Pharmacokinetics and Metabolism of Melflufen, an Alkylating Peptide-Drug Conjugate, in Patients with Relapsed Refractory Multiple Myeloma.

Melphalan flufenamide (melflufen) is a novel lipophilic peptide-drug conjugate recently approved in the European Union and the United Kingdom for the treatment of relapsed refractory multiple myeloma. Melflufen rapidly crosses the cell membrane, and inside tumor cells, melflufen utilizes peptidases and esterases to release entrapped hydrophilic metabolites with alkylating activity. In vitro, in whole blood, melflufen was rapidly distributed into blood cells and quickly converted to its main metabolite melphalan, with maximum cellular concentrations of noncovalently bound melflufen and melphalan after 1 and 6 minutes, respectively. Melphalan outflow from blood cells was slow, with peak concentrations in plasma after 25 minutes. The pharmacokinetics of melflufen was best described by a 2-compartment model. Following a 30-minutes intravenous infusion of 40 mg in 27 patients with relapsed refactory multiple myeloma, mean half-life in the α phase of the curve was 1.24 minutes, half-life in the ß phase of the curve 26.7 minutes, and clearance 13.4 L/min. Desethyl-melflufen exposure was below 20% compared to melflufen. Based on population analysis (298 patients with relapsed refactory multiple myeloma), the melphalan pharmacokinetics were well characterized by a 3-compartment model with melflufen dosing into a peripheral compartment, assuming instantaneous distribution of melflufen into cells and subsequent rapid metabolism to melphalan. Mean clearance and central and deep peripheral volumes of distribution were 22.4 L/h, 2.70 L, and 51.3 L, respectively. Clearance increased and maximum concentration decreased with increasing body weight and estimated glomerular filtration rate. In conclusion, melflufen administration differs from melphalan administration by a more rapid distribution into cells, which, in conjunction with a rapid intracellular metabolism, allows for higher maximum concentrations of alkylating agents, and by a more extensive distribution of melphalan to peripheral tissues.

Clinical Impact of Melphalan Pharmacokinetics on Transplantation Outcomes in Children Undergoing Hematopoietic Stem Cell Transplantation.

Melphalan is widely used for hematopoietic stem cell transplantation (HSCT) conditioning. However, the relationship between its pharmacokinetic (PK) and transplantation outcomes in children has not been thoroughly investigated. We prospectively analyzed the relationship between melphalan area under the curve (AUC) and transplantation outcome and examined the development of a predictive model for melphalan clearance in children. This study included 43 children aged 0 to 19 years who underwent HSCT following a melphalan-based conditioning regimen from 2017 to 2021. In univariable analysis, high-melphalan AUC resulted in a significantly lower cumulative incidence of acute graft-versus-host disease and a higher cumulative incidence of thrombotic microangiopathy, although no significant difference was observed in survival. Regression analysis of a randomly selected derivation cohort (n = 21) revealed the following covariate PK model: predicted melphalan clearance (mL/min) = 6.47 × 24-h urinary creatinine excretion rate (CER, g/day) × 24-h creatinine clearance rate (CCR, mL/min) + 92.8. In the validation cohort (n = 22), the measured melphalan clearance values were significantly correlated with those calculated based on the prediction equation (R2 = 0.663). These results indicate that melphalan exposure may be optimized by adjusting the melphalan dose according to CER and CCR.

Challenges associated with test dose pharmacokinetic predictions of high dose melphalan exposure in patients with multiple myeloma.

