A single 24-hour plasma sample does not predict the carboplatin AUC from carboplatin-paclitaxel combinations or from a high-dose carboplatin-thiotepa-cyclophosphamide regimen

Purpose: It has been observed that the area under the free carboplatin concentration in plasma ultrafiltrate versus time curve (AUC) is related to toxicity and tumour response. For this reason, it can be important to measure the carboplatin AUC and subsequently adjust the dose to achieve a predefined target AUC. The use of limited sampling strategies enables relatively simple measurement and calculation of actual carboplatin AUCs. Methods: We studied the performance of a limited sampling model, based on a single 24-h sample (the Ghazal-Aswad model), in 52 patients who received carboplatin in two different chemotherapy regimens (a carboplatin-paclitaxel combination and a high-dose carboplatin-thiotepa-cyclophosphamide combination). Results: The measured mean AUC in our population was 4.1 min · mg/ml (median 3.9, range 1.9–6.3, SD 1.0 min · mg/ml). With the limited sampling model, the predicted mean AUC was 4.4 min · mg/ml (median 4.2, range 2.4–8.4, SD 1.2 min · mg/ml). Statistical analysis revealed that the model was slightly biased (MPE%, 6.5%), but imprecise (RMSE%, 20.6%) in our study population. Conclusion: Although easy and attractive to use, the Ghazal-Aswad formula is not precise enough to predict the carboplatin AUC, and needs to be evaluated prospectively in other patient populations. Received: 15 April 1998 / Accepted: 3 September 1998     

Preclinical toxicity of a geldanamycin analog, 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), in rats and dogs: potential clinical relevance

Purpose 17-DMAG is a hydrophilic derivative of the molecular chaperone inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17-AAG; NSC-330507), which is currently being evaluated for the treatment of cancer in clinical trials. 17-DMAG offers a potential advantage over 17-AAG because its aqueous solubility eliminates the need for complicated formulations that are currently used for administration of 17-AAG. In addition, 17-DMAG undergoes only limited metabolism compared to 17-AAG. The present results are from preclinical toxicity studies evaluating 17-DMAG in rats and dogs.Methods Doses of 0, 2.4, 12 and 24 mg/m² per day were administered to rats, while dogs received doses of 0, 8 or 16 mg/m² per day. In both species, 17-DMAG was administered i.v. (slow bolus for rats; 1-h infusion for dogs) daily for 5 days. An additional cohort of dogs received 16 mg/m² per day orally for 5 days. Clinical observations were noted, and standard hematology and clinical chemistry parameters were monitored. Selected tissues were evaluated microscopically for drug-related lesions. Tissue and plasma 17-DMAG concentrations were measured by HPLC/MS at selected time-points on days 1 and 5.Results Daily i.v. administration of 17-DMAG at doses of 24 mg/m² per day in rats or 16 mg/m² per day in dogs produced lethality on day 6, approximately 24 h following the last dose. Body weight loss was common in rats and dogs. Drug-related gastrointestinal, bone marrow and hepatic toxicities were also common in rats and dogs. Dogs also exhibited signs of renal and gallbladder toxicity. Plasma concentrations of 17-DMAG increased proportionately with dose in rats and disproportionately with dose in dogs. In rat tissues, however, only fourfold to sixfold increases in 17-DMAG concentrations were observed with a tenfold increase in dose. The highest concentrations of 17-DMAG were found in the liver of rats, with progressively lower concentrations in the spleen, lung, kidney and plasma. Regardless of the route of administration, higher drug concentrations were present in plasma (rat and dog) and tissue (rat) samples obtained on day 5 compared to those obtained on day 1. Although plasma concentrations decreased with time, 17-DMAG was still detected in dog plasma for at least 24 h after drug administration.Conclusions With the recent approval of 17-DMAG for clinical use, the data generated from these preclinical studies will provide guidance to clinicians as they administer this drug to their patients. The MTD of 17-DMAG was 12 mg/m² per day in rats and 8 mg/m² per day in dogs; therefore, the recommended starting dose for phase I trial is 1.3 mg/m² per day for 5 days. Gastrointestinal and bone marrow toxicity were dose-limiting in rats, and gastrointestinal, renal, gallbladder and bone marrow toxicity were dose-limiting in dogs. All adverse effects were fully reversible in surviving animals after treatment was complete.E.R. Glaze and A.L. Lambert contributed equally to this work.     

