Measure Of Drug Effect Research Articles

Testing drug additivity based on monotherapies.

Under the Loewe additivity, constant relative potency between two drugs is a sufficient condition for the two drugs to be additive. Implicit in this condition is that one drug acts like a dilution of the other. Geometrically, it means that the dose-response curve of one drug is a copy of another that is shifted horizontally by a constant over the log-dose axis. Such phenomenon is often referred to as parallelism. Thus, testing drug additivity is equivalent to the demonstration of parallelism between two dose-response curves. Current methods used for testing parallelism are usually based on significance tests for differences between parameters in the dose-response curves of the monotherapies. A p-value of less than 0.05 is indicative of non-parallelism. The p-value-based methods, however, may be fundamentally flawed because an increase in either sample size or precision of the assay used to measure drug effect may result in more frequent rejection of parallel lines for a trivial difference. Moreover, similarity (difference) between model parameters does not necessarily translate into the similarity (difference) between the two response curves. As a result, a test may conclude that the model parameters are similar (different), yet there is little assurance on the similarity between the two dose-response curves. In this paper, we introduce a Bayesian approach to directly test the hypothesis that the two drugs have a constant relative potency. An important utility of our proposed method is in aiding go/no-go decisions concerning two drug combination studies. It is illustrated with both a simulated example and a real-life example.

Abstract 1723: Effect and mechanism of PF299804 alone and in combination with STAT3 inhibitor in human sarcoma cell lines

Abstract Background: Curative treatment of sarcomas is achieved by surgical resection, supplemented with neoadjuvant chemotherapy and postoperative radiation. Approximately 50% of patients will eventually die. We previously reported that 78% (36/46) of our cohort of patients with soft tissue sarcoma were positive for total EGFR/HER1. The EGFR/HER1 pathway is an important molecular target; its inhibition is now well established clinically in several epithelial-origin tumors. No pan-HER inhibitors have yet been tested in sarcomas. The principal aim of this project was to investigate the effect and mechanism of PF299804 (an irreversible pan-HER inhibitor) therapy alone and in combination with STAT3 inhibitor in human sarcoma cell lines. Methods: PF299804 mono-therapy and in combination with STAT3 inhibitor (S3I-201) were investigated in a panel of 12 human sarcoma cell lines. Crystal-violet colorimetric and clonogenic assays were used to measure drug effects. Soft agar colony formation assay was used to evaluate anchorage-independent growth (the ability to evade anoikis). For assessing potential mechanisms, we investigated expression and activity of EGFR signalling by Western blot. Results: HER family receptors (EGFR/HER1, HER2 and HER3) were positively expressed in the sarcoma cell lines representing liposarcoma (778 and 449b), fibrosarcoma (SW684 and HT1080), synovial sarcoma (SW980), fibrous histocytoma (GCT) and osteosarcoma (143B, HOS, MG63, SJSA, U2-OS and Saos-2). IC50 values of PF299804 were more than 1µM in these cell lines, which was about 1000-fold higher than the sensitive control lung cell line PC9. Mechanism studies by Western blot assay found that 200nM PF299804 (emulating total plasma exposure measured in human clinical trial) dramatically suppressed the activation of both EGFR/HER1 and HER2, as well as their representative downstream signalling factors Erk1/2, p38MAPK and SAPK/JNK in ras/raf/MAPK and AKT in PI3K/AKT pathways, but not of STAT3. Combination therapy using PF299804 and STAT3 inhibitor S3I-201 achieved synergistic anti-proliferation in 3 out of 4 sarcoma cell lines (449B, 778, 143B and HOS), representing different subtype, grade, recurrence and metastasis: 449B and 778 are primary well-differentiated and its recurrent liposarcoma cell lines; HOS and 143B are low-metastatic and high- metastatic (HOS with k-ras oncogene transformation) osteosarcoma cell lines, respectively. This synergistic effect was associated with additional down-regulation of phosphorylated STAT3. Conclusion: Although the second generation irreversible pan-HER inhibitor PF299804 inactivated HER family and downstream pathways, it encountered resistance at least partially due to the STAT3 activation. Therefore, addition of STAT3 inhibitor in PF299804 therapy may block STAT3 activation and achieve synergistic anti-proliferation in sarcoma cell lines. Citation Format: Xiaochun Wang, David Goldstein, Philip Crowe, Jia-Lin Yang. Effect and mechanism of PF299804 alone and in combination with STAT3 inhibitor in human sarcoma cell lines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1723. doi:10.1158/1538-7445.AM2014-1723

