). The enhanced tumor drug delivery by ABI-009 corresponded with significantly greater tumor growth inhibition (TGI: ABI-009 69.6% vs oral sirolimus 24.3%, p &amp;lt; 0.00001; vs oral everolimus 36.2%, p = 0.0023) and longer animal survival (median OS: ABI-009 not reached vs oral sirolimus 21 days, p &amp;lt; 0.05; vs oral everolimus 19 days, p &amp;lt; 0.05). mTOR pathway inhibition in tissues is being assessed. Conclusions: Compared with equal weekly dose of oral mTOR inhibitors, ABI-009 at clinically relevant dose of administered IV demonstrated significantly greater tumor drug delivery, stronger antitumor activity, and prolonged animal survival. These advantages observed in this nonclinical study support the clinical investigation of ABI-009 in numerous oncology indications. Citation Format: Shihe Hou, Anita Schmid, Neil Desai. ABI-009 (nab-Sirolimus) improves tumor accumulation and antitumor activity over oral mTOR inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 348.

Effect of Sirolimus Exposure on the Need for Preemptive Antiviral Therapy for Cytomeglovirus Infection after Allogeneic Hematopoietic Stem Cell Transplantation.

The current study evaluates the clinical effect of sirolimus exposure on the occurrence of cytomegalovirus (CMV) DNAemia necessitating preemptive antiviral therapy. A total of 167 consecutive recipients of reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT) who received sirolimus- and tacrolimus-based graft-versus-host disease (GVHD) prophylaxis and whose CMV serostatus was positive for donors and/or recipients were included in this multicenter retrospective study. A parametric model with consecutive sirolimus blood levels describing the time to CMV DNAemia-RAT was developed using NONMEM version 7.4. Overall, 122 of 167 patients (73%) were allografted from an unrelated donor, and the donor CMV-serostatus was negative in 51 cases (31%). Fifty-six recipients (34%) developed CMV DNAemia necessitating preemptive therapy, with a cumulative incidence of 36% at a median follow-up of 25 months. Time to CMV DNAemia necessitating preemptive therapy was best described using a Gompertz function. CMV DNAemia necessitating preemptive therapy-predicting factors were antithymocyte globulin-based conditioning regimen (hazard ratio [HR], 2.2; 95% confidence interval [CI], 1.1 to 4.1; P < .01) and sirolimus concentration (HR, .94; 95% CI, .87 to .99; P < .01). The risk of CMV DNAemia-RAT decreased by 6% for each 1 ng/mL increase in sirolimus trough concentration. In conclusion, we provide evidence on the association between sirolimus blood concentration and incidence of CMV DNAemia necessitating preemptive therapy in allo-HSCT recipients. Moreover, this study presents the first predictive model describing the time to CMV DNAemia necessitating preemptive antiviral therapy as a function of sirolimus drug concentration.

Significant effect of infection and food intake on sirolimus pharmacokinetics and exposure in pediatric patients with acute lymphoblastic leukemia

BackgroundSirolimus is increasingly investigated as a new targeted therapy in pediatric populations. To date, population pharmacokinetic (PK) studies have identified several factors that explain in part the large between-patient variability in sirolimus PK. However, within-patient variability in sirolimus PK is not well documented. This study presents examples of model-based PK-guided dosing of sirolimus in children with acute lymphoblastic leukemia (ALL), where patients experienced significant changes in sirolimus blood concentrations due to infection and food intake during the treatment period. MethodsClinical PK data were obtained as part of a prospective pilot study of sirolimus combined with multiagent chemotherapy in pediatric patients with ALL (ClinicalTrial.gov identifier: NCT01658007). A PK model-informed loading dose of 1.8 mg/m2 every 8 h was started on the first day of sirolimus treatment. Subsequent doses were adjusted based on concentration measurements the first blood draw scheduled 24 h into the regimen on the morning of day 2. Sirolimus blood concentrations were determined by a validated LC-MS/MS assay. All dosing recommendations were generated in real time using the PK model with Bayesian estimation. ResultsThree patients were enrolled in this study. Two patients achieved target concentration attainment with the PK model-informed loading dose on day 1 of sirolimus treatment. Subsequent unexpected high sirolimus concentrations were observed in two patients, where patients had flulike symptoms such as fever and cough. A sudden decrease in sirolimus concentrations was observed in one patient after switching sirolimus administration from the fed to the fasting state. ConclusionsThis study highlights within-patient fluctuations in sirolimus concentrations associated with intercurrent infection and with changes in diet. These findings highlight the challenge of maintaining a target sirolimus concentration as a patient's clinical status changes, and the benefit of intensive monitoring of therapeutic drug levels in children treated with sirolimus. Intra-patient alternations in sirolimus PK due to similar disease/food interactions may be relevant in pediatric patients treated with sirolimus for other disease indications.

