Steep Dose-response Relationship Research Articles

Dynamic hydrogen peroxide levels reveal a rate-dependent sensitivity in B-cell lymphoma signaling

Although in vivo extracellular microenvironments are dynamic, most in vitro studies are conducted under static conditions. Here, we exposed diffuse large B-cell lymphoma (DLBCL) cells to gradient increases in the concentration of hydrogen peroxide (H2O2), thereby capturing some of the dynamics of the tumour microenvironment. Subsequently, we measured the phosphorylation response of B-cell receptor (BCR) signalling proteins CD79a, SYK and PLCγ2 at a high temporal resolution via single-cell phospho-specific flow cytometry. We demonstrated that the cells respond bimodally to static extracellular H2O2, where the percentage of cells that respond is mainly determined by the concentration. Computational analysis revealed that the bimodality results from a combination of a steep dose–response relationship and cell-to-cell variability in the response threshold. Dynamic gradient inputs of varying durations indicated that the H2O2 concentration is not the only determinant of the signalling response, as cells exposed to more shallow gradients respond at lower H2O2 levels. A minimal model of the proximal BCR network qualitatively reproduced the experimental findings and uncovered a rate-dependent sensitivity to H2O2, where a lower rate of increase correlates to a higher sensitivity. These findings will bring us closer to understanding how cells process information from their complex and dynamic in vivo environments.

Determinants of the survival benefit associated with statins in patients with acute heart failure.

AimsThe benefit of statins in patients with heart failure (HF) remains controversial and the mechanism of action is largely speculative. We investigated the determinants of the survival benefit associated with statins in HF patients.Methods and resultsWe enrolled 1680 acute HF patients receiving statins and 2157 patients not receiving statins admitted between 2009 and 2016. The left ventricular (LV) global longitudinal strain (GLS) was assessed as a measure of myocardial contractility. The primary outcome was 5 year all‐cause mortality. Statin therapy was independently associated with improved survival in patients with HF with preserved ejection fraction (HFpEF) [adjusted hazard ratio (HR) 0.781, 95% confidence interval (CI) 0.621–0.981, P = 0.034], but not in those with HF with reduced EF (HFrEF) (adjusted HR 0.881, 95% CI 0.712–1.090, P = 0.244). Mortality reduction associated with statin therapy was significant in patients with ischaemic HF (adjusted HR 0.775, 95% CI 0.607–0.989, P = 0.040), but not in those with non‐ischaemic HF (adjusted HR 0.895, 95% CI 0.734–1.092, P = 0.275). The relative magnitude of survival benefit with statin therapy increased as LV‐EF and LV‐GLS increased, with a steeper dose–response relationship in patients with ischaemic HF. In the subgroup of patients with ischaemic HF, survival benefit with statin therapy was confined to those ≤75 years of age.ConclusionsOur study suggests that the survival benefit of statins is confined to patients with HFpEF and those with ischaemic HF. Myocardial contractility may modulate the prognostic effects of statins in HF patients, particularly when the aetiology is ischaemic rather than non‐ischaemic.

Ligelizumab for Chronic Spontaneous Urticaria

M Maure, AM Gimenez-Arnau, G Sussman. N Engl J Med. 2019;381(14):1321–371332 To determine the efficacy of a next generation, high affinity, humanized monoclonal anti-IgE antibody in the treatment of chronic spontaneous urticaria (CSU). Patients (n = 382) were 18–75 years old with moderate to severe CSU who were not controlled with maximum medical management. The patients were randomized 2:2:2:1:1:1 to receive one of the following subcutaneous regimens: 240 mg of ligelizumab every four weeks, 72 mg of ligelizumab every four weeks, 24 mg of ligelizumab every four weeks, 300 mg of omalizumab every four weeks, placebo every four weeks, or a single 120 mg dose of ligelizumab at week zero followed by placebo …

Steep Dose-response Relationship between Maximum Hippocampal Dose and Memory Deficits following Hippocampal Avoidance Whole Brain Radiation Therapy (HA-WBRT) for Brain Metastases: A Secondary Analysis of NRG/RTOG 0933

