Norepinephrine Transporter Inhibitor Research Articles

Atomoxetine on neurogenic orthostatic hypotension: a randomized, double-blind, placebo-controlled crossover trial

PurposeWe previously reported that single doses of the norepinephrine transporter inhibitor, atomoxetine, increased standing blood pressure (BP) and ameliorated symptoms in patients with neurogenic orthostatic hypotension (nOH). We aimed to evaluate the effect of atomoxetine over four weeks in patients with nOH.MethodsA randomized, double-blind, placebo-controlled crossover clinical trial between July 2016 and May 2021 was carried out with an initial open-label, single-dose phase (10 or 18 mg atomoxetine), followed by a 1-week wash-out, and a subsequent double-blind 4-week treatment sequence (period 1: atomoxetine followed by placebo) or vice versa (period 2). The trial included a 2-week wash-out period. The primary endpoint was symptoms of nOH as measured by the orthostatic hypotension questionnaire (OHQ) assessed at 2 weeks.ResultsA total of 68 patients were screened, 40 were randomized, and 37 completed the study. We found no differences in the OHQ composite score between atomoxetine and placebo at 2 weeks (−0.3 ± 1.7 versus −0.4 ± 1.5; P = 0.806) and 4 weeks (−0.6 ± 2.4 versus −0.5 ± 1.6; P = 0.251). There were no differences either in the OHSA scores at 2 weeks (3 ± 1.9 versus 4 ± 2.1; P = 0.062) and at 4 weeks (3 ± 2.2 versus 3 ± 2.0; P = 1.000) or in the OH daily activity scores (OHDAS) at 2 weeks (4 ± 3.0 versus 5 ± 3.1, P = 0.102) and 4 weeks (4 ± 3.0 versus 4 ± 2.7, P = 0.095). Atomoxetine was well-tolerated.ConclusionsWhile previous evidence suggested that acute doses of atomoxetine might be efficacious in treating nOH; results of this clinical trial indicated that it was not superior to placebo to ameliorate symptoms of nOH.Trial registrationClinicalTrials.gov; NCT02316821.

Effects of SRI-32743, a Novel Quinazoline Structure-Based Compound, on HIV-1 Tat and Cocaine Interaction with Norepinephrine Transporter.

Prolonged exposure to HIV-1 transactivator of transcription (Tat) protein dysregulates monoamine transmission, a physiological change implicated as a key factor in promoting neurocognitive disorders among people living with HIV. We have demonstrated that in vivo expression of Tat in Tat transgenic mice decreases dopamine uptake through both dopamine transporter (DAT) and norepinephrine transporter (NET) in the prefrontal cortex. Further, our novel allosteric inhibitor of monoamine transporters, SRI-32743, has been shown to attenuate Tat-inhibited dopamine transport through DAT and alleviates Tat-potentiated cognitive impairments. The current study reports the pharmacological profiles of SRI-32743 in basal and Tat-induced inhibition of human NET (hNET) function. SRI-32743 exhibited less affinity for hNET binding than desipramine, a classical NET inhibitor, but displayed similar potency for inhibiting hDAT and hNET activity. SRI-32743 concentration-dependently increased hNET affinity for [3H]DA uptake but preserved the Vmax of dopamine transport. SRI-32743 slowed the cocaine-mediated dissociation of [3H]Nisoxetine binding and reduced both [3H]DA and [3H]MPP+ efflux but did not affect d-amphetamine-mediated [3H]DA release through hNET. Finally, we determined that SRI-32743 attenuated a recombinant Tat1-86-induced decrease in [3H]DA uptake via hNET. Our findings demonstrated that SRI-32743 allosterically disrupts the recombinant Tat1-86-hNET interaction, suggesting a potential treatment for HIV-infected individuals with concurrent cocaine abuse.

Stereochemical optimization of N,2-substituted cycloalkylamines as norepinephrine reuptake inhibitors.

