Real-world Impact of Fremanezumab on Migraine-Related Health Care Resource Utilization in Patients with Comorbidities, Acute Medication Overuse, and/or Unsatisfactory Prior Migraine Preventive Response.

INTRODUCTION: Fremanezumab, a humanized monoclonal antibody targeting calcitonin gene-related peptide, is indicated for preventive treatment of migraine in adults. Real-world evidence assessing the effect of fremanezumab on migraine-related medication use, health care resource utilization (HCRU), and costs in patient populations with comorbidities, acute medication overuse (AMO), and/or unsatisfactory prior migraine preventive response (UPMPR) is needed. METHODS: Data for this US, retrospective claims analysis were obtained from the Merative® MarketScan® Commercial and supplemental databases. Eligible adults with migraine initiated fremanezumab between 1 September 2018 and 30 June 2019 (date of earliest fremanezumab claim is the index date), had ≥ 12 months of continuous enrollment prior to initiation (preindex period) and ≥ 6 months of data following initiation (postindex period; variable follow-up after 6 months), and had certain preindex migraine comorbidities (depression, anxiety, and cardiovascular disease), potential AMO, or UPMPR. Changes in migraine-related concomitant acute and preventive medication use, HCRU, and costs were assessed pre- versus postindex. RESULTS: In total, 3193 patients met the eligibility criteria. From pre- to postindex, mean (SD) per patient per month (PPPM) number of migraine-related acute medication and preventive medication claims (excluding fremanezumab), respectively, decreased from 0.97 (0.90) to 0.86 (0.87) (P < 0.001) and 0.94 (0.74) to 0.81 (0.75) (P < 0.001). Migraine-related outpatient and neurologist office visits, emergency department visits, and other outpatient services PPPM decreased pre- versus postindex (P < 0.001 for all), resulting in a reduction in mean (SD) total health care costs PPPM from US$541 (US$858) to US$490 (US$974) (P = 0.003). Patients showed high adherence and persistence rates, with mean (SD) proportion of days covered of 0.71 (0.29), medication possession ratio of 0.74 (0.31), and persistence duration of 160.3 (33.2) days 6 months postindex. CONCLUSIONS: Patients with certain migraine comorbidities, potential AMO, and/or UPMPR in a real-world setting had reduced migraine-related medication use, HCRU, and costs following initiation of fremanezumab. Graphical abstract available for this article.

Burden of migraine with acute medication overuse or psychiatric comorbidities and treatment with CGRP pathway-targeted monoclonal antibodies: A review.

Migraine is a complex and often debilitating neurological disease that affects more than 1 billion people worldwide. It is characterized by moderate-to-intense, throbbing headache attacks that are worsened by activity and is associated with nausea, vomiting, and sensitivity to light and sound. Migraine, ranked the second leading cause of years lived with disability by the World Health Organization, can diminish patients' quality of life and bring significant personal and economic burden. Furthermore, migraine patients with a history of acute medication overuse (AMO) or psychiatric comorbidities, such as depression or anxiety, may experience even greater impairment and burden, and their migraine may be more difficult-to-treat. Appropriate treatment of migraine is essential to reduce this burden and improve patient outcomes, especially for those with AMO or psychiatric comorbidities. There are several available preventive treatment options for migraine, though many of these are not migraine-specific and may have limited efficacy and/or poor tolerability. The calcitonin gene-related peptide pathway plays a key role in the pathophysiology of migraine, and monoclonal antibodies that target the calcitonin gene-related peptide pathway have been developed as specific preventive treatments for migraine. Four of these monoclonal antibodies have been approved for the preventive treatment of migraine after demonstrating favorable safety and efficacy profiles. These treatments offer substantial benefits for migraine patients, including those with AMO or common psychiatric comorbidities, by reducing monthly headache days and migraine days, days of acute medication use, and disability measures, as well as improving quality of life.

Reducing the Burden of Migraine: Safety and Efficacy of CGRP Pathway-Targeted Preventive Treatments.

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.

Real-world effectiveness after initiating fremanezumab treatment in US patients with episodic and chronic migraine or difficult-to-treat migraine.

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).

Efficacy and quality-of-life improvements with fremanezumab treatment in patients with difficult-to-treat migraine with associated neurological dysfunction.

BACKGROUND AND PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Effects of fremanezumab in patients with chronic migraine and comorbid depression: Subgroup analysis of the randomized HALO CM study.

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 < 0.001). More patients achieved a ≥50% reduction in headache days of at least moderate severity with fremanezumab (quarterly: 31/78 [39.7%]; monthly: 39/96 [40.6%]) than placebo (9/67 [13.4%]; both p < 0.001). Compared with placebo, fremanezumab improved PGIC and HIT-6 scores. CONCLUSIONS: Fremanezumab demonstrated efficacy in the preventive treatment of CM and reduced headache impact in patients with comorbid depression.

Immunogenicity of biologic therapies for migraine: a review of current evidence.

