Vasopressin V2 receptor ( IC50 = 14 nM ); Vasopressin V1 receptor ( IC50 = 1.2 μM )
The primary molecular target of Mozavaptan HCl is the vasopressin V2 receptor, a G-protein coupled receptor (GPCR) located primarily in the kidney. By competitively antagonizing the V2 receptor, Mozavaptan blocks the action of arginine vasopressin (AVP). This inhibition prevents the insertion of aquaporin-2 water channels into the apical membrane of collecting duct cells, thereby reducing water reabsorption. The result is an increase in urine volume (aquaresis) without a significant loss of electrolytes, which is a key feature of its mechanism of action. Its selectivity for V2 over V1 receptors is crucial for minimizing vasoconstrictor effects associated with V1 receptor activation.

Mozavaptan (OPC-31260) is around 100 times more specific for the V2 receptor and competitively inhibits AVP binding to the plasma membrane of rat kidney (V2 receptor) and liver (V1 receptor). Rat liver has a [3H]-AVP Kd value of 1.1 nM, while rat kidney has a concentration of 1.38 nM. Mozavaptan considerably decreased the Kd of [3H]-AVP in the rat liver and kidney (Kd for V1 receptor was 2.47 nM and 5.51 nM at dosages of 0.3 μM and 1 μM, respectively; Kd at 2.4 nM and 1 μM). At 0.3 μM and 1 μM dosages, the concentration of V2 receptor is 4.03 nM [1].

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OPC-31260, a benzazepine derivative, has been studied for its ability to antagonize the binding of arginine vasopressin (AVP) to receptors in rat liver (V1) and kidney (V2) plasma membranes, for antagonism of the antidiuretic action of AVP in alcohol-anaesthetized rats and for diuretic action in conscious normal rats. 2. OPC-31260 caused a competitive displacement of [3H]-AVP binding to both V1 and V2 receptors with IC50 values of 1.2 +/- 0.2 x 10(-6) M and 1.4 +/- 0.2 x 10(-8) M, respectively [1].
In vitro, Mozavaptan HCl has been characterized for its binding affinity and antagonistic activity at the vasopressin V2 receptor. In radioligand binding assays using HeLa cells expressing the human receptor, it has a Ki of 9.42 nM. Its functional antagonism is demonstrated by its ability to inhibit AVP-induced cAMP production in cells expressing the V2 receptor. The IC₅₀ for this inhibition is 14 nM, confirming its potent antagonist activity. The compound's selectivity is further evidenced by its much weaker activity at the V1 receptor (IC₅₀ = 1.2 µM).

The oral medication mozavaptan (OPC-31260; 1–30 mg/kg) dose-dependently enhances urine flow and lowers urine osmolality in hydrated conscious rats [1]. In rats that have been sedated with alcohol and loaded with water, mozavaptan (OPC-31260; 10-100 μg/kg; intravenous; male Sprague-Dawley rats) therapy suppresses exogenous arginine vasopressin (AVP) in a dose-dependent way. impact of antidiuretics[1].

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Mozavaptan (OPC-31260; 1-30 mg/kg; oral administration; hydrated conscious rats) treatment increases urine flow and lowers urine osmolality in a dose-dependent manner[1].
Mozavaptan (OPC-31260; 10-100 μg/kg; intravenous injection; male Sprague-Dawley rats) treatment dose-dependently blocks the antidiuretic effect of exogenously administered arginine vasopressin (AVP) in rats anesthetized with alcohol and loaded with water[1].

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OPC-31260 at doses of 10 to 100 micrograms kg-1, i.v., inhibited the antidiuretic action of exogenously administered AVP in water-loaded, alcohol-anaesthetized rats in a dose-dependent manner. OPC-31260 did not exert an antidiuretic activity suggesting that it is not a partial V2 receptor agonist. 4. After oral administration at doses of 1 to 30 mg kg-1 in normal conscious rats, OPC-31260 dose-dependently increased urine flow and decreased urine osmolality. The diuretic action of OPC-31260 was characterized as aquaresis, the mode of diuretic action being different from previously known diuretic agents such as furosemide, hydrochlorothiazide and spironolactone. 5. The results indicate that OPC-31260 is a selective V2 receptor antagonist and behaves as an aquaretic agent. OPC-31260 will be a useful tool in studying the physiological role of AVP and in the treatment of various conditions characterized by water retention [1].

