Sirolimus Concentrations Research Articles

A randomized controlled trial to evaluate efficacy and safety of early conversion to a low-dose calcineurin inhibitor combined with sirolimus in renal transplant patients.

Background:The calcineurin inhibitor (CNI)-based immune maintenance regimen that is commonly used after renal transplantation has greatly improved early graft survival after transplantation; however, the long-term prognosis of grafts has not been significantly improved. The nephrotoxicity of CNI drugs is one of the main risk factors for the poor long-term prognosis of grafts. Sirolimus (SRL) has been employed as an immunosuppressant in clinical practice for over 20 years and has been found to have no nephrotoxic effects on grafts. Presently, the regimen and timing of SRL application after renal transplantation vary, and clinical data are scarce. Multicenter prospective randomized controlled studies are particularly rare. This study aims to investigate the effects of early conversion to a low-dose CNI combined with SRL on the long-term prognosis of renal transplantation.Methods:Patients who receive four weeks of a standard regimen with CNI + mycophenolic acid (MPA) + glucocorticoid after renal transplantation in multiple transplant centers across China will be included in this study. At week 5, after the operation, patients in the experimental group will receive an additional administration of SRL, a reduction in the CNI drug doses, withdrawal of MPA medication, and maintenance of glucocorticoids. In addition, patients in the control group will receive the maintained standard of care. The patients’ vital signs, routine blood tests, routine urine tests, blood biochemistry, serum creatinine, BK virus (BKV)/ cytomegalovirus (CMV), and trough concentrations of CNI drugs and SRL at the baseline and weeks 12, 24, 36, 48, 72, and 104 after conversion will be recorded. Patient survival, graft survival, and estimated glomerular filtration rate will be calculated, and concomitant medications and adverse events will also be recorded.Conclusion:The study data will be utilized to evaluate the efficacy and safety of early conversion to low-dose CNIs combined with SRL in renal transplant patients.Trial registration:Chinese Clinical Trial Registry, ChiCTR1800017277.

Activated Carbon for Drug Delivery from Composite Biomaterials: The Effect of Grinding on Sirolimus Binding and Release.

Activated carbon (AC) could be potentially useful as a drug carrier in fiber polymer scaffolds destined for prolonged drug delivery. To be introduced, AC must be ground into smaller-sized particles to be introduced in scaffolds, as most biocompatible scaffolds consist of fibers with a diameter of less than 1 µm. In this study, the adsorption of sirolimus (SRL) from phosphate-buffered saline (PBS) solution and blood plasma (BP) onto AC of AX-21 type, as well as the release of SRL from AC depending on its fragmentation, were studied. Two-stage grinding of the AC, first with a ball mill, and then with a bead mill, was performed. Grinding with a bead mill was performed either in water or in polyvinylpyrrolidone to prevent aggregation of AC particles. Dynamic light scattering and scanning electron microscopy (SEM) demonstrated that the size of the particles obtained after grinding with a ball mill was 100–10,000 nm, and after grinding with a bead mill, 100–300 nm. Adsorption in PBS was significantly higher than in BP for all fractions, and depended on SRL concentration. The fraction obtained after grinding with a ball mill showed maximal SRL adsorption, both in PBS and BP, and slow SRL release, in comparison with other fractions. The 100–300 nm AC fractions were able to adsorb and completely release SRL into BP, in contrast to other fractions, which strongly bound a significant amount of SRL. The data obtained are to be used for controlled SRL delivery, and thus in the modification of drug delivery in biological media.

Flexible 3D Nanonetworked Silica Film as a Polymer-Free Drug-Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus.

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110µm) by only 0.4 percent (110.45µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p <0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

Efficacy and Safety of Topical Mechanistic Target of Rapamycin Inhibitors for Facial Angiofibromas in Patients with Tuberous Sclerosis Complex: A Systematic Review and Network Meta-Analysis.