The norepinephrine transporter (NET), encoded by the SLC6A2 gene, is one of three key monoamine neurotransmitter transporters. Inhibition of NET-mediated reuptake of norepinephrine by monoamine reuptake inhibitors has been the main therapeutic strategy to treat disorders such as depression, ADHD and Parkinson's disease. Nevertheless, lack of efficacy as well as risk of adverse effects are still common for these treatments underscoring the necessity to improve drug discovery efforts for this target. In this study, we developed new inhibitors based on 4-((2-(3,4-dichlorophenyl)cyclopentyl)amino)butan-1-ol (8), a potent NET inhibitor, which emerged from earlier virtual screening efforts using a predictive proteochemometric model. Hence, we optimized the N,2-substituted cycloalkylamine scaffold in three regions to design twenty new derivatives. To establish structure-activity relationships for these NET inhibitors, all novel compounds were tested utilizing an impedance-based 'transporter activity through receptor activation' assay. Moreover, all stereoisomers of the most potent compound (27) were synthesized and evaluated for their inhibitory potencies. Initial screening indicated that modifications in the cyclopentylamine moiety and phenyl substitutions decreased NET inhibition compared to 8, emphasizing the importance of the five-membered ring, secondary amine and dichloro-substitution pattern in NET binding. Substituting the original butylalcohol at the R 2 position with a rigid cyclohexanol yielded lead compound 27, with potency similar to reference inhibitor nisoxetine. Pharmacological characterization of all eight stereoisomers of 27 revealed varying inhibitory potencies, favoring a trans-orientation of the N,2-substituted cyclopentyl moiety. Molecular docking highlighted key interactions and the impact of a hydrophilic region in the binding pocket. This study presents a novel set of moderate to highly potent NET inhibitors, elucidating the influence of molecular orientation in the NET binding pocket and offering valuable insights into drug discovery efforts for monoamine transport-related treatments.

Netarsudil-induced reticular epithelial oedema: An uncommon side effect

Netarsudil ophthalmic solution 0.02% (Netalo) is a new drug in the armamentarium for lowering intraocular pressure in open-angle glaucoma or ocular hypertension. It is a rho-associated protein kinase (ROCK) and norepinephrine transporter inhibitor with multiple mechanisms of action at various cellular levels. Apart from its effect on glaucoma, it has been reported to be beneficial in acute corneal endothelial damage. Its reported common side effects are conjunctival hyperaemia, corneal verticillata and subconjunctival haemorrhage. Corneal oedema arising from its use has been infrequently reported from abroad. We have presented two cases of such oedema acutely induced by Netarsudil, in the absence of any pre-existing corneal problems and which resolved on discontinuation. Such incidences warrant further studies to understand their clinical significance, the mechanism of corneal oedema arising from ROCK inhibitors and the use of these drugs in patients with compromised corneas.

Combined In Vivo Microdialysis and PET Studies to Validate [11C]Yohimbine Binding as a Marker of Noradrenaline Release.

The noradrenaline system attracts attention for its role in mood disorders and neurodegenerative diseases but the lack of well-validated methods impairs our understanding when assessing its function and release in vivo. This study combines simultaneous positron emission tomography (PET) and microdialysis to explore if [11C]yohimbine, a selective antagonist radioligand of the α2 adrenoceptors, may be used to assess in vivo changes in synaptic noradrenaline during acute pharmacological challenges. Anesthetised Göttingen minipigs were positioned in a head holder in a PET/CT device. Microdialysis probes were placed in the thalamus, striatum and cortex and dialysis samples were collected every 10 min. Three 90 min [11C]yohimbine scans were acquired: at baseline and at two timepoints after the administration of amphetamine (1-10 mg/kg), a non-specific releaser of dopamine and noradrenaline, or nisoxetine (1 mg/kg), a specific noradrenaline transporter inhibitor. [11C]yohimbine volumes of distribution (VT) were obtained using the Logan kinetic model. Both challenges induced a significant decrease in yohimbine VT, with time courses reflecting their different mechanisms of action. Dialysis samples revealed a significant increase in noradrenaline extracellular concentrations after challenge and an inverse correlation with changes in yohimbine VT. These data suggest that [11C]yohimbine can be used to evaluate acute variations in synaptic noradrenaline concentrations after pharmacological challenges.