An exploratory study of the combined effects of orally administered methylphenidate and delta-9-tetrahydrocannabinol (THC) on cardiovascular function, subjective effects, and performance in healthy adults

Methylphenidate (MPH) is commonly prescribed for the treatment of Attention Deficit Hyperactivity Disorder (ADHD), and is often used illicitly by young adults. Illicit users often coadminister MPH with marijuana. Little is known about physiologic and subjective effects of these substances used in combination. In this double-blind, cross-over experiment, sixteen healthy adult subjects free from psychiatric illness (including ADHD) and reporting modest levels of marijuana use participated in 6 experimental sessions wherein all combinations of placebo or 10mg oral doses of delta-9-tetrahydocannibinol (THC); and 0mg, 10mg and 40mg of MPH were administered. Sessions were separated by at least 48hours. Vital signs, subjective effects, and performance measure were collected. THC and MPH showed additive effects on heart rate and rate pressure product (e.g., peak heart rate for 10mg THC+0mg, 10mg, and 40mg MPH=89.1, 95.9, 102.0 beats/min, respectively). Main effects of THC and MPH were also observed on a range of subjective measures of drug effects, and significant THC dose × MPH dose interactions were found on measures of “Feel Drug,” “Good Effects,” and “Take Drug Again.” THC increased commission errors on a continuous performance test (CPT) and MPH reduced reaction time variability on this measure. Effects of THC, MPH, and their combination were variable on a measure of working memory (n-back task), though in general, MPH decreased reaction times and THC mitigated these effects. These results suggest that the combination of low to moderate doses of MPH and THC produces unique effects on cardiovascular function, subjective effects and performance measures.

Straight talk with...Jamie Heywood.

Last month, Genentech launched an unusual five-year research pact. The San Francisco subsidiary of the drug giant Roche partnered with Cambridge, Massachusetts-based PatientsLikeMe to mine the online patient network's database of real-world experiences. In exchange for an undisclosed fee, Genentech now has access to nearly all of the information collected by PatientsLikeMe, which currently includes more than 250,000 members with 2,000 different conditions. The hope is that studying the network will help Genentech learn how to stratify patient populations more precisely and measure drug effectiveness better, among other things.At the helm of PatientsLikeMe is Jamie Heywood, a mechanical engineer by training who devised the idea for the platform ten years ago when he noticed some striking similarities between the information asked of online dating websites and clinical trial portals. With his brother Benjamin and friend Jeff Cole, Heywood founded PatientsLikeMe later that same year. Nicholette Zeliadt spoke to Heywood about where the crowdsourcing site stands a decade on from its inception and what this new partnership with Genentech will mean for open-participation research.

Abstract C278: Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas.