Previous studies have suggested that the topical mechanistic target of rapamycin (mTOR) inhibitors may be effective in treating facial angiofibromas in patients with tuberous sclerosis complex (TSC). Various concentrations of topical sirolimus for TSC have been tested, but their comparative efficacy and safety remained unclear. To assess the effects of topical mTOR inhibitors in treating facial angiofibromas, we conducted a systematic review and network meta-analysis (NMA) and searched MEDLINE, Embase, and Cochrane Library for relevant randomized controlled trials on 14 February 2022. The Cochrane Collaboration tool was used to assess the risk of bias of included trials. Our outcomes were clinical improvement and severe adverse events leading to withdrawal. We included three trials on 261 TSC patients with facial angiofibromas. The NMA found when compared with placebo, facial angiofibromas significantly improved following the application of various concentrations of topical sirolimus (risk ratio being 3.87, 2.70, 4.43, and 3.34 for 0.05%, 0.1%, 0.2%, and 1%, respectively). When compared with placebo, all concentrations of topical sirolimus did not differ in severe adverse events leading to withdrawal. The ranking analysis suggested topical sirolimus 0.2% as the most effective drug. In conclusion, topical sirolimus 0.05–1% are effective and safe in treating facial angiofibromas in patients with TSC, with topical sirolimus 0.2% being the most effective.

Population Pharmacokinetic Analysis and Dosing Optimization of Sirolimus in Children With Tuberous Sclerosis Complex.

Sirolimus is confirmed to be effective in the treatment of tuberous sclerosis complex (TSC) and related disorders. The study aims to establish a population pharmacokinetic model of oral sirolimus for children with TSC and provide an evidence-based approach for individualization of sirolimus dosing in the pediatric population. A total of 64 children were recruited in this multicenter, retrospective pharmacokinetic study. Whole-blood concentrations of sirolimus, demographic, and clinical information were collected and analyzed using a nonlinear mixed-effects population modeling method. The final model was internally and externally validated. Then Monte Carlo simulations were performed to evaluate and optimize the dosing regimens. In addition, the efficacy and safety of sirolimus therapy was assessed retrospectively in patients with epilepsy or cardiac rhabdomyomas associated with TSC. Finally, the sirolimus pharmacokinetic profile was described by a 1-compartment model with first-order absorption and elimination along with body weight and total daily dose as significant covariates. The typical population parameter estimates of apparent volume of distribution and apparent clearance were 69.48 L and 2.79 L/h, respectively. Simulations demonstrated that dosage regimens stratified by body surface area may be more appropriate for children with TSC. These findings could be used to inform individualized dosing strategies of sirolimus for pediatric patients with TSC.

Особенности диагностики и лечения диффузного лимфангиоматоза у ребенка 8 лет

Lymphangiomatosis – heterogenic disease with generalized or multifocal lymphatic vessels proliferation in bones and extraosseous tissues. We report a case of 2-year monitoring of 8-year-old boy with diffuse lymphangiomatosis. We have described clinical manifestation, surgery, differential diagnosis, Sirolimus treatment, and changes in MRI-images. Prolonged unsuccessful chylothorax, that mimics pneumonia with exudative pleuritis at the onset, treatment was a distinctive feature of this rare disease. The absence of guidelines and certified for children use drugs prompted our multidisciplinary team to make a decision to prescribe off-label Sirolimus as a pathogenetic therapy for this patient. Annual admissions for examination and modulating of drug`s dose allow to correct the treatment according to serum concentration of Sirolimus and MRI changings in the dynamics. Personalized target therapy has resulted in positive outcomes in the treatment of such difficult patient Key words: children, chylotorax, lymphangiomatosis, Sirolimus

Management of Psychiatric Disorders in Patients with Chronic Kidney Diseases.

Management of Psychiatric Disorders in Patients with Chronic Kidney Diseases.

Optimization of Initial Dose Regimen for Sirolimus in Pediatric Patients With Lymphangioma.

Sirolimus is an effective oral treatment for pediatric patients with lymphangioma. The present clinical study in 15 children (0.12–16.39 years of age) examines the effects of underlying factors on sirolimus concentrations through application of a population pharmacokinetic model. Using Monte Carlo simulation, an initial dose regimen for sirolimus in pediatric patients with lymphangioma is presented. It is found that the lower the body weight, the higher the clearance rate and sirolimus clearances are 0.31–0.17 L/h/kg in pediatric patients with lymphangioma whose weights are 5–60 kg, respectively. The doses of sirolimus, 0.07, 0.06, 0.05 mg/kg/day are recommended for weights of 5–10, 10–24.5 and 24.5–60 kg in children with lymphangioma. This study is the first to establish a population pharmacokinetic model for sirolimus and to recommend initial doses in pediatric patients with lymphangioma. Large scale, prospective studies are needed in the future.