Rationalizing the Binding Modes of PET Radiotracers Targeting the Norepinephrine Transporter

A new PET radiotracer 18F-AF78 showing great potential for clinical application has been reported recently. It belongs to a new generation of phenethylguanidine-based norepinephrine transporter (NET)-targeting radiotracers. Although many efforts have been made to develop NET inhibitors as antidepressants, systemic investigations of the structure-activity relationships (SARs) of NET-targeting radiotracers have rarely been performed. Without changing the phenethylguanidine pharmacophore and 3-fluoropropyl moiety that is crucial for easy labeling, six new analogs of 18F-AF78 with different meta-substituents on the benzene-ring were synthesized and evaluated in a competitive cellular uptake assay and in in vivo animal experiments in rats. Computational modeling of these tracers was established to quantitatively rationalize the interaction between the radiotracers and NET. Using non-radiolabeled reference compounds, a competitive cellular uptake assay showed a decrease in NET-transporting affinity from meta-fluorine to iodine (0.42 and 6.51 µM, respectively), with meta-OH being the least active (22.67 µM). Furthermore, in vivo animal studies with radioisotopes showed that heart-to-blood ratios agreed with the cellular experiments, with AF78(F) exhibiting the highest cardiac uptake. This result correlates positively with the electronegativity rather than the atomic radius of the meta-substituent. Computational modeling studies revealed a crucial influence of halogen substituents on the radiotracer-NET interaction, whereby a T-shaped π-π stacking interaction between the benzene-ring of the tracer and the amino acid residues surrounding the NET binding site made major contributions to the different affinities, in accordance with the pharmacological data. The SARs were characterized by in vitro and in vivo evaluation, and computational modeling quantitatively rationalized the interaction between radiotracers and the NET binding site. These findings pave the way for further evaluation in different species and underline the potential of AF78(F) for clinical application, e.g., cardiac innervation imaging or molecular imaging of neuroendocrine tumors.

Meta-analysis on the efficacy of the norepinephrine reuptake inhibitors reboxetine and atomoxetine for the treatment of schizophrenia and attention deficit hyperactivity disorder.

Norepinephrine transporter inhibitors that can alter the level of neurotransmitter in the brain are used to treat neurological disorders. However, a number of studies have reported their limited significance as a result of their slow onset of action and moderate efficacy. To determine the effects of norepinephrine reuptake inhibitors (NRIs), reboxetine and atomoxetine on schizophrenia and attention deficit hyperactivity disorder (ADHD). Relevant articles published between 2000 and 2022 were searched in the MEDLINE, CINAHL (via Ebsco), Web of Science and Scopus databases. Among the various NRIs, studies concerning the 2 potent drugs - reboxetine and atomoxetine - were selected for analysis. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were estimated, along with the exploration of heterogeneity and publication bias, using RevMan software. A total of 14 eligible studies with a combined sample size of 970 patients were included. Using a random effects model, an OR of 0.55 (0.32-0.94), a Tau2 value of 0.23, a ÷2 value of 12.31, 8 degrees of freedom (df), an I2 of 35%, a Z value of 2.19, and a p-value of 0.03 were recorded for reboxetine. Atomoxetine had an OR of 0.35 (0.13-0.97), a Tau2 value of 0.58, a ÷2 value of 7.31, 4 df, an I2 of 45%, a Z value of 1.53, and a p-value of 0.04. All results were statistically significant with a low risk of publication bias, as was evident from the p-values >0.05 derived from the Egger's test and the Begg's test. These drugs provided comparable changes to control drugs in Hamilton Depression Rating Scale (HAM-D) scores, Positive and Negative Syndrome Scale (PANSS) scores and ADHD ratings. This confirms the efficacy of reboxetine for the treatment of schizophrenia and atomoxetine for the treatment of ADHD. The present meta-analysis suggests that NRIs are efficacious and therefore they are potential candidate drugs for the treatment of schizophrenia and ADHD.

Atomoxetine Decreases Mitochondrial Biogenesis, Fission and Fusion In Human Neuron-like Cells But Does Not Alter Antioxidant Defences.