AIM: To evaluate the accuracy of melphalan test dose pharmacokinetic (PK) predictions of the subsequent high dose (HDM) area under the concentration-versus-time curve (AUC) and to identify sources of prediction error (PE). METHODS: A prospective multicentre PK study was conducted in 40 myeloma patients of median age 60 (range:35-71) years using a 20 mg/m2 test dose administered 1-3 days prior to HDM (predominantly 180 mg/m2). PK data were collected post the test and high doses to compare predicted versus actual AUCs determined using the trapezoidal rule. Test and high dose infusion concentration, volume and duration and the time from preparation to infusion were compared using the paired Wilcoxin rank sign test. The impact of Melphalan administration parameters on PE was evaluated using the Mann-Whitney test. The predictive capacity of a previously published population PK (PopPK) model was also examined. RESULTS: Predicted HDM AUC was within 15% of the observed values in only 63% of patients when analysed using the trapezoidal rule and 70% of patients using PopPK. Test dose infusion concentration, volume, duration and time from preparation to infusion were significantly lower than for HDM (p < 0.005). Test dose administration within 15 min of reconstitution (n = 5) was associated with significantly lower PE than administration times of 16-60 min (n = 22), p < 0.05. Test and HDM infusion concentrations were lower in patients with large PE (> ± 15%), but the differences were not significant (p = 0.078, 0.228, respectively). CONCLUSION: Test dose PK has the potential to predict subsequent HDM exposure to achieve a target AUC once melphalan administration parameters are optimised to account for stability issues in the formulation.

Melphalan: Recent insights on synthetic, analytical and medicinal aspects.

Cancer is an uncontrolled expansion of atypical cells in the body. These unusual cells are labelled as cancerous or malignant cells. Melphalan, an anticancer drug which is imperatively recognized under the class of alkylating agents. It exhibits broad spectrum antitumor activity, as observed in ovarian cancer, breast cancer, etc. However, it is mainly utilized in the management of multiple myeloma. Several studies across the globe suggest that resistance to melphalan is the major concern that leads to relapsed myeloma. In the present paper, several pivotal approaches to compensate resistance associated with melphalan have been discussed. Numerous chemical and formulation developments concerning melphalan to enhance its salient characteristics and targeted profile have also been portrayed. The rationale of the current article also summarizes the recent analytical methods, structure-activity relationship, pharmacokinetics, interactions, potential adverse effects along with medicinal updates of melphalan. Special attention is also laid on their synthetic developments viz. melphalan derivatives, conjugates and prodrugs along with encouraging insights and research findings.

Population Pharmacokinetics of Melphalan for Pediatric Patients Undergoing Hematopoietic Cell Transplantation.

Melphalan is an alkylating agent used as part of conditioning prior to pediatric hematopoietic cell transplantation (HCT). We performed a single-center, prospective pharmacokinetic study of 37 pediatric patients undergoing HCT from March 2015 to 2019. The primary objective was to develop and validate a population pharmacokinetic model for melphalan in a diverse group of pediatric HCT recipients. Nonlinear mixed-effects modeling was implemented to describe plasma concentration-time data of melphalan. A 2-compartment, proportional error model with weight on clearance best fit the data. Final parameter estimates were clearance, 19.1 L/h/25 kg; volume of the central compartment, 8.5 L/25 kg; volume of the peripheral compartment, 5.8 L/25 kg; and intercompartmental clearance 12.4 L/h/25 kg. Residual unexplained variability was low, at 12.5%. Results suggest the empiric weight-based dosing (mg/kg) used in children <12 kg or 2 years of age may result in subtherapeutic exposure. Model-based dosing of melphalan in pediatric HCT may help inform individualized dosing strategies to improve clinical outcomes and limit drug-related adverse events in pediatric HCT recipients.

Test-dose pharmacokinetics guided melphalan dose adjustment in reduced intensity conditioning allogeneic transplant for non-malignant disorders.