Abstract Topoisomerase I (Top1) is the molecular target for a number of drugs used in cancer chemotherapy. Several third generation Top1 inhibitors are being evaluated, including the indenoisoquinolines (NSC 725776 and NSC743400) which are currently in clinical trials at the National Cancer Institute. We previously reported the development and validation of a quantitative ELISA to measure Top1 levels in cells and solid tissues [PloS ONE (2012) 7(12)]. We observed a large variation in baseline Top1 levels in xenografts and human patient biopsies using the published method. Baseline Top1 levels in needle biopsies for some patients were too low to allow for the reporting of a drug effect. We have modified our tissue processing procedures to improve assay sensitivity. We have also demonstrated the fitness of the assay in a clinical trial of the indenoisoquinolines for canine lymphoma as a stepping stone to human clinical trials. Baseline Top1 levels in canine lymphoma patients varied greatly, consistent with our previous findings in xenografts and a limited number of human tumor biopsies. These data suggest that it may not be possible to measure drug effect based on post-dose Top1 levels alone, but will require paired pre-dose and post-dose specimens from the same patient. Decreased Top1 levels following therapy (compared to pre-dose) were detected in tumors from a number of dogs, each treated with one of three indenoisoquinolines (NSC706744, NSC 725776 and NSC743400), demonstrating evidence of target engagement as predicted by in vitro and xenograft models. Measurement of baseline Top1 levels in this trial will be correlated with the degree of drug-related target reduction and evidence of drug efficacy in the dogs enrolled on this study. Funded by NCI Contract No. HHSN261200800001E. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C278. Citation Format: Thomas D. Pfister, Katerine V. Ferry-Galow, Tariq Mohabbat, Robert J. Kinders, Chand Khanna, Christina Mazcko, Ralph E. Parchment, Yves Pommier, Joseph E. Tomaszewski, James H. Doroshow. Topoisomerase 1 immunoassay provides proof of target engagement by the indenoisoquinoline class of topoisomerase 1 inhibitors in canine lymphomas. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C278.

Dynamic Contrast-Enhanced MRI Evaluation of Cerebral Cavernous Malformations

The aim of this study is to quantitatively evaluate the behavior of CNS cavernous malformations (CCMs) using a dynamic contrast-enhanced MRI (DCEMRI) technique sensitive for slow transfer rates of gadolinium. The prospective study was approved by the institutional review board and was HIPPA compliant. Written informed consent was obtained from 14 subjects with familial CCMs (4 men and 10 women, ages 22-76years, mean 48.1years). Following routine anatomic MRI of the brain, DCEMRI was performed for six slices, using T1 mapping with partial inversion recovery (TAPIR) to calculate T1 values, following administration of 0.025mmol/kg gadolinium DTPA. The transfer rate (Ki) was calculated using the Patlak model, and Ki within CCMs was compared to normal-appearing white matter as well as to 17 normal control subjects previously studied. All subjects had typical MRI appearance of CCMs. Thirty-nine CCMs were studied using DCEMRI. Ki was low or normal in 12 lesions and elevated from 1.4 to 12 times higher than background in the remaining 27 lesions. Ki ranged from 2.1E-6 to 9.63E-4min(-1), mean 3.55E-4. Normal-appearing white matter in the CCM patients had a mean Ki of 1.57E-4, not statistically different from mean WM Ki of 1.47E-4 in controls. TAPIR-based DCEMRI technique permits quantifiable assessment of CCMs in vivo and reveals considerable differences not seen with conventional MRI. Potential applications include correlation with biologic behavior such as lesion growth or hemorrage, and measurement of drug effects.

Chloride Channel Inhibition Reduces Tail Regeneration in the Developing Vertebrate Ambystoma Mexicanum

Regeneration is dependent on ion signaling which may be activated by endogenous bioelectric fields (EF) in response to the wounding. EF modulation by electrical stimulation (ES) or pharmacological ion channel manipulation alters regenerative capacity. Satellite cell proliferation during ES in the invertebrate, P. clarkii was dependent on K+ and Ca2+ flux (unpublished results). We hypothesize that regeneration in the vertebrate, Ambystoma mexicanum are mediated by intact cellular ion channel activity. Ambystoma hatchlings were raised in welled plates and Holtfreter's solution (2 ml). Tails were amputated 2mm proximal of the tip and imaged on days 0, 2, 4, and 9. Ion channel regulation of regeneration was assessed by inhibiting K+ channels with tetraethylammonium (TEA), Na+/K+ ATPase with ouabain (OB), and Cl− channels with DIDS. Uncut controls measured drug effects on normal growth. Tail tip growth determined regenerative capacity in cut hatchlings. OB and TEA had no effect on regeneration. Cl− channel blockade (DIDS) decreased regeneration from 0.276±0.003 to 0.193±0.002 mm/day (p<0.05) but did not alter uncut, control growth. Thus, ion channels may be critical to vertebrate regeneration by modulating proliferation via cell volume control. Specific ion channel gene expression will further assess the effects of bioelectric fields on vertebrate regeneration capacity.

