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Geenen JJJ, Dackus GMHE, Schouten PC, Pluim D, Marchetti S, Sonke GS, Jóźwiak K, Huitema ADR, Beijnen JH, Schellens JHM, Linn SC. A Phase I dose-escalation study of two cycles carboplatin-olaparib followed by olaparib monotherapy in patients with advanced cancer. Int J Cancer 2021; 148:3041-3050. [PMID: 33539540 PMCID: PMC8248128 DOI: 10.1002/ijc.33498] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 12/18/2020] [Accepted: 12/21/2020] [Indexed: 12/21/2022]
Abstract
Preclinical studies have shown synergistic effects when combining PARP1/2 inhibitors and platinum drugs in BRCA1/2 mutated cancer cell models. After a formulation change of olaparib from capsules to tablets, we initiated a dose finding study of olaparib tablets bidaily (BID) continuously with carboplatin to prepare comparative studies in this patient group. Patients were included in a 3 + 3 dose‐escalation schedule: olaparib 25 mg BID and carboplatin area under the curve (AUC) 3 mg*min/mL d1/d22, olaparib 25 mg BID and carboplatin AUC 4 mg*min/mL d1/d22, followed by increasing dose‐levels of olaparib from 50 mg BID, 75 mg BID, to 100 mg BID with carboplatin at AUC 4 mg*min/mL d1/d22. After two cycles, patients continued olaparib 300 mg BID as monotherapy. Primary objective was to assess the maximum tolerable dose (MTD). Twenty‐four patients with a confirmed diagnosis of advanced cancer were included. Most common adverse events were nausea (46%), fatigue (33%) and platelet count decrease (33%). Dose‐level 3 (olaparib 75 mg BID and carboplatin AUC 4 mg*min/mL; n = 6) was defined as MTD. Fourteen out of 24 patients (56%) had a partial response as best response (RECIST 1.1). Systemic exposure of the olaparib tablet formulation appeared comparable to the previous capsule formulation with olaparib tablet AUC0‐12 of 16.3 μg/mL*h at MTD. Polymers of ADP‐ribose levels in peripheral blood mononuclear cells were reduced by 98.7% ± 0.14% at Day 8 compared to Day 1 for dose‐level 3. Olaparib tablets 75 mg BID and carboplatin AUC 4 mg*min/mL for two cycles preceding olaparib monotherapy 300 mg is a feasible and tolerable treatment schedule for patients with advanced cancer.
What's new?
Preclinical studies have shown synergistic effects when combining PARP1/2‐inhibitors and platinum drugs in BRCA1/2 mutated cancer cell models. This phase I trial of olaparib tablets combined with carboplatin in advanced cancer patients showed that the combination has an acceptable side‐effect profile. The maximum tolerable dose was olaparib tablets 75 mg BID and carboplatin AUC 4 mg*min/ml. The observed preliminary anti‐tumor activity was encouraging, with 58% of patients having a decrease in tumor volume of more than 30%. This study shows that the tablet formulation of olaparib can be administered safely in combination with carboplatin, compared to the previous capsule formulation.
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102
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Leenstra B, van Ginkel DJ, Huitema ADR, Verhoeven BAN, Vonken EJ, de Borst GJ. Fibrinogen Degradation Speed as a Predictor of Major Bleeding Complications During Catheter Directed Thrombolysis in Patients with Acute Lower Limb Ischaemia. Eur J Vasc Endovasc Surg 2021; 61:861-862. [PMID: 33583709 DOI: 10.1016/j.ejvs.2020.12.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 11/29/2020] [Accepted: 12/10/2020] [Indexed: 10/22/2022]
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103
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Nijstad AL, Nierkens S, Lindemans CA, Boelens JJ, Bierings M, Versluys AB, van der Elst KCM, Huitema ADR. Population pharmacokinetics of clofarabine for allogeneic hematopoietic cell transplantation in paediatric patients. Br J Clin Pharmacol 2021; 87:3218-3226. [PMID: 33444472 PMCID: PMC8359279 DOI: 10.1111/bcp.14738] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/23/2020] [Accepted: 01/06/2021] [Indexed: 12/17/2022] Open
Abstract
Aims Clofarabine has recently been evaluated as part of the conditioning regimen for allogeneic hematopoietic stem cell transplantation (HCT) in children. Pharmacokinetic (PK) exposure of different agents commonly used in conditioning regimens is strongly related to HCT outcome. Consequently, the PK of clofarabine may be important for outcome. This report describes the population PK of clofarabine in paediatric patients and one adult. Methods From 80 paediatric (0.5–18 years) and 1 adult patient (37 years), 805 plasma concentrations were included in pharmacokinetic analyses using nonlinear mixed effects modelling. Results A two‐compartment model adequately described the PK of clofarabine. Body weight and estimated glomerular filtration rate (eGFR) were included as covariates. Clearance was differentiated into nonrenal and renal clearance (approximately 55% of total clearance), resulting in population estimates of 24.0 L/h (95% confidence interval [CI] 13.7–34.4) and 29.8 L/h (95% CI 23.9–36.1) for a patient of 70 kg with normal renal function, respectively. Unexplained interindividual variability in clearance was 17.8% (95% CI 14.6–22.4). A high variability in exposure was observed (range area under the curveT0‐inf 1.8–6.0 mg/L*h) after body surface area (BSA) based dosing. Interestingly, children with low body weight had a lower exposure than children with a higher body weight, which indicates that the currently practised BSA‐based dosing is not adequate for clofarabine. Conclusion A clofarabine dosing algorithm based on this PK model, using body weight and eGFR, results in a more predictable exposure than BSA‐based dosing. However, the exact target exposure needs to be further investigated.