Immunosuppressive Drug Measurement by Liquid Chromatography Coupled to Tandem Mass Spectrometry: Interlaboratory Comparison in the Korean Clinical Laboratories.

BackgroundLiquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is increasingly used for immunosuppressive drug tests. However, most LC-MS/MS tests are laboratory-developed and their agreement is unknown in different Korean laboratories. This interlaboratory comparison study evaluated test reproducibility and identified potential error sources.MethodsTest samples containing three concentrations of tacrolimus, sirolimus, everolimus, cyclosporine, and mycophenolic acid were prepared by pooling surplus samples from patients undergoing routine therapeutic drug monitoring and tested in duplicate in the participating 10 clinical laboratories. Reconstitution and storage experiments were conducted for the commonly used commercial calibrator set. The robust estimators of reproducibility parameters were calculated. Spearman’s rank correlation coefficient (rho, ρ) was used to evaluate the correlation between drugs. Multiple linear regression was used to determine whether the experimental conditions alter the calibration curves.ResultsThe reproducibility coefficient of variation exceeded 10% only for sirolimus concentrations 1 and 2 (10.8% and 12.5%, respectively) and everolimus concentrations 1 and 2 (12.3% and 11.4%, respectively). The percent difference values showed weak correlations between sirolimus and everolimus (ρ=0.334, P =0.175). The everolimus calibration curve slope was significantly altered after reconstitution following prolonged 5°C storage (P =0.015 for 14 days; P =0.025 for 28 days); the expected differences at 6 ng/mL were 0.598% for 14 days and 0.384% for 28 days.ConclusionsLC-MS/MS test reproducibility for immunosuppressive drugs seems to be good in the Korean clinical laboratories. Continuous efforts are required to achieve test standardization and harmonization, especially for sirolimus and everolimus.

Population Pharmacokinetics and Initial Dose Optimization of Sirolimus Improving Drug Blood Level for Seizure Control in Pediatric Patients With Tuberous Sclerosis Complex.

The purposes of this study were to explore the population pharmacokinetics and initial dose optimization of sirolimus improving drug blood level for seizure control in pediatric patients with tuberous sclerosis complex (TSC). Eighty pediatric patients diagnosed with TSC-related epilepsy were included for analysis. Sirolimus concentrations, physiological and biochemical indexes, and drug combination were collected to build a nonlinear mixed effect (NONMEM) model. Initial dose optimization was simulated by the Monte Carlo method. The weight and concomitant medication of oxcarbazepine affected sirolimus clearance. Without oxcarbazepine, for once-daily sirolimus regimen, the doses of 0.07, 0.06, 0.05, 0.04, and 0.03 mg/kg/day were recommended for weights of 5–7.5, 7.5–11.5, 11.5–19, 19–40, and 40–70 kg, respectively; for twice-daily sirolimus regimen, the doses of 0.05, 0.04, and 0.03 were recommended for weights of 5–8, 8–20, and 20–70 kg, respectively. With oxcarbazepine, for once-daily sirolimus regimen, the doses of 0.09, 0.08, 0.07, 0.06, 0.05, and 0.04 mg/kg/day were recommended for weights of 5–7.5, 7.5–10, 10–13.5, 13.5–20, 20–35, and 35–70 kg, respectively; for twice-daily sirolimus regimen, the doses of 0.06, 0.05, 0.04, and 0.03 were recommended for weights of 5–7, 7–14.5, 14.5–38, and 38–70 kg, respectively. The present study was the first to establish a population pharmacokinetic model of sirolimus improving drug blood level for seizure control in pediatric patients with TSC and recommend the initial dosage regimen.

Development and Validation of a Bioanalytical LC-MS/MS Method for Simultaneous Determination of Sirolimus in Porcine Whole Blood and Lung Tissue and Pharmacokinetic Application with Coronary Stents.

