DETQ, an allosteric potentiator of the dopamine D1 receptor, was tested in therapeutic models that were known to respond to D1 agonists. Because of a species difference in affinity for DETQ, all ...rodent experiments used transgenic mice expressing the human D1 receptor (hD1 mice). When given alone, DETQ reversed the locomotor depression caused by a low dose of reserpine. DETQ also acted synergistically with L-DOPA to reverse the strong hypokinesia seen with a higher dose of reserpine. These results indicate potential as both monotherapy and adjunct treatment in Parkinson's disease. DETQ markedly increased release of both acetylcholine and histamine in the prefrontal cortex, and increased levels of histamine metabolites in the striatum. In the hippocampus, the combination of DETQ and the cholinesterase inhibitor rivastigmine increased ACh to a greater degree than either agent alone. DETQ also increased phosphorylation of the AMPA receptor (GluR1) and the transcription factor CREB in the striatum, consistent with enhanced synaptic plasticity. In the Y-maze, DETQ increased arm entries but (unlike a D1 agonist) did not reduce spontaneous alternation between arms at high doses. DETQ enhanced wakefulness in EEG studies in hD1 mice and decreased immobility in the forced-swim test, a model for antidepressant-like activity. In rhesus monkeys, DETQ increased spontaneous eye-blink rate, a measure that is known to be depressed in Parkinson's disease. Together, these results provide support for potential utility of D1 potentiators in the treatment of several neuropsychiatric disorders, including Parkinson's disease, Alzheimer's disease, cognitive impairment in schizophrenia, and major depressive disorder.
•The dopamine D1 potentiator DETQ was tested in humanized D1 mice and rhesus monkeys.•Actions of DETQ were dependent on endogenous dopaminergic tone.•DETQ displayed a behavioral profile consistent with central D1 receptor activation.•Neurochemical actions of DETQ support potential pro-cognitive effects.•D1 potentiators show promise for Parkinson's disease and other CNS disorders.
Clinical development of catechol-based orthosteric agonists of the dopamine D1 receptor has thus far been unsuccessful due to multiple challenges. To address these issues, we identified LY3154207 (3) ...as a novel, potent, and subtype selective human D1 positive allosteric modulator (PAM) with minimal allosteric agonist activity. Conformational studies showed LY3154207 adopts an unusual boat conformation, and a binding pose with the human D1 receptor was proposed based on this observation. In contrast to orthosteric agonists, LY3154207 showed a distinct pharmacological profile without a bell-shaped dose-response relationship or tachyphylaxis in preclinical models. Identification of a crystalline form of free LY3154207 from the discovery lots was not successful. Instead, a novel cocrystal form with superior solubility was discovered and determined to be suitable for development. This cocrystal form was advanced to clinical development as a potential first-in-class D1 PAM and is now in phase 2 studies for Lewy body dementia.
Allosteric potentiators amplify the sensitivity of physiologic control circuits, a mode of action that could provide therapeutic advantages. This hypothesis was tested with the dopamine D1 receptor ...potentiator DETQ 2-(2,6-dichlorophenyl)-1-((1S,3R)-3-(hydroxymethyl)-5-(2-hydroxypropan-2-yl)-1-methyl-3,4-dihydroisoquinolin-2(1H)-yl)ethan-1-one. In human embryonic kidney 293 (HEK293) cells expressing the human D1 receptor, DETQ induced a 21-fold leftward shift in the cAMP response to dopamine, with a K
of 26 nM. The maximum response to DETQ alone was ∼12% of the maximum response to dopamine, suggesting weak allosteric agonist activity. DETQ was ∼30-fold less potent at rat and mouse D1 receptors and was inactive at the human D5 receptor. To enable studies in rodents, an hD1 knock-in mouse was generated. DETQ (3-20 mg/kg orally) caused a robust (∼10-fold) increase in locomotor activity (LMA) in habituated hD1 mice but was inactive in wild-type mice. The LMA response to DETQ was blocked by the D1 antagonist SCH39166 and was dependent on endogenous dopamine. LMA reached a plateau at higher doses (30-240 mg/kg) even though free brain levels of DETQ continued to increase over the entire dose range. In contrast, the D1 agonists SKF 82958, A-77636, and dihydrexidine showed bell-shaped dose-response curves with a profound reduction in LMA at higher doses; video-tracking confirmed that the reduction in LMA caused by SKF 82958 was due to competing stereotyped behaviors. When dosed daily for 4 days, DETQ continued to elicit an increase in LMA, whereas the D1 agonist A-77636 showed complete tachyphylaxis by day 2. These results confirm that allosteric potentiators may have advantages compared with direct-acting agonists.