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Verheijen RB, van Duijl TT, van den Heuvel MM, Vessies D, Muller M, Beijnen JH, Janssen JM, Schellens JHM, Steeghs N, van den Broek D, Huitema ADR. Monitoring of EGFR mutations in circulating tumor DNA of non-small cell lung cancer patients treated with EGFR inhibitors. Cancer Chemother Pharmacol 2021; 87:269-276. [PMID: 33484280 DOI: 10.1007/s00280-021-04230-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 01/05/2021] [Indexed: 11/29/2022]
Abstract
PURPOSE We studied EGFR mutations in circulating tumor DNA (ctDNA) and explored their role in predicting the progression-free survival (PFS) of non-small cell lung cancer (NSCLC) patients treated with erlotinib or gefitinib. METHODS The L858R, T790M mutations and exon 19 deletions were quantified in plasma using digital droplet polymerase chain reaction (ddPCR). The dynamics of ctDNA mutations over time and relationships with PFS were explored. RESULTS In total, 249 plasma samples (1-13 per patient) were available from 68 NSCLC patients. The T790M and L858R or exon 19 deletion were found in the ctDNA of 49 and 56% patients, respectively. The median (range) concentration in these samples were 7.3 (5.1-3688.7), 11.7 (5.1-12,393.3) and 27.9 (5.9-2896.7) copies/mL, respectively. Using local polynomial regression, the number of copies of EGFR mutations per mL increased several months prior to progression on standard response evaluation. CONCLUSION This change was more pronounced for the driver mutations than for the resistance mutations. In conclusion, quantification of EGFR mutations in plasma ctDNA was predictive of treatment outcomes in NSCLC patients. In particular, an increase in driver mutation copy number could predict disease progression.
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105
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Janssen JM, Jacobs BAW, Roosendaal J, Derissen EJB, Marchetti S, Beijnen JH, Huitema ADR, Dorlo TPC. Population Pharmacokinetics of Intracellular 5-Fluorouridine 5'-Triphosphate and its Relationship with Hand-and-Foot Syndrome in Patients Treated with Capecitabine. AAPS JOURNAL 2021; 23:23. [PMID: 33417061 DOI: 10.1208/s12248-020-00533-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 11/04/2020] [Indexed: 11/30/2022]
Abstract
Capecitabine is an oral pro-drug of 5-fluorouracil. Patients with solid tumours who are treated with capecitabine may develop hand-and-foot syndrome (HFS) as side effect. This might be a result of accumulation of intracellular metabolites. We characterised the pharmacokinetics (PK) of 5-fluorouridine 5'-triphosphate (FUTP) in peripheral blood mononuclear cells (PBMCs) and assessed the relationship between exposure to capecitabine or its metabolites and the development of HFS. Plasma and intracellular capecitabine PK data and ordered categorical HFS data was available. A previously developed model describing the PK of capecitabine and metabolites was extended to describe the intracellular FUTP concentrations. Subsequently, a continuous-time Markov model was developed to describe the development of HFS during treatment with capecitabine. The influences of capecitabine and metabolite concentrations on the development of HFS were evaluated. The PK of intracellular FUTP was described by an one-compartment model with first-order elimination (ke,FUTP was 0.028 h-1 (95% confidence interval 0.022-0.039)) where the FUTP influx rate was proportional to the 5-FU plasma concentrations. The predicted individual intracellular FUTP concentration was identified as a significant predictor for the development and severity of HFS. Simulations demonstrated a clear exposure-response relationship. The intracellular FUTP concentrations were successfully described and a significant relationship between these intracellular concentrations and the development and severity of HFS was identified. This model can be used to simulate future dosing regimens and thereby optimise treatment with capecitabine.
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Ten Ham RMT, van Nuland M, Vreman RA, de Graaf LG, Rosing H, Bergman AM, Huitema ADR, Beijnen JH, Hövels AM. Cost-Effectiveness Assessment of Monitoring Abiraterone Levels in Metastatic Castration-Resistant Prostate Cancer Patients. VALUE IN HEALTH : THE JOURNAL OF THE INTERNATIONAL SOCIETY FOR PHARMACOECONOMICS AND OUTCOMES RESEARCH 2021; 24:121-128. [PMID: 33431146 DOI: 10.1016/j.jval.2020.04.1838] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 02/28/2020] [Accepted: 04/26/2020] [Indexed: 06/12/2023]
Abstract
OBJECTIVES Abiraterone acetate is registered for the treatment of metastatic castration-sensitive and resistant prostate cancer (mCRPC). Treatment outcome is associated with plasma trough concentrations (Cmin) of abiraterone. Patients with a plasma Cmin below the target of 8.4 ng/mL may benefit from treatment optimization by dose increase or concomitant intake with food. This study aims to investigate the cost-effectiveness of monitoring abiraterone Cmin in patients with mCRPC. METHODS A Markov model was built with health states progression-free survival, progressed disease, and death. The benefits of monitoring abiraterone Cmin followed by a dose increase or food intervention were modeled via a difference in the percentage of patients achieving adequate Cmin taking a healthcare payer perspective. Deterministic and probabilistic sensitivity analyses were performed to assess uncertainties and their impac to the incremental cost-effectiveness ratio (ICER). RESULTS Monitoring abiraterone followed by a dose increase resulted in 0.149 incremental quality-adjusted life-years (QALYs) with €22 145 incremental costs and an ICER of €177 821/QALY. The food intervention assumed equal effects and estimated incremental costs of €7599, resulting in an ICER of €61 019/QALY. The likelihoods of therapeutic drug monitoring (TDM) with a dose increase or food intervention being cost-effective were 8.04%and 81.9%, respectively. CONCLUSIONS Monitoring abiraterone followed by a dose increase is not cost-effective in patients with mCRPC from a healthcare payer perspective. Monitoring in combination with a food intervention is likely to be cost-effective. This cost-effectiveness assessment may assist decision making in future integration of abiraterone TDM followed by a food intervention into standard abiraterone acetate treatment practices of mCRPC patients.