Sirolimus is a hydrophobic macrolide compound that has been used for long-term immunosuppressive therapy, prevention of restenosis, and treatment of lymphangioleiomyomatosis. In this study, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated for the simultaneous determination of sirolimus in both porcine whole blood and lung tissue. Blood and lung tissue homogenates were deproteinized with acetonitrile and injected into the LC-MS/MS system for analysis using the positive electrospray ionization mode. The drug was separated on a C18 reversed phase column with a gradient mobile phase (ammonium formate buffer (5 mM) with 0.1% formic acid and acetonitrile) at 0.2 mL/min. The selected reaction monitoring transitions of m/z 931.5 → 864.4 and m/z 809.5 → 756.5 were applied for sirolimus and ascomycin (the internal standard, IS), respectively. The method was selective and linear over a concentration range of 0.5–50 ng/mL. The method was validated for sensitivity, accuracy, precision, extraction recovery, matrix effect, and stability in porcine whole blood and lung tissue homogenates, and all values were within acceptable ranges. The method was applied to a pharmacokinetic study to quantitate sirolimus levels in porcine blood and its distribution in lung tissue following the application of stents in the porcine coronary arteries. It enabled the quantification of sirolimus concentration until 2 and 14 days in blood and in lung tissue, respectively. This method would be appropriate for both routine porcine pharmacokinetic and bio-distribution studies of sirolimus formulations.

Sirolimus is effective for primary relapsed/refractory autoimmune cytopenia: a multicenter study

Autoimmune cytopenia includes autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), and Evans syndrome (ES) caused by abnormal activation of autoimmunity and has a considerable refractory/relapse rate. To evaluate the efficacy and toxicity of sirolimus of primary relapsed/refractory autoimmune cytopenia, records of 45 patients with primary relapsed/refractory AIHA, ES, or ITP from October 2016 to January 2019 in two institutions, were collected; there were 3 pediatric patients and 42 adult patients. The median age at diagnosis was 31 (1-84) years. Patients were treated for a median of 14 (6-39) months and followed-up for a median of 18 (10-40) months. Thirty-eight patients responded to sirolimus, with 28 complete responses (CRs) and a median of 2 (2-5) months to response. Five patients had mucositis; the incidences of other adverse events were all less than 5%. Four patients relapsed, making the CR and overall response rate 46.7% and 75.6% at the end of follow-up. There were no differences in patient age, sex, time from diagnosis to sirolimus, serum sirolimus concentration, and disease distribution between CR and non-CR patients, or between responders and nonresponders, though AIHA patients were likely to relapse less and respond better. In conclusion, sirolimus is effective for patients with primary relapsed/refractory autoimmune cytopenia with a low relapse rate and good tolerance.

Size exclusion chromatography: An effective tool for the estimation of Sirolimus levels

Sirolimus, a lipophilic macrolide, is a well-known immunosuppressant drug used for coating coronary stents and for preventing rejection of kidney transplants in humans. Since Sirolimus is a relatively large molecule with an average mass 914.172 g/mol, size exclusion chromatography (SEC) was employed for exploring its potential for the estimation of Sirolimus content from blood samples. When human blood samples were spiked with known concentrations of Sirolimus, it was observed that it could be estimated with an average recovery of >90% and relative standard deviation <5%. Results indicated that Sirolimus could be estimated with impressive accuracy and repeatability by SEC technique.

Determination of sirolimus in blood by high-performance liquid chromatography with ultraviolet detection - Experience and review