Compound Ranking Based on a New Mathematical Measure of Effectiveness Using Time Course Data from Cell-Based Assays

The half maximal inhibitory concentration (IC₅₀) has several limitations that make it unsuitable for examining a large number of compounds in cytotoxicity studies, particularly when multiple exposure periods are tested. This article proposes a new approach to measure drug effectiveness, which allows ranking compounds according to their toxic effects on live cells. This effectiveness measure, which combines all exposure times tested, compares the growth rates of a particular cell line in the presence of the compound with its growth rate in the presence of DMSO alone. Our approach allows measuring a wider spectrum of toxicity than the IC₅₀ approach, and allows automatic analyses of a large number of compounds. It can be easily implemented in linear regression software, provides a comparable measure of effectiveness for each investigated compound (both toxic and non-toxic), and allows statistically testing the null hypothesis that a compound is non-toxic versus the alternative that it is toxic. Importantly, our approach allows defining an automated decision rule for deciding whether a compound is significantly toxic. As an illustration, we describe the results of a cellbased study of the cytotoxicity of 24 analogs of novobiocin, a C-terminal inhibitor of heat shock protein 90 (Hsp90); the compounds were ranked in order of cytotoxicity to a panel of 18 cancer cell lines and 1 normal cell line. Our approach may also be a good alternative to computing the half maximal effective concentration (EC₅₀) in studies searching for compounds that promote cell growth.

Bispectral Index Dynamics During Propofol Hypnosis Is Similar in Red-Haired and Dark-Haired Subjects

We have previously shown that red hair is associated with increased desflurane requirement for immobility, compared with dark hair. The effect of red hair on IV anesthetic requirement remains unknown. We tested the hypothesis that the propofol concentration in the effect site associated with half maximal electroencephalogram response, Ce50, is at least 50% higher in subjects with red hair. We modeled the propofol concentration versus electroencephalogram response relationship using a 2-step approach in 29 healthy dark- and red-haired volunteers receiving a propofol infusion to produce loss of consciousness. Bispectral Index (BIS) was the measure of drug effect. The parameters of a 3-compartment pharmacokinetic model were fit to measured arterial propofol concentrations. The relationship between effect-site propofol concentration (Ce) and BIS was characterized using a sigmoid Emax model. Model performance and accuracy of the estimated parameters were evaluated using accepted metrics and bootstrap resampling. The effect of hair color on the Ce50 for BIS response in the final model was assessed using a threshold of 6.63 (P<0.01) in reduction of -2 log likelihood. The influence of body weight on the model was also assessed. The inclusion of hair color as a model covariate did not improve either the pharmacokinetic or the pharmacodynamic model. A separate analysis for the dark- and red-haired subjects estimated a median (95% confidence interval) Ce50 BIS of 2.71 μg/mL (2.28-3.36 μg/mL) and 2.57 μg/mL (1.68-3.60 μg/mL), respectively. Body weight was a significant covariate for the CL1 and V1. Red hair phenotype does not affect the pharmacokinetics or pharmacodynamics of propofol.

Effects of atomoxetine on locomotor activity and impulsivity in the spontaneously hypertensive rat

Atomoxetine (ATX) is a commonly used non-stimulant treatment for Attention deficit hyperactivity disorder (ADHD). It primarily acts to increase noradrenalin levels; however, at higher doses it can increase dopamine levels. To date there has been no investigations into the effects of orally-administered ATX in the most commonly used model of ADHD, the spontaneously hypertensive rat (SHR). The aim of this study was to describe the effects of doses thought to be selective (0.15mg/kg) and non-selective (0.3mg/kg) for noradrenalin on behavioural measures in the SHR. Firstly, we examined the effects of acute and chronic ATX on locomotor activity including sensitisation and cross-sensitisation to amphetamine. Secondly, we measured drug effects on impulsivity using a T-maze delay discounting paradigm. We found no effect of ATX on locomotor activity and no evidence for sensitisation or cross-sensitisation. Furthermore, there were no differences in T-maze performance, indicating no effects on impulsivity at these doses. The absence of behavioural sensitisation supports previous claims of superior safety relative to psychostimulants for the doses administered. There was also no effect on impulsivity; however, we suggest that was confounded by stress specific to SHRs. Implications for future studies, behavioural assessment of SHRs and their use as a model of ADHD are discussed.