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Pieters TT, Huitema ADR, Rookmaaker MB, Kramers C. [Pharmacotherapy in patients with loss of renal function]. NEDERLANDS TIJDSCHRIFT VOOR GENEESKUNDE 2020; 164:D5089. [PMID: 33651495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
When dosing renally excreted drugs in patients with kidney disease, it is important to have a reliable estimate of renal function. The estimated glomerular filtration rate (eGFR) is often used in the clinic, although this measure can be inaccurate in certain situations. Choosing the appropriate drug and dosage should therefore not be solely based on the eGFR. In this review, we discuss the physiology behind renal function estimation and drug dosing and propose a step by step approach to dosing renally excreted drugs in patients with kidney disease.
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108
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Mueller-Schoell A, Groenland SL, Scherf-Clavel O, van Dyk M, Huisinga W, Michelet R, Jaehde U, Steeghs N, Huitema ADR, Kloft C. Correction to: Therapeutic drug monitoring of oral targeted antineoplastic drugs. Eur J Clin Pharmacol 2020; 77:465. [PMID: 33320282 DOI: 10.1007/s00228-020-03067-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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109
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Bruin MAC, Korse CM, van Wijnen B, de Jong VMT, Linn SC, van Triest B, Rosing H, Beijnen JH, van den Broek D, Huitema ADR. A real or apparent decrease in glomerular filtration rate in patients using olaparib? Eur J Clin Pharmacol 2020; 77:179-188. [PMID: 33319340 PMCID: PMC7803870 DOI: 10.1007/s00228-020-03070-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 12/08/2020] [Indexed: 11/25/2022]
Abstract
Purpose Olaparib is a poly (ADP-ribose) polymerase (PARP) inhibitor indicated for ovarian and metastatic breast cancer. Increased serum creatinine levels have been observed in patients taking olaparib, but the underlying mechanism is unknown. This study aimed to investigate if patients receiving olaparib have increased creatinine levels during olaparib treatment and whether this actually relates to a declined glomerular filtration rate (GFR). Methods We retrospectively identified patients using olaparib at the Netherlands Cancer Institute – Antoni van Leeuwenhoek (NKI-AVL) from 2012 until 2020. Patients with at least one plasma or serum sample available at baseline/off treatment and during olaparib treatment were included. Cystatin C levels were measured, creatinine levels were available and renal function was determined by calculating the estimated glomerular filtration rate (eGFR) using the Creatinine Equation (CKD-EPI 2009) and the Cystatin C Equation (CKD-EPI 2012). Results In total, 66 patients were included. Olaparib treatment was associated with a 14% increase in median creatinine from 72 (inter quartile range (IQR): 22) μmol/L before/off treatment to 82 (IQR: 20) μmol/L during treatment (p < 0.001) and a 13% decrease in median creatinine-derived eGFR from 86 (IQR: 26) mL/min/1.73 m2 before/off treatment to 75 (IQR: 29) mL/min/1.73 m2 during treatment (p < 0.001). Olaparib treatment had no significant effect on median cystatin C levels (p = 0.520) and the median cystatin C–derived eGFR (p = 0.918). Conclusions This study demonstrates that olaparib likely causes inhibition of renal transporters leading to a reversible and dose-dependent increase in creatinine and does not affect GFR, since the median cystatin C–derived eGFR was comparable before/off treatment and during treatment of olaparib. Using the creatinine-derived eGFR can give an underestimation of GFR in patients taking olaparib. Therefore, an alternative renal marker such as cystatin C should be used to accurately calculate eGFR in patients taking olaparib.
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Huiskamp LFJ, Chargi N, Devriese LA, May AM, Huitema ADR, de Bree R. The Predictive Value of Low Skeletal Muscle Mass Assessed on Cross-Sectional Imaging for Anti-Cancer Drug Toxicity: A Systematic Review and Meta-Analysis. J Clin Med 2020; 9:jcm9113780. [PMID: 33238530 PMCID: PMC7700117 DOI: 10.3390/jcm9113780] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/17/2020] [Accepted: 11/20/2020] [Indexed: 12/19/2022] Open
Abstract
Low skeletal muscle mass (LSMM) is increasingly recognized for its predictive value for adverse events in cancer patients. In specific, the predictive value of LSMM has been demonstrated for anti-cancer drug toxicity in a variety of cancer types and anti-cancer drugs. However, due to the limited sample size and study populations focused on a single cancer type, an overall predictive value of LSMM for anti-cancer drug toxicity remains unknown. Therefore, this review aims to provide a comprehensive overview of the predictive value of LSMM and perform a meta-analysis to analyse the overall effect. A systematic search was conducted of MEDLINE, Scopus, EMBASE, and Cochrane. Inclusion criteria were skeletal muscle mass (SMM) evaluated with computed tomography (CT) or magnetic resonance imaging (MRI), articles published in English, SMM studied in humans, SMM measurement normalized for height, and patients did not receive an intervention to treat or prevent LSMM. A meta-analysis was performed using a random-effects model and expressed in odds ratio (OR) with 95% confidence interval (CI). Heterogeneity was assessed using χ2 and I2 statistics. The search yielded 907 studies. 31 studies were included in the systematic review. Sample sizes ranged from 21 to 414 patients. The occurrence of LSMM ranged from 12.2% to 89.0%. The most frequently studied cancer types were oesophageal, renal, colorectal, breast, and head and neck cancer. Patients with LSMM had a higher risk of severe toxicity (OR 4.08; 95% CI 2.48-6.70; p < 0.001) and dose-limiting toxicity (OR 2.24; 95% CI 1.28-3.92; p < 0.001) compared to patients without LSMM. To conclude, the predictive value of LSMM for anti-cancer drug toxicity can be observed across cancer types. This information increases the need for further research into interventions that could treat LSMM as well as the possibility to adapt treatment regimens based on the presence of LSMM.