AIMS: We studied melphalan pharmacokinetics (PK) and feasibility of melphalan full-dose adjustment based on test-dose PK in children and young adults with non-malignant disorders (NMD) undergoing allogeneic hematopoietic cell transplantation (HCT) using reduced intensity conditioning (RIC) containing alemtuzumab, fludarabine and melphalan. METHODS: Patients received test-dose melphalan (10% of planned full-dose) prior to conditioning. Blood samples for PK were obtained around test and full-dose melphalan (140 mg/m2 or 4.7 mg/kg in patients <10 kg). Melphalan concentration was measured by liquid chromatography electrospray ionization tandem mass-spectrometry assay and data were analysed using a population-PK model and Bayesian estimation. Test and full-dose melphalan clearance estimates were evaluated by pairwise Wilcoxon test and Bland-Altman plot. RESULTS: Twenty-four patients undergoing 25 transplants were included in the final analysis. Patients received standard full-dose melphalan in 17 transplants, with median area under the concentration-time curve (AUC) of 5.5 mg*h/L (range, 3.0-9.5 mg*h/L). Patients received test-dose melphalan in 23 transplants with a test-dose PK predicted full-dose AUC range of 2.9-16.8 mg*h/L. In seven transplants where patients had baseline organ impairment, test-dose PK predicted higher exposure for standard full-dose (median AUC 13.8 mg*h/L). Melphalan full-dose was adjusted in these patients, with achievement of desired target AUC (3.6-5.4 mg*h/L) and no excess toxicity. Mean ratio of test-dose clearance to full-dose clearance was 1.03. Twenty of 22 patients (91%) were within the 95% confidence intervals of the clearance ratio. CONCLUSION: Melphalan test-dose PK reliably predicts full-dose PK and allows for accurate adjustment of full-dose melphalan in RIC-HCT for NMD. This approach can avoid excess toxicity from increased systemic exposure, especially in patients with organ impairment.

Melphalan Flufenamide (Melflufen): First Approval.

Melphalan flufenamide (melflufen, Pepaxto®) is a peptide conjugated alkylating drug developed by Oncopeptides for the treatment of multiple myeloma (MM) and amyloid light-chain amyloidosis. It is an ethyl ester of a lipophilic dipeptide consisting of melphalan and para-fluoro-L-phenylalanine. Due to its lipophilicity, melphalan flufenamide is rapidly transported across the cell membrane and almost immediately hydrolyzed by aminopeptidases in the cytoplasm to yield more hydrophilic alkylating molecules, such as melphalan and desethyl-melflufen. Like other nitrogen mustard drugs, melphalan flufenamide exerts antitumor activity through DNA crosslinking. In February 2021, melphalan flufenamide, in combination with dexamethasone, received its first approval in the USA for the treatment of adults with relapsed or refractory (r/r) MM who have received at least four prior lines of therapy and whose disease is refractory to at least one proteasome inhibitor (PI), one immunomodulatory agent, and one CD38-directed monoclonal antibody. A multinational clinical study of melphalan flufenamide in amyloid light-chain amyloidosis is underway across several countries, and preclinical studies for various haematological and solid cancers are underway. This article summarizes the milestones in the development of melphalan flufenamide leading to this first approval.

Pharmacokinetics and Efficacy of Generic Melphalan Is Comparable to Innovator Formulation in Patients With Multiple Myeloma Undergoing Autologous Stem Cell Transplantation.

BACKGROUND: High-dose melphalan (MEL) is the standard conditioning regimen used for autologous stem cell transplantation (ASCT) in patients with multiple myeloma (MM). Generic MEL is routinely used in various transplant centers across the world including ours due to its reduced cost and ease of availability. We compared the pharmacokinetics (PK) and the clinical efficacy of generic MEL with that of the innovator formulation in MM patients undergoing ASCT. PATIENTS AND METHODS: Sixty-three patients diagnosed with MM receiving high-dose MEL were included in this study. MEL levels in plasma were measured using a liquid chromatography tandem mass spectrometry (HPLC/MS-MS) protocol and non-linear mixed effects modeling was used to evaluate the PK of the data. RESULTS: The interindividual variability (IIV) in MEL area under the concentration versus time curve (AUC) and clearance (CL) were 4.39, 5.88-fold for generic, and 4.34, 6.85-fold for the innovator formulation, respectively. The median MEL AUC and CL were comparable between the 2 formulations. The population PK analysis showed age and creatinine CL as the only significant covariates explaining IIV in MEL AUC/CL. Analysis of MEL PK parameters with clinical outcome showed no significant differences in terms of onset and severity of mucositis, day to neutrophil and platelet engraftment, as well as response status on day 100 post ASCT between patients receiving generic or innovator formulations of MEL. In addition, neither MEL AUC nor CL was found to be associated with day +100 response. CONCLUSION: Our study suggests that the PK and efficacy of the generic MEL is comparable to the innovator formulation.