Atomoxetine (ATX) is a presynaptic norepinephrine transporter (NET) inhibitor widely prescribed for attention-deficit/hyperactivity disorder (ADHD) due to its low abuse potential and absence of psychostimulant effects. While NET inhibition is implicated in the clinical response, several additional pharmacoactivities may contribute to clinical efficacy or unwanted side effects. We recently reported that ATX can dose-dependently alter mitochondrial function and cellular redox status. Here, we assessed potential alterations in mitochondrial biogenesis, mitochondrial dynamics and cellular antioxidant capacity following high- and low-dose ATX treatment of differentiated human neuroblastoma cells. Human SH-SY5Y neuroblastoma cells were treated with ATX (1, 5, 10, 20 and 50 μM) for 7 days under differentiation culture conditions. Changes in the expression levels of protein markers for mitochondrial biogenesis, fusion and fission as well as of antioxidant proteins were analysed by Western blot. High-dose ATX (50 μM) reduced while low-dose ATX (10 μM) increased mitochondrial biogenesis as evidenced by parallel changes in SDHA, COX-I, PGC1α and TFAM expression. High-dose ATX also reduced mitochondrial fusion as evidenced by OPA1 and MFN2 downregulation, and mitochondrial fission as indicated by DRP1 and Fis1 downregulation. In contrast, ATX did not alter expression of the antioxidant enzymes SOD1 and catalase, the phase II transcription factor Nfr2, or the Nfr2-regulated antioxidant enzyme NQO1. Clinical responses and side effects of ATX may be mediated by dose-dependent modulation of mitochondrial biogenesis and dynamics as well as NET inhibition.

Effects of Atomoxetine on Motor and Cognitive Behaviors and Brain Electrophysiological Activity of Dopamine Transporter Knockout Rats.

Changes in dopaminergic and noradrenergic transmission are considered to be the underlying cause of attention deficit and hyperactivity disorder (ADHD). Atomoxetine (ATX) is a selective norepinephrine transporter (NET) inhibitor that is currently used for ADHD treatment. In this study, we aimed to evaluate the effect of atomoxetine on the behavior and brain activity of dopamine transporter knockout (DAT-KO) rats, which are characterized by an ADHD-like behavioral phenotype. Prepulse inhibition (PPI) was assessed in DAT-KO and wild type rats after saline and ATX injections, as well as behavioral parameters in the Hebb–Williams maze and power spectra and coherence of electrophysiological activity. DAT-KO rats demonstrated a pronounced behavioral and electrophysiological phenotype, characterized by hyperactivity, increased number of errors in the maze, repetitive behaviors and disrupted PPI, changes in cortical and striatal power spectra and interareal coherence. Atomoxetine significantly improved PPI and decreased repetitive behaviors in DAT-KO rats and influenced behavior of wild-type rats. ATX also led to significant changes in power spectra and coherence of DAT-KO and wild type rats. Assessment of noradrenergic modulation effects in DAT-KO provides insight into the intricate interplay of monoaminergic systems, although further research is still required to fully understand the complexity of this interaction.

Bilateral allergic contact dermatitis due to Netarsudil

Netarsudil is a rho-associated coiled-coil-containing protein kinase inhibitor and norepinephrine transporter inhibitor, which decreases the intra-ocular pressure by increasing the aqueous outflow and decreasing the aqueous production. However, netarsudil has been reported to cause adverse effects attributed to its vasodilator property. The common side effects associated with its use are conjunctival hyperemia, corneal verticillata, and conjunctival hemorrhages. This report describes a case of allergic contact dermatitis 3 months after initiating netarsudil eye drops in a 78-year-old man.

Abstract P063: Long-term Efficacy Of Atomoxetine For The Treatment Of Symptomatic Neurogenic Orthostatic Hypotension

Patients with neurogenic orthostatic hypotension (NOH) are at risk for syncope, falls and have poor quality of life. Only two drugs (midodrine, droxidopa) are FDA-approved for the treatment of NOH. We previously reported that atomoxetine, a norepinephrine transporter inhibitor, acutely improved upright blood pressure and symptoms in NOH, mostly in multiple system atrophy (MSA) patients. However, the long-term efficacy of atomoxetine for the treatment of NOH is unknown. We hypothesize chronic treatment with atomoxetine improves pre-syncopal symptoms in NOH We conducted multicenter, randomized, double-blind, placebo-controlled, 2X2 crossover design with initial atomoxetine dose-titration phase. NOH patients were randomized to two, 4-week treatment sequence (period 1: atomoxetine (10 or 18 mg TID) followed by placebo) or vice versa (period 2). The primary outcome was a reduction in pre-syncopal symptoms using the orthostatic hypotension questionnaire (OHQ) composite score, calculated from the OH symptoms Assessment (OHSA) and the OH Daily Activity Scale (OHDAS). Secondary endpoints were orthostatic vital signs. We screened 68 patients, 48 were enrolled in the dose-titration and 40 were randomized (68 ± 8 yo, %60 males, BMI 26.2 ± 4.8 kg/m 2 ). We found no difference in the OHQ score between atomoxetine and placebo at 2-week (4.8±2.4 vs 4.5±2.1, P=0.73). Sub-analyses between MSA and non-MSA patients showed significant decline in OHSA with atomoxetine (2.6±1.8 vs 3.6±1.8, p=0.03) in non-MSA patients, specifically in vision disturbance (p=0.04) and in weakness (p=0.03). At 4-week, atomoxetine effect on upright SBP persisted (3.4±20.61 vs. -5.5±14.82 mm Hg, p=0.037). Atomoxetine was well-tolerated. Even though we found no significant reduction in OHQ with atomoxetine. Sub-analyses based on diagnosis, found that non-MSA patients had a significant improvement in OHSA. Atomoxetine effect on upright SBP persisted after 4-week treatment suggesting no tachyphylaxis.