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Bruin MAC, Dekker D, Venekamp N, Tibben M, Rosing H, de Lange DW, Beijnen JH, Huitema ADR. Toxicological analysis of azide and cyanide for azide intoxications using gas chromatography. Basic Clin Pharmacol Toxicol 2020; 128:534-541. [PMID: 33090684 PMCID: PMC7984282 DOI: 10.1111/bcpt.13523] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 10/09/2020] [Accepted: 10/13/2020] [Indexed: 11/30/2022]
Abstract
Azide is a highly toxic chemical agent to human being. Accidental, but also intentional exposure to azide occurs. To be able to confirm azide ingestion, we developed a method to identify and quantify azide in biological matrices. Cyanide was included in the method to evaluate suggested in vivo production of cyanide after azide ingestion. Azide in biological matrices was first derivatized by propionic anhydride to form propionyl azide. Simultaneously, cyanide was converted into hydrogen cyanide. After thermal rearrangement of propionyl azide, ethyl isocyanate was formed, separated together with hydrogen cyanide by gas chromatography (GC) and detected using a nitrogen phosphorous detector (NPD). The method was linear from 1.0‐100 µg/mL for both analytes, and azide was stable in human plasma at −20°C for at least 49 days. Azide was measured in the gastric content of two cases of suspected azide ingestion (case 1:1.2 mg/mL, case 2:1.5 mg/mL). Cyanide was only identified in the gastric content of case 1 (approximately 1.4 µg/mL). Furthermore, azide was quantified in plasma (19 µg/mL), serum (24 µg/mL), cell pellet (21 µg/mL) and urine (3.0 µg/mL) of case 2. This method can be used to confirm azide and cyanide exposure, and azide concentrations can be quantified in several biological matrices.
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Hendrikx JJMA, Beijnen JH, Huitema ADR. Is Bodyweight-Based Dosing Truly Better Than Flat Dosing for Panitumumab? [Letter]. Clin Pharmacol 2020; 12:177-178. [PMID: 33162757 PMCID: PMC7610198 DOI: 10.2147/cpaa.s282866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 10/03/2020] [Indexed: 12/29/2022] Open
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McCune JS, McKiernan JS, van Maarseveen E, Huitema ADR, Randolph TW, Deeg HJ, Nakamura R, Baker KS. Prediction of Acute Graft versus Host Disease and Relapse by Endogenous Metabolomic Compounds in Patients Receiving Personalized Busulfan-Based Conditioning. J Proteome Res 2020; 20:684-694. [PMID: 33064008 DOI: 10.1021/acs.jproteome.0c00599] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Busulfan-based conditioning is the most commonly used high-dose conditioning regimen for allogeneic hematopoietic cell transplant (HCT). The alkylating agent busulfan has a narrow therapeutic index, with busulfan doses personalized to a target plasma exposure (targeted busulfan). Using a global pharmacometabonomics approach, we sought to identify novel biomarkers of relapse or acute graft versus host disease (GVHD) in a cohort of 84 patients receiving targeted busulfan before allogeneic HCT. A total of 763 endogenous metabolomic compounds (EMCs) were quantitated in 230 longitudinal blood samples before, during, and shortly after intravenous busulfan administration. We performed both univariate linear regression and pathway enrichment analyses using global testing. The cysteine/methionine pathway and the glycine, serine, and threonine metabolism pathway were most associated with relapse. The latter be explained by the fact that glutathione S-transferases conjugate both busulfan and glutathione, which contains glycine as a component. The d-arginine and d-ornithine metabolism pathway and arginine and proline metabolism pathway were most associated with acute GVHD. None of these associations were significant after correcting for false discovery rate (FDR) with a strict cutoff of FDR-adjusted p < 0.1. Although larger studies are needed to substantiate these findings, the results show that EMCs may be used as predictive biomarkers in HCT patients.