BACKGROUND: Monoclonal antibodies (mAbs) targeting the calcitonin gene-related peptide (CGRP) pathway have been shown to be effective in migraine prevention. Eptinezumab, erenumab, fremanezumab, and galcanezumb have shown efficacy in clinical trials along with favorable safety and tolerability profiles. Although erenumab is a human mAb and the others have been humanized to varying degrees, they all have the capacity to provoke immune reactions. The present review article aims to discuss the current relationship between mAbs targeting the CGRP pathway (CGRP mAbs) and immunogenicity and their potential clinical implications. FINDINGS: The incidence of patients developing anti-drug antibodies (ADAs), their titer, and clinical significance are highly variable and depend on a variety of different drug and patient factors. Neutralizing ADAs (NAbs) bind to and inhibit or reduce the pharmacologic activity of the biologic drug molecule, whereas non-neutralizing antibodies (Non-NAbs) bind to the biologic drug molecule without affecting pharmacologic activity in an in vitro test, although pharmacokinetics and drug clearance may be affected. A direct comparison of immunogenicity data across clinical trials with different biologics is not possible due to a lack of standardized assays. Several phase 2, phase 3, and long-term studies evaluating CGRP mAbs for migraine prevention have reported immunogenicity data (5 studies each for eptinezumab, erenumab, fremanezumab, and galcanezumab). Across these studies, prevalence of ADAs varied, ranging from < 1% to ~ 18%. Neutralizing ADAs were slightly less common, with a prevalence ranging from 0 to 12%. Adverse events related to ADA formation were rare. CONCLUSIONS: As more CGRP mAb studies are conducted and more long-term follow-up data become available, evidence is increasing that immunogenicity rates of biologic therapies for migraine are low, and adverse events related to ADAs are rare. Taken together, these results add to the growing body of evidence for the safety and tolerability of this class of migraine medications.

Reversion From Chronic Migraine to Episodic Migraine in Patients Treated With Fremanezumab: Post Hoc Analysis From HALO CM Study.

BACKGROUND: Migraine preventive medications are used to reduce headache frequency, severity, and duration. In patients with chronic migraine (CM), reversion to episodic migraine (EM) is an important treatment goal. OBJECTIVE: To evaluate the effect of fremanezumab on the rate of reversion from CM to EM. METHODS: This phase 3, randomized, double-blind, placebo-controlled, parallel-group trial included a 28-day pretreatment period and a 3-month treatment period. Patients with CM received subcutaneous fremanezumab quarterly (675 mg at baseline) or monthly (675 mg at baseline; 225 mg at Weeks 4 and 8), or placebo. Post hoc analyses evaluated the proportion of patients who reverted from CM to EM, defined as either a reduction to an average of <15 headache days per month during the 3-month treatment period or a reduction to <15 headache days per month in all 3 months of the treatment period. RESULTS: This analysis included data from 1088 CM patients (quarterly, n = 366; monthly, n = 365; placebo, n = 357). More fremanezumab-treated patients with CM reverted to EM using either the monthly average number of headache days criteria for reversion (quarterly: 50.5% [185/366], P = .108; monthly: 53.7% [196/365], P = .012; vs placebo: 44.5% [159/357]) or the monthly headache day count at Months 1, 2, and 3 criteria for reversion (quarterly: 31.2% [114/366], P = .008; monthly: 33.7% [123/365], P = .001; vs placebo: 22.4% [80/357]). Patients with CM who reported previous topiramate or onabotulinumtoxinA use, concomitant preventive medication use, or medication overuse were less likely to revert to EM. CONCLUSIONS: Fremanezumab may offer the benefit of reversion from CM to EM, based on a reduction in the number of headache days over 3 months of treatment.

No "Wearing-Off Effect" Seen in Quarterly or Monthly Dosing of Fremanezumab: Subanalysis of a Randomized Long-Term Study.

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.

The impact of fremanezumab on medication overuse in patients with chronic migraine: subgroup analysis of the HALO CM study.

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 < 0.0001) in patients with MO and without MO (quarterly - 1.4 [- 2.3 to - 0.5], 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.

Metabolism of megestrol acetate in vitro and the role of oxidative metabolites.

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.

Methamphetamine-induced toxicity: an updated review on issues related to hyperthermia.

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.

Evaluation of utility of pharmacokinetic studies in phase I trials of two oncology drugs.

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.

Effect of ring-constrained phenylpropyloxyethylamines on sigma receptors.

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.

σ Receptor antagonist attenuation of methamphetamine-induced neurotoxicity is correlated to body temperature modulation.

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 METH-induced 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.

Pharmacological evaluation of SN79, a sigma (σ) receptor ligand, against methamphetamine-induced neurotoxicity in vivo.

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.

The evaluation of AZ66, an optimized sigma receptor antagonist, against methamphetamine-induced dopaminergic neurotoxicity and memory impairment in mice.

Sigma (σ) receptors have recently been identified as potential targets for the development of novel therapeutics aimed at mitigating the effects of methamphetamine. Particularly, σ receptors are believed to mitigate some of the neurotoxic effects of methamphetamine through modulation of dopamine, dopamine transporters and body temperature. Furthermore, recent evidence suggests that targeting σ receptors may prevent cognitive impairments produced by methamphetamine. In the present study, an optimized σ receptor antagonist, AZ66, was evaluated against methamphetamine-induced neurotoxicity and cognitive dysfunction. AZ66 was found to be highly selective for σ receptors compared to 64 other sites tested. Pretreatment of male, Swiss Webster mice with i.p. dosing of AZ66 significantly attenuated methamphetamine-induced striatal dopamine depletions, striatal dopamine transporter reductions and hyperthermia. Additionally, neurotoxic dosing with methamphetamine caused significant memory impairment in the object recognition test, which was attenuated when animals were pretreated with AZ66; similar trends were observed in the step-through passive avoidance test. Taken together, these results suggest that targeting σ receptors may provide neuroprotection against the neurotoxicity and cognitive impairments produced by methamphetamine.

In vitro evaluation of guanidine analogs as sigma receptor ligands for potential anti-stroke therapeutics.

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.