NRG/RTOG 0933 was a phase II study suggesting that HA-WBRT for brain metastases may help to preserve cognitive function. However, hippocampal dose constraints in clinical trials conducted to date have been driven predominantly by feasibility of sparing while maintaining adequate coverage of the at-risk areas, as the radiation tolerance of the hippocampus remains uncertain. The purpose of this study was to perform an analysis of hippocampal radiation dose-volume effects and memory decline following HA-WBRT using a prospectively collected multi-institutional dataset. 113 patients received HA-WBRT on RTOG 0933. All patients received 30 Gy in 10 fractions. Memory was measured by the Hopkins Verbal Learning Test-Revised (HVLT-R) Delayed Recall (DR) and Total Recall (TR) at baseline and 6 months after radiation. Dose–volume histograms (DVH) were generated for the composite bilateral hippocampi. Dose–response data were fitted to a nonlinear model for D100%, D50%, and Dmax to the bilateral hippocampi. The primary endpoint was memory decline, measured by HVLT-R DR and TR at baseline and 6 months after completion of radiation therapy. The Reliable Change Index (RCI) was used to measure a clinically meaningful decline between baseline and 6 months for HVLT-R DR and TR, defined as a raw score change greater than or equal to 3. Models were also repeated using an RCI threshold raw change score of greater than or equal to 5. Evaluations of statistical significance used the Fisher Exact Test. 27 patients had complete DVH data available in addition to both baseline and 6-month cognitive testing. D100% was per protocol (≤9 Gy) in all cases. Dmax was per protocol (≤16 Gy) in 23 cases, had an acceptable variation (≤17 Gy) in 3 cases and an unacceptable deviation (20 Gy) in 1 case. There was a steep dose-response relationship between higher maximum dose to the bilateral hippocampi and deterioration in short-term memory using a raw score change greater than or equal to 3. For example, a Dmax = 14Gy was associated with a 10% risk and Dmax = 16Gy was associated with a 25% risk (underpowered, p = 0.139). When evaluating for a raw score change of greater than or equal to 5, there was a steep dose-response for Dmax and deterioration in short term memory according to both HVLT-DR and TR, and a significant relationship between maximum dose to the bilateral hippocampi and performance on HVLT-TR (p = 0.028). These data demonstrate a steep dose relationship between maximum dose to the bilateral hippocampi and deterioration in short term memory, even amongst patients who met hippocampal constraints according to the protocol, suggesting that tighter constraints may be beneficial. Future investigations with larger sample sizes will be important to confirm these findings.

Local Control After Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer

Numerous dose and fractionation schedules have been used to treat medically inoperable stage I non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) or stereotactic ablative radiation therapy. We evaluated published experiences with SBRT to determine local control (LC) rates as a function of SBRT dose. One hundred sixty published articles reporting LC rates after SBRT for stage I NSCLC were identified. Quality of the series was assessed by evaluating the number of patients in the study, homogeneity of the dose regimen, length of follow-up time, and reporting of LC. Clinical data including 1, 2, 3, and 5-year tumor control probabilities for stages T1, T2, and combined T1 and T2 as a function of the biological effective dose were fitted to the linear quadratic, universal survival curve, and regrowth models. Forty-six studies met inclusion criteria. As measured by the goodness of fit χ2/ndf, with ndf as the number of degrees of freedom, none of the models were ideal fits for the data. Of the 3 models, the regrowth model provides the best fit to the clinical data. For the regrowth model, the fitting yielded an α-to-β ratio of approximately 25Gy for T1 tumors, 19Gy for T2 tumors, and 21Gy for T1 and T2 combined. To achieve the maximal LC rate, the predicted physical dose schemes when prescribed at the periphery of the planning target volume are 43±1Gy in 3 fractions, 47±1Gy in 4 fractions, and 50±1Gy in 5 fractions for combined T1 and T2 tumors. Early-stage NSCLC is radioresponsive when treated with SBRT or stereotactic ablative radiation therapy. A steep dose-response relationship exists with high rates of durable LC when physical doses of 43-50Gy are delivered in 3 to 5 fractions.