Measured Drug Effect and Cardiovascular Outcomes in Patients Receiving Platelet P2Y12Receptor Antagonists

THE CLINICAL EFFICACY OF ORAL P2Y12 ANTAGOnists in reducing recurrent cardiovascular events in patients with acute coronary syndromes (ACS) treated with percutaneous coronary intervention (PCI) or with either a conservative or early invasive strategy is well established. However, the effect of clopidogrel on P2Y12-mediated platelet reactivity varies widely among individuals. Platelet function tests are now clinically available that can measure P2Y12-mediated platelet reactivity, thereby providing a measurement of drug effect in patients treated with a P2Y12-receptor antagonist. Platelet function testing has provided a measure of certainty to the understanding of cardiovascular diseases: agents that provide powerful and consistent inhibition of P2Y12-mediated reactivity reduce postprocedural myocardial infarction and stent thrombosis, confirming the mechanistic hypothesis that P2Y12-receptor signaling is a major component of pathophysiological thrombus formation in patients with ACS treated with PCI. In turn, however, platelet function testing has added uncertainty because if platelet reactivity among patients while receiving treatment (“on-treatment” reactivity) is a measure of the risk of future events, then the comparative benefit of the newer, more expensive P2Y12 antagonists may uniquely depend on the magnitude of the effect of clopidogrel in a particular individual (however, different drugs may differentially affect the P2Y12 site. This concept of selective intensive antiplatelet therapy based on a measured drug effect, which has not been proven in a definitive, randomized trial, has provoked intense debate in the cardiology community. Although substantial data indirectly support the validity of the platelet function testing hypothesis, randomized trials to date have been limited by insufficient power, insufficient pharmacodynamic intervention, and potential selection bias for low-risk patients. Platelet function testing was not systematically performed in the trial that demonstrated the superiority of prasugrel over clopidogrel in patients with ACS treated with PCI. It is therefore speculative whether the benefit of prasugrel could be greatest in patients who demonstrate the least drug effect while receiving clopidogrel or could be minimal in patients treated with clopidogrel who display a potent drug effect. In this issue of JAMA, Gurbel and colleagues report the results of the platelet function substudy of the Targeted Platelet Inhibition to Clarify the Optimal Strategy to Medically Manage Acute Coronary Syndromes (TRILOGY ACS) trial, which included 2564 patients, approximately 28% of those enrolled in the overall trial. In the overall trial, prasugrel was not superior to clopidogrel in reducing recurrent cardiovascular events in medically managed patients with ACS who were not intended to undergo revascularization. In the current study, the investigators measured on-treatment reactivity at several time points over the course of follow-up using the VerifyNow P2Y12 test, which has been previously shown to reliably measure the P2Y12 effect of clopidogrel and prasugrel as well as correlate with active metabolite exposure of both drugs. The goals of the platelet function substudy were 2-fold: to confirm that prasugrel at the doses used provided a greater drug effect (ie, lower on-treatment reactivity) than clopidogrel and to determine whether there was an association between the achieved level of reactivity over time and clinical outcomes, irrespective of study drug assignment. At all time points tested, patients randomly assigned to receive 10 mg of prasugrel (or 5-mg prasugrel if aged 75 years or weight 60 kg) displayed significantly lower levels of on-treatment reactivity than those

Manipulating brain connectivity with δ9-tetrahydrocannabinol: A pharmacological resting state FMRI study