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de Weger VA, Vermunt MAC, Stuurman FE, Burylo AM, Damoiseaux D, Hendrikx JJMA, Sawicki E, Moes JJ, Huitema ADR, Nuijen B, Rosing H, Mergui-Roelvink M, Beijnen JH, Marchetti S. A Phase 1 Dose-Escalation Study of Low-Dose Metronomic Treatment With Novel Oral Paclitaxel Formulations in Combination With Ritonavir in Patients With Advanced Solid Tumors. Clin Pharmacol Drug Dev 2020; 10:607-621. [PMID: 33021083 DOI: 10.1002/cpdd.880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 09/08/2020] [Indexed: 01/08/2023]
Abstract
ModraPac001 (MP1) and ModraPac005 (MP5) are novel oral paclitaxel formulations that are coadministered with the cytochrome P450 3A4 inhibitor ritonavir (r), enabling daily low-dose metronomic (LDM) treatment. The primary aim of this study was to determine the safety, pharmacokinetics and maximum tolerated dose (MTD) of MP1/r and MP5/r. The second aim was to establish the recommended phase 2 dose (RP2D) as LDM treatment. This was an open-label phase 1 trial. Patients with advanced solid tumors were enrolled according to a classical 3+3 design. After initial employment of the MP1 capsule, the MP5 tablet was introduced. Safety was assessed using the Common Terminology Criteria for Adverse Events version 4.02. Pharmacokinetic sampling was performed on days 1, 2, 8, and 22 for determination of paclitaxel and ritonavir plasma concentrations. In this study, 37 patients were treated with up to twice-daily 30-mg paclitaxel combined with twice-daily 100-mg ritonavir (MP5/r 30-30/100-100) in 9 dose levels. Dose-limiting toxicities were nausea, (febrile) neutropenia, dehydration and vomiting. At the MTD/RP2D of MP5/r 20-20/100-100, the maximum paclitaxel plasma concentration and area under the concentration-time curve until 24 hours were 34.6 ng/mL (coefficient of variation, 79%) and 255 ng • h/mL (coefficient of variation, 62%), respectively. Stable disease was observed as best response in 15 of 31 evaluable patients. Based on these results, LDM therapy with oral paclitaxel coadministrated with ritonavir was considered feasible and safe. The MTD and RP2D were determined as MP5/r 20-20/100-100. Further clinical development of MP5/r as an LDM concept, including potential combination treatment, is warranted.
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Schmidt KT, Huitema ADR, Dorlo TPC, Peer CJ, Cordes LM, Sciuto L, Wroblewski S, Pommier Y, Madan RA, Thomas A, Figg WD. Population pharmacokinetic analysis of nanoparticle-bound and free camptothecin after administration of NLG207 in adults with advanced solid tumors. Cancer Chemother Pharmacol 2020; 86:475-486. [PMID: 32897402 PMCID: PMC7515962 DOI: 10.1007/s00280-020-04134-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 08/22/2020] [Indexed: 12/27/2022]
Abstract
PURPOSE NLG207 (formerly CRLX101) is a nanoparticle-drug conjugate (NDC) of the potent topoisomerase I inhibitor, camptothecin (CPT). The present study sought to characterize the complex pharmacokinetics (PK) of NLG207 and better describe CPT release from nanoparticles using a population PK (popPK) model. METHODS From 27 patients enrolled on two phase II clinical trials (NCT02769962 and NCT03531827), dense sampling was performed up to 48 h post-administration of NLG207 during cycle one and six of treatment; samples were also collected at ~ 360 h post-dose. Conjugated and free CPT concentrations were quantified from each sample, resulting in 477 observations to build a popPK model using non-linear mixed-effects modeling. RESULTS The PK of NLG207 was characterized by combining two linear two-compartment models with first-order kinetics each to describe nanoparticle-bound (conjugated) and free CPT. Allometric scaling based on body weight provided the best body-size descriptor for all PK parameters. The typical volumes of distribution of the conjugated CPT central and free CPT central compartments were 3.16 L (BSV CV%; 18.1%) and 21.1 L (CV%; 79.8%), respectively. CPT release from the nanoparticle formulation was characterized via an initial rapid clearance of 5.71 L/h (CV%; 62.6%), which decreased via first-order decay (estimated half-life of 0.307 h) to the steady-state value of 0.0988 L/h (CV%; 33.5%) by ~ 4 h after end of infusion. Renal clearance of free CPT was 0.874 L/h (CV%; 42.2%). CONCLUSION The popPK model confirmed nanoparticle behavior of conjugated CPT and mechanistically characterized CPT release from NLG207. The current analysis provides a strong foundation for future study as a potential predictive tool in ongoing NLG207 clinical trials.
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Koemans WJ, van Sandick JW, Huitema ADR. Reply to: Comments on "Systemic exposure of oxaliplatin and docetaxel in gastric patients with peritonitis carcinomatosis treated with intraperitoneal hyperthermic chemotherapy". EUROPEAN JOURNAL OF SURGICAL ONCOLOGY 2020; 46:2343. [PMID: 32981795 DOI: 10.1016/j.ejso.2020.09.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 09/18/2020] [Indexed: 11/30/2022]
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Sikma MA, Hunault CC, Van Maarseveen EM, Huitema ADR, Van de Graaf EA, Kirkels JH, Verhaar MC, Grutters JC, Kesecioglu J, De Lange DW. High Variability of Whole-Blood Tacrolimus Pharmacokinetics Early After Thoracic Organ Transplantation. Eur J Drug Metab Pharmacokinet 2020; 45:123-134. [PMID: 31745812 PMCID: PMC6994432 DOI: 10.1007/s13318-019-00591-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Background and Objective Oral tacrolimus is initiated perioperatively in heart and lung transplantation patients. There have been few studies on oral tacrolimus pharmacokinetics early post-transplantation, even though tacrolimus-related toxicity may occur early, potentially leading to morbidity and mortality. Therefore, we aimed to study the pharmacokinetics of oral tacrolimus in thoracic organ recipients during the first days after transplantation. Methods We conducted a pharmacokinetic study in 30 thoracic organ transplants at intensive care at the University Medical Center Utrecht in the first week post-transplantation. Twelve-hour whole-blood tacrolimus profiles were examined using high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) and analysed via population pharmacokinetic modelling. Results The concentration–time profiles showed high variability. Concentrations at 12 h were outside the target range in 69% of the cases. A two-compartment model with mixed first-order and zero-order absorption adequately described tacrolimus concentrations. The typical value of the apparent clearance was 19.6 L/h (95% CI 16.2–22.9), and the apparent distribution volumes of central and peripheral compartments, V1 and V2, were 231 L (95% CI 199–267) and 521 L (95% CI 441–634), respectively. Inter-occasion (dose-to-dose) variability far exceeded the interindividual variability (IIV), with an estimated variability in relative bioavailability of 55% (95% CI 48.5–64.4). Conclusions The high variability of tacrolimus pharmacokinetics early after thoracic organ transplantation is largely due to excessive variability in bioavailability, making individualised dosing based on measured concentrations futile. To bypass this bioavailability issue, we suggest administering tacrolimus intravenously and aiming below the upper therapeutic range early post-transplantation. Clinical Trial Registraion: NTR 3912/EudraCT 2012-001909-24. Electronic supplementary material The online version of this article (10.1007/s13318-019-00591-7) contains supplementary material, which is available to authorized users.