Impact of frailty, melphalan pharmacokinetics, and pharmacogenetics on outcomes post autologous hematopoietic cell transplantation for multiple myeloma.

Autologous hematopoietic cell transplantation (auto-HCT) using melphalan is the standard of care in the management of myeloma. Auto-HCT is a safe procedure with tolerable toxicity except in Asian-Indians. We hypothesized either one or a combination of factors: (1) frailty (assessed by IMWG frailty score), (2) generic melphalan pharmacokinetic area under the curve (AUC) assessed by high-performance liquid chromatography, and (3) pharmacogenetics of glutathione S-transferase (GSTP1) assessed by Sanger sequencing, to be associated with toxicity and survival outcomes post auto-HCT. Disease response was evaluated by IMWG response criteria at day +100 post auto-HCT. Gastrointestinal (GI) toxicity, infections, hospital stay, progression-free survival (PFS) were also recorded. A total of 35 patients were evaluated over 2 years (2016-2018). Frailty, not HCT-comorbidity index correlated with GI toxicity and infections. Overall there was an 11-fold variation in melphalan AUC with a median of 27.88 mg h/L (10.06-110.26). Patients with AUC more than the median had more GI toxicity and infections. Patients with wild-type GSTP1 polymorphism had more GI toxicity and infections. Frailty, AUC, or GSTP1 polymorphism did not impact hospitalization duration or PFS. A combination of the factors frailty, melphalan pharmacokinetics, and pharmacogenetics impacts GI toxicity and infections after auto-HCT in myeloma.

Population pharmacokinetics of carboplatin, etoposide and melphalan in children: a re-evaluation of paediatric dosing formulas for carboplatin in patients with normal or mild impairment of renal function.

AIMS: Carboplatin dosage is calculated by using the estimated glomerular filtration rate (GFR) to achieve a target plasma area under the plasma concentration-time curve (AUC). The aims of the present study were to investigate factors that influence the pharmacokinetics of carboplatin in children with high-risk neuroblastoma, and whether target exposures for carboplatin were achieved using current treatment protocols. METHODS: Data on children receiving high-dose carboplatin, etoposide and melphalan for neuroblastoma were obtained from two study sites [European International Society for Paediatric Oncology (SIOP) Neuroblastoma study, Children's Hospital at Westmead; n = 51]. A population pharmacokinetic model was built for carboplatin to evaluate various dosing formulas. The pharmacokinetics of etoposide and melphalan was also investigated. The final model was used to simulate whether target carboplatin AUC (16.4 mg ml-1 ·min) would be achieved using the paediatric Newell formula, modified Calvert formula and weight-based dosing. RESULTS: Allometric weight was the only significant, independent covariate for the pharmacokinetic parameters of carboplatin, etoposide and melphalan. The paediatric Newell formula and modified Calvert formula were suitable for achieving the target AUC of carboplatin for children with a GFR <100 ml min-1 1.73 m-2 but not for those with a GFR ≥100 ml min-1 1.73 m-2 . A weight-based dosing regimen of 50 mg kg-1 achieved the target AUC more consistently than the other formulas, regardless of renal function. CONCLUSIONS: GFR did not appear to influence the pharmacokinetics of carboplatin after adjusting pharmacokinetic parameters for weight. This model-based approach validates the use of weight-based dosing as an appropriate alternative for carboplatin in children with either mild renal impairment or normal renal function.

Pharmacokinetic-Pharmacodynamic Model of Neutropenia in Patients With Myeloma Receiving High-Dose Melphalan for Autologous Stem Cell Transplant.