Dose-response relationships of the sigmoid for urgency syndrome after gynecological radiotherapy

Purpose: To find out what organs and doses are most relevant for ‘radiation-induced urgency syndrome’ in order to derive the corresponding dose–response relationships as an aid for avoiding the syndrome in the future.Material and methods: From a larger group of gynecological cancer survivors followed-up 2–14 years, we identified 98 whom had undergone external beam radiation therapy but not brachytherapy and not having a stoma. Of those survivors, 24 developed urgency syndrome. Based on the loading factor from a factor analysis, and symptom frequency, 15 symptoms were weighted together to a score interpreted as the intensity of radiation-induced urgency symptom. On reactivated dose plans, we contoured the small intestine, sigmoid colon and the rectum (separate from the anal-sphincter region) and we exported the dose-volume histograms for each survivor. Dose–response relationships from respective risk organ and urgency syndrome were estimated by fitting the data to the Probit, RS, LKB and gEUD models.Results: The rectum and sigmoid colon have steep dose–response relationships for urgency syndrome for Probit, RS and LKB. The dose–response parameters for the rectum were D50: 51.3, 51.4, and 51.3 Gy, γ50 = 1.19 for all models, s was 7.0e−09 for RS and n was 9.9 × 107 for LKB. For Sigmoid colon, D50 were 51.6, 51.6, and 51.5 Gy, γ50 were 1.20, 1.25, and 1.27, s was 2.8 for RS and n was 0.079 for LKB.Conclusions: Primarily the dose to sigmoid colon as well as the rectum is related to urgency syndrome among gynecological cancer survivors. Separate delineation of the rectum and sigmoid colon in order to incorporate the dose–response results may aid in reduction of the incidence of the urgency syndrome.

Hydrogen cynide and cyanide salts: sodium, potassium, calcium, as CN-. Documentation of proposed values of occupational exposure limits (OELs)

Hydrogen cynide and cyanide salts: sodium, potassium, calcium, as CN-. Documentation of proposed values of occupational exposure limits (OELs)

A Model for Precise and Uniform Pelvic- and Limb-Sparing Abdominal Irradiation to Study the Radiation-Induced Gastrointestinal Syndrome in Mice Using Small Animal Irradiation Systems.

Background and Purpose:Currently, no readily available mitigators exist for acute abdominal radiation injury. Here, we present an animal model for precise and homogenous limb-sparing abdominal irradiation (LSAIR) to study the radiation-induced gastrointestinal syndrome (RIGS).Materials and Methods:The LSAIR technique was developed using the small animal radiation research platform (SARRP) with image guidance capabilities. We delivered LSAIR at doses between 14 and 18 Gy on 8- to 10-week-old male C57BL/6 mice. Histological analysis was performed to confirm that the observed mortality was due to acute abdominal radiation injury.Results:A steep dose–response relationship was found for survival, with no deaths seen at doses below 16 Gy and 100% mortality at above 17 Gy. All deaths occurred between 6 and 10 days after irradiation, consistent with the onset of RIGS. This was further confirmed by histological analysis showing clear differences in the number of regenerative intestinal crypts between animals receiving sublethal (14 Gy) and 100% lethal (18 Gy) radiation.Conclusion:The developed LSAIR technique provides uniform dose delivery with a clear dose response, consistent with acute abdominal radiation injury on histological examination. This model can provide a useful tool for researchers investigating the development of mitigators for accidental or clinical high-dose abdominal irradiation.

In vivo Pharmacodynamic Evaluation of Omadacycline (PTK 0796) against Staphylococcus aureus (SA) in the Murine Thigh Infection Model

