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Purpose: There are many phase I trials of oncology drug combinations, very few of which report clinically significant pharmacokinetic interactions. We hypothesized that the utility of such pharmacokinetic drug–drug interaction (DDI) studies is low in the absence of a mechanistic hypothesis.Experimental Design: We retrospectively reviewed 152 phase I (two drug) combination studies published between 2007 and 2011.Results: Only 28 (18%) studies had an implicit or explicit rationale, either inhibition/induction of a drug-metabolizing enzyme or transporter, cosubstrates for the same enzyme or transporter, potential for end-organ toxicity, or protein binding. Only 12 (8%) studies demonstrated a statistically significant DDI, on the basis of change in clearance (or area under the curve) of parent drug and/or active metabolite. There was a strong association between a rationale and a demonstrable drug interaction, as only 2% of studies without a rationale demonstrated a DDI, compared with 32% of studies with a rationale (Fisher exact test; P < 10−6).Conclusion: DDI studies should not be routinely performed as part of phase I trials of oncology combinations. Clin Cancer Res; 19(21); 6039–43. ©2013 AACR.

PDF file - 134K, Table S1. Data collection form. Table S2. Collected data.

Objective To evaluate the efficacy of fremanezumab in patients with chronic migraine (CM) and moderate to severe depression. Background Fremanezumab, a fully humanized monoclonal antibody that selectively targets calcitonin gene–related peptide, has been approved for the preventive treatment of migraine in adults. CM and depression are highly comorbid. Methods The 12‐week, Phase 3 HALO trial randomized patients with CM to fremanezumab quarterly (675 mg/placebo/placebo), fremanezumab monthly (675/225/225 mg), or placebo. Post hoc analyses evaluated the effects of fremanezumab in patients with moderate to severe depression (baseline 9‐item Patient Health Questionnaire sum score ≥10) on monthly number of headache days of at least moderate severity; monthly migraine days; Patient Global Impression of Change (PGIC); 6‐item Headache Impact Test (HIT‐6) scores; and depression. Results For the 219/1121 (19.5%) patients with moderate to severe depression at baseline, fremanezumab was associated with a significant reduction in monthly number of headache days of at least moderate severity for active treatment versus placebo (least‐squares mean change ± standard error for quarterly dosing: −5.3 ± 0.77; for monthly dosing: −5.5 ± 0.72; and for placebo: −2.2 ± 0.81; both p

Background Fremanezumab, a fully humanized monoclonal antibody (mAb; IgG2Δa) that selectively targets calcitonin gene-related peptide (CGRP), is approved for the preventive treatment of migraine in adults. The efficacy and safety of fremanezumab for migraine prevention have been demonstrated in randomized, double-blind, placebo-controlled trials. Real-world effectiveness data are needed to complement clinical trial data. This study assessed the effectiveness of fremanezumab across different subgroups of adult patients with episodic migraine (EM), chronic migraine (CM), or difficult-to-treat (DTT) migraine in real-world clinical settings. Methods This retrospective, panel-based online chart review used electronic case report forms. Patient inclusion criteria were a physician diagnosis of EM or CM; age ≥ 18 years at the time of first fremanezumab initiation; ≥ 1 dose of fremanezumab treatment; ≥ 1 follow-up visit since first initiation; and ≥ 2 measurements of monthly migraine days (MMD; with 1 within a month before or at first initiation and ≥ 1 after first initiation). Changes in MMD and monthly headache days were assessed during the follow-up period. These endpoints were evaluated in subgroups of patients by migraine type (EM/CM) and in subgroups with DTT migraine (diagnosis of medication overuse [MO], major depressive disorder [MDD], generalized anxiety disorder [GAD], or prior exposure to a different CGRP pathway–targeted mAb [CGRP mAb]). Results Data were collected from 421 clinicians and 1003 patients. Mean (percent) reductions from baseline in MMD at Month 6 were − 7.7 (77.0%) in EM patients, − 10.1 (68.7%) in CM patients, − 10.8 (80.6%) in the MO subgroup, − 9.9 (68.3%) in the MDD subgroup, − 9.5 (66.4%) in the GAD subgroup, and − 9.0 (68.7%) in the prior CGRP mAb exposure subgroup. Improvements in MDD or GAD severity were reported by 45.5% and 45.8% of patients with comorbid MDD or GAD, respectively. Conclusions In this real-world study, fremanezumab demonstrated effectiveness for migraine regardless of migraine type or the presence of factors contributing to DTT migraine (MO, GAD, MDD, or prior exposure to a different CGRP mAb).