A single-sample assay for the estimation of the area under the free carboplatin plasma concentration versus time curve

 The aim of this study was to develop and validate a simple and rapid method for the estimation of the area under the free carboplatin plasma concentration versus time curve (AUC). The relationship between the carboplatin AUC and the total plasma platinum (Pt) concentration 24 h after treatment was studied using data from 49 patients treated with 20–1600 mg/m² carboplatin as a 60–100 min infusion (median 60 min). The relationship was confirmed by the in vitro incubation of carboplatin in human plasma and prospectively validated in 13 ovarian cancer patients. Free carboplatin was separated by ultrafiltration (MW cut off 30,000), and free and total Pt measured by atomic absorption spectrophotometry. There was a linear relationship in vivo between the 24 h (median 24.4; range 16.3–27.3 h) total plasma Pt concentration (μM) and free carboplatin AUC (mg/ml.min): AUC=(24 h Pt+0.3)/0.82 (r ²=0.93, AUC median 5.8 (0.13–28)mg/ml.min, 24 h Pt median 4.4 (0.1–23) μM). A similar relationship was observed in vitro [AUC=(24 h Pt +0.1)/0.93 (r ²=0.98, AUC median 7.9 (2.0–17) mg/ml.min, 24 h Pt median 7.1 (1.8–15) μM)]. The relationship derived from the in vivo data gave an unbiased and reasonably accurate estimate of the measured carboplatin AUC in 13 patients (AUC=5.1–8.7 mg/ml.min, GFR=59–129 ml/min, infusion time 30–45 min, 24 h sampling time 22.9–24.5 h), giving a percentage mean error of −4.2% and root mean squared percentage error of 11.5%. These results show that the analysis of a single blood sample taken 24 h after carboplatin administration can be used to produce an unbiased and reasonably accurate measure of the free carboplatin AUC. Unlike published limited sampling strategies, this method is not complicated by the need to accurately control the duration of the carboplatin infusion or the time at which the sample is taken. Received: 13 January 1995/Accepted: 14 May 1995     

Limited sampling models for simultaneous estimation of the pharmacokinetics of irinotecan and its active metabolite SN-38