Sirolimus exposure and the occurrence of cytomegalovirus DNAemia after allogeneic hematopoietic stem cell transplantation.

Sirolimus appears to protect against cytomegalovirus (CMV) in organ transplant recipients. The effect of this drug in allogeneic hematopoietic stem cell transplantation recipients remains unexplored. By means of multivariate continuous-time Markov model analyses, we identified 3 independent covariates that significantly impacted the risk of CMV DNAemia: recipient/donor CMV serostatus, tacrolimus exposure, and sirolimus exposure. CMV-seropositive recipients with CMV-seronegative donors had a significantly higher probability of having detectable CMV DNAemia. Increasing the tacrolimus trough concentration from 0 to 16ng/mL increased the probability of patients having detectable CMV DNAemia by 40% (from 40% to 80%), whereas this probability decreased by 25% (from 40% to 15%) when trough concentrations of sirolimus increased from 0 to 16ng/mL. Sensitivity analysis showed that sirolimus exposure between 0 and 6ng/mL has no or negligible effect on CMV DNAemia, but levels >8ng/mL significantly decreased the number of detectable CMV DNAemia cases (the risk ratios decreased from 0.68 to 0.21 when whole blood sirolimus concentrations changed from 8 to 18ng/mL, P<.01). In conclusion, we used a pharmacometric statistical tool to provide the first clinical evidence that fewer CMV DNAemia events become detectable as sirolimus exposure increases.

Effect of CYP3A4 and CYP3A5 Genetic Polymorphisms on the Pharmacokinetics of Sirolimus in Healthy Chinese Volunteers.

Sirolimus is a promising immunosuppressive drug for preventing the rejection of organ transplants. However, inter-individual variability in sirolimus pharmacokinetics causes adverse drug reactions, compromising therapeutic efficacy. Sirolimus is primarily metabolized by cytochrome CYP3A4 and CYP3A5. This study aimed to clarify the effect of CYP3A genetic polymorphisms, including the CYP3A4*1G and CYP3A5*3 polymorphisms, on the pharmacokinetics of sirolimus. Thirty-one healthy Chinese volunteers were included in this study. Their genotypes were determined using the Sequenom MassARRAY iPLEX platform, and blood sirolimus concentrations at different time points were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated using WinNonlin version 5.2 software. The allele frequencies of CYP3A4*1G and CYP3A5*3 were 25.8% and 71.0%, respectively. In CYP3A4*1G carriers (n = 13), the area under the curve AUC0-144, AUC0-∞, and Cmax were significantly lower (P < 0.05) than CYP3A4*1/*1 homozygous subjects (n = 18). Briefly, the AUC0-144, AUC0-∞, and Cmax of *1G/*1G carrier were 315.2 ± 91.5, 372.0 ± 108.2, and 10.2 ± 1.6 ng/mL, respectively, and those of *1/*1 G*1/*1 G carrier were 440.8 ± 130.6, 537.4 ± 167.5, and 13.7 ± 4.3, respectively, whereas those of CYP3A4*1/*1 homozygous subjects were 540.2 ± 150.6, 626.6 ± 166.9, and 19.8 ± 7.5 ng/mL, respectively. In CYP3A5-nonexpressing subjects (*3/*3 homozygous carriers, n = 15), the AUC0-144 and Cmax were 549.6 ± 137.9 and 19.9 ± 7.9 ng/mL, respectively, and were significantly higher (P < 0.05) than the values in CYP3A5-expressing subjects (*1/*1homozygous carrier, n = 2; 314.2 ± 129.3 and 10.3 ± 2.2 ng/mL; *1/*3 heterozygous carrier, n = 15; 440.2 ± 146.3 and 14.6 ± 5.1 ng/mL, respectively). CYP3A4 and CYP3A5 genetic polymorphisms are important factors affecting pharmacokinetic parameters of sirolimus. Our data support the monitoring of blood sirolimus concentrations, especially in CYP3A5*1 and CYP3A4*1 G carriers, to ensure accurate dosing in the clinical setting.