Migraine is a highly disabling and often chronic neurological disease that affects more than one billion people globally. Preventive migraine treatment is recommended for individuals who have frequent and/or disabling attacks; however, many of the medications used for migraine prevention (e.g., antiepileptics, antidepressants, antihypertensives) were not specifically developed for migraine, and often have limited efficacy or poor tolerability. Four monoclonal antibodies targeting the calcitonin gene-related peptide (CGRP) pathway, which is believed to play a crucial role in the pathophysiology of migraine, have been approved by the US Food and Drug Administration for the preventive treatment of migraine in adults. All four migraine-specific treatments have demonstrated efficacy based on reductions in monthly days with migraine for patients with both episodic and chronic migraine, including those with comorbidities. They have also demonstrated favorable safety and tolerability profiles. Based on these accounts, CGRP pathway-targeted monoclonal antibodies have the potential to revolutionize preventive treatment for patients with migraine.

Objective To evaluate whether quarterly or monthly administration of fremanezumab for migraine prevention exhibits a pattern of decreased efficacy toward the end of the dosing interval (wearing-off effect). Background The main goals of migraine preventive treatment are to reduce the frequency, severity, and duration of migraine attacks, and migraine-associated disability. Wearing-off refers to the phenomenon whereby clinical symptoms return or worsen before the next dose of a drug is due and has been reported previously with migraine preventive medications. Design and methods This was a long-term, 12-month, multicenter, randomized, double-blind, parallel-group phase 3 study (NCT02638103) that included chronic (CM) and episodic migraine (EM) patients who rolled over from the 12-week phase 3 HALO CM (NCT02621931) and EM trials (NCT02629861), as well as an additional subset of 312 new patients. Patients with CM or EM received fremanezumab either monthly or quarterly. In this post hoc analysis, for selected months, the difference in the average number of migraine days between weeks 1-2 and weeks 3-4, between weeks 1-3 and week 4, and between weeks 1-2 and weeks 11-12 were calculated. Results A total of 1890 patients (CM, 1110; EM, 780) were enrolled. At months 3, 6, 9, and 15, there were no substantial differences in mean weekly migraine days between weeks 1-2 and weeks 3-4 or between weeks 1-3 and week 4 with quarterly or monthly fremanezumab in the CM or EM subgroups. There were no substantial increases in mean weekly migraine days between weeks 1-2 and weeks 11-12 during the first quarter of treatment (months 1-3) or the second quarter of treatment (months 4-6) with quarterly or monthly fremanezumab in the CM or EM subgroups. Across both dosing subgroups in CM and EM patients, the mean weekly number of migraine days decreased substantially (30%-42%) during the first 2 weeks; decreases in weekly migraine days remained steady during the last 2 weeks of the first quarter, with a similar maintenance of response during the second quarter. Conclusions This analysis of data from a long-term, phase 3 study showed that patients receiving quarterly fremanezumab or monthly fremanezumab did not experience a wearing-off effect toward the end of the dosing interval.

Fremanezumab, a fully humanized monoclonal antibody (IgG2Δa) that selectively targets calcitonin-gene-related peptide, has demonstrated efficacy as a preventive treatment for adults with episodic migraine or chronic migraine and inadequate response to two to four prior preventive treatment classes in the phase 3b FOCUS study. In this post hoc analysis, efficacy and effects on quality-of-life outcomes for fremanezumab were evaluated in subgroups of patients with and without aura or similar neurological symptoms, here referred to as migraine with or without associated neurological dysfunction.In the FOCUS study, 838 patients were randomized (1:1:1) to quarterly fremanezumab, monthly fremanezumab or matched placebo for 12 weeks of double-blind treatment. For this post hoc analysis, subgroups of patients with migraine with and without associated neurological dysfunction at baseline were identified based on patient response to questions about symptoms.In patients with migraine with associated neurological dysfunction at baseline, fremanezumab significantly reduced monthly average days with neurological symptoms (quarterly, -1.7 days; monthly, -1.8 days) compared to placebo (-0.5 days; both p ≤ 0.01). In comparison with placebo, both dosing regimens of fremanezumab yielded greater reductions in monthly migraine days over 12 weeks (p 0.0001) and improvements in Headache Impact Test 6 and Migraine-Specific Quality of Life scores over the last 4 weeks (p 0.05), regardless of neurological dysfunction at baseline.Fremanezumab reduced days with neurological symptoms, effectively prevented migraine, and improved quality of life in patients with migraine with associated neurological dysfunction, including those with previous inadequate response to two to four migraine preventive medication classes.