ABSTRACT
Introduction: The purpose of this study was to describe and compare the performance of balance and walking tests in relation to self‐reported fall history in adults with myotonic dystrophy ...type 1 (DM1). Methods: Twenty‐two (13 male) participants with DM1 completed, a 6‐month fall history questionnaire, the modified Dynamic Gait Index (mDGI), limits of stability (LoS) testing, and 10‐m walking tests. Results: Mean (SD) falls in 6 months was 3.7 (3.1), and 19 (86%) participants reported at least 1 fall. Significant differences in mDGI scores (P = 0.006) and 10‐m fast walking gait velocity (P = 0.02) were found between those who had been classified as “fallers” and those who had been classified as “nonfallers.” Significant correlations were found between mDGI scores and 10‐m walking time. Discussion: Falls are common in DM1, and the mDGI may have potential to distinguish fallers from nonfallers, whereas the LoS failed to detect such impairment. Future studies should further explore use of the mDGI in DM1. Muscle Nerve 58: 694–699, 2018
The neopentylidene-neopentyl complex (PNP)TiCHtBu(CH2 tBu) (1; (PNP− = N2-P(CHMe2)2-4-methylphenyl2) extrudes neopentane in neat fluorobenzene under mild conditions (25 °C) to generate the transient ...titanium alkylidyne (PNP)TiCtBu (A), which subsequently undergoes regioselective 1,2-CH bond addition of a fluorobenzene across the TiC linkage to generate (PNP)TiCHtBu(o-FC6H4) (2). Kinetic and mechanistic studies suggest that the C−H activation process is pseudo-first-order in titanium, with the α-hydrogen abstraction being the rate-determining step and the post-rate-determining step being the C−H bond activation of fluorobenzene. At 100 °C complex 2 does not equilibrate back to A and the preference for C−H activation in benzene versus fluorobenzene is 2:3, respectively. Compound 1 also reacts readily, and in most cases cleanly, with a series of hydrofluoroarenes (HArF), to form a family of alkylidene-arylfluoride derivatives of the type (PNP)TiCHtBu(ArF). Thermolysis of the latter compounds generates the titanium alkylidene-fluoride (PNP)TiCHtBu(F) (14) by a β-fluoride elimination, concurrent with formation of o-benzyne. β-Fluoride elimination to yield 14 occurs from 2 under elevated temperatures with k average = 4.96(16) × 10−5 s−1 and with activation parameters ΔH ⧧ = 29(1) kcal/mol and ΔS ⧧ = −3(4) cal/mol·K. It was found that β-fluoride elimination is accelerated when electron-rich groups are adjacent to the fluoride group, thus implying that a positive charge buildup at the arylfluoride ring occurs in the activated complex of 2. The alkylidene derivative (PNP)TiCHSiMe3(CH2SiMe3) (15) also undergoes α-hydrogen abstraction to form the putative (PNP)Ti’CSiMe3 (B) at higher temperatures (>70 °C) and dehydrofluorinates the same series of HArF when the reaction mixture is thermolyzed at >100 °C over 72 h to produce o-benzyne products and the fluoride analogue (PNP)TiCHSiMe3(F) (26). Only in the case of the substrate 1,2-F2C6H4 can the kinetic C−H activation product (PNP)TiCHSiMe3(o,m-F2C6H3) be isolated and crystallographically characterized. 1-Fluorohexane and fluorocyclohexane can also be dehydrofluorinated by intermediates A and B. No intermediates are observed, but in the case of 1-fluorohexane, the terminal olefin is spectroscopically identified. The dehydrofluorination of HArF and hydrofluoroalkanes (HAlF) can be made cyclic via the quantitative conversion of the alkylidene-fluorides to 1 and 15, by means of transmetalation with LiCH2XMe3 (X = C and Si), and the reactivity of 1 with halobenzenes is also presented and discussed.
Abstract only
Allosteric potentiators increase the affinity of endogenousagonist, in effect amplifying physiological control circuits. Because a potentiator should depend onendogenous tone, its ...effects are predicted to be self‐limiting and less proneto rapid tolerance development compared to direct‐acting agonists. Our objective was to test this hypothesis using DETQ, a novel allosteric potentiator of the dopamine D1 receptor.
Although DETQ has high affinity for the human D1 receptor, it is 70‐fold less potent at the mouse and rat D1 receptors, limiting its use as a pharmacological tool in rodents. To overcome this limitation, we created a transgenic knock‐in mouse expressing the human D1 receptor (hD1). Homozygotes showed normal behavior and breeding.
After oral dosing, DETQ caused a dose‐dependent 10‐fold increase in locomotor activity in habituated hD1 mice but not in wild‐type mice, implying a requirement for the human D1 receptor. The increase in locomotor activity was blocked by the D1 antagonist SCH39166 and by pretreatment with a high dose of reserpine, indicating that the behavioral response is dependent on endogenous dopamine release. At higher doses, the response to DETQ reached a plateau even though brain concentrations of unbound drug continued to rise. In contrast, the D1 agonists SKF82958 and A‐77636 showed bell‐shaped dose‐response curves, with a profound decrease in locomotor activity at the highest doses. The suppression of locomotor activity at high doses was due to engagement of competing stereotyped behaviors such as intense grooming. The stereotyped behaviors were not seen with DETQ, providing evidence that the response to DETQ is less liable to cause over stimulation. In repeated dosing over four days, the locomotor response to DETQ was maintained, whereas the response to A‐77636 showed rapid tolerance.