Early Conversion from Calcineurin Inhibitors to Sirolimus in Liver Transplant Patients with Renal Dysfunction: A Systemic and Splanchnic Hemodynamic Study

Aims: It has been demonstrated that sirolimus, a potent immnunosuppressant agent, allowing a reduction of nephrotoxic effects of CNIs. We have evaluated whether conversion from a CNIs to sirolimus reduces nephrotoxicity in liver transplant recipients. We have also investigated whether this effect is accompanied to systemic, splanchnic and renal hemodynamic changes. Material and methods: Twelve patients with a suboptimal renal function, defined as an estimated glomerular filtration rate (GFR) of less than 50 ml/min, were included. Hemodynamic parameters were measured by doppler. Both measurements were performed in baseline (pre conversion to sirolimus) and 30 and 90 days after sirolimus . Results: The target range for whole blood sirolimus concentration was between 5 and 12 mg/ml. There was a significant difference in GFR at 30 (57 ± 20 ml/min) and 90 (58 ± 21 ml/min) days in patients switching to sirolimus compared to those observed during the administration of CNIs (39 ± 9 ml/min, p<0.05). This effect on renal hemodynamic is accompanied by a significant reduction in mean arterial pressure. No significant changes were observed in the other parameters studied. Conclusion: Our results suggest that early withdrawal of CNIs is a safe option, which allows an improvement in renal hemodynamic in liver transplant recipients.

Reduced sirolimus systemic exposure and improved bioresorbable polymer properties: new allies for the treatment of patients with coronary artery disease.

This prospective, first-in-man, open-label multicenter study sought to assess the pharmacokinetics of sirolimus after Ultimaster drug-eluting stent implantation (coated with sirolimus and bioabsorbable co-polymer) in patients with de novo coronary artery disease (the TCD-10023 PK study). The primary endpoint was sirolimus concentration in peripheral whole blood at 28days after stent implantation. In addition, safety, tolerability, therapeutic outcome and vasomotor response after stent implantation were studied. Twenty patients were enrolled in the study. Blood samples for the measurements of sirolimus concentration were collected at eight time points during first 48h, at 7days and 28days after stent implantation. Patients underwent 6-month angiographic and up to 12months clinical follow-up. At 28days, only two of 20 patients had sirolimus concentrations above lower limit of quantification (20.0pg/mL). The highest sirolimus blood concentration was 105pg/mL. The median maximum concentration was 36.8pg/mL (range 22.9-41.5pg/mL) for stent 3.0×15mm and 87.2pg/mL (range 60.0-105.0pg/mL) for 3×28mm stent. The median systemic exposure, as measured by the area under the time-concentration curve, was 8.3ngh/mL (range 6.47-28.0ngh/mL). At 6months, endothelial function was well preserved, and up to 12months, there were no signs of sirolimus toxicity nor any other safety concerns. Our results demonstrate that implantation of Ultimaster stent resulted in almost nondetectable sirolimus in blood after 28days. These findings were translated into exceptional safety profile, without any sign of systemic toxicity.

Long‐term evaluation of analytical methods used in sirolimus therapeutic drug monitoring

Results of therapeutic monitoring of sirolimus blood concentrations are assay and laboratory dependent. This study compared performance over time of the IMx microparticle enzyme immunoassay (MEIA), Architect chemiluminescent microparticle immunoassay (CMIA), and liquid chromatography with mass spectrometric detection (LC/MS/MS) as part of a proficiency testing scheme. Pooled samples from sirolimus-treated patients and whole-blood samples spiked with known quantities of sirolimus were assayed monthly between 2004 and 2012. When results of pooled patient samples were compared with LC/MS/MS, the MEIA assay showed an overall mean percent bias of -2.3% ± 11.2% that, although initially positive, became increasingly negative from 2007 through 2009. The CMIA, which replaced the MEIA assay, had a mean percent bias of 21.9% ± 12.3%, remaining stable from 2007 through 2012. Similarly, for spiked samples, the MEIA showed an increasingly negative bias over time vs. LC/MS/MS, whereas CMIA maintained a stable positive bias. Based on comparison of immunoassay measurements on individual patient samples, CMIA values were more than 25% higher than MEIA values. These results highlight the importance of continued proficiency testing and regular monitoring of sirolimus assay performance. Clinicians must be aware of the methodology used and adjust target levels accordingly to avoid potential effects on efficacy and toxicity.