Background We evaluated the efficacy of fremanezumab, a fully humanized monoclonal antibody that selectively targets calcitonin gene-related peptide, in patients with chronic migraine (CM) with and without medication overuse (MO). Methods In a 12-week, phase 3 trial, patients with CM were randomized to fremanezumab quarterly (675 mg/placebo/placebo), monthly (675 mg/225 mg/225 mg), or placebo. Post hoc analyses assessed the impact of fremanezumab in patients with and without MO (monthly use of acute headache medication ≥15 days, migraine-specific acute medication ≥10 days, or combination medication ≥10 days) on efficacy outcomes, including headache days of at least moderate severity (HDs), and six-item Headache Impact Test (HIT-6) and Migraine-Specific Quality of Life (MSQoL) questionnaire scores. Results Of 1130 patients enrolled, 587 (51.9%) had baseline MO. Fremanezumab reduced placebo-adjusted least-squares mean (95% confidence interval) monthly HDs (− 2.2 [− 3.1 to − 1.2] and − 2.7 [− 3.7 to − 1.8]; P P = 0.0026; monthly − 1.4 [− 2.3 to − 0.6], P = 0.0017). Significantly more fremanezumab-treated patients had ≥ 50% reduction in HDs versus placebo, regardless of baseline MO (with: quarterly 70/201 [34.8%], monthly 78/198 [39.4%] vs placebo 26/188 [13.8%]; without: quarterly 71/174 [40.8%], monthly 75/177 [42.4%] vs placebo 41/183 [22.4%]). Fremanezumab improved HIT-6 and MSQoL scores. Significantly more fremanezumab-treated patients reverted to no MO (quarterly 111/201 [55.2%], monthly 120/198 [60.6%]) versus placebo (87/188 [46.3%]). Conclusions Fremanezumab is effective for prevention of migraine in patients with CM, regardless of MO, and demonstrated a benefit over placebo in reducing MO. Trial registration ClinicalTrials.gov NCT02621931 (HALO CM), registered December 12, 2012.

The sigma-2 receptor has been cloned and identified as Tmem97, which is a transmembrane protein involved in intracellular Ca2+ regulation and cholesterol homeostasis. Since its discovery, the sigma-2 receptor has been an extremely controversial target, and many efforts have been made to elucidate the functional role of this receptor during physiological and pathological conditions. Recently, this receptor has been proposed as a potential target to treat neuropathic pain due to the ability of sigma-2 receptor agonists to relieve mechanical hyperalgesia in mice model of chronic pain. In the present work, we developed a highly selective sigma-2 receptor ligand (sigma-1/sigma-2 selectivity ratio > 1000), 1-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-3-methyl-1H- benzo[d]imidazol-2(3H)-one (CM398), with an encouraging in vitro and in vivo pharmacological profile in rodents. In particular, radioligand binding studies demonstrated that CM398 had preferential affinity for sigma-2 receptor compared with sigma-1 receptor and at least four other neurotransmitter receptors sites, including the norepinephrine transporter. Following oral administration, CM398 showed rapid absorption and peak plasma concentration (Cmax) occurred within 10 min of dosing. Moreover, the compound showed adequate, absolute oral bioavailability of 29.0%. Finally, CM398 showed promising anti-inflammatory analgesic effects in the formalin model of inflammatory pain in mice. The results collected in this study provide more evidence that selective sigma-2 receptor ligands can be useful tools in the development of novel pain therapeutics and altogether, these data suggest that CM398 is a suitable lead candidate for further evaluation.