In vitro and in vivo pharmacological characterization of dasotraline, a dual dopamine and norepinephrine transporter inhibitor in vivo

Inhibitors of dopamine transporters (DAT), norepinephrine transporters (NET) and serotonin transporters (SERT) are effective treatments for neuropsychiatric diseases. Dasotraline [(1R,4 S)− 4-(3,4-dichlorophenyl)− 1,2,3,4-tetrahydro-1-naphthalenamine, also known as SEP-225289) was evaluated for its inhibitory potency at DAT, NET and SERT using in vitro and in vivo assays. In vitro radiometric functional uptake studies showed preferential inhibition by dasotraline of hDAT (IC50 =3 nM) and hNET (IC50 =4 nM relative to hSERT(IC50 =15 nM). In mouse ex vivo occupancy studies, dasotraline demonstrated total plasma concentration-dependent occupancy at DAT, NET and SERT. Determination of the TO50 (50% transporter occupancy) were 32, 109 and 276 ng/ml, respectively. In SPECT imaging studies in baboons, dasotraline (0.2 mg/kg iv) displaced radiotracer binding to DAT by 87% but only 20% at NET and SERT. Rat microdialysis studies were performed in prefrontal cortex and striatum. Dasotraline produced sustained (>4 h) increases in dopamine and norepinephrine concentrations. Dasotraline was also more potent at increasing synaptic dopamine in the striatum, and norepinephrine in the prefrontal cortex than serotonin in these regions. In summary, dasotraline preferentially inhibits DAT and NET relative to SERT. Together, the occupancy and neurochemical profile of dasotraline provide a mechanistic basis for the treatment of diseases that have an underlying causality involving dopamine and norepinephrine dysfunction.

Time-Dependent Monitoring of Dopamine in the Brain of Live Embryonic Zebrafish Using Electrochemically Pretreated Carbon Fiber Microelectrodes.

Neurotransmitters are involved in functions related to signaling, stress response, and pathological disorder development, and thus, their real-time monitoring at the site of production is important for observing the changes related to these disorders. Here, we demonstrate the first time-dependent quantification of dopamine in the brains of live zebrafish embryos using electrochemically pretreated carbon fiber microelectrodes (CFMEs) utilizing differential pulse voltammetry as the measurement technique. The pretreatment of the CFMEs in 0.1 M NaOH held at a potential of +1.0 V for 600 s improves the sensitivity toward dopamine and allows for reliable measurements in low ionic strength media. We demonstrate the measurement of extracellular dopamine concentrations in the zebrafish brain during late embryogenesis. The extracellular dopamine concentration in the tectum of zebrafish varies between 200 and 400 nM. The conventional pharmacological manipulation of neurotransmitter levels in the brain demonstrates the selective detection of dopamine at the implantation site. Exposure to the dopamine transporter inhibitor nomifensine induces an increase in extracellular dopamine from 201.9 (±34.9) nM to 352.2 (±20.0) nM, while exposure to the norepinephrine transporter inhibitor desipramine does not lead to a significant modulation of the measured signal. Furthermore, we report the quantitative assessment of the catecholamine stress response of embryos to tricaine, an anesthetic frequently used in zebrafish assays. Exposure to tricaine induces a short-lived increase in brain dopamine from 198.6 (±15.7) nM to a maximum of 278.8 (±14.0) nM. Thus, in vivo electrochemistry can detect real-time changes in zebrafish neurochemical physiology resulting from drug exposure.