ABCB1 haplotype influences the sirolimus dose requirements in Chinese renal transplant recipients

Sirolimus, an immunosuppressive drug used to prevent organ rejection after renal transplantation, has a narrow therapeutic index and a large inter-individual variability of pharmacokinetics. The aim of this study was to analyse the dose-normalized trough blood concentrations (C0 /D ratio) of sirolimus in patients with different genotypes and attempt to investigate the possible associations between ABCB1/CYP3A5 genotypes and sirolimus dose requirements in Chinese renal transplant recipients. Blood samples were collected from 85 Chinese renal transplant recipients who were treated with sirolimus for at least 3 months and polymorphisms of the ABCB1 and CYP3A5 were determined by the SNaPShot multiplex assay. The blood concentrations of sirolimus were determined with HPLC. A significant allele-dependent effect was observed between the CYP3A5*3 polymorphism and the C0 /D ratio of sirolimus. The patients bearing at least one CYP3A5*1 allele had a lower sirolimus C0/D ratio compared with those with a homozygous CYP3A5*3 genotype (p < 0.05). No significant differences of sirolimus C0/D ratios were observed among various ABCB1 1236C>T, 2677G>T/A and 3435C>T genotype groups. However, haplotype analysis including ABCB1 1236C>T, 2677G>T/A and 3435C>T SNPs showed that the mean sirolimus C0/D of subjects carrying the CGC/CGC diplotype was about 30% lower compared with those carrying the CGC/TTT or TTT/TTT diplotype, whether or not they expressed the CYP3A5 (p < 0.05). These results demonstrated that the haplotype of ABCB1 might be a better index for the prediction of sirolimus blood concentration than single SNPs. Genotyping of ABCB1 and CYP3A5 might help to optimize individualized sirolimus treatments for Chinese renal transplant recipients.

Comparative bioavailability and pharmacokinetics of sirolimus tablets in healthy Chinese volunteers

Although sirolimus tablets and oral solutions have been used in clinical practice, no study has been reported on the pharmacokinetics and bioavailability of a single-dose of sirolimus tablets in healthy Chinese volunteers. The purpose of this study was to compare the bioavailability and pharmacokinetic (PK) properties of two different 1-mg sirolimus tablets in healthy Chinese male volunteers and evaluate whether a generic tablet of sirolimus meets the criteria for bioequivalence from the State Food and Drug Administration (SFDA) of China when compared with a reference product. A total of 24 healthy Chinese volunteers was eligible for this 6 mg single dose, randomized-sequence, open-label, 2-period crossover study. Blood samples were collected before dosing and at 0.25, 0.50, 0.75, 1.0, 1.5, 2, 3, 4, 8, 12, 24, 48, 72, 120, 168, 216, and 264 hours after dosing. Whole blood sirolimus concentration was analyzed by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Pharmacokinetic properties of sirolimus were assessed using noncompartmental analysis. The mean (range) Cmax values of the test and the reference were 15.25 (8.48 - 24.40) and 13.43 (7.90 - 22.90) ng/ml; AUC0-t values were 475.65 (293.33 - 1049.86) and 451.96 (221.52 - 809.11) ng/h/ml. The medians (range) tmax values were 2.0 (1.0 - 8.0) and 2.0 (1.0 - 8.0) hours, respectively. The 90% confidence intervals (CIs) for the ratios of Cmax, AUC0-264, and AUC0-∞ were 103.7% to 124.4%, 97.5% to 113.6%, and 98.0% to 114.8%, respectively. In this single-dose crossover study the test sirolimus tablets met the criteria for bioequivalence in terms of both rate and extent. Each sirolimus formulation was well tolerated during the study.