BackgroundOmadacycline is a novel aminomethylcycline antibiotic in development for acute bacterial skin and skin structure infection (ABSSSI) and community acquired bacterial pneumonia (CABP). The goal of the study was to determine the PK/PD targets in the murine thigh infection model against a diverse group of SA pathogens including MRSA.Methods10 SA strains (4 MSSA, 6 MRSA) were utilized. MICs were determined using CLSI methods. Single dose murine plasma PK was previously determined in our lab and used for PK/PD analyses. The neutropenic murine thigh infection model was utilized for all treatment studies and drug dosing was by subcutaneous route. Four-fold increasing doses of omadacycline (0.25–64 mg/kg) were administered q12h to groups of mice infected with each strain. Treatment outcome was measured by determining organism burden in the thighs (CFU) at the end of each experiment (24 hours). The Emax Hill equation was used to model the dose–response data to the PK/PD index AUC/MIC. The magnitude of the PK/PD index AUC/MIC associated with net stasis and 1-log kill were determined in the thigh model for all strains.ResultsMICs ranged from 0.25–0.5 mg/L. At the start of therapy, mice had 7.1 ± 0.3 log10 CFU/thigh. In control mice, the organism burden increased 2.3 ± 0.3 log10 CFU/thigh over 24 hours. There was a relatively steep dose–response relationship observed with escalating doses of omadacycline. Maximal organism reductions were 4–5 log10 CFU/thigh compared with untreated controls. Stasis and 1 log-kill (from start of therapy) was observed against each strain. The AUC/MIC magnitude associated with stasis and 1-log kill endpoints are shown in the table.SA Group (n = 10)24 hours Static Dose (mg/kg)Stasis AUC/ MIC24 hours 1 log kill Dose (mg/kg)1 log kill AUC/MICMean13.923.745.778.1Median13.021.939.857.7Std Dev4.310.631.479.5ConclusionOmadacycline demonstrated in vivo potency against a diverse group of SA pathogens including MRSA strains. Stasis 24 hours AUC/MIC targets were approximately 24. This is very similar to previous studies of omadacycline against S. pneumoniae (stasis AUC/MIC 18) and other PK/PD evaluations of tetracycline-class antibiotics. 1-log kill targets were only 2–3 fold more than stasis targets for each strain. This data should provide useful in the dose-regimen optimization of omadacycline.Disclosures D. R. Andes, Paratek: Grant Investigator, Research support

OP.4C.10] CLINICALLY IMPORTANT DIFFERENCES IN SYSTOLIC AMBULATORY BLOOD PRESSURE IN PATIENTS SWITCHED BETWEEN ALTERNATE NIFEDIPINE OSMOTIC DELIVERY FORMULATIONS

Objective: Anecdotal evidence suggested clinically important systolic blood pressure (SBP) differences occurred in our patients whose nifedipine was being switched by pharmacies between AdN (Adalat XL – a formulation providing zero order release from the GastroIntestinal Therapeutic System - GITS) and MyN (Mylan-nifedipine ER - a formulation providing a delayed first-order release from the Osmotic Release Oral System - OROS). In vitro dissolution studies showed greater lag time to initial release from MyN and declining release at end of dosing interval. The objective of this study was to use Ambulatory Blood Pressure Monitoring (ABPM) to examine whether differences in overall effectiveness and duration of action exist between these two nifedipine formulations. Design and method: A randomized cross-over trial studied 20 patients receiving daily morning AdN vs. MyN 60 mg. After each 2-week period, 24-h ABPM was done. SBP data for 24 h and last 8 h (22:00 - 06:00 h) were examined using a Generalized Additive Mixed Model (GAMM). The software (R) used 2560 data points to model SBP population curves and compare them statistically. Results: GAMM of SBP over time showed MyN mean ± SE SBP was 2.59 ± 1.09 mmHg higher for 24 h (p = 0.0173) and 4.18 ± 1.6 mmHg higher for last 8 h (p = 0.0098). Mean 24-h SBP was > = 2 mmHg higher, while taking MyN in 50% of patients while SBP for last 8 h ranged as high as 18 mmHg higher while taking MyN.Conclusions: Clinically meaningful differences in SBP were seen in a cohort of patients when taking MyN compared to when they were taking AdN. This was likely based on differences in release profiles. For nifedipine, a potent vasodilator with a steep dose-response relationship and a 2-hour half-life, differences in timing and/or extent of delivery over as little as 6 h could allow clinically important changes in SBP. These data support the conclusion that formulations using differing release technologies are not suitable for bioequivalence testing. Undisclosed switching of nifedipine formulations by pharmacies can lead to an undesirable increase in variability in BP control.

IRES inhibition induces terminal differentiation and synchronized death in triple-negative breast cancer and glioblastoma cells.