High-dose melphalan (HDM) is part of the conditioning regimen in patients with multiple myeloma (MM) receiving autologous stem cell transplantation (ASCT). However, individual sensitivity to melphalan varies, and many patients experience severe toxicities. Prolonged severe neutropenia is one of the most severe toxicities and contributes to potentially life-threatening infections and failure of ASCT. Granulocyte-colony stimulating factor (G-CSF) is given to stimulate neutrophil proliferation after melphalan administration. The aim of this study was to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model capable of predicting neutrophil kinetics in individual patients with MM undergoing ASCT with high-dose melphalan and G-CSF administration. The extended PK/PD model incorporated several covariates, including G-CSF regimen, stem cell dose, hematocrit, sex, creatinine clearance, p53 fold change, and race. The resulting model explained portions of interindividual variability in melphalan exposure, therapeutic effect, and feedback regulation of G-CSF on neutrophils, thus enabling simulation of various doses and prediction of neutropenia duration.

The pharmacokinetics and pharmacodynamics of busulfan when combined with melphalan as conditioning in adult autologous stem cell transplant recipients.

Busulfan (Bu) is an alkylating agent widely used in conditioning regimes prior to stem cell transplantation (SCT), most commonly in combination with cyclophosphamide (Bu-cy) or fludarabine (Bu-flu) as myeloablative conditioning prior to allograft or with high-dose melphalan (Bu-mel) prior to autologous SCT. Despite many decades of Bu use, initially orally but now intravenously (IV), a paucity of pharmacokinetic (PK) and pharmacodynamic (PD) data exists to inform evidence-based guidelines as how best to balance the efficacy and toxicity of this agent. This is a non-randomized retrospective real-world study at three hospitals investigating the role of PK guidance in dosing Bu in the setting of IV Bu-mel autologous SCT. The primary intent was to examine how effectively PK assessment could be used to achieve a desirable drug exposure and to evaluate factors, particularly, age, sex, actual weight, body mass index (BMI), body surface area (BSA), disease, number of prior treatments, renal function, and the use of concomitant medications that may influence Bu exposure. All patients underwent PK analysis on a test dose of Bu (1.6 mg/kg, i.e., 50% of the first dose) on D-7 and subsequently received a second 1.6 mg/kg dose on D-6. Bu dose was calculated using actual body weight (ABW) if patients were less than ideal body weight (IBW), or adjusted ideal body weight (AIBW) if ABW was greater than IBW. Thereafter, at the discretion of the investigator, the group was divided into two; a weight-based cohort at two hospitals and a PK-guided cohort at the third hospital. Thirty-seven patients received PK-adjusted dosing guided by the results of the initial PK results, targeting a specific Bu exposure expressed as the area-under-the-concentration-versus-time curve (AUC) of between 4000 and 5000 µmol min/day (median 4800). The remaining 27 patients received unadjusted weight-based doses with a further three doses of 3.2 mg/kg of Bu infused over 180 min (D-5 to - 3) irrespective of their initial PK results. For the purposes of the analysis, we selected a target AUC of 4800 µmol min/day in this group, equivalent to the median targeted AUC in the PK-adjusted group. All patients subsequently had repeated PK analysis on D-5 after receiving their "therapeutic" Bu dose. Mel (140 mg/m2 or 100 mg/m2) IV was given on D-2. Sixty-four adult patients were enrolled. Patients who received PK-guided Bu dosing received a higher median Bu dose than the unadjusted weight-based cohort (3.5 mg/kg vs 3.2 mg/kg respectively, p = 0.007). Eighty-one percent (30/37) of patients in the PK-guided group achieved their target AUC (± 15%) compared with 56% (15/27) in the weight-based cohort (p = 0.027). The respective median AUCs of 5064 µmol min/day (range 3639-6157 µmol min/day) and 4854 µmol min/day (range 3251-6305 µmol min/day) were not significantly different (p = 0.16). Multivariate analysis identified ABW as the only independent variable that affected the relationship between Bu dosing and exposure (p = 0.02) with heavier patients achieving lower than anticipated AUCs for the dose they received. On D-5, within the weight-based cohort, the mean AUCs were 12% higher than anticipated based on initial D-7 PK. No correlation between AUC and grade 3-4 transplant-related toxicities were observed, although only three patients had AUCs > 6000 µmol min/day. These results suggest that PK-directed Bu dosing may be of benefit in achieving a target level of drug exposure, with larger studies needed to determine the clinical significance of this strategy.

