Unique pharmacological properties of etrasimod among S1P receptor modulators

Abstract

Etrasimod (ADP334) is an oral, once-daily, selective sphingosine 1-phosphate (S1P)_1,4,5 receptor modulator for the treatment of moderately to severely active ulcerative colitis and in development for the treatment of immune-mediated inflammatory diseases. Interaction between S1P and its five receptor subtypes (S1P₁-S1P₅) plays a role in several physiologic systems, including the cardiovascular and immune systems. Since differences in S1PR binding and downstream intracellular signaling could contribute to distinct profiles of drug efficacy and safety, we directly compared the S1P_1-5 selectivity profile of etrasimod to three marketed S1PR modulators: fingolimod, ozanimod, and siponimod. Using both heterologous expression systems and human umbilical vein endothelial cells that spontaneously express S1P₁, we profiled key S1P₁ downstream signaling pathways and found that etrasimod had similar potency to the other tested S1PR modulators in promoting β-arrestin recruitment and S1P₁ internalization. However, etrasimod was notably less potent than other S1PR modulators in assays measuring S1P₁-mediated G protein activation (GTPγS binding and cAMP inhibition). Relatively lower potency of etrasimod in inducing G protein signaling corresponded to significantly diminished activation of human cardiac G protein-coupled inwardly rectifying potassium channels when compared to ozanimod. Together with pharmacokinetic properties, this pharmacologic profile of etrasimod may contribute to the positive benefit risk profile of etrasimod observed during the phase III ELEVATE UC 52 and ELEVATE UC 12 trials in patients with moderately to severely active ulcerative colitis.

Keywords: etrasimod; pharmacodynamics; pharmacokinetics; sphingosine 1‐phosphate receptor modulator.

Fig. 1

S1P receptor downstream signaling. Etrasimod selectively activates S1P₁, S1P₄, and S1P₅ (colored blue), with no detectable activity on S1P₂ or S1P₃ (colored purple). AMP, adenosine monophosphate; cAMP, cyclic adenosine monophosphate; Cdc42, Cell division control protein 42 homolog; GIRK, G protein‐coupled inwardly rectifying potassium; PI3K, phosphoinositide 3‐kinase; S1P, sphingosine 1‐phosphate.

Fig. 2

Concentration–response curves in cell lines stably transduced to express hS1P₁ for (A) β‐arrestin recruitment, (B) receptor internalization, (C) GTPγS binding, and (D) cAMP inhibition. All assays were performed in media with identical protein concentration (0.1% BSA). Error bars represent standard deviation. Panels (A–D) present technical replicates. (A) and (D): n = 4; (B) and (C): n = 3. BSA, bovine serum albumin; n, number of tests; S1P, sphingosine 1‐phosphate.

Fig. 3

Concentration–response curves for cAMP assay using HUVECs known to naturally express S1P₁. Error bars represent standard deviation (n = 4). This figure presents technical replicates. HUVEC, human umbilical vein endothelial cells; n, number of tests; S1P, sphingosine 1‐phosphate.

Fig. 4

Calculated relative bias of S1PR modulators in activating G protein‐dependent signaling (GTPγS and cAMP) versus G protein‐independent signaling (β‐arrestin and receptor internalization). The relative bias factors were calculated using the formula ΔΔlog(E _max/EC₅₀) and normalized to the bias of S1P that was given as 0. Assays presented in plot group (A) were performed using cell lines stably transduced with hS1P₁. In plot group (B), the cAMP assay was performed using HUVEC cells naturally expressing S1P₁. The values represent the fold change relative to the bias calculated for S1P and given as 0. EC₅₀, concentration required for 50% of the maximum effect; HUVEC, human umbilical vein endothelial cells; S1P, sphingosine 1‐phosphate; S1PR, sphingosine 1‐phosphate receptor.

Fig. 5

Effect of S1P receptor modulators on cardiac tissue. (A) mRNA expression levels of S1PR modulators in human cardiac tissues from the right atrium and sinoatrial node normalized to human Ribosomal Protein S9. Data represent mean values measured for four donors. Error bars represent standard deviation. (B) Activity of etrasimod, ozanimod, and fingolimod(P) in promoting GIRK channel activity in human atrial cardiomyocytes. Data represent mean values measured for six donors. Error bars represent standard deviation. Two‐way ANOVA was used to compare the activity of etrasimod and ozanimod (**P = 0.0057, ***P = 0.0009). Corresponding values for comparing the activity of etrasimod and fingolimod(P) were P = 0.1097 and P = 0.3275, respectively. ANOVA, analysis of variance; GIRK, G protein‐coupled inwardly rectifying potassium; S1P, sphingosine 1‐phosphate; S1PR, sphingosine 1‐phosphate receptor.