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Ectopic antidiuretic hormone syndrome is a medical emergency characterized by dilutional hyponatremia. Clinical effectiveness of the vasopressin V2 receptor antagonist mozavaptan was evaluated in 16 patients. In short-term (7-day) treatment with the drug, serum sodium concentration (mean ± standard deviation) significantly (P = 0.002) increased from 122.8 ± 6.7 to 133.3 ± 8.3 mEq/l, and symptoms due to hyponatremia were improved. On the basis of these results, mozavaptan (Physuline(®)) was approved as an orphan drug for the treatment of the syndrome in 2006 in Japan. During the 43 months following its launch, 100 patients have been treated with the drug; overall clinical effects of the drug were found similar to those of this clinical trial. Clinically, mozavaptan may allow hyponatremic patients to be treated by aggressive cancer chemotherapy with platinum-containing drugs. Moreover, the drug may free patients from strict fluid-intake restrictions and thereby improve their quality of life[2].
In vivo, Mozavaptan HCl acts as an aquaretic agent, promoting the excretion of water without affecting electrolyte balance. This effect is a direct result of its V2 receptor antagonism in the kidney. It is orally active, making it suitable for chronic administration. The compound has been studied in animal models and clinical settings for conditions characterized by water retention, such as SIADH and congestive heart failure. Its ability to increase urine output and correct hyponatremia has been demonstrated, highlighting its therapeutic potential.

To determine binding kinetic constants, liver or kidney plasma membranes are incubated with increasing concentrations of [3H]-AVP with or without excess (1 μM) unlabelled AVP to obtain a saturation curve. Mozavaptan interacts either noncompetitively or competitively, as determined by examining the saturation binding of [3H]-AVP in liver membranes at concentrations of 0.3 μM and 1 μM, and in kidney membranes at concentrations of 3 nM and 10 nM. The Scatchard method is used to plot the data on the saturation curve, and regression analysis is used to fit the data.
For in vitro receptor binding assays, Mozavaptan HCl is evaluated using membrane preparations from cells expressing the human vasopressin V2 or V1 receptors. A standard protocol involves incubating the membranes with a radiolabeled antagonist, such as [³H]-AVP or a selective V2 ligand, and varying concentrations of Mozavaptan. The amount of bound radioligand is measured, and the concentration required to displace 50% of the specific binding (IC₅₀) is determined. This data is used to calculate the inhibitor constant (Kᵢ), which is a measure of its binding affinity.

Cell-based in vitro assays for Mozavaptan HCl involve cells that heterologously express the vasopressin V2 receptor. The compound's antagonist activity is assessed by measuring its ability to inhibit AVP-induced signaling. Cells are pre-incubated with Mozavaptan and then stimulated with AVP. The accumulation of cyclic AMP (cAMP), a downstream second messenger of V2 receptor activation, is then measured. The reduction in cAMP levels by Mozavaptan indicates its functional antagonism. This assay allows for the determination of IC₅₀ values for functional inhibition.

Animal/Disease Models: Hydrated conscious rat (300-350 g) [1]
Doses: 1 mg/kg, 3 mg/kg, 10 mg/kg, 30 mg/kg
Route of Administration: Oral
Experimental Results: Dose-dependent increase in urinary flow and diminished urine osmolarity.

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Dissolved in 3% ethanol (v/v), 1.67% glucose (w/v) and 0.3% NaCl (w/v); 10, 30, 100μg/kg;
i.v. injection;
Male Sprague-Dawley rats.

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This open-label, multicenter study protocol was approved by the Institutional Review Board of each participating medical institution prior to its inception; written informed consent was obtained from all patients.
Recruited were inpatients aged 20 to <75 years who had malignant tumors that might cause ectopic ADH syndrome as well as the diagnostic criteria of ectopic ADH syndrome as defined by Bartter and Schwartz such as serum sodium concentration ≤124 mEq/l, persistent urinary sodium excretion, normal renal, adrenal, and thyroid function, and no evidence of edema or dehydration.
Following a ≤2-day placebo administration period during which baseline data were collected, patients were given orally mozavaptan (single 30 mg tablet) once daily for 7 days, or where this was difficult, 3 days was allowed. Fluid restriction was used throughout the study period only for patients in whom it had already begun. Treatment of hyponatremia with demeclocycline, lithium chloride, or urea was not permitted.
The primary endpoint was serum sodium concentration. Blood samples were collected immediately before dosing on each test day. Clinical symptoms associated with hyponatremia such as anorexia, nausea/vomiting, headache, and CNS symptoms were recorded. Urine volume, urinary osmolality, urinary electrolyte (sodium, potassium, chloride) excretion, serum electrolyte (potassium, chloride) concentration, serum osmolality, and plasma ADH concentration were measured. New medical problems or exacerbations of those already existing were reported as adverse events.
In each case, the serum sodium level after the final administration of the study drug was compared with baseline value. The patients are divided into three