Internal ribosome entry site (IRES)-mediated translation is a specialized mode of protein synthesis which malignant cells depend on to survive adverse microenvironmental conditions. Our lab recently reported the identification of a group of compounds which selectively interfere with IRES-mediated translation, completely blocking de novo IGF1R synthesis, and differentially modulating synthesis of the two c-Myc isoforms. Here, we examine the phenotypic consequences of sustained IRES inhibition in human triple-negative breast carcinoma and glioblastoma cells. A sudden loss of viability affects the entire tumor cell population after ∼72-h continuous exposure to the lead compound. The extraordinarily steep dose-response relationship (Hill-Slope coefficients −15 to −35) and extensive physical connections established between the cells indicate that the cells respond to IRES inhibition collectively as a population rather than as individual cells. Prior to death, the treated cells exhibit prominent features of terminal differentiation, with marked gains in cytoskeletal organization, planar polarity, and formation of tight junctions or neuronal processes. In addition to IGF1R and Myc, specific changes in connexin 43, BiP, CHOP, p21, and p27 also correlate with phenotypic outcome. This unusual mode of tumor cell death is absolutely dependent on exceeding a critical threshold in cell density, suggesting that a quorum-sensing mechanism may be operative. Death of putative tumor stem cells visualized in situ helps to explain the inability of tumor cells to recover and repopulate once the compound is removed. Together, these findings support the concept that IRES-mediated translation is of fundamental importance to maintenance of the undifferentiated phenotype and survival of undifferentiated malignant cells.Electronic supplementary materialThe online version of this article (doi:10.1007/s13277-016-5161-4) contains supplementary material, which is available to authorized users.

In Vivo Pharmacodynamic Target Assessment of Delafloxacin against Staphylococcus aureus, Streptococcus pneumoniae, and Klebsiella pneumoniae in a Murine Lung Infection Model.

Delafloxacin is a broad-spectrum anionic fluoroquinolone under development for the treatment of bacterial pneumonia. The goal of the study was to determine the pharmacokinetic/pharmacodynamic (PK/PD) targets in the murine lung infection model for Staphylococcus aureus, Streptococcus pneumoniae, and Klebsiella pneumoniae Four isolates of each species were utilized for in vivo studies: for S. aureus, one methicillin-susceptible and three methicillin-resistant isolates; S. pneumoniae, two penicillin-susceptible and two penicillin-resistant isolates; K. pneumoniae, one wild-type and three extended-spectrum beta-lactamase-producing isolates. MICs were determined using CLSI methods. A neutropenic murine lung infection model was utilized for all treatment studies, and drug dosing was by the subcutaneous route. Single-dose plasma pharmacokinetics was determined in the mouse model after administration of 2.5, 10, 40, and 160 mg/kg. For in vivo studies, 4-fold-increasing doses of delafloxacin (range, 0.03 to 160 mg/kg) were administered every 6 h (q6h) to infected mice. Treatment outcome was measured by determining organism burden in the lung (CFU counts) at the end of each experiment (24 h). The Hill equation for maximum effect (Emax) was used to model the dose-response data. The magnitude of the PK/PD index, the area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC), associated with net stasis and 1-log kill endpoints was determined in the lung model for all isolates. MICs ranged from 0.004 to 1 mg/liter. Single-dose PK parameter ranges include the following: for maximum concentration of drug in serum (Cmax), 2 to 70.7 mg/liter; AUC from 0 h to infinity (AUC0-∞), 2.8 to 152 mg · h/liter; half-life (t1/2), 0.7 to 1 h. At the start of therapy mice had 6.3 ± 0.09 log10 CFU/lung. In control mice the organism burden increased 2.1 ± 0.44 log10 CFU/lung over the study period. There was a relatively steep dose-response relationship observed with escalating doses of delafloxacin. Maximal organism reductions ranged from 2 log10 to more than 4 log10 The median free-drug AUC/MIC magnitude associated with net stasis for each species group was 1.45, 0.56, and 40.3 for S. aureus, S. pneumoniae, and K. pneumoniae, respectively. AUC/MIC targets for the 1-log kill endpoint were 2- to 5-fold higher. Delafloxacin demonstrated in vitro and in vivo potency against a diverse group of pathogens, including those with phenotypic drug resistance to other classes. These results have potential relevance for clinical dose selection and evaluation of susceptibility breakpoints for delafloxacin for the treatment of lower respiratory tract infections involving these pathogens.

Therapeutic drug monitoring in cancer – Are we missing a trick?