Pharmacokinetics of High-Dose Propylene Glycol-Free Melphalan in Multiple Myeloma Patients Undergoing Autologous Hematopoietic Cell Transplantation.

High-dose melphalan followed by autologous stem cell transplant (ASCT) is standard of care for eligible patients with multiple myeloma (MM). Evomela (propylene glycol-free melphalan HCl [PG-Free Mel]; Spectrum Pharmaceuticals, Irvine, CA) was approved by the US Food and Drug Administration as conditioning therapy for ASCT in MM in 2 daily 100-mg/m2 doses for a total dose of 200 mg/m2. In this phase II, open-label study PG-Free Mel (Evomela) conditioning was given at single dose of 200 mg/m2 on day -2 pre-ASCT to establish pharmacokinetic (PK) parameters and safety. Twenty-four patients (median age, 64 years) were enrolled between August 2016 and February 2017. Myeloablation followed by successful neutrophil engraftment occurred at a median of 10 days in all patients. Peak melphalan concentration was observed at 10 minutes after infusion, whereas there was considerable variation in the maximum plasma concentration (Cmax) and area under concentration time curve (AUC). Median Cmax was 7380 ng/mL (interquartile range [IQR], 6522 to 8027). Similarly, median AUC was 533,552 ng/mL∙min (IQR, 450,850 to 662,936). PG-Free Mel had an acceptable safety profile regardless of the exposure, with no mortality and an overall response rate of 96% and a very good partial response rate of 75%. In conclusion, although PG-Free Mel at a single dose of 200 mg/m2 was safe, considerable PK variability was observed with the highest quartile having an ~3-fold higher AUC than the first quartile, suggesting that strategies for higher targeted exposure could be explored in future trials to optimize clinical benefit.

Pharmacokinetics, Tissue Localization, Toxicity, and Treatment Efficacy in the First Small Animal (Rabbit) Model of Intra-Arterial Chemotherapy for Retinoblastoma.

Purpose: Current intra-arterial chemotherapy (IAC) drug regimens for retinoblastoma have ocular and vascular toxicities. No small-animal model of IAC exists to test drug efficacy and toxicity in vivo for IAC drug discovery. The purpose of this study was to develop a small-animal model of IAC and to analyze the ocular tissue penetration, distribution, pharmacokinetics, and treatment efficacy. Methods: Following selective ophthalmic artery (OA) catheterization, melphalan (0.4 to 1.2 mg/kg) was injected. For pharmacokinetic studies, rabbits were euthanized at 0.5, 1, 2, 4, or 6 hours following intra-OA infusion. Drug levels were determined in vitreous, retina, and blood by liquid chromatography tandem mass spectrometry. To assess toxicity, angiograms, photography, fluorescein angiography, and histopathology were performed. For in situ tissue drug distribution, matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) was performed. The tumor model was created by combined subretinal/intravitreal injection of human WERI-Rb1 retinoblastoma cells; the tumor was treated in vivo with intra-arterial melphalan or saline; and induction of tumor death was measured by cleaved caspase-3 activity. Results: OA was selectively catheterized for 79 of 79 (100%) eyes in 47 of 47 (100%) rabbits, and melphalan was delivered successfully in 31 of 31 (100%) eyes, without evidence of vascular occlusion or retinal damage. For treated eyes, maximum concentration (Cmax) in the retina was 4.95 µM and area under the curve (AUC0→∞) was 5.26 µM·h. Treated eye vitreous Cmax was 2.24 µM and AUC0→∞ was 4.19 µM·h. Vitreous Cmax for the treated eye was >100-fold higher than for the untreated eye (P = 0.01), and AUC0→∞ was ∼50-fold higher (P = 0.01). Histology-directed MALDI-IMS revealed highest drug localization within the retina. Peripheral blood Cmax was 1.04 µM and AUC0→∞ was 2.07 µM·h. Combined subretinal/intravitreal injection of human retinoblastoma cells led to intra-retinal tumors and subretinal/vitreous seeds, which could be effectively killed in vivo with intra-arterial melphalan. Conclusions: This first small-animal model of IAC has excellent vitreous and retinal tissue drug penetration, achieving levels sufficient to kill human retinoblastoma cells, facilitating future IAC drug discovery.