Resting state-functional magnetic resonance imaging (RS-FMRI) is a neuroimaging technique that allows repeated assessments of functional connectivity in resting state. While task-related FMRI is limited to indirectly measured drug effects in areas affected by the task, resting state can show direct CNS effects across all brain networks. Hence, RS-FMRI could be an objective measure for compounds affecting the CNS. Several studies on the effects of cannabinoid receptor type 1 (CB(1))-receptor agonist δ(9)-tetrahydrocannabinol (THC) on task-dependent FMRI have been performed. However, no studies on the effects of cannabinoids on resting state networks using RS-FMRI have been published. Therefore, we investigated the effects of THC on functional brain connectivity using RS-FMRI. Twelve healthy volunteers (9 male, 3 female) inhaled 2, 6 and 6 mg THC or placebo with 90-minute intervals in a randomized, double blind, cross-over trial. Eight RS-FMRI scans of 8 min were obtained per occasion. Subjects rated subjective psychedelic effects on a visual analog scale after each scan, as pharmacodynamic effect measures. Drug-induced effects on functional connectivity were examined using dual regression with FSL software (FMRIB Analysis Group, Oxford). Eight maps of voxel-wise connectivity throughout the entire brain were provided per RS-FMRI series with eight predefined resting-state networks of interest. These maps were used in a mixed effects model group analysis to determine brain regions with a statistically significant drug-by-time interaction. Statistical images were cluster-corrected, and results were Bonferroni-corrected across multiple contrasts. THC administration increased functional connectivity in the sensorimotor network, and was associated with dissociable lateralized connectivity changes in the right and left dorsal visual stream networks. The brain regions showing connectivity changes included the cerebellum and dorsal frontal cortical regions. Clear increases were found for feeling high, external perception, heart rate and cortisol, whereas prolactin decreased. This study shows that THC induces both increases and (to a lesser extent) decreases in functional brain connectivity, mainly in brain regions with high densities of CB(1)-receptors. Some of the involved regions could be functionally related to robust THC-induced CNS-effects that have been found in previous studies (Zuurman et al., 2008), such as postural stability, feeling high and altered time perception.

Abstract 3763: Treatment of soft tissue sarcoma cells by EGFR and/or STAT3 inhibitors

Abstract Background: We previously found Epidermal Growth Factor Receptor (EGFR) inhibitor can block liposarcoma cell EGFR (HER1) survival signalling. However, it did not interfere with HER2 regulated Janus Kinases (JAK), and Signal Transducer and Activator of Transcription (STAT) signal transduction. Our research suggested JAK/STAT may be one mechanism for EGFR inhibitor resistance. Targeting both EGFR and STAT3, which has never been tested in sarcoma may overcome this problem. The principal aim of this preliminary study was to investigate the effect and mechanism of both STAT3 inhibitor alone and in combination with EGFR inhibitor in the treatment of soft tissue sarcoma (STS) cell lines. Methods: STAT3 inhibitor (S3I-201) mono-therapy or in combination with EGFR inhibitor Gefitinib was investigated in 7 STS cell lines (449b, 778, SW872, SW684, SW982, GCT and HT1080). Crystal-violet colorimetric and clonogenic assays were used to measure drug effects. For assessing a potential role of treatment, we investigated expression and activity of STAT and EGFR by Western blot and immunohistochemistry staining before and after treatment. Data were analysed using Chou &amp; Talalay method and CalcuSyn software. Results: All 7 STS cell lines expressed phosphorylated/total STAT3 and EGFR. Anti-proliferative and anti-clonogenic effects of S3I-201 monotherapy on STS were dose- and time-dependent. Sensitive cells to S3I-201 (IC50 Δ50μM) were HT1080, SW684, GCT and SW982 (90% HT1080 were inhibited at day 3 post-administration of 25μM drug), partially sensitive cells were 449B and 778, and non-sensitive cells (IC50 ≤ 200μM) were SW872 (only 29% SW872 were inhibited at day 5 with 200μM S3I-201). Western blot analysis of whole-cell lysates from HT1080 showed phosphorylated STAT3 (pSTAT3) levels were significantly diminished after S3I-201 treatment, whereas pSTAT3 were not down-regulated in resistant cells SW872. IC50 of Gefitinib monotherapy on STS were 20 - 40μM, and 778 had minor effect (33% cells were inhibited after 5 days treatment). Combination therapy with Gefitinib and S3I-201 achieved synergistic antiproliferative effect (mean CIs &amp;lt; 0.90) in 6/7 STS cell lines (CI: 449b (0.3-1), 778 (0.1-0.2), SW872 (0.6-0.7), SW684 (0.2-0.5), GCT (0.3-0.4) and HT1080 (0.5-0.6)), except SW982 (1-1.2). For the most synergistic 778 cells, the drug reduction index for Gefitinib and S3I-201 was 5.9 and 12.7. Although treatment with Gefitinib alone inhibited pSTAT3 expression on serum-starved 778, EGF stimulation reversed the inhibition function. However in combination therapy, STAT3 phosphorylation was not induced by EGF stimulation. Conclusion: Combination therapy targeting both EGFR and STAT3 is a worthwhile treatment to pursue in anti-sarcoma therapy. Further studies will focus on potential mechanisms as well as the anti-sarcoma effect in the animal models. These results will have a clinical implication in treatment of STS in the future. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3763. doi:1538-7445.AM2012-3763