In hD1 mice treated with a low dose of reserpine, DETQ restored locomotor activity to untreated control levels; this model is relevant to stand‐alone therapy in mild‐to‐moderate Parkinson's disease. Versus a higher dose of reserpine, DETQ acted synergistically with L‐DOPA in restoring locomotor activity. DETQ also increased wakefulness and decreased sleep and was found to be effective in a behavioral despair model. We also compared DETQ with SKF82958 for efficacy in the Y‐maze. While both compounds enhanced the number of arm entries in a dose–dependent fashion, mice treated with DETQ maintained spontaneous alternation even at high doses, whereas mice treated with higher doses of SKF82958 showed an increased prevalence to return to the same arm (asign of cognitive dysfunction). Finally, DETQ increased spontaneous eye blink rate in the rhesus monkey, a response related to central D1 activation.
These results confirm that D1 potentiators may possess advantages over D1 agonists for the treatment of Parkinson's disease and other CNS disorders.
Abstract only
DETQ is a potent and selective dopamine D1 receptor potentiator that is active in several behavioral models (see abstracts by Heinz et al and Svensson et al at this meeting). We wished ...to explore the neurochemical basis for the behavioral effects of DETQ. Due to low affinity of DETQ in rodents, the current studies were carried out in transgenic mice in which both copies of the murine D1 receptor were replaced with its human counterpart (hD1 mice) (see Svensson et al). Receptor expression in hD1 mice was characterized using autoradiography of the D1‐selective antagonist 3H‐SCH23390. The pattern of D1 receptor distribution was very similar in wild‐type and hD1 mice, but the absolute level of expression was about 50% lower in hD1 mice. Using microdialysis in freely moving hD1 mice, DETQ and the D1 agonist SKF82958 increased extracellular levels of acetylcholine and histamine in cortical and subcortical areas. At a high dose we also observed enhanced extracellular levels of norepinephrine in the prefrontal cortex. Furthermore, a low dose of DETQ elevated hippocampal acetylcholine levels in an additive fashion with the acetylcholinesterase inhibitor rivastigmine. Brain levels of the histamine metabolites tele‐methylhistamine and tele‐methylimidazole acetic acid were also elevated in both microdialysate and post‐mortem tissue samples. The increases in brain histamine metabolites produced by DETQ were not present in wild‐type mice, indicating that the effects were mediated via the D1 receptor. Overall, these neurochemical changes correlated with brain exposure of DETQ and also with the behavioral effects (see Svensson et al.)
Effects on brain cyclic nucleotide levels were studied after microwave fixation of the forebran. Levels of cGMP were elevated in the striatum after both DETQ and SKF82958. Further changes in downstream signaling were explored measuring phosphorylation of the transcription factor CREB and the AMPA receptor GluR1. Both DETQ and SKF82958 increased pCREB and pGluR1 in the brain. Together, these data provide neurochemical evidence for enhanced synaptic plasticity of DETQ and SKF82958.
In conclusion, our in vivo neurochemical data support the proposal that the D1 potentiator DETQ selectively enhances D1 receptor function in the brain. Studies of neurotransmitter release, second messengers, and downstream signaling support a potential utility for D1 potentiators to enhance cognitive function in CNS disorders.
Support or Funding Information
All authors are current or past employees of Eli Lilly & Co
Multi‐cancer gene panels for hereditary cancer syndromes (hereditary cancer panels, HCPs) are widely available, and some laboratories have programs that limit patients' out‐of‐pocket (OOP) cost ...share. However, little is known about practices by cancer genetic counselors for discussing and ordering an HCP and how insurance reimbursement and patient out‐of‐pocket share impact these practices. We conducted a survey of cancer genetic counselors based in the United States through the National Society of Genetic Counselors to assess the impact of reimbursement and patient OOP share on ordering of an HCP and hereditary cancer genetic counseling. Data analyses were conducted using chi‐square and t tests. We received 135 responses (16% response rate). We found that the vast majority of respondents (94%, 127/135) ordered an HCP for patients rather than single‐gene tests to assess hereditary cancer predisposition. Two‐thirds of respondents reported that their institution had no protocol related to discussing HCPs with patients. Most respondents (84%, 114/135) indicated clinical indications and patients' requests as important in selecting and ordering HCPs, while 42%, 57/135, considered reimbursement and patient OOP share factors important. We found statistically significant differences in reporting of insurance as a frequently used payment method for HCPs and in‐person genetic counseling (84% versus 59%, respectively, p < 0.0001). Perceived patient willingness to pay more than $100 was significantly higher for HCPs than for genetic counseling(41% versus 22%, respectively, p < 0.01). In sum, genetic counselors' widespread selection and ordering of HCPs is driven more by clinical indications and patient preferences than payment considerations. Respondents perceived that testing is more often reimbursed by insurance than genetic counseling, and patients are more willing to pay for an HCP than for genetic counseling. Policy efforts should address this incongruence in reimbursement and patient OOP share. Patient‐centered communication should educate patients on the benefit of genetic counseling.
PDF