Sirolimus (SRL) is a potent immunosuppressant. Therapeutic drug monitoring (TDM) of SRL is required to optimize the therapy. Immunoassay, high-performance liquid chromatography with ultraviolet detection (HPLC-UV), and HPLC with mass-spectrometric detection (HPLC-MS or HPLC/MS/MS) have been used in the analysis of SRL. The purpose of this study was to share our experience in validating a HPLC-UV method for analyzing SRL and to have an overview of HPLC-UV methods used in SRL assay. A validated HPLC/UV method developed by Wyeth-Ayerst Research with minor modification was use to determine SRL concentration in human whole blood. An Alltima C18 column (5 μm, 150 × 2.1 mm) was used as the stationary phase. The mobile phase was 60% acetonitrile in water, and the flow rate was 0.5 mL/min. Samples were prepared by spiking human whole blood (0.5 mL) with the internal standard (IS) and designated amount of SRL, except blank. Zinc sulfate (50 g/L, 1 mL) and acetone (1 mL) were used for hemolysis and deproteinization. After alkalizing supernatant with 100 mM NaOH (0.2 or 0.3 mL), 1-chlorobutane (2 mL) was used for extraction. The 1-chlorobutane layer was dried, reconstituted with mobile phase and back extracted with 0.5 mL of n-hexane. The limitation of quantification was 2.5 ng/mL and the standard curve was linear at the concentration range of 2.5-75 ng/mL. The intraday and interday coefficients of variation were 2.1-5.2% and 2.8-5.7%, respectively. The intraday and interday relative errors were -0.03-5.3% and 0.7-3.3%, respectively. The recoveries for SRL and the IS were 78.5-92.8% and 76.9 ± 3.9%, respectively. The samples were proven to be stable after 3 freeze/thaw cycles, and the extract was stable over 24 hr at an autosampler set to 4°C. In addition to an overview of the chemical properties of SRL, different HPLC-UV methods for the quantification of SRL were provided to identify analytic parameters that are critical for the establishment of HPLC-UV assay for SRL.

Initial Dosage Recommendation for Sirolimus in Children With Tuberous Sclerosis Complex.

Sirolimus is already used in the treatment of tuberous sclerosis complex (TSC), however, with narrow therapeutic range and considerable inter- and intra-individual pharmacokinetic variability, making it hard to develop an appropriate sirolimus initial dosage regimen, especially in children with TSC. The aim of this study was to recommend the optimal sirolimus initial dosing regimen in pediatric patients with TSC. Underlying physiological and genetic factors were collected to explore the effects on clinical sirolimus concentrations by establishing a nonlinear mixed effect (NONMEM) model, and to further simulate the optimal sirolimus initial dosing regimen using Monte Carlo method in pediatric patients with TSC. The once-daily regimen and the twice-daily regimen were recommended, respectively. For once-daily regimen, the dosages of 0.10, 0.07, 0.05, 0.04, 0.03 mg/kg/day were recommended for children with weights of 5–10, 10–20, 20–30, 30–50, and 50–60 kg, respectively. For twice-daily regimen, the dosages of 0.04, 0.03, 0.02 mg/kg/day (the daily dose was divided evenly into two doses) were recommended for children with weights of 5–20, 20–40, 40–60 kg, respectively. The initial dosages of sirolimus in children with TSC were recommended for the first time.

Ex vivo immunological evaluation of stable mixed chimeric patients after matched related donor allogeneic transplantation in sickle cell disease

Background aimsAllogeneic hematopoietic stem cell transplantation is curative for sickle cell disease, and the use of matched related donors, non-myeloablative conditioning and sirolimus immunosuppression results in stable mixed chimerism without graft-versus-host disease (GVHD). However, the time to terminate sirolimus while maintaining mixed chimerism is unclear. MethodsIn this study, we developed a two-way mixed lymphocyte reaction (MLR) to evaluate ex vivo immunoreaction in mixed chimeric patients. ResultsIn co-culture of peripheral blood mononuclear cells (PBMCs) from two healthy controls (without irradiation), we detected proliferation at various ratios of PBMC mixtures (1:9 to 9:1) as well as various concentrations of sirolimus, suggesting that two-way MLR is applicable to patients (having >10% chimerism) undergoing sirolimus treatment. In two-way MLR using PBMCs (including donor and recipient cells) from mixed chimeric patients (n = 28), greater ex vivo proliferation was observed <6 months compared with >6 months post-transplant and healthy control PBMC monoculture. Robust ex vivo proliferation was observed in a patient with acute GVHD, and persistent ex vivo proliferation (until 2 years) was observed in a patient with decreasing donor chimerism. ConclusionsIn summary, we demonstrated that in two-way MLR, ex vivo immunoreaction decreases to low levels ~6 months post-transplant. These findings suggest a rationale to continue immunosuppression for 6 months.