Simultaneous measurement of extracellular dopamine and dopamine transporter occupancy by cocaine analogs in squirrel monkeys

Several classes of drugs bind to the dopamine transporter (DAT) with high affinity, but some are weaker positive reinforcers than cocaine, suggesting that affinity for and occupancy of the DAT is not the only determinant of a drug's reinforcing effectiveness. Other factors such as the rate of onset have been positively and strongly correlated with the reinforcing effects of DAT inhibitors in nonhuman primates. In the current studies, we examined the effects of acute systemic administration of cocaine and three cocaine analogs (RTI-150, RTI-177, and RTI-366) on binding to DAT in squirrel monkey brain using positron emission tomography (PET) neuroimaging. During the PET scan, we also measured drug effects on dopamine (DA) levels in the caudate using in vivo microdialysis. In general, our results suggest a lack of concordance between drug occupancy at DAT and changes in DA levels. These studies also indicate that acute cocaine administration decreases the availability of plasma membrane DAT for binding, even after cocaine is no longer blocking DA uptake as evidence by a return to basal DA levels.

Electroencephalogram-based pharmacodynamic measures: a review.

Pharmacokinetics and pharmacodynamics can provide a useful modeling framework for predicting drug activity and can serve as a basis for dose optimization. Determining a suitable biomarker or surrogate measure of drug effect for pharmacodynamic models can be challenging. The electroencephalograph is a widely-available and non-invasive tool for recording brain-wave activity simultaneously from multiple brain regions. Certain drug classes (such as drugs that act on the central nervous system) also generate a reproducible electroencephalogram (EEG) effect. Characterization of such a drug-induced EEG effect can produce pharmacokinetic/pharmacodynamic models useful for titrating drug levels and expediting development of chemically-similar drug analogs. This paper reviews the relevant concepts involved in pharmacokinetic/pharmacodynamic modeling using EEG-based pharmacodynamic measures. In addition, examples of such models for various drugs are organized by drug activity as well as chemical structure and presented.

Effects of cold pressor pain on the abuse liability of intranasal oxycodone in male and female prescription opioid abusers

BackgroundApproximately 1.9 million persons in the U.S. have prescription opioid use disorders often with concomitant bodily pain, but systematic data on the impact of pain on abuse liability of opioids is lacking. The purpose of this study was to determine whether pain alters the intranasal abuse liability of oxycodone, a commonly prescribed and abused analgesic, in males and females. MethodsSporadic prescription opioid abusers (10 females, 10 males) participated in this mixed (between and within-subject), randomized inpatient study. Experimental sessions (n=6) tested intranasal placebo, oxycodone 15 or 30mg/70kg during cold pressor testing (CPT) and a warm water control. Observer- and subject-rated drug effect measures, analgesia, physiologic and cognitive effects were assessed. ResultsThe CPT significantly increased blood pressure, heart rate, pain, stress, and “opiate desire” compared to the no-pain control but did not alter opioid liking, high or street value. Intranasal oxycodone produced effects within 10min, significantly decreasing pain and significantly increasing subjective measures of abuse liability (e.g., high). Females had higher ratings of street value, high, and liking for one or both active doses. ConclusionsThe CPT was a reliably painful and stressful stimulus that did not diminish the abuse liability of intranasal oxycodone. Females were more sensitive to oxycodone on several abuse liability measures that warrant further follow-up. Snorting oxycodone rapidly produced psychoactive effects indicative of substantial abuse liability.