Therapeutic drug monitoring (TDM) can be defined as the measurement of drug in biological samples to individualise treatment by adapting drug dose to improve efficacy and/or reduce toxicity. The cytotoxic drugs are characterised by steep dose–response relationships and narrow therapeutic windows. Inter-individual pharmacokinetic (PK) variability is often substantial. There are, however, a multitude of reasons why TDM has never been fully implemented in daily oncology practice. These include difficulties in establishing appropriate concentration target, common use of combination chemotherapies and the paucity of published data from pharmacological trials.The situation is different with targeted therapies. The large interindividual PK variability is influenced by the pharmacogenetic background of the patient (e.g. cytochrome P450 and ABC transporters polymorphisms), patient characteristics such as adherence to treatment and environmental factors (drug–drug interactions). Retrospective studies have shown that targeted drug exposure correlates with treatment response in various cancers. Evidence for imatinib currently exists, others are emerging for compounds including nilotinib, dasatinib, erlotinib, sunitinib, sorafenib and mammalian target of rapamycin (mTOR) inhibitors. Applications for TDM during oral targeted therapies may best be reserved for particular situations including lack of therapeutic response, severe or unexpected toxicities, anticipated drug–drug interactions and concerns over adherence treatment. There are still few data with monoclonal antibodies (mAbs) in favour of TDM approaches, even if data showed encouraging results with rituximab and cetuximab. TDM of mAbs is not yet supported by scientific evidence. Considerable effort should be made for targeted therapies to better define concentration–effect relationships and to perform comparative randomised trials of classic dosing versus pharmacokinetically-guided adaptive dosing.

Radiation Therapy in Locally Advanced Non-Small-Cell Lung Cancer: An Overview of Dose/Fractionation Strategies to Improve Outcomes

SUMMARY Local disease control and survival rates of locally advanced non-small-cell lung cancer patients are still poor, even with the best combination of chemotherapy and radiotherapy. Radiotherapy dose is believed to play a major role in controlling local disease, due a steep dose–response relationship for lung cancer, and therefore there is a strong biological rationale to escalate/accelerate the dose. In previous years, several prospective trials explored this option and obtained contrasting results, and recent technical advances in radiotherapy raise the issue of which approach should be considered the most appropriate for future studies. In this article, we briefly review selected prospective Phase I–III trials testing escalation/altered fractionation and focus on future perspectives in this field.

Pharmacokinetics and Pharmacodynamics of Intraperitoneal Cancer Chemotherapeutics

Peritoneal carcinomatosis remains a significant cause of morbidity and is a marker of poor prognosis in a range of malignancies, including those of the gastrointestinal and gynaecological tracts. In these cases, regional therapy has been explored as a treatment strategy to take advantage of the prolonged confinement of such tumours within the peritoneal cavity and the steep dose-response relationship for most cytotoxic agents. The pharmacokinetic rationale is based on exploiting the peritoneal-plasma barrier, which slows the rate of drug clearance from the peritoneal to systemic compartments and creates a concentration differential in favour of the peritoneal cavity. This allows higher drug concentrations, and thus increased cytotoxicity, to be achieved at the site of a tumour within the peritoneal cavity. There is pharmacodynamic evidence from a number of clinical trials to support the translation of these pharmacokinetic advantages of intraperitoneal chemotherapy into clinical benefit. However, its clinical application remains controversial because of concerns regarding intraperitoneal drug distribution, technical challenges and toxicity associated with regional drug delivery and the clinical relevance of the studies undertaken. The purpose of this review is to summarize the pharmacokinetic rationale of intraperitoneal drug delivery, review the pharmacodynamic studies performed in ovarian, colorectal and gastric cancers, and outline the future directions and challenges in the clinical application of this mode of treatment.