Irinotecan (CPT-11) is a novel topoisomerase I inhibitor with clinical activity in human malignancies. The objective of this study was to develop efficient limited sampling models (LSMs) to estimate simultaneously the area under the plasma concentration versus time curves (AUC) for both CPT-11 and its active metabolite SN-38. A total of 64 pharmacokinetic sets (24-h sampling) were obtained in phase I studies at doses ranging from 50 to 750 mg/m² (0.5-h i.v. infusion). The patients were randomly assigned to a training data set (n=32) and a test set (n=32). Multiple linear regression analyses were used to determine the optimal LSMs based on the correlation coefficient (r), bias (MPE%, percentage of mean prediction error), and precision (RMSE%, percentage of root mean squared prediction error). Of these LSMs, the ones including maximal concentrations of CPT-11 (0.5 h, the end of the i.v. infusion) and metabolite SN-38 ( 1 h) were favored along with predictive precision and clinical constraints. Several bivariate models including a 6-h time point as the last sampling time (or 7 h) were found to be highly predictive of either the CPT-11 AUC or the SN-38 AUC. The chosen sampling time points were the ones that allowed the best compromise between the accurate determination of either compound alone with the same sampling times. The simultaneously best prediction of both CPT-11 and SN-38 AUCs was obtained with sampling time points harvested at 0.5, 1, and 6 h (or 7 h). With these sampling time points a trivariate model was selected for the determination of CPT-11 AUC namely, CPT-11 AUC (ng h ml^–1)=0.820×C_0.5h+0.402×C_1h+15.47 ×C_6h+928, and a corresponding model was selected for the determination of metabolite AUC, i.e., SN-38 AUC (ng h ml^–1)=4.05×C_0.5h–0.81×C_1h+23.01×C_6h–69.78, whereC(t) is the concentration in nanograms per milliliter of either compound at a given timet. These models performed well with the test data sets for CPT-11 AUC (r=0.98, MPE%=–1.4, RMSE%=13.9) and for SN-38 AUC (r=0.95, MPE%=–6.5, RMSE%=37.7). In addition to the determination of AUCs (and hence clearance), these models also allow the determination of the maximal concentrations of both compounds, which might be needed for pharmacodynamics studies. Other bi- and trivariate models including other time points are also presented. These LSMs not only will facilitate ongoing and future clinical trials by significantly reducing the number of blood samples needed for pharmacokinetics studies but will hopefully contribute to a better knowledge of pharmacokinetic-pharmacodynamic relationships for both CPT-11 and its active metabolite SN-38.Abbreviations CPT-11 (7-Ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxy-camptothecin - SN-38 7-ethyl-10-hydroxy-camptothecin - AUC area under the plasma concentration versus time curve - MPE% percentage of mean prediction error (bias) - RMSE% percentage root mean squared prediction error (precision) - MRT mean residence time - Vdss volume of distribution at steady state - CL total body clearance     

Development of a pharmacokinetic limited sampling model for temozolomide and its active metabolite MTIC

Purpose To develop a pharmacokinetic limited sampling model (LSM) for temozolomide and its metabolite MTIC in infants and children.Methods LSMs consisting of either two or four samples were determined using a modification of the D-optimality algorithm. This accounted for prior distribution of temozolomide and MTIC pharmacokinetic parameters based on full pharmacokinetic sampling from 38 patients with 120 pharmacokinetic studies (dosage range 145–200 mg/m² per day orally). Accuracy and bias of each LSM were determined relative to the full sampling method. We also assessed the predictive performance of the LSMs using Monte-Carlo simulations.Results The four strategies generated from the D-optimality algorithm were as follows: LSM 1=0.25, 1.25, and 3 h; LSM 2=0.25, 1.25, and 6 h; LSM 3=0.25, 0.5, 1.25, and 3 h; LSM 4=0.25, 0.5, 1.25, and 6 h. LSM 2 demonstrated the best combination of low bias [0.1% (–8.9%, 11%) and 11% (4.3%, 15%)] and high accuracy [–1.0% (–12%, 24%) and 14% (7.9%, 37%)] for temozolomide clearance and MTIC AUC, respectively. Furthermore, adding a fourth sample (e.g., LSM 4) did not substantially decrease the bias or increase the accuracy for temozolomide clearance or MTIC AUC. Results from Monte-Carlo simulations also revealed that LSM 2 had the best combination of lowest bias (0.1±6.1% and –0.8±6.5%), and the highest accuracy (4.5±4.1% and 5.0±4.3%) for temozolomide clearance and MTIC apparent clearance, respectively.Conclusions Using data derived from our population analysis, the sampling times for a limited sample pharmacokinetic model for temozolomide and MTIC in children are prior to the temozolomide dose, and 15 min, 1.25 h and 6 h after the dose.This work was presented at AACR 2002 Annual Meeting.     