463 PHARMACOKINETIC INTERACTIONS BETWEEN THE HCV PROTEASE INHIBITOR BOCEPREVIR AND SIROLIMUS IN HEALTHY SUBJECTS

Background and Aims: Boceprevir is a potent, orally administered, ketoamide inhibitor of the hepatitis C virus (HCV) NS3 protease. HCV-related end-stage liver disease and hepatocellular carcinoma are frequent causes of liver transplantation. Sirolimus is a macrolide immunosuppressant frequently used for the prophylaxis of transplant rejection. This study was conducted to evaluate the pharmacokinetic interaction of boceprevir and sirolimus in healthy volunteers. Methods: In this open-label, 3-period, fixed-sequence trial, 12 subjects received single-dose sirolimus (2mg) in period 1 and boceprevir (800mg TID for 6 days) in period 2 with an intervening washout of 14 days. Period 3 immediately followed period 2 with no intervening washout: subjects received sirolimus (2mg SD) plus boceprevir (800mg TID) on day 1 and boceprevir (800mg TID) thereafter for 9 days. Blood samples were collected for the pharmacokinetic assessment of sirolimus and boceprevir. Safety assessments included electrocardiograms, vital signs, clinical laboratory tests, physical examination, and adverse event monitoring. Results: Twelve healthy volunteers were enrolled and 11 completed the trial. Coadministration of boceprevir and sirolimus was well tolerated. Boceprevir co-administration increased the geometric mean AUC0–∞ and Cmax of sirolimus by 8.1-fold and 4.8-fold, respectively, with the corresponding 90% CIs of (7.08, 9.32) for AUC0–∞ and (3.99, 5.88) for Cmax. The elimination half-life of sirolimus increased from 82.5 h to 98.3 h, and the apparent clearance decreased from 9.62 L/min to 1.18 L/min, respectively, with boceprevir coadministration. Sirolimus co-administration did not affect the pharmacokinetics of boceprevir (AUC0–8h and Cmax GMR [90%CI] of 1.0 [0.89, 1.01] and 0.9 [0.82, 1.07], respectively). Conclusions: Concomitant administration of boceprevir and sirolimus resulted in increased steady-state exposures of sirolimus in healthy subjects. The magnitude of the potential interaction between sirolimus and boceprevir in organ transplant patients is not known, but could potentially be higher and more variable than that seen in healthy volunteers. Dose adjustment of sirolimus and/or prolongation of the dosing interval should be anticipated when administered with boceprevir, and should be guided by close monitoring of sirolimus blood concentrations, and frequent assessment of renal function and sirolimus-related side effects.

Drug Jelly Dosage as an Alternative to Gavage for Long-Term Oral Drug Administration in Rhesus Monkeys

Introduction: Rhesus monkeys are often used as recipients in preclinical transplantation studies. The long-term oral administration of immunosuppressive agents to transplanted rhesus monkeys is one of the major challenges in such studies. Gavage, a frequently employed method, has the disadvantage of producing stress in restrained animals. To avoid this problem, we tested an alternative method for oral dosing of sirolimus (SRL) in rhesus monkeys. Methods: An oral solution of SRL was mixed with gelatin stock at 45°C and then cooled to 4°C to form a jelly dosage. Animal behavior of jelly dosing technique and gavage dosing technique was observed, the oral bioequivalence of these two dosage forms was evaluated, and the whole blood levels of SRL for long-term drug delivery were assayed. For the bioequivalence study, 4 rhesus monkeys were enrolled in a two-phase randomized crossover design. In each phase, the animals received SLR oral solution or jelly at a dosage of 0.6 mg/kg. 10 monkeys were then given either SRL oral solution or jelly for one month at a dosage of 0.2 mg/kg/day. After the administration, whole blood SRL concentrations were measured by high-performance liquid chromatography assay (HPLC). Results: The jelly dosing technique appears to enhance the compliance of the animals to gavage, and all the animals in the SRL jelly group learned to voluntarily consume the jelly after a short period of training. The jelly dosage form of SRL displayed sustained release and bioequivalence to the oral solution. The SRL whole blood level for long-term drug delivery was 2.97±1.91 ng/mL in the jelly group and 3.13±2.03 ng/mL in the oral solution group. The difference between these two means was not significant.[Figure 1][Figure 2]Conclusion: The jelly dosing technique described here is convenient and effective for oral administration of SRL in rhesus monkeys and may be adapted for administration of other drugs.

Systemic exposure of sirolimus after coronary stent implantation in patients with de novo coronary lesions: Supralimus-Core® pharmacokinetic study

ObjectivesThis study was conducted to assess the systemic drug release and distribution of sirolimus-eluting coronary stents. MethodsTwenty patients with coronary artery disease (CAD) were treated with 1, 2, or 3 a newly designed metallic stents. Blood samples were drawn at 14 time points to determine the pharmacokinetic of sirolimus. Whole blood concentrations of sirolimus were determined by using a sensitive validated high-performance liquid chromatography mass spectrometry/mass spectrometry method. ResultsMinimal measurable blood levels were detectable at 7 days. Across all dose levels, individual Tmax values ranged from 1.00 hour and 12.00 hours; individual Cmax ranged from 0.73 ng/mL and 4.13 ng/mL. ConclusionThis study confirms the limited exposure of the systemic circulation of the eluted drug with the use of the Supralimus-Core® Sirolimus-Eluting Coronary Stent System (Sahajanand Medical Technologies Pvt. Ltd., Surat, India). In this study, sirolimus concentration in systemic circulation is to be safe, well-tolerated and short-lived.