1. Aprepitant, an oral antiemetic, commonly used in the prevention of chemotherapy-induced nausea and vomiting, is primarily metabolized by CYP3A4. Aprepitant glucuronidation has yet to be evaluated in humans. The contribution of human UDP-glucuronosyltransferase (UGT) isoforms to the metabolism of aprepitant was investigated by performing kinetic studies, inhibition studies and correlation analyses. In addition, aprepitant was evaluated as an inhibitor of UGTs. 2. Glucuronidation of aprepitant was catalyzed by UGT1A4 (82%), UGT1A3 (12%) and UGT1A8 (6%) and Kms were 161.6 ± 15.6, 69.4 ± 1.9 and 197.1 ± 28.2 µM, respectively. Aprepitant glucuronidation was significantly correlated with both UGT1A4 substrates anastrazole and imipramine (rs = 0.77, p

1. There is limited knowledge regarding the metabolism of megestrol acetate (MA), as it was approved by FDA in 1971, prior to the availability of modern tools for identifying specific drug-metabolizing enzymes. We determined the cytochrome P450s (P450s) and UDP-glucuronosyltransferases (UGTs) that metabolize MA, identified oxidative metabolites and determined pharmacologic activity at the progesterone, androgen and glucocorticoid receptors (PR, AR and GR, respectively). 2. Oxidative metabolites were produced using human liver microsomes (HLMs), and isolated for mass spectral (MS) and nuclear magnetic resonance (NMR) analyses. We screened recombinant P450s using MA at 62 μM (HLM Km for metabolite 1; M1) and 28 μM (HLM Km for metabolite 2; M2). UGT isoforms were simultaneously incubated with UDPGA, nicotinamide adenine dinucleotide phosphate (NADPH), CYP3A4 and MA. Metabolites were evaluated for pharmacologic activity on the PR, AR and GR. CYP3A4 and CYP3A5 are responsible for oxidative metabolism of 62 μM MA. 3. At 28 μM substrate concentration, CYP3A4 was the only contributing enzyme. Mass spectral and NMR data suggest metabolism of MA to two alcohols. After oxidation, MA is converted into two secondary glucuronides by UGT2B17 among other UGTs. MA, M1 and M2 had significant pharmacologic activity on the PR while only MA showed activity on the AR and GR.

A series of ring-constrained phenylpropyloxyethylamines, partial opioid structure analogs and derivatives of a previously studied sigma (σ) receptor ligand, was synthesized and evaluated at σ and opioid receptors for receptor selectivity. The results of this study identified several compounds with nanomolar affinity at both σ receptor subtypes. Compounds 6 and 9 had the highest selectivity for both σ receptor subtypes, compared to μ opioid receptors. In addition, compounds 6 and 9 significantly reduced the convulsive effects of cocaine in mice, which would be consistent with antagonism of σ receptors.

Methamphetamine is a highly addictive psychostimulant drug of abuse, causing hyperthermia and neurotoxicity at high doses. Currently, there is no clinically proven pharmacotherapy to treat these effects of methamphetamine, necessitating identification of potential novel therapeutic targets. Earlier studies showed that methamphetamine binds to sigma ( σ ) receptors in the brain at physiologically relevant concentrations, where it “acts in part as an agonist.” SN79 (6-acetyl-3-(4-(4-(4-florophenyl)piperazin-1-yl)butyl)benzo[ d ]oxazol-2( 3H )-one) was synthesized as a putative σ receptor antagonist with nanomolar affinity and selectivity for σ receptors over 57 other binding sites. SN79 pretreatment afforded protection against methamphetamine-induced hyperthermia and striatal dopaminergic and serotonergic neurotoxicity in male, Swiss Webster mice (measured as depletions in striatal dopamine and serotonin levels, and reductions in striatal dopamine and serotonin transporter expression levels). In contrast, di-o-tolylguanidine (DTG), a well established σ receptor agonist, increased the lethal effects of methamphetamine, although it did not further exacerbate methamphetamine-induced hyperthermia. Together, the data implicate σ receptors in the direct modulation of some effects of methamphetamine such as lethality, while having a modulatory role which can mitigate other methamphetamine-induced effects such as hyperthermia and neurotoxicity.