Abstract 5358: Pediatric preclinical testing program (PPTP) evaluation of the non-camptothecin topoisomerase 1 targeted agent Genz644282

Abstract Background: Genz644282, a non camptothecin topoisomerase I poison, was developed from a lead compound 8,9-dimethoxy-5-(2-N,N-dimethylaminoethyl)-2,3-methylenedioxy-5-H-dibenzo[c,h] [1,6]naphthyridin-6-one (ARC111, topovale). In non-clinical testing ARC111 had equivalent or superior activity to irinotecan, and induced regression in a topotecan insensitive tumor xenograft. ARC111 also differentiated itself from other camptothecin derivatives in that it was not a substrate for the ABCG2 drug transporter. Methods: The PPTP includes a molecularly characterized in vitro panel of cell lines (n=27) and in vivo panel of xenografts (n=61) representing most of the common types of childhood solid tumors and childhood acute lymphoblastic leukemia (ALL). Genz664282 (provided by Genzyme Corporation) was tested in vitro at concentrations from 0.1 nM to 1 μM with 96 hr exposure to drug. Genz664282 was administered IP, three times weekly for 2 weeks at a dose of 1 – 4 mg/kg for either 1 or two cycles. Three measures of antitumor activity were used: 1) an objective response measure modeled after the clinical setting; 2) a treated to control (T/C) tumor volume measure; and 3) a time to event (4-fold increase in tumor volume) measure based on the median event-free survival (EFS) of treated and control animals for each xenograft. Results: In vitro Genz644282 exerted potent cytotoxic activity with a median IC50 of 1.19 nM (range 0.186 – 23.3 nM). There was no cell type selectivity. In vivo at 4 mg/kg (MTD) for two cycles, Genz644282 induced maintained complete responses (MCR) in 8/8 models including tumor lines poorly responsive to topotecan. Dose response evaluation (1 cycle of treatment) against 3 tumor lines least sensitive to topotecan showed Genz644282 induced 2MCR and 1CR at 4 mg/kg, and 2CR and 1 MCR at 2 mg/kg, but no regressions were observed at 1 mg/kg, suggesting a steep dose response relationship. Further testing at 2 mg/kg (1 cycle) induced 4MCR, 1CR and 2PR in 17 tumor lines (41%), mainly in sarcoma models (6/7), particularly osteosarcoma (4/6). Conclusions: At the 2 mg/kg dose level administered for one cycle of treatment, Genz644282 demonstrated a high level of activity inducing regressions in 7 of 17 models evaluated, with particularly high activity in osteosarcoma models. The models included tumors intrinsically insensitive to topotecan. As with other topoisomerase I poisons, how accurately this data will translate to clinical activity will depend upon the drug exposures that can be achieved in children treated with this agent. (Supported by NO1-CM91003-03) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5358. doi:10.1158/1538-7445.AM2011-5358

Efficacy and pharmacokinetic/pharmacodynamic evaluation of the Aurora kinase A inhibitor MLN8237 against preclinical models of pediatric cancer

PurposeTo gain a greater understanding of the potential of the Aurora kinase A inhibitor MLN8237 in the treatment of pediatric malignancies.MethodsThe activity of MLN8237 was evaluated against 28 neuroblastoma and Ewing sarcoma cell lines, and its in vivo efficacy was studied over a range of doses against 12 pediatric tumor xenograft models. Pharmacokinetic, pharmacodynamic, and genomic studies were undertaken.ResultsIn vitro neuroblastoma cell lines were generally more sensitive to MLN8237 than Ewing sarcoma lines. MLN8237 demonstrated significant activity in vivo against solid tumor models at the maximum tolerated dose (MTD); however, only 2 of 6 neuroblastoma models had objective responses at 0.25MTD. In contrast, MLN8237 induced objective responses at its MTD and at 0.5MTD in three ALL models and in two out of three at 0.25MTD. Pharmacokinetic studies at 0.5MTD demonstrated a T max of 0.5 h, C max of 24.8 μM, AUC(0–24) of 60.3 μM h, and 12 h trough level of 1.2 μM. Mitotic indices increased 6–12 h after MLN8237 administration. AURKA copy number variation was frequent in xenografts, and expression was highly correlated with copy number.ConclusionsObjective responses were more frequent in tumors with decreased AURKA copy number (5/8) compared to those with increased gene copy number (2/14). This report confirms the significant activity against both solid tumor and ALL xenografts at the MTD, with a steep dose response. These data support clinical development of MLN8237 in childhood cancer. Because of the steep dose–response relationship, such studies should target achieving trough levels of 1 μM or higher for sustained periods of treatment.Electronic supplementary materialThe online version of this article (doi:10.1007/s00280-011-1618-8) contains supplementary material, which is available to authorized users.