A limited sampling strategy for estimation of the cladribine plasma area under the concentration versus time curve after intermittent i.v. infusion,s.c. injection,and oral administration

 Cladribine is a newly developed antimetabolite with promising activity in lymphoproliferative disorders. Recent pharmacokinetics investigations have suggested that there is a relationship between its plasma area under the concentration versus time curve (AUC) and the degree of neutropenia posttreatment as well as the therapeutic outcome in hairy-cell leukemia. To enable a simple estimation of the plasma AUC, a limited sampling strategy was developed. Stepwise linear regression was used to determine which were the most important data points for estimation of the plasma AUC after 2-h i.v. infusion, s.c. injection (5 mg/m²), and oral administration (10 mg/m²) in 27 patients. The most important data points after i.v. infusion in 12 patients were 1, 4, and 24 h, in order of importance. The AUC could be estimated as 2.9081×C _1h ⁺5.1851×C _4h ⁺20.3265×C _24h .The accuracy and precision (mean value±SD for the determined/estimated AUC was 0.99±0.053) of the model could not be increased by the addition of more data points. A somewhat lower accuracy and precision (0.96± 0.089) was seen with the 2-, 4-, and 24-h data points. These were used to test the regression technique prospectively for the estimation of the AUC after i.v. administration in another set of 10 patients. The accuracy and precision of the estimation of the AUC was similar in this group (1.01±0.109). In all, 11 patients were treated orally (10 mg/m²) and 10 patients were treated by s.c. injection (5 mg/m²). The most important data points for estimation of the AUC were 2.5, 24, and 0.5 h after oral administration (AUC=0.8630×C _0.5 h+ 4.2337×C _2.5h ⁺45.4364×C _24h ) and 9, 1, and 16 h after s.c. injection (AUC=1.8821×C _1h +16.4256×C _9h ⁺ 25.4518×C _16h ). The accuracy and precision were 1.01±0.064 after oral dosing and 0.99±0.11 after s.c. injection. The derived mathematical models are reliable for estimation of the plasma AUC of cladribine after 2-h i.v. infusion, oral administration, and s.c. injection. Received: 8 October 1995/Accepted: 1 March 1996     

Disposition of the prodrug 4-(bis (2-chloroethyl) amino) benzoyl-L-glutamic acid and its active parent drug in mice

A novel therapy for improving selectivity in cancer chemotherapy aims to modify distribution of a cytotoxic drug by generating it selectively at tumour sites. In this approach an antibody-enzyme conjugate is allowed to localise at the tumour sites before injecting a prodrug which is converted to an active drug specifically by the targeted enzyme in the conjugate. We present here pharmacokinetic studies on the prodrug 4-(bis (2-chloroethyl) amino) benzoyl-L-glutamic acid and its activated derivative, benzoic acid mustard. The glutamic acid is cleaved from the prodrug to form the active drug by carboxypeptidase G2 (CPG2), an enzyme from Pseudomonas sp., which is not found in mammalian cells. The prodrug and its parent active drug were rapidly distributed in plasma and tissues after administration of prodrug or active drug (41 mumol kg-1 intraperitoneally) to mice bearing human choriocarcinoma xenografts. Prodrug and active drug both followed a two-compartment kinetic model. Prodrug was eliminated more rapidly (t1/2 alpha = 0.12 h, t1/2 beta = 0.70 h) than active drug (t1/2 alpha = 0.37 h, t1/2 beta = 1.61 h). Conversion of the prodrug to the activated parent drug was detected within 5 min of administration to mice which had previously received a F(ab')2-anti-human chorionic gonadotrophin antibody (W14A) conjugated to the enzyme, CPG2 (1,000 U kg-1). Tumour was the only tissue that activated all the prodrug reaching the site. It contained the highest concentration of targeted enzyme conjugate capable of catalysing the reaction of prodrug to drug. Plasma and other tissues were also capable of activating the prodrug but active drug production was limited by the amount of enzyme present. The active drug measured in plasma and tissues other than tumour was attributable to residual antibody-enzyme conjugate at non-tumour sites. Low levels of conjugate in tissues and plasma militate against the advantage of tumour localised enzyme therefore necessitating removal of non-localised enzyme.     