Background Methamphetamine (METH) causes hyperthermia and dopaminergic neurotoxicity in the rodent striatum. METH interacts with σ receptors and σ receptor antagonists normally mitigate METH-induced hyperthermia and dopaminergic neurotoxicity. The present study was undertaken because in two experiments, pretreatment with σ receptor antagonists failed to attenuate METHinduced hyperthermia in mice. This allowed us to determine whether the ability of σ receptor antagonists (AZ66 and AC927) to mitigate METH-induced neurotoxicity depends upon their ability to modulate METH-induced hyperthermia. Methods Mice were treated using a repeated dosing paradigm and body temperatures recorded. Striatal dopamine was measured one week post-treatment. Results The data indicate that the ability of σ receptor antagonists to attenuate METH-induced dopaminergic neurotoxicity is linked to their ability to block METH-induced hyperthermia. Conclusion The ability of σ receptor antagonists to mitigate METH-induced hyperthermia may contribute to its neuroprotective actions.

Currently, the only Food and Drug Administration-approved treatment of acute stroke is recombinant tissue plasminogen activator, which must be administered within 6 hours after stroke onset. The pan-selective σ-receptor agonist N,N'-di-o-tolyl-guanidine (o-DTG) has been shown to reduce infarct volume in rats after middle cerebral artery occlusion, even when administered 24 hours after stroke. DTG derivatives were synthesized to develop novel compounds with greater potency than o-DTG. Fluorometric Ca(2+) imaging was used in cultured cortical neurons to screen compounds for their capacity to reduce ischemia- and acidosis-evoked cytosolic Ca(2+) overload, which has been linked to stroke-induced neurodegeneration. In both assays, migration of the methyl moiety produced no significant differences, but removal of the group increased potency of the compound for inhibiting acidosis-induced [Ca(2+)](i) elevations. Chloro and bromo substitution of the methyl moiety in the meta and para positions increased potency by ≤160%, but fluoro substitutions had no effect. The most potent DTG derivative tested was N,N'-di-p-bromo-phenyl-guanidine (p-BrDPhG), which had an IC(50) of 2.2 µM in the ischemia assay, compared with 74.7 μM for o-DTG. Microglial migration assays also showed that p-BrDPhG is more potent than o-DTG in this marker for microglial activation, which is also linked to neuronal injury after stroke. Radioligand binding studies showed that p-BrDPhG is a pan-selective σ ligand. Experiments using the σ-1 receptor-selective antagonist 1-[2-(3,4-dichlorophenyl)ethyl]-4-methylpiperazine dihydrochloride (BD-1063) demonstrated that p-BrDPhG blocks Ca(2+) overload via σ-1 receptor activation. The study identified four compounds that may be more effective than o-DTG for the treatment of ischemic stroke at delayed time points.

Object Despite the role of aging in development of neurological and neurodegenerative diseases, the effects of age are often disregarded in experimental design of preclinical studies. Functional assessment increases the clinical relevance of animal models of neurological disease and adds value beyond traditional histological measures. However, the relationship between age and functional impairment has not been systematically assessed through a battery of functional tests. Methods In this study, various sensorimotor and behavioral tests were used to evaluate effects of aging on functional performance in naive animals. Sensorimotor measures included locomotor activity; Rotarod, inclined plane, and grip-strength testing; and modified Neurological Severity Score. The Morris water maze was used to examine differences in learning and memory, and the elevated plus maze and forced swim test were used to assess anxiety-like and depressive-like behaviors, respectively. Results Older Sprague-Dawley rats (18–20 months) were found to perform significantly worse on the inclined plane tests, and they exhibited alterations in elevated-plus maze and forced swim test compared with young adult rats (3–4 months). Specifically, older rats exhibited reduced exploration of open arms in elevated plus maze and higher immobility time in forced swim test. Spatial acquisition and reference memory were diminished in older rats compared with those in young adult rats. Conclusions This study demonstrates clear differences between naive young adult and older animals, which may have implications in functional assessment for preclinical models of neurological disease.