Initial testing of the hypoxia‐activated prodrug PR‐104 by the pediatric preclinical testing program

PR-104 is rapidly hydrolyzed to PR-104A in vivo, which is activated by reduction to the corresponding 5-hydroxylamine (PR-104H) and amine (PR-104M) to produce DNA interstrand cross-links. PR-104 activation can occur via hypoxia-dependent reductases and also independently of hypoxia by aldo-keto reductase (AKR) 1C3. PR-104A was tested against the PPTP in vitro panel (10 nM to 100 µM), and PR-104 in vivo using a weekly × 6 schedule at its maximum tolerated dose (MTD) of 550 mg/kg. Subsequently PR-104 was tested at 270 and 110 mg/kg. Pharmacokinetics for PR-104 and its metabolites were determined, as were levels of AKR1C3 RNA and protein in xenografts. In vitro, the leukemia models were most sensitive to PR-104A. In vivo, PR-104 induced objective responses at its MTD in 21/34 solid tumor models and maintained complete responses against 7/7 acute lymphoblastic leukemia (ALL) models. At 270 mg/kg and lower dose levels, PR-104 did not induce solid tumor regressions, suggesting a steep dose-response relationship. Pharmacokinetic analysis suggests higher systemic exposures to PR-104A and its metabolites in mice compared to those achievable in patients. Levels of AKR1C3 protein did not correlate with tumor responsiveness. As monotherapy, PR-104 demonstrated a high level of activity against both solid tumor and ALL models at its MTD, but the activity was almost completely lost at half the MTD dose for solid tumors. Pharmacokinetic data at the PR-104 MTD from human trials suggest that PR-104 metabolites may not reach the plasma exposures in children that were associated with high-level preclinical activity.

Physical workload and accelerated occurrence of lumbar spine diseases: risk and rate advancement periods in a German multicenter case–control study

In a German multicenter case-control study of lumbar disc diseases, we calculated risk and rate advancement periods (RAP) for physical workload. Patients aged 25-70 years with clinically and radiologically verified lumbar disc herniation (286 males, 278 females) or symptomatic lumbar disc narrowing (145 males, 206 females) were compared with population control subjects (453 males and 448 females). For this analysis, all manual handling of objects of about ≥5 kg and postures with trunk inclination of ≥20 °, as assessed by technical experts, were included in the calculation of cumulative lumbar load, determined by biomechanical model calculations. Logistic regression analysis was applied to calculate RAP, adjusted for region. We found a steep positive dose-response relationship between age and lumbar disc narrowing among men as well as women; however, we did not find a monotonic increase in lumbar disc herniation risk with age. As a monotonic increase in disease risk with age constitutes a fundamental assumption underlying the RAP concept, we restricted our RAP analysis to cases with symptomatic lumbar disc narrowing. Among men, there was a positive dose-response relationship between the cumulative lumbar load and the acceleration of lumbar disc narrowing. In the highest exposure category, a RAP of 28.0 years [95% confidence interval (95% CI) 9.7-46.3 years] was found. Among women, the RAP was 8.8 years (95% CI 2.4-15.2 years) in the highest exposure category. This study emphasizes the conceptual importance of risk acceleration - causation not only comprises the occurrence of a disease (that without a specific exposure would not have occurred at all) but also the accelerated occurrence of a disease (that without exposure would have occurred later in life).

The role of intensity-modulated radiotherapy in head and neck cancer

Intensity-modulated radiotherapy (IMRT) has been a significant technological advance in the field of radiotherapy in recent years. IMRT allows sparing of normal tissue while delivering radical radiation doses to the target volumes. The role of IMRT for parotid salivary gland sparing in head and neck cancer is well established. The utility of IMRT for pharyngeal constrictor muscle and cochlear sparing requires investigation in clinical trials. The current evidence supporting the use of IMRT in various head and neck subsites has been summarized. Sparing of organs at risk allows for dose-escalation to the target volumes, taking advantage of the steep dose-response relationship for squamous cell carcinomas to improve treatment outcomes in advanced head and neck cancers. However, dose-escalation could result in increased radiation toxicity (acute and late), which has to be studied in detail. The future of IMRT in head and neck cancers lies in exploring the use of biological imaging for dose-escalation using targeted dose painting.