Molecular Imaging-Derived Biomarker of Cardiac Nerve Integrity — Introducing High NET Affinity PET Probe 18F-AF78

Background: Radiolabeled agents that are substrates for the norepinephrine transporter (NET) can be used to quantify cardiac sympathetic nervous conditions and have been demonstrated to identify high-risk congestive heart failure (HF) patients prone to arrhythmic events. We aimed to fully characterize the kinetic profile of the novel 18F-labeled NET probe AF78 for PET imaging of the cardiac sympathetic nervous system (SNS) among various species.Methods: 18F-AF78 was compared to norepinephrine (NE) and established SNS radiotracers by employing in vitro cell assays, followed by an in vivo PET imaging approach with healthy rats, rabbits and nonhuman primates (NHPs). Additionally, chase protocols were performed in NHPs with NET inhibitor desipramine (DMI) and the NE releasing stimulator tyramine (TYR) to investigate retention kinetics in cardiac SNS.Results: Relative to other SNS radiotracers, 18F-AF78 showed higher transport affinity via NET in a cell-based competitive uptake assay (IC50 0.42 ± 0.14 µM), almost identical to that of NE (IC50, 0.50 ± 0.16 µM, n.s.). In rabbits and NHPs, initial cardiac uptake was significantly reduced by NET inhibition. Furthermore, cardiac tracer retention was not affected by a DMI chase protocol but was markedly reduced by intermittent TYR chase, thereby suggesting that 18F-AF78 is stored and can be released via the synaptic vesicular turnover process. Computational modeling hypothesized the formation of a T-shaped π-π stacking at the binding site, suggesting a rationale for the high affinity of 18F-AF78.Conclusion: 18F-AF78 demonstrated high in vitro NET affinity and advantageous in vivo radiotracer kinetics across various species, indicating that 18F-AF78 is an SNS imaging agent with strong potential to guide specific interventions in cardiovascular medicine.

Differential Potency of Venlafaxine, Paroxetine, and Atomoxetine to Inhibit Serotonin and Norepinephrine Reuptake in Patients With Major Depressive Disorder

BackgroundVenlafaxine is a dual serotonin (5-HT) and norepinephrine reuptake inhibitor. The specific dose at which it begins to efficiently engage the norepinephrine transporter (NET) remained to be determined. Paroxetine is generally considered as a selective 5-HT reuptake inhibitor but exhibits some affinity for NET. Atomoxetine is a NET inhibitor but also has some affinity for the 5-HT reuptake transporter (SERT).MethodsThis study examined the effects of forced titration of venlafaxine from 75 to 300 mg/d, paroxetine from 20 to 50 mg/d, or atomoxetine from 25 to 80 mg/d in 32 patients with major depressive disorder. Inhibition of SERT was estimated using the depletion of whole-blood 5-HT. Inhibition of NET was assessed using the attenuation of the systolic blood pressure produced by i.v. injections of tyramine.ResultsAll 3 medications significantly reduced 5-HT levels at the initiating regimens: venlafaxine and paroxetine by approximately 60% and atomoxetine by 16%. The 3 subsequent regimens of venlafaxine and paroxetine reduced 5-HT levels by over 90%, but the highest dose of atomoxetine only reached a 40% inhibition. Atomoxetine dose dependently inhibited the tyramine pressor response from the lowest dose, venlafaxine from 225 mg/d, and paroxetine left it unaltered throughout.ConclusionThese results confirm that venlafaxine and paroxetine are potent SERT inhibitors over their usual therapeutic range but that venlafaxine starts inhibiting NET only at 225 mg/d, whereas paroxetine remains selective for SERT up to 50 mg/d. Atomoxetine dose dependently inhibits NET from a low dose but does not inhibit SERT to a clinically relevant degree.