Methamphetamine is currently one of the most widely abused drugs worldwide, with hyperthermia being a leading cause of death in methamphetamine overdose situations. Methamphetamine-induced hyperthermia involves a variety of cellular mechanisms, including increases in hypothalamic interleukin-1 beta (IL-1β) expression. Methamphetamine also interacts with sigma receptors and previous studies have shown that sigma receptor antagonists mitigate many of the behavioral and physiological effects of methamphetamine, including hyperthermia. The purpose of the current study was to determine if the attenuation of methamphetamine-induced hyperthermia by the sigma receptor antagonists, AZ66 and SN79, is associated with a concomitant attenuation of IL-1β mRNA expression, particularly in the hypothalamus. Methamphetamine produced dose- and time-dependent increases in core body temperature and IL-1β mRNA expression in the hypothalamus, striatum, and cortex in male, Swiss Webster mice. Pretreatment with the sigma receptor antagonists, AZ66 and SN79, significantly attenuated methamphetamine-induced hyperthermia, but further potentiated IL-1β mRNA in the mouse hypothalamus when compared to animals treated with methamphetamine alone. These findings suggest sigma receptor antagonists attenuate methamphetamine-induced hyperthermia through a different mechanism from that involved in the modulation of hypothalamic IL-1β mRNA expression.

Ketamine is an NMDA antagonist and dissociative anesthetic that has been shown to display rapid acting and prolonged antidepressant activity in small-scale human clinical trials. Ketamine also binds to σ receptors, which are believed to be protein targets for a potential new class of antidepressant medications. The purpose of this study was to determine the involvement of σ receptors in the antidepressant-like actions of ketamine. Competition binding assays were performed to assess the affinity of ketamine for σ 1 and σ 2 receptors. The antidepressant-like effects of ketamine were assessed in vitro using a neurite outgrowth model and PC12 cells, and in vivo using the forced swim test. The σ receptor antagonists, NE-100 and BD1047, were evaluated in conjunction with ketamine in these assays to determine the involvement of σ receptors in the antidepressant-like effects of ketamine. Ketamine bound to both σ 1 and σ 2 receptors with μM affinities. Additionally, ketamine potentiated NGF-induced neurite outgrowth in PC12 cells and this effect was attenuated in the presence of NE-100. Ketamine also displayed antidepressant-like effects in the forced swim test; however, these effects were not attenuated by pretreatment with NE-100 or BD1047. Taken together, these data suggest that σ receptor-mediated neuronal remodeling may contribute to the antidepressant effects of ketamine.

Reports of methamphetamine-related emergency room visits suggest that elevated body temperature is a universal presenting symptom, with lethal overdoses generally associated with extreme hyperthermia. This review summarizes the available information on methamphetamine toxicity as it pertains to elevations in body temperature. First, a brief overview of thermoregulatory mechanisms is presented. Next, central and peripheral targets that have been considered for potential involvement in methamphetamine hyperthermia are discussed. Finally, future areas of investigation are proposed, as further studies are needed to provide greater insight into the mechanisms that mediate the alterations in body temperature elicited by methamphetamine.

Understanding drug metabolism is essential for identifying drug–drug interactions (DDIs). As new data concerning a drug's pharmacokinetics arise, updates to drug labels and administration procedures should rapidly follow. However, the US Food and Drug Administration (FDA) has inconsistently updated drug labels, based on new research findings (i.e., in peer-reviewed publications). In this Commentary, we highlight recent findings on the metabolism of imatinib and argue for a more stringent protocol for updating drug labels. Clinical Pharmacology & Therapeutics (2013); 94 3, 302–304. doi:10.1038/clpt.2013.109

Despite the role of aging in development of neurological and neurodegenerative diseases, the effects of age are often disregarded in experimental design of preclinical studies. Functional assessment increases the clinical relevance of animal models of neurological disease and adds value beyond traditional histological measures. However, the relationship between age and functional impairment has not been systematically assessed through a battery of functional tests.In this study, various sensorimotor and behavioral tests were used to evaluate effects of aging on functional performance in naive animals. Sensorimotor measures included locomotor activity; Rotarod, inclined plane, and grip-strength testing; and modified Neurological Severity Score. The Morris water maze was used to examine differences in learning and memory, and the elevated plus maze and forced swim test were used to assess anxiety-like and depressive-like behaviors, respectively.Older Sprague-Dawley rats (18-20 months) were found to perform significantly worse on the inclined plane tests, and they exhibited alterations in elevated-plus maze and forced swim test compared with young adult rats (3-4 months). Specifically, older rats exhibited reduced exploration of open arms in elevated plus maze and higher immobility time in forced swim test. Spatial acquisition and reference memory were diminished in older rats compared with those in young adult rats.This study demonstrates clear differences between naive young adult and older animals, which may have implications in functional assessment for preclinical models of neurological disease.