Association between the Interleukin-17A -197G>A (rs2275913) Polymorphism and Risk of Digestive Cancer

Interleukin-17A (IL-17A) is a multifunctional cytokine which plays a crucial role in the initiation andprogression of cancer. To date, several studies have investigated associations between IL-17A -197G>A (rs2275913)polymorphism and digestive cancer risk, but the results remain conflicting. We here aimed to confirm the roleof this single nucleotide polymorphism (SNP) in susceptibility to digestive cancer through a systemic reviewand meta-analysis. Ten eligible case-control studies were identified by searching electronic databases, involving3,087 cases and 3,815 controls. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were usedto estimate the strength of the association. The results of overall analyses indicated that the variant A allele wasassociated with an increased risk of digestive cancer (AA vs GG: OR=1.51, 95%CI=1.18-1.93; AA vs GG+GA:OR=1.45, 95%CI=1.12-1.87; A vs G: OR=1.21, 95%CI=1.05-1.39). In subgroup analysis stratified by specificcancer type, elevated risk among studies of gastric cancer was found (AA vs GG: OR=1.68, 95%CI=1.24-2.28;AA vs GG+GA: OR=1.62, 95%CI=1.16-2.26; A vs G: OR=1.23, 95%CI=1.04-1.46). According to ethnicity, therewas evidence in the Asian populations for an association between this polymorphism and cancer risk (GA vs GG:OR=1.19, 95%CI=1.05-1.36; AA vs GG: OR=1.56, 95%CI=1.15-2.12; AA+GA vs GG: OR=1.28, 95%CI=1.13-1.44; AA vs GG+GA: OR=1.42, 95%CI=1.01-2.00; A vs G: OR=1.24, 95%CI=1.08-1.44), while in the Caucasianpopulations an association was found in the recessive model (AA vs GG+GA: OR=1.62, 95%CI=1.17-2.24). Inconclusion, the results of this meta-analysis suggest that the IL-17A -197G>A polymorphism contributes to anincreased risk of human digestive cancer, both in the Asian and Caucasian populations and especially for gastriccancer.     

Quantitative relationship between pharmacokinetics of unchanged cisplatin and nephrotoxicity in rats: importance of area under the concentration-time curve (AUC) as the major toxicodynamic determinant in vivo

 Purpose: The major pharmacokinetic parameters of unchanged cisplatin (CDDP) related to nephrotoxicity were evaluated in rats in vivo using a pharmacodynamic model. Methods: CDDP was administered according to various dosing schedules (single bolus, intermittent bolus, or continuous infusion). Unchanged CDDP in plasma and urine was quantified using high-performance liquid chromatography (HPLC). The pharmacokinetics were assessed by model-independent methods. The relationship between pharmacokinetics and BUN levels was evaluated using a sigmoid maximum response (E_max) model. Results: Unchanged CDDP showed linear pharmacokinetics after single bolus injections of 1 to 5 mg/kg CDDP. Nephrotoxicity was ameliorated following intermittent bolus injection (1 mg/kg per day for 5 days) and continuous infusions (over 2 and 3 h) of the same CDDP doses (5 mg/kg), although these dosing schedules did not change the area under the concentration-time curve (AUC), total clearance (Clt), urinary excretion of unchanged CDDP or kidney platinum levels significantly. The maximum BUN level, as a nephrotoxicity marker, showed dose-related increases after single bolus injection of 1 to 5 mg/kg CDDP and after 3-h infusion of 5 to 25 mg/kg. The pharmacodynamic relationship between the maximum BUN level and C_max and between the maximum BUN level and AUC were apparently different between single bolus injection and 3-h infusion. The maximum BUN level was related to the AUC calculated by plasma concentrations of unchanged CDDP greater than the threshold level (AUC_>Cmin), a relationship most successfully described by the signoid E_max model, regardless of CDDP dose and schedule. The plasma threshold level of unchanged CDDP was determined as 0.9 μgPt/ml in rats. Conclusions: The present results substantiated the importance of C×T (AUC) value as an indicator of CDDP-induced nephrotoxicity in vivo as well as of tumor cell-killing effect of CDDP in vitro. The AUC_>Cmin of unchanged CDDP was found to be an important pharmacokinetic parameter predicting CDDP nephrotoxicity. Received: 12 February 1996 / Accepted: 5 September 1996     