Population Pharmacokinetics and Optimal Sampling Strategy for Model-Based Precision Dosing of Melphalan in Patients Undergoing Hematopoietic Stem Cell Transplantation.

BACKGROUND: High-dose melphalan is an important component of conditioning regimens for patients undergoing hematopoietic stem cell transplantation. The current dosing strategy based on body surface area results in a high incidence of oral mucositis and gastrointestinal and liver toxicity. Pharmacokinetically guided dosing will individualize exposure and help minimize overexposure-related toxicity. OBJECTIVE: The purpose of this study was to develop a population pharmacokinetic model and optimal sampling strategy. METHODS: A population pharmacokinetic model was developed with NONMEM using 98 observations collected from 15 adult patients given the standard dose of 140 or 200 mg/m2 by intravenous infusion. The determinant-optimal sampling strategy was explored with PopED software. Individual area under the curve estimates were generated by Bayesian estimation using full and the proposed sparse sampling data. The predictive performance of the optimal sampling strategy was evaluated based on bias and precision estimates. The feasibility of the optimal sampling strategy was tested using pharmacokinetic data from five pediatric patients. RESULTS: A two-compartment model best described the data. The final model included body weight and creatinine clearance as predictors of clearance. The determinant-optimal sampling strategies (and windows) were identified at 0.08 (0.08-0.19), 0.61 (0.33-0.90), 2.0 (1.3-2.7), and 4.0 (3.6-4.0) h post-infusion. An excellent correlation was observed between area under the curve estimates obtained with the full and the proposed four-sample strategy (R 2 = 0.98; p < 0.01) with a mean bias of -2.2% and precision of 9.4%. A similar relationship was observed in children (R 2 = 0.99; p < 0.01). CONCLUSIONS: The developed pharmacokinetic model-based sparse sampling strategy promises to achieve the target area under the curve as part of precision dosing.

Surgical versus percutaneous isolated pelvic perfusion (IPP) for advanced melanoma: comparison in terms of melphalan pharmacokinetic pelvic bio-availability.

BACKGROUND: Isolated pelvic perfusion (IPP) can be used to treat unresectable melanoma metastases of the pelvis. IPP can be performed either by surgical or percutaneous approaches, using different balloon catheters. The aim of this study was to examine whether the surgical and percutaneous approaches were comparable with respect to tumor drug exposure in the pelvis. METHODS: A pharmacokinetic study was performed in 5 melanoma patients treated with surgical IPP and five with percutaneous IPP. Both groups received melphalan at the dose of 30 mg/m2. Melphalan pharmacokinetic analyses were performed and the main parameter used to evaluate pelvic tumor drug-exposure was the ratio of areas under the melphalan plasma concentration curves in the pelvis and the systemic compartment, during the perfusion time (AUC0 to 20). Non-parametric Mann-Whitney tests were employed for statistical comparisons. RESULTS: The median and interquartile range (IQR) values of the ratios between melphalan AUC0 to 20 in pelvic and systemic compartments were 7.9 (IQR 7.2 to 9.9) and 5 (IQR 4 to 7.9) for surgical and percutaneous IPPs, respectively (p = 0.209). CONCLUSIONS: Tumor exposure to drug using these two methods did not statistically differ and both methods, therefore, can be adopted interchangeably, utilizing a perfusion blood flow rate of approximately 120 ml/min. The small sample size is a limitation of this study but our preliminary results can be used to calculate the effect size of a larger trial. Trial Registration Clinical Trials.gov Identifier NCT01920516; date of trial registration: August 6, 2013.