Methamphetamine interacts with sigma receptors at physiologically relevant concentrations suggesting a potential site for pharmacologic intervention. In the present study, a previous sigma receptor ligand, CM156, was optimized for metabolic stability, and the lead analog was evaluated against the behavioral effects of methamphetamine. Radioligand binding studies demonstrated that the lead analog, AZ66, displayed high nanomolar affinity for both sigma-1 and sigma-2 receptors (2.4 ± 0.63 and 0.51 ± 0.15, respectively). In addition, AZ66 had preferential affinity for sigma receptors compared to seven other sites and a significantly longer half-life than its predecessor, CM156, in vitro and in vivo. Pretreatment of male, Swiss Webster mice with intraperitoneal (10–20 mg/kg) or oral (20–30 mg/kg) dosing of AZ66 significantly attenuated the acute locomotor stimulatory effects of methamphetamine. Additionally, AZ66 (10–20 mg/kg, i.p.) significantly reduced the expression and development of behavioral sensitization induced by repeated methamphetamine administration. Taken together, these data indicate that sigma receptors can be targeted to mitigate the acute and subchronic behavioral effects of methamphetamine and AZ66 represents a viable lead compound in the development of novel therapeutics against methamphetamine-induced behaviors.

A series of novel indole-based analogues were prepared and their affinities for sigma receptors were determined using in vitro radioligand binding assays. The results of this study identified several compounds with nanomolar sigma-2 affinity and significant selectivity over sigma-1 receptors. In particular, 2-(4-(3-(4-fluorophenyl)indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (9f) was found to display high affinity at sigma-2 receptors with good selectivity (σ-1/σ-2 = 395). The pharmacological binding profile for this compound was established with other relevant nonsigma sites.

Methamphetamine interacts with sigma (σ) receptors and AC927, a selective σ receptor ligand, protects against methamphetamine-induced dopaminergic neurotoxicity. In the present study, the effects of AC927 on methamphetamine-induced hyperthermia and striatal serotonergic neurotoxicity were evaluated. Male, Swiss Webster mice were injected (i.p.) every two hours, for a total of four times, with one of the following treatments: Saline + Saline; Saline + Methamphetamine (5 mg/kg); AC927 (5, 10, 20 mg/kg) + Methamphetamine (5 mg/kg); or AC927 (5, 10, 20 mg/kg) + Saline. Pretreatment with AC927 (10 mg/kg) significantly attenuated methamphetamine-induced striatal serotonin depletions, striatal serotonin transporter reductions, and hyperthermia. At the doses tested, AC927 itself had no significant effects on serotonin levels, serotonin transporter expression, or body temperature. To evaluate the effects of higher ambient temperature on methamphetamine-induced neurotoxicity, groups of mice were treated at 37°C. Overall, there was an inverse correlation between the body temperature of the animals and striatal serotonin levels. Together, the data suggest that AC927 (10 mg/kg) protects against methamphetamine-induced neurotoxicity. The reduction of methamphetamine-induced hyperthermia by AC927 may contribute to the observed neuroprotection in vivo.

A series of pyridylpiperazines was synthesized and analyzed for sigma receptor binding affinity to determine the optimal pyridyl nitrogen position and chain length for the sigma(1) and sigma(2) receptor recognition. The (3-pyridyl)piperazines and (4-pyridyl)piperazines favor sigma(1) receptors, while previously studied (2-pyridyl)piperazines favor sigma(2) receptors.

Drug abuse is currently a large economic and societal burden in countries around the globe. Many drugs of abuse currently lack adequate therapies aimed at treating both the addiction and negative complications often associated with their use. Sigma-1 receptors were discovered over 30 years ago and have recently become targets for the development of pharmacotherapies aimed at treating substance abuse and addiction. In vivo preclinical studies have revealed that sigma receptor ligands are able to ameliorate select behavioral effects of many drugs of abuse including cocaine, methamphetamine, ethanol and nicotine. In addition, recent studies have begun to elucidate the mechanisms by which sigma-1 receptors modulate the effects of these drugs on neurotransmission, gene regulation and neuroplasticity. Overall, these recent findings suggest that compounds targeting sigma-1 receptors may represent a potential new class of therapeutics aimed at treating drug abuse. Future studies involving clinical populations will be critical for validating the therapeutic potential of sigma-1 receptor ligands for the treatment of substance abuse.