Patterns of pathological response to neoadjuvant chemotherapy and its clinical implications in patients undergoing interval cytoreductive surgery for advanced serous epithelial ovarian cancer- A study by the Indian Network for Development of Peritoneal Surface Oncology (INDEPSO)

ObjectivesThe goals were to study• The pattern of pathological response to neoadjuvant chemotherapy (NACT) and its clinical implications• The impact of chemotherapy response grade (CRG) on survivalMethodsA retrospective analysis of patients undergoing interval cytoreductive surgery (CRS) between January 2013 to December 2017 was performed. The surgical and pathological reports were analyzed and surgical and pathological PCI compared. The pathological response to chemotherapy was assessed using the score developed by Bohm. et al.ResultsIn 79 patients, it was observed that sites involved by disease first like ovaries and pelvic peritoneum (lower region) were the last to respond preceded by the omentum, right upper quadrant (RUQ) peritoneum (upper region) and parietal peritoneum (middle region). Microscopic residual disease was seen in 20.2% in normal looking areas of peritoneum and in 20% with no gross residual disease in the RUQ. Visual inspection during surgery overestimated the disease extent in 40.5% and underestimated it in 15.1%.There was no difference in the progression free (p = 0.587) and overall survival (p = 0.157) between patients with CRG 1, 2 and 3 (poor, moderate, and complete/near complete response, respectively). Retroperitoneal nodes were positive in 0% with CRG 3, 27.5% with CRG 2 and 72.7% with CRG 1 (p < 0.0001).ConclusionsThe pathological response to NACT follows a specific pattern. Visual inspection is of limited value in assessing disease extent following NACT. Surgery following NACT should target sites involved before NACT and not just residual disease. The response in regional nodes should be included in chemotherapy response scores.     

The association of cigarette smoking and pathological response to neoadjuvant platinum-based chemotherapy in patients undergoing treatment for urinary bladder cancer - A prospective European multicenter observational study of the EAU Young Academic Urologists (YAU) urothelial carcinoma working group

ObjectiveTo prospectively study the impact of smoking on pathological response to neoadjuvant chemotherapy (NAC) in patients undergoing radical cystectomy (RC) for urothelial carcinoma of the bladder (UCB).Materials & methodsWe collected standard clinicopathological variables, including smoking status (never, former, current) in patients undergoing NAC and RC for UCB at 12 European tertiary care centers between 12/2013-12/2015. Clinicopathological variables were compared according to smoking status. Multivariable logistic regression models were built to assess the association of smoking status and a) complete (no residual disease), b) partial (residual, non-muscle invasive disease), c) no pathological response (residual muscle invasive or lymph node positive disease). Kaplan-Meier and Cox regression analyses were employed to study the impact of response to NAC on survival.Results and limitationsOur final cohort consisted of 167 NAC patients with a median follow-up of 15 months (interquartile range (IQR) 9–26 months) of whom 48 (29%), 69 (41%), and 50 (30%) where never, former, and current smokers, respectively. Smoking was significantly associated with advanced age (p = 0.013), worse ECOG performance status (p = 0.049), and decreased pathological response to NAC (p = 0.045). On multivariable logistic regression analyses, former and current smoking status was significantly associated with lower odds of complete pathological response (odds ratio (OR) 0.37, 95% confidence interval (CI) 0.16–0.87, p = 0.023, and OR 0.34, 95% CI 0.13–0.85, p = 0.021), while current smoking status was significantly associated with a greater likelihood of no pathological response (OR 2.49, 95% CI 1.02–6.06, p = 0.045). Response to NAC was confirmed as powerful predictor of survival.ConclusionsSmoking status is adversely associated with pathological response to NAC. Smokers should be informed about these adverse effects, counseled regarding smoking cessation, and possibly be considered for immunotherpeutics as they may be more effective in smokers.