Melphalan hydrochloride for the treatment of multiple myeloma.

INTRODUCTION: Multiple myeloma (MM) is an incurable disease characterized by clonal plasma cell proliferation and overproduction of monoclonal paraprotein, hypercalcemia, renal failure, anemia, osteolytic bone lesions, and infections. Melphalan, a nitrogen mustard, is an alkylating agent synthesized in 1953, and it has been used in multiple myeloma therapy for fifty years. Although novel agents have been introduced in the past few decades improving prognosis of the disease, melphalan still maintains a crucial role in the treatment of MM acting both as cytotoxic agent through damage to DNA, and as immunostimulatory drug by inhibiting Interleukin-6, as well as interaction with dendritic cells, and immunogenic effects in tumor microenvironment. Areas covered: This review focuses on available data about melphalan pharmacology and its role in clinical practice. Expert opinion: Melphalan remains crucial in therapy of multiple myeloma because of its good manageability, safety profile, efficacy, and economic sustainability. These characteristics make it pivotal also for new regimens in combination with novel agents.

Development of an assay for cellular efflux of pharmaceutically active agents and its relevance to understanding drug interactions.

Drug interactions may dictate the failure or success of a treatment. Patients undergoing hematopoietic stem cell transplantation (HSCT) are exposed to various types of drugs, and understanding how these drugs interact is of the utmost importance. The pharmacokinetics of busulfan, melphalan, and cyclophosphamide, drugs commonly used for HSCT, are known to be affected by a variety of other drugs with differing molecular structures. We hypothesized that these structurally unrelated drugs affect the transport of DNA-alkylating agents. To test this hypothesis, we developed a flow cytometry assay that used 5-carboxyfluorescein diacetate acetoxymethyl ester, which is cleaved by nonspecific intracellular esterases to 5-carboxyfluorescein (5-CF), a fluorescent ligand for the drug transporter MRP1. A decreased 5-CF efflux in the presence of a test compound suggests competitive inhibition. We demonstrated that chlorambucil, 4-hydroperoxycyclophosphamide, ketoconazole, ethacrynic acid, everolimus, and sirolimus strongly inhibited 5-CF efflux in lymphoma and leukemia cell lines. The efflux of these drugs partially depends on the glutathione (GSH) level, and their cytotoxicity is synergistic with inhibited GSH synthesis. This is consistent with the hypothesis that their GSH-conjugated products are ligands of a common cellular drug transporter. Our results may explain clinical observations on the effects of various drugs on the pharmacokinetics and pharmacodynamics of alkylating agents, and the assay may be used to deduce interaction mechanisms of drugs transported by a common system.

Associations of High-Dose Melphalan Pharmacokinetics and Outcomes in the Setting of a Randomized Cryotherapy Trial.

High-dose melphalan followed by autologous stem cell transplantation remains the standard of care for eligible patients with multiple myeloma, but disease response and toxicity, including severe mucositis, varies among patients. Our randomized trial investigated duration of cryotherapy (2 and 6 h) for reduction of mucositis prevalence and severity and explored factors associated with variability in pharmacokinetics and outcomes from melphalan therapy. The results demonstrate that 2-h is at least as effective as 6-h cryotherapy in decreasing severe mucositis. From a population pharmacokinetic model, we identified that fat-free mass, hematocrit, and creatinine clearance were significant covariates, as reported previously. Furthermore, we observed the rs4240803 SLC7A5 polymorphism was significantly associated with pharmacokinetic variability, and pharmacokinetics was associated with both mucositis and neutropenia. However, melphalan exposure was not associated with progression-free or overall survival in our dataset. These findings contribute to ongoing efforts to personalize melphalan dosing in transplant patients.