Droxidopa for Treatment of Refractory Orthostatic Hypotension in Patients with AL Amyloidosis: A Case Series

BackgroundOrthostatic hypotension due to autonomic dysfunction is a well-known complication of light chain (AL) amyloidosis, which can become progressively debilitating and difficult to manage. Treatment of the underlying plasma cell dyscrasia will eventually decrease further amyloid deposition. Management of orthostatic hypotension secondary to AL amyloidosis improves quality of life and facilitates delivery of plasma cell therapy. Pharmacologic interventions include fludrocortisone, sympathomimetic agents such as midodrine, droxidopa, the acetylcholinesterase inhibitor pyridostigmine or the norepinephrine transporter (NET) inhibitor atomoxetine. Fludrocortisone is often poorly tolerated in amyloid patients because it may exacerbate edema. Droxidopa is a synthetic amino acid analog that is directly metabolized to norepinephrine by dopa-decarboxylase, which increases blood pressure (BP) by inducing peripheral arterial and venous vasoconstriction.AimsTo assess the effectiveness of droxidopa in patients with AL amyloidosis with severe orthostatic hypotension refractory to midodrine. Also, to describe effective dose of droxidopa, duration of therapy, adverse effects and reasons for discontinuation.MethodsA regional retrospective study was done in patients with AL amyloidosis with severe, refractory orthostatic hypotension who received droxidopa. Retrospective data was reviewed from 2018 to 2021 at a single academic center in the United States.ResultsFive patients with AL amyloidosis were included in the study; three patients had lambda-restricted plasma cell dyscrasia and two had multiple myeloma (MM) associated AL amyloidosis (both kappa light chain restricted). Of the five patients, all had cardiac, renal, autonomic nervous system and peripheral nervous system involvement and two of the five had gastrointestinal involvement as well. Given their poor performance status and advanced organ involvement, none of the patients were eligible for high-dose intravenous melphalan with autologous peripheral blood stem cell transplantation (HDM/SCT), and thus were treated with cyclophosphamide, bortezomib and dexamethasone (CyBorD). All patients achieved very good partial response to complete hematologic response. The main findings are summarized in table 1.All patients had severe, symptomatic orthostatic hypotension that was objectively defined as a decrease in systolic blood pressure by 20 millimeters of mercury (mmHg) or a decrease in diastolic blood pressure of 10 mmHg from supine to either sitting or standing in the clinic or at home (Freeman R consensus statement on the definition of orthostatic hypotension, 2011). Initial treatment for all patients included midodrine, ranging from 5 to 30mg TID based on individual tolerance. Three of the patients also were initially treated with fludrocortisone 0.05 to 0.2mg daily (use limited by fluid retention). Only one patient was on pyridostigmine 30mg TID (case 5). Given persistence of symptoms despite therapy, droxidopa was started at 100mg TID in all patients, and the dose was titrated as tolerated. None required the maximal approved dose of 600mg TID.The indication to start droxidopa was based on refractory, symptomatic orthostatic hypotension in all five patients. After initiation of droxidopa, all except for one patient reported improvement both in symptoms of lightheadedness as well as measurements of orthostatic blood pressure values. By the end of this study, three patients continued treatment with droxidopa (cases 1-3); one was weaned-off after resolution of symptoms (case 5) and one was discontinued due to supine hypertension (case 4).ConclusionData shows that droxidopa is an effective treatment of orthostatic hypotension refractory to midodrine in patients with AL amyloidosis. Slow titration may be important to minimize rapid changes in blood pressure. Further studies are warranted to assess droxidopa's safety and compare with other treatments for orthostatic hypotension. [Display omitted] DisclosuresHughes: Amgen: Speakers Bureau; Rigel: Other: Advisory Board, Research Funding; Abbvie: Speakers Bureau; Karyopharm: Other: Advisory Board, Speakers Bureau. Sanchorawala: Celgene: Research Funding; Takeda: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Caelum: Membership on an entity's Board of Directors or advisory committees, Research Funding; Regeneron: Membership on an entity's Board of Directors or advisory committees; Proclara: Membership on an entity's Board of Directors or advisory committees; Oncopeptide: Research Funding; Karyopharm: Research Funding; Sorrento: Research Funding; Pfizer: Honoraria. Sloan: Nuvectis: Consultancy; Abbvie: Consultancy; Stemline: Consultancy; Astrazeneca: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees; Pharmacosmos: Membership on an entity's Board of Directors or advisory committees.

Predictors of the Pressor Response to the Norepinephrine Transporter Inhibitor, Atomoxetine, in Neurogenic Orthostatic Hypotension.

[Figure: see text].

