Effects of OPC-51803, a Novel, Nonpeptide Vasopressin V2-Receptor Agonist, on Micturition Frequency in Brattleboro and Aged Rats

Therapeutic potentials of nonpeptidic V2R agonists for partial cNDI-causing V2R mutants

Loss-of-function mutations in the type 2 vasopressin receptor (V2R) are a major cause of congenital nephrogenic diabetes insipidus (cNDI). In the context of partial cNDI, the response to desmopressin (dDAVP) is partially, but not entirely, diminished. For those with the partial cNDI, restoration of V2R function would offer a prospective therapeutic approach. In this study, we revealed that OPC-51803 (OPC5) and its structurally related V2R agonists could functionally restore V2R mutants causing partial cNDI by inducing prolonged signal activation. The OPC5-related agonists exhibited functional selectivity by inducing signaling through the Gs-cAMP pathway while not recruiting β-arrestin1/2. We found that six cNDI-related V2R partial mutants (V882.53M, Y1283.41S, L1614.47P, T2736.37M, S3298.47R and S3338.51del) displayed varying degrees of plasma membrane expression levels and exhibited moderately impaired signaling function. Several OPC5-related agonists induced higher cAMP responses than AVP at V2R mutants after prolonged agonist stimulation, suggesting their potential effectiveness in compensating impaired V2R-mediated function. Furthermore, docking analysis revealed that the differential interaction of agonists with L3127.40 caused altered coordination of TM7, potentially contributing to the functional selectivity of signaling. These findings suggest that nonpeptide V2R agonists could hold promise as potential drug candidates for addressing partial cNDI.

Identification of novel selective V2 receptor non-peptide agonists

Peptides with agonist activity at the vasopressin V(2) receptor are used clinically to treat fluid homeostasis disorders such as polyuria and central diabetes insipidus. Of these peptides, the most commonly used is desmopressin, which displays poor bioavailability as well as potent activity at the V(1b) receptor, with possible stress-related adverse effects. Thus, there is a strong need for the development of small molecule chemistries with selective V(2) receptor agonist activity. Using the functional cell-based assay Receptor Selection and Amplification Technology (R-SAT((R))), a screening effort identified three small molecule chemotypes (AC-94544, AC-88324, and AC-110484) with selective agonist activity at the V(2) receptor. One of these compounds, AC-94544, displayed over 180-fold selectivity at the V(2) receptor compared to related vasopressin and oxytocin receptors and no activity at 28 other G protein-coupled receptors (GPCRs). All three compounds also showed partial agonist activity at the V(2) receptor in a cAMP accumulation assay. In addition, in a rat model of central diabetes insipidus, AC-94544 was able to significantly reduce urine output in a dose-dependent manner. Thus, AC-94544, AC-88324, and AC-110484 represent novel opportunities for the treatment of disorders associated with V(2) receptor agonist deficiency.

The effect of vasopressin and related compounds at V1a and V2 receptors in animal models relevant to human disease

Vasopressin, a neurohypophyseal peptide hormone, is the endogenous agonist at V1a, V1b and V2 receptors. The most important physiological function of vasopressin is the maintenance of water homeostasis through interaction with V2 receptors in the kidney. Vasopressin and related compounds are used in various clinical settings such as acute variceal bleeding associated with portal hypertension, septic shock, diabetes insipidus and coagulation disorders. The effect in the former two indications relates to the V1a receptor, and in the two latter indications the effect relates to the V2 receptor. Vasopressin and related compounds have demonstrated activity in animal models of portal hypertension, sepsis and septic shock, diabetes insipidus and coagulation disorders. The use of the compounds in animal models is reviewed. Generally, the effect of vasopressin and related compounds in animal models reflect the activity in the clinical setting, but in some cases important species differences exist.