TRPC4/5 inhibitors: Phase I results and proof of concept studies

Abstract

Transient receptor potential canonical (TRPC) ion channels are expressed in areas of the brain responsible for processing emotion and mood and have been implicated in the pathophysiology of internalizing disorders such as major depressive disorder and anxiety disorders. This review outlines the rationale for targeting TRPC ion channels for drug development, with specific focus on TRPC4 and TRPC5. We provide preclinical evidence that the lack of TRPC4 and TRPC5 channels or its pharmacological inhibition attenuate fear and anxiety without impairing other behaviors in mice. We also report on clinical studies of BI 1358894, a small molecule inhibitor of TRPC4/5 ion channels, demonstrating reduced psychological and physiological responses to induced anxiety/panic-like symptoms in healthy volunteers. Furthermore, we highlight an imaging study that investigated the acute effects of BI 1358894 and showed reduced activation in several brain regions involved in emotional processing. We conclude that these findings demonstrate a critical role for TRPC4 and TRPC5 in emotional processing, even though it remains an open question if the biological signatures of TRPC4/5 inhibition reported here translate into clinical efficacy and indicate that a TRPC4/5 inhibitor might provide a more effective treatment of internalizing disorders.

Keywords: Anxiety; Emotional processing; Major depressive disorder; Negative valence systems; Neuroimaging; Transient receptor potential canonical ion channels.

Fig. 1

GPCR activation and regulation of TRPC channels. Binding of an agonist to GPCR initiates a signaling cascade, stimulation of G protein causes phospholipase C-mediated hydrolysis of PIP₂ to IP₃ and diacylglycerol (DAG). IP₃ binds to IP₃ receptor, a ligand-gated ion channel on the endoplasmic reticulum (ER), which leads to the release of Ca²⁺ from the internal ER stores. This Ca²⁺ depletion in turn, allows stromal interaction molecule 1 (STIM1) to aggregate, followed by the activation of the TRPC channels in the plasma membrane, allowing Ca²⁺ to enter the cell that orchestrates cellular functions [85, 86]. DAG, diacylglycerol; GPCR, G protein coupled receptor; IP_{3 ,} inositol-triphosphate; PIP₂, bisphosphate; PLC, phospholipase C; TRPC, transient receptor potential canonical. Adapted from Selvaraj S, et al. CNS Neurol Disord Drug Targets. 2010;9:94–104. 10.2174/18715271079096665.

Fig. 2

Preclinical data in mouse models indicates that the TRPC4/5 inhibitor HC-070 has anxiolytic and anti-depressant effects. (A–C) HC-070 attenuates CCK-4-induced EPSCs recorded from the basolateral amygdala in a slice preparation. (A) Representative traces before and after CCK-4 application in the presence of vehicle. (B) Representative traces before and after CCK-4 application in the presence or absence of HC-070. (C) Quantitation of the results (n = 8). HC-070 was pre-incubated with the slice. CCK-4 was applied at the time indicated. Error bars represent the SEM (*p < 0.05, **p < 0.001, Tukey’s multiple comparisons test following two-way analysis of variance [ANOVA]). The holding potential was − 70 mV. (D & E) HC-070 decreases anxiety in a standard EPM. (D) Mice were administered vehicle or 0.3, 1, or 3 mg/kg HC-070 orally 60 min prior to EPM. The positive control, 1.5 mg/kg diazepam, was administered IP 30 min prior to testing. At 3 mg/kg, HC-070 significantly increased the number of open arm entries compared to the oral control (**p < 0.01, Dunnett’s post-hoc test following one-way ANOVA). The positive control, 1.5 mg/kg diazepam, also increased open arm entries (*p < 0.05, t-test). Animals that jumped or fell off the EPM during the test were excluded, such that the sample size (n) differed between groups. Each animal is shown on the graph (circles) and the horizontal lines represent the mean. (E) Average plasma and brain exposures from satellite animals dosed with 0.3, 1, or 3 mg/kg HC-070, 60 min post-dosing. Error bars show standard deviation. (F) Effects of HC-070 on CSD-induced fear hyper-reactivity. In the tone CS memory test, freezing was also measured in the inter-trial intervals (ITIs) between CS presentations. The left panel presents the fear expression curve in ITIs between CSs using the average freezing per pair of consecutive ITIs. The right panel presents the average freezing across all 12 ITIs. Here also, HC-070 reduced fear memory in CSD mice, as indicated by the increased rate at which their freezing level during the ITIs attenuated compared with CSD-VEH mice, i.e., faster extinction learning. ANOVA, analysis of variance; CCK-4, cholecystokinin-tetrapeptide; CS, conditioned stimulus; CSD, chronic social defeat; EPM, elevated plus maze; EPSC, excitatory postsynaptic current; ITI, inter-trial interval; SEM, standard error of the mean; TRPC, transient receptor potential conical; VEH, vehicle. Reproduced from Just S, et al. PLoS One. 2018;13(1):e0191225 under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).

Fig. 3

In the CCK-4 challenge study, BI 1358894 reduced psychological and physiological responses. Mean effect–time profiles of (A) PSS change from baseline (± SD); (B) EVAS change from baseline (± SD). As well as intra-individual and mean comparisons of (C) maximum PSS sum intensity score and (D) maximum EVAS scores. Mean effect–time profiles of (E) ACTH and (F) cortisol (± SD) in blood during the CCK-4 challenge after a single administration of BI 1358894 100 mg or placebo are presented. A single dose of BI 1358894 or placebo were administered 5 h prior to CCK-4 challenge. ACTH, adrenocorticotropic hormone; CCK-4, cholecystokinin-tetrapeptide; E_max, maximum PSS/EVAS score or change from baseline; EVAS, emotional faces visual analog scale; PSS, Panic Symptom Scale; SD, standard deviation. Reproduced from Goettel M, et al. CNS Drugs. 2023;37(12):1099–110 with permission from Springer Nature.

Fig. 4

In the fMRI study, BI 1358894 significantly reduced activation in several brain regions involved in emotional processing. Effects of placebo, citalopram, and BI 1358894 on mean % BOLD signal change shown in ROIs for the faces and scenes task, respectively. Box plots illustrate the median across participants of the average % BOLD signal change within each ROI, with notches indicating the 95% confidence interval of the median; the lower whisker shows quartile 1–1.5 x the interquartile range; the upper whisker shows quartile 3 + 1.5 x the interquartile range. Horizontal brackets above the box plots indicate differences in adjusted means from placebo at *p < 0.05 and **p < 0.01 (ANOVA). Brain slices illustrate the difference in % BOLD signal change between placebo and each respective compound; blue color indicates a decrease in % BOLD signal change in the compound group compared with placebo, red color indicates an increase in % BOLD signal change in the compound group compared with placebo. ANOVA, analysis of variance; BOLD, blood oxygenation level dependent; fMRI, functional magnetic resonance imaging; ROI, regions of interest. Reproduced from Grimm S, et al. Eur Neuropsychopharmacol. 2022;65:44–5 under the terms of the Creative Commons CC-BY License (http://creativecommons.org/licenses/by/4.0/).