Inhibition of T Helper Cell Differentiation by Tacrolimus or Sirolimus Results in Reduced B-Cell Activation: Effects on T Follicular Helper Cells

The effect of immunosuppressive drugs on the generation of T follicular helper (Tfh) cells, specialized in supporting B-cell differentiation, is largely unknown. We examined whether the calcineurin inhibitor tacrolimus (TAC) and the mammalian target of rapamycin (mtor) inhibitor sirolimus (SRL) inhibit Tfh cell differentiation, and affect subsequent B-cell functions. Isolated naive T cells were polarized into Tfh-like cells in the presence of TAC or SRL. To demonstrate their functionality, we co-cultured these cells with isolated B cells in the presence of alloantigen and studied the activation and differentiation of these B cells. Tfh-like cells were defined as CD4+CXCR5+ T cells, expressing immunoinhibitory programmed death protein 1 (pd1) and inducible T-cell costimulator (icos). We found that TAC and SRL significantly inhibited Tfh-like cell differentiation. Therapeutic concentrations of TAC and SRL reduced the percentage of pd1+ and icos+ Tfh cells compared to controls. In addition, T cells grown in the presence of TAC or SRL expressed less IL-21 and provided less B-cell help. TAC and SRL both inhibited Tfh-dependent alloantigen-activated B-cell proliferation and differentiation into plasma cells and transitional B cells.In conclusion, TAC and SRL inhibited the differentiation of naive T cells into functional Tfh-like cells, a finding that can be extrapolated to immunosuppressive regimens in transplant patients.

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 3896: Distinct pharmacokinetics, tissue distribution and CNS penetration of ABI-009 (nab-Sirolimus)

Abstract Background: Activation of the mTOR signaling pathway is frequently observed in multiple types of cancer. The poor solubility and low oral bioavailability of the mTOR inhibitor sirolimus limit its development as an anticancer therapy. ABI-009 (nab-sirolimus) is an injectable nanoparticle form of human albumin-bound sirolimus developed with a proprietary nanoparticle albumin-bound (nab®) technology. Currently, numerous phase 1 and 2 clinical studies are ongoing with ABI-009, including a registrational phase 2 study for the treatment of malignant perivascular epithelioid cell carcinoma (PEComa), and various oncology (bladder cancer, soft-tissue sarcomas, neuroendocrine tumors, colorectal cancer, glioblastoma, and various childhood cancers) as well as in non-oncology indications (pulmonary arterial hypertension (PAH), pediatric epilepsy, and mitochondrial diseases). Several nonclinical studies were conducted to evaluate pharmacokinetics, tissue distribution and in particular, CNS penetration of ABI-009. Methods: Rats were intravenously (IV) administered with a single dose of ABI-009 at 1.7, 9.5, and 17 mg/kg. Blood and organs were collected at 2, 8, 24, 72, and 120 hrs to analyze for sirolimus concentrations. Results: There is a generally linear dose response with sirolimus concentrations in blood, heart, lung, liver, and pancreas following a single dose of IV ABI-009. Sirolimus concentrations in blood and well-perfused organs had high peaks at earlier time points but dropped quickly with time, with the highest concentrations observed in lung. In contrast, sirolimus concentrations in brain rose slowly at first, but maintained at a steady level over time. After 5 days, sirolimus level in the brain was similar to other organs, suggesting substantial and prolonged drug distribution to the brain with ABI-009. Organ/blood ratios of most organs increased with time, with the brain/blood ratios increasing more significantly over time. Higher initial dose of ABI-009 resulted in increased brain/blood ratios. Conclusions: ABI-009 administered IV demonstrated a distinct PK profile compared with oral mTOR inhibitors. The PK of ABI-009 is characterized by higher Cmax and AUC, and rapid tissue distribution. Combined with efficient tumor penetration observed in a xenograft study, results of this study support the potential use of ABI-009 for the treatment of cancers in different organ sites, including lung, brain, liver, and pancreas. These findings also warrant further clinical studies in non-oncology indications including PAH and disorders involving the CNS. Citation Format: Shihe Hou, Anita Schmid, Neil Desai. Distinct pharmacokinetics, tissue distribution and CNS penetration of ABI-009 (nab-Sirolimus) [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 3896.

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.