Pharmacokinetics and pharmacodynamics – is there anything new?

Pharmacokinetics and pharmacodynamics – is there anything new?

Progesterone effects on the discriminative stimulus, subjective and performance effects of triazolam in healthy, premenopausal women.

There is accumulating evidence that sex plays a critical role in drug abuse. Female sex hormones have been shown to affect central nervous system function and modulate the effects of drugs of abuse. For example, γ-aminobutyric acid type A (GABA(A)) receptor function is positively modulated by progesterone metabolites. There is evidence from preclinical in-vitro and in-vivo studies as well as some clinical research suggesting that progesterone and its metabolites may enhance the behavioral effects of benzodiazepines, which also serve as positive modulators of GABA(A) receptors. The purpose of this experiment was to determine the independent and combined discriminative stimulus, subjective and psychomotor effects of progesterone and triazolam in healthy adult premenopausal women. Oral micronized progesterone (100 mg), triazolam (0.06, 0.12 and 0.25 mg/70 kg) and placebo were administered to healthy, premenopausal women (n=9) under conditions of low circulating sex hormones. Triazolam alone functioned as a discriminative stimulus and produced prototypical sedative-like effects (e.g., performance impairment, enhanced reports of sedative effects). Progesterone alone produced sedative-like effects on several subjective and performance measures, and the dose combination effects of progesterone and triazolam on several subjective measures of drug effect were similar to the summation of the two drug effects in isolation. Progesterone did not substitute for or modify the discriminative stimulus effects of triazolam. These results suggest that the parent hormone, progesterone, and triazolam have discordant neuropharmacological mechanisms of action. Additional research is necessary to determine the degree to which neurosteroids influence sex differences in benzodiazepine use and abuse.

Measuring drug effects on exercise endurance under extreme environmental conditions in rats using motorized wheels

ObjectivesExercise capacity in laboratory animals is typically measured using treadmills which require large spatial allocation and have poor habituation efficacy, making it unsuitable for high throughput application. We present a novel rat exercise system involving motorized rodent wheels that has high habituation efficiency, and due to small spatial allocation allows for high throughput experimentation.MethodsFemale Sprague Dawley rats were habituated to maintain position in motorized wheels at low speed for 10 min daily. Wheel speed was increased incrementally over 10 days. On testing days, animals received i.p. injections of nifedipine (40 mpk), or iron sucrose (5 x 1 mpk daily) or vehicle. Animals were then exposed to escalating exercise burden under hypoxia. Exhaust signs included sliding, hanging, tail position, and time until self motivated movement after removal from wheel.Results&gt;90% of rats ran proficiently within 10 days of habituation. Nifedipine significantly decreased time run to exhaust. Iron sucrose on the other hand significantly enhanced exercise performance under hypoxia vs. control.ConclusionWe established a novel, ergonomic, and efficient system to measure exercise capacity in rats under hypoxia for high throughput experimentation. This system has application in various disciplines, including exercise physiology, environmental medicine, and drug development.

145 Novel Immunoassay for Therapeutic Drug Monitoring of mTOR-Inhibitors after Heart and Lung Transplantation

Therapeutic drug monitoring (TDM) of immunosuppressive drugs after transplantation like the mTOR-inhibitors sirolimus (SRL) or everolimus (ERL) is based on measuring blood levels alone. But this often results in under- or over-immunosuppression leading to rejection or infection, respectively. Earlier studies have shown the potential value of measuring pharmacodynamic drug effects for TDM. Therefore we developed an assay to measure drug effects on the mTOR-pathway.