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Heinhuis KM, IJzerman NS, Koenen AM, van der Graaf WTA, Haas RL, Beijnen JH, Huitema ADR, van Houdt WJ, Steeghs N. PropAngio study protocol: a neoadjuvant trial on the efficacy of propranolol monotherapy in cutaneous angiosarcoma-a proof of principle study. BMJ Open 2020; 10:e039449. [PMID: 32912994 PMCID: PMC7485254 DOI: 10.1136/bmjopen-2020-039449] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
INTRODUCTION Angiosarcoma is a rare and aggressive malignancy with a high metastatic potential and recurrence rate. Despite optimal treatment with surgery, with or without radiation, the prognosis remains poor and, therefore, new treatment strategies are warranted. Recently, propranolol has effectively been repurposed for the treatment of infantile haemangioma. Propranolol is a β3-sparing antagonist of the β-adrenergic receptor. In infantile haemangioma, the β1, β2 and β3 receptors are highly expressed. Angiosarcoma has several similarities with haemangioma, including its high β-adrenergic receptor expression and the supposedly important role of vascular endothelial growth factor in malignant growth. As a result, propranolol has been administered small scale in individual angiosarcoma cases with promising results. The precise effect of propranolol, however, is not yet established. METHODS AND ANALYSIS The goal of this neoadjuvant window of opportunity study is to prospectively evaluate the activity of propranolol monotherapy in patients with cutaneous angiosarcoma. The neoadjuvant setting provides a good opportunity to rapidly evaluate both the clinical response and histological response, without a significant delay in standard anticancer treatment. Fourteen patients with primary, recurrent or metastatic cutaneous angiosarcoma will be included. Propranolol will be administered orally in an escalating dose during 3-6 weeks, before the initiation of standard treatment. The primary endpoint is clinical response according to Response Evaluation Criteria in Solid Tumours, as measured on consecutive coloured photographs or CT/MRI. The histological response will be determined as secondary endpoint, comparing the difference in proliferation index before and after propranolol by measuring the change in immunohistochemistry staining of Ki-67. The study will be considered positive when at least three patients have a response to propranolol. ETHICS AND DISSEMINATION Ethical approval was obtained from the Medical Ethical Committee of the Netherlands Cancer Institute. Independent of the outcome, results of this study will be shared and submitted for publication in an international peer-reviewed journal. TRIAL REGISTRATION NUMBER NL8118; registry through the Netherlands Trial Register.
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van Nuland M, Rosing H, Huitema ADR, Beijnen JH. Predictive Value of Microdose Pharmacokinetics. Clin Pharmacokinet 2020; 58:1221-1236. [PMID: 31030372 DOI: 10.1007/s40262-019-00769-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phase 0 microdose trials are exploratory studies to early assess human pharmacokinetics of new chemical entities, while limiting drug exposure and risks for participants. The microdose concept is based on the assumption that microdose pharmacokinetics can be extrapolated to pharmacokinetics of a therapeutic dose. However, it is unknown whether microdose pharmacokinetics are actually indicative of the pharmacokinetics at therapeutic dose. The aim of this review is to investigate the predictive value of microdose pharmacokinetics and to identify drug characteristics that may influence the scalability of these parameters. The predictive value of microdose pharmacokinetics was determined for 46 compounds and showed adequate predictability for 28 of 41 orally administered drugs (68%) and 15 of 16 intravenously administered drugs (94%). Microdose pharmacokinetics were considered predictive if the mean observed values of the microdose and the therapeutic dose were within twofold. Nonlinearity may be caused by saturation of enzyme and transporter systems, such as intestinal and hepatic efflux and uptake transporters. The high degree of success regarding linear pharmacokinetics shows that phase 0 microdose trials can be used as an early human model for determination of drug pharmacokinetics.
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Nijstad AL, van Eijkelenburg NKA, Kraal KCJM, Meijs MJM, de Kanter CTMM, Lilien MR, Huitema ADR. Cisplatin and carboplatin pharmacokinetics in a pediatric patient with hepatoblastoma receiving peritoneal dialysis. Cancer Chemother Pharmacol 2020; 86:445-449. [PMID: 32816154 PMCID: PMC7479000 DOI: 10.1007/s00280-020-04130-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 08/13/2020] [Indexed: 11/30/2022]
Abstract
Purpose Cisplatin and carboplatin are frequently used drugs in the treatment of pediatric hepatoblastoma. Dosing guidelines for these drugs in children requiring peritoneal dialysis are lacking. Here, we describe the case of a 3-year-old boy with pre-existing end-stage renal disease on peritoneal dialysis, requiring treatment with cisplatin and carboplatin for hepatoblastoma. Methods Pharmacokinetic data were generated to support clinical dosing decisions, with the aim of adequate exposure and minimal toxicity. In the first chemotherapy cycle, 25% of the standard cisplatin dose and 75% of the carboplatin dose, calculated using the pediatric Calvert formula, were administered. Free platinum concentrations were determined in plasma ultrafiltrate and dialysate samples drawn after administration of cis- and carboplatin. Results Cisplatin was well tolerated and the observed AUC of cisplatin were 15.3 and 14.3 mg/L h in cycles 1 and 3, respectively. The calculated AUC of carboplatin in cycle 1 (9.8 mg/mL min) exceeded target AUC of 6.5 mg/mL min and toxicity was observed; therefore, the dose was reduced in cycles 2 and 3. The observed AUC in cycles 2 and 3 was 5.4 and 5.7 mg/mL min respectively. Platinum concentrations in the dialysate showed that 3–4% of the total dose of cisplatin and 10–12% of the total dose of carboplatin were excreted via peritoneal dialysis. Chemotherapy enabled extended hemihepatectomy and complete remission was achieved. Conclusion This report shows that it is feasible to measure AUCs for both drugs and to individualize the dose of these drugs according to the PK results and clinical parameters. Our advice for future cases would be to calculate the starting dose of carboplatin using the (pediatric) Calvert formula, assuming a dialytic clearance of zero, and to adjust the dose if required, based on therapeutic drug monitoring.