Label-free high-throughput screening assay for the identification of norepinephrine transporter (NET/SLC6A2) inhibitors

The human norepinephrine transporter (NET) is an established drug target for a wide range of psychiatric disorders. Conventional methods that are used to functionally characterize NET inhibitors are based on the use of radiolabeled or fluorescent substrates. These methods are highly informative, but pose limitations to either high-throughput screening (HTS) adaptation or physiologically accurate representation of the endogenous uptake events. Recently, we developed a label-free functional assay based on the activation of G protein-coupled receptors by a transported substrate, termed the TRACT assay. In this study, the TRACT assay technology was applied to NET expressed in a doxycycline-inducible HEK 293 JumpIn cell line. Three endogenous substrates of NET—norepinephrine (NE), dopamine (DA) and epinephrine (EP)—were compared in the characterization of the reference NET inhibitor nisoxetine. The resulting assay, using NE as a substrate, was validated in a manual HTS set-up with a Z′ = 0.55. The inhibitory potencies of several reported NET inhibitors from the TRACT assay showed positive correlation with those from an established fluorescent substrate uptake assay. These findings demonstrate the suitability of the TRACT assay for HTS characterization and screening of NET inhibitors and provide a basis for investigation of other solute carrier transporters with label-free biosensors.

Rhopressa-induced corneal edema: a case report

BackgroundRhopressa (netarsudil) has recently been added to the arsenal of treatment for open-angle glaucoma. It is an effective norepinephrine transporter and Rho-associated protein kinase (ROCK) inhibitor used to decrease intraocular pressure (IOP), with the most common side effect being conjunctival hyperemia.Case presentationWe report a unique case of Rhopressa-induced corneal edema in a 79-year-old African-American woman, which resolved after discontinuation. She had a history of smoking one cigarette per day and did not consume alcohol. She had no history of corneal edema or uveitis.ConclusionsPrevious case reports have documented patients with Rhopressa-induced corneal edema; however, they have all had a preexisting history of corneal edema or uveitis. We believe that this is a unique case of Rhopressa-induced corneal edema in a relatively healthy eye. While Rhopressa is effective in managing glaucoma, there may be effects of treatment that are still unknown. We will discuss clinical findings of our case, along with a review of previous literature on Rhopressa and novel ROCK inhibitors. We hope that we can add to the existing body of literature and invite further investigation of Rhopressa and ROCK inhibitors and their effects on the cornea.

Computer-aided drug design and in silico pharmacokinetics predictions of some potential antipsychotic agents

The target of many drugs for the treatment of psychiatric disorders and other related neurological conditions are majorly relied on monoaminergic systems. In continuation of our previous study, computer-aided drug design approach was employed to design some new inhibitors of norepinephrine transporter as potential antipsychotic agents. The significant contribution of some descriptors (AlogP, AATS7i and ATSC3p) in the developed QSAR model and the result of molecular docking simulations from our previous study informed the selection of compound 2 as the lead compound for the design of some new inhibitors in the present study. Subsequently, ten (10) hypothetical inhibitors were designed that showed better pharmacological properties as potential antipsychotic agents when compared the results with an FDA approved antispychotic drug (Atomoxetine). The molecular docking analysis of the designed inhibitors revealed good biochemical interactions toward the active site of the biological target (receptor) with better binding affinities ranges from -7.2 to -7.6 kcal/mol compared to the binding affinity of the lead compound and the referenced drug (Atomoxetine) which were found to be 7.1 kcal/mol and 6.5 kcal/mol, respectively. An appreciable number of hydrogen bonds were associated between the amino acid residues of the protein target and all the designed inhibitors when compared the result to that of the lead compound. Likewise, the computed numerical values of all the descriptors in the designed inhibitors were significantly increased. These remarkable properties observed in the designed inhibitors could be ascribed to the structural modification via electrophilic substitutions (NH2, -OH, –OCH3, -CH3, NO2, -CF3, -F and Cl) at different positions of the lead compound owing to the influence of heteroatoms in the substituents as revealed by the descriptors in the developed QSAR model of our previous study. Similarly, drug-likeness and bioavailability evaluation showed that none of the designed inhibitors violates Lipinski's rule of five. The ADMET properties also revealed that all the designed inhibitors possessed excellent pharmacological attributes. Furthermore, toxicity risk assessments of some selected designed inhibitors showed that most of the selected inhibitors are non-AMES mutagenicity and none of these inhibitors is carcinogens. Against this background, the hypothetical designed inhibitors could be subjected to further experimental investigations and in vitro evaluations before it could be developed and optimized as novel antipsychotic agents/ drug candidates.