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Groenland SL, Geel DR, Janssen JM, de Vries N, Rosing H, Beijnen JH, Burgers JA, Smit EF, Huitema ADR, Steeghs N. Exposure-Response Analyses of Anaplastic Lymphoma Kinase Inhibitors Crizotinib and Alectinib in Non-Small Cell Lung Cancer Patients. Clin Pharmacol Ther 2020; 109:394-402. [PMID: 32686074 PMCID: PMC7891593 DOI: 10.1002/cpt.1989] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/30/2020] [Indexed: 12/19/2022]
Abstract
Crizotinib and alectinib are anaplastic lymphoma kinase (ALK)-inhibitors indicated for the treatment of ALK-positive metastatic non-small cell lung cancer (NSCLC). At the currently used fixed doses, interindividual variability in exposure is high. The aim of this study was to investigate whether minimum plasma concentrations (Cmin ) of crizotinib and alectinib are related to efficacy and toxicity. An observational study was performed, in which ALK-positive NSCLC patients who were treated with crizotinib and alectinib and from whom pharmacokinetic samples were collected in routine care, were included in the study. Exposure-response analyses were explored using previously proposed Cmin thresholds of 235 ng/mL for crizotinib and 435 ng/mL for alectinib. Forty-eight crizotinib and 52 alectinib patients were included. For crizotinib, median progression-free survival (mPFS) was 5.7 vs. 17.4 months for patients with Cmin < 235 ng/mL (48%) and ≥ 235 ng/mL, respectively (P = 0.08). In multivariable analysis, Cmin < 235 ng/mL resulted in a hazard ratio (HR) of 1.79 (95% confidence interval (CI), 0.90-3.59, P = 0.100). In a pooled analysis of all crizotinib patients (not only ALK-positive, n = 79), the HR was 2.15 (95% CI, 1.21-3.84, P = 0.009). For alectinib, mPFS was 12.6 months vs. not estimable (95% CI, 19.8-not estimable) for patients with Cmin < 435 ng/mL (37%) and ≥ 435 ng/mL, respectively (P = 0.04). Multivariable analysis resulted in an HR of 4.29 (95% CI, 1.33-13.90, P = 0.015). In conclusion, PFS of crizotinib and alectinib treated NSCLC patients is prolonged in patients with Cmin ≥ 235 ng/mL and 435 ng/mL, respectively. Therefore, therapeutic drug monitoring should be part of routine clinical management for these agents.
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Koemans WJ, van der Kaaij RT, Wassenaar ECE, Grootscholten C, Boot H, Boerma D, Los M, Imhof O, Schellens JHM, Rosing H, Huitema ADR, van Sandick JW. Systemic exposure of oxaliplatin and docetaxel in gastric cancer patients with peritonitis carcinomatosis treated with intraperitoneal hyperthermic chemotherapy. Eur J Surg Oncol 2020; 47:486-489. [PMID: 32800401 DOI: 10.1016/j.ejso.2020.07.037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 07/28/2020] [Indexed: 12/27/2022] Open
Abstract
In the PERISCOPE I study, gastric cancer patients with limited peritoneal dissemination were treated with systemic chemotherapy followed by (sub)total gastrectomy, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) with 460 mg/m2 hyperthermic oxaliplatin followed by normothermic docetaxel in escalating doses (0, 50, 75 mg/m2). In total, 25 patients completed the study protocol. Plasma samples were collected before the start of the HIPEC procedure, after oxaliplatin washing, after docetaxel washing and the following morning. Median peak plasma concentrations were 5.5∗10-3 mg/ml for oxaliplatin, 89∗10-6 mg/ml for docetaxel (dose 50 mg/m2) and 113∗10-6 mg/ml for docetacel (dose 75 mg/m2). The following morning median plasma concentrations were 32% and 4% of the measured peak concentrations for oxaliplatin and docetaxel, respectively. For both cytostatic agents, no correlation was found between intraperitoneal fluid concentration and peak plasma concentration. High doses oxaliplatin and docetaxel can be given intraperitoneally without causing potentially toxic systemic concentrations.
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Roosendaal J, Rosing H, Lucas L, Gebretensae A, Huitema ADR, van Dongen MG, Beijnen JH, Oganesian A. Mass balance and metabolite profiling of 14C-guadecitabine in patients with advanced cancer. Invest New Drugs 2020; 38:1085-1095. [PMID: 31605293 PMCID: PMC7340650 DOI: 10.1007/s10637-019-00854-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/09/2019] [Indexed: 11/25/2022]
Abstract
Purpose The objective of this mass balance trial was to determine the excretory pathways and metabolic profile of the novel anticancer agent guadecitabine in humans after administration of a 14C-radiolabeled dose of guadecitabine. Experimental design Included patients received at least one cycle of 45 mg/m2 guadecitabine subcutaneously as once-daily doses on Days 1 to 5 of a 28-day cycle, of which the 5th (last) dose in the first cycle was spiked with 14C-radiolabeled guadecitabine. Using different mass spectrometric techniques in combination with off-line liquid scintillation counting, the exposure and excretion of 14C-guadecitabine and metabolites in the systemic circulation, excreta, and intracellular target site were established. Results Five patients were enrolled in the mass balance trial. 14C-guadecitabine radioactivity was rapidly and almost exclusively excreted in urine, with an average amount of radioactivity recovered of 90.2%. After uptake in the systemic circulation, guadecitabine was converted into ß-decitabine (active anomer), and from ß-decitabine into the presumably inactive metabolites M1-M5. All identified metabolites in plasma and urine were ß-decitabine related products, suggesting almost complete conversion via cleavage of the phosphodiester bond between ß-decitabine and deoxyguanosine prior to further elimination. ß-decitabine enters the intracellular activation pathway, leading to detectable ß-decitabine-triphosphate and DNA incorporated ß-decitabine levels in peripheral blood mononuclear cells, providing confirmation that the drug reaches its DNA target site. Conclusion The metabolic and excretory pathways of guadecitabine and its metabolites were successfully characterized after subcutaneous guadecitabine administration in cancer patients. These data support the clinical evaluation of safety and efficacy of the subcutaneous guadecitabine drug product.
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Roosendaal J, Groenland SL, Rosing H, Lucas L, Venekamp N, Nuijen B, Huitema ADR, Beijnen JH, Steeghs N. Determination of the absolute bioavailability of oral imatinib using a stable isotopically labeled intravenous imatinib-d8 microdose. Eur J Clin Pharmacol 2020; 76:1075-1082. [PMID: 32430518 PMCID: PMC7351863 DOI: 10.1007/s00228-020-02888-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 04/30/2020] [Indexed: 12/27/2022]
Abstract
PURPOSE The aim of this study was to ascertain whether the absolute bioavailability of oral imatinib (Glivec®) during steady state plasma pharmacokinetics in cancer patients could be determined through a concomitant intravenous administration of a single 100 μg microdose of deuterium labeled imatinib (imatinib-d8). Secondly, the usefulness of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was investigated for simultaneous analysis of orally and intravenously administered imatinib. METHODS Included patients were on a stable daily dose of 400 mg oral imatinib prior to study participation. On day 1, patients received a 100 μg intravenous imatinib-d8 microdose 2.5 h after intake of the oral dose. Plasma samples were collected for 48 h. Imatinib and imatinib-d8 concentrations were simultaneously quantified using a validated LC-MS/MS assay. The absolute bioavailability was calculated by comparing the dose-normalized exposure with unlabeled and stable isotopically labeled imatinib in plasma. RESULTS A total of six patients were enrolled. All patients had a history of gastrointestinal stromal tumors (GIST). The median absolute bioavailability of oral imatinib at steady state was 76% (range 44-106%). Imatinib and imatinib-d8 plasma concentrations were quantified in all collected plasma samples, with no samples below the limit of quantification for imatinib-d8. CONCLUSION The absolute bioavailability of imatinib was successfully estimated at steady state plasma pharmacokinetics using the stable isotopically labeled microdose trial design. This study exhibits the use of a stable isotopically labeled intravenous microdose to determine the absolute bioavailability of an oral anticancer agent in patients with LC-MS/MS as the analytical tool.
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IJzerman NS, Groenland SL, Koenen AM, Kerst M, van der Graaf WTA, Rosing H, Beijnen JH, Huitema ADR, Steeghs N. Therapeutic drug monitoring of imatinib in patients with gastrointestinal stromal tumours - Results from daily clinical practice. Eur J Cancer 2020; 136:140-148. [PMID: 32688207 DOI: 10.1016/j.ejca.2020.05.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/13/2020] [Accepted: 05/19/2020] [Indexed: 11/20/2022]
Abstract
AIM Higher imatinib exposure is correlated with longer time to progression, while the variability in exposure is high. This provides a strong rationale for therapeutic drug monitoring, which has therefore been implemented in routine clinical practice in our institute. The aim of this study is to evaluate whether pharmacokinetically (PK)-guided dose increases are feasible in daily clinical practice and result in an improved exposure (Cmin≥1100 ng/mL) and longer progression-free survival (PFS). METHODS This retrospective study included all patients with a gastrointestinal stromal tumour (GIST) in the Netherlands Cancer Institute who started imatinib treatment at a dose of 400 mg and of whom PK plasma samples were available. Of these patients, minimum plasma concentrations (Cmin) of imatinib, frequency and successfulness of PK-guided dose increases and PFS in the palliative treatment setting were analysed. RESULTS In total, 169 consecutive patients were included, of whom 1402 PK samples were collected. In 126 patients (75%), Cmin was below the efficacy threshold of 1100 ng/mL. In 78 of these patients (62%), a PK-guided dose increase was performed, which was successful in 49 patients (63%). PFS was similar in patients with and without imatinib dose increase. However, due to the small number of patients with progressive disease, no definite conclusions on the effect on PFS could yet be drawn. CONCLUSION This is the largest cohort evaluating PK-guided dose increases of imatinib in patients with GIST in routine clinical practice and demonstrating its feasibility. PK-guided dose increases should be applied to optimise exposure in the significant subset of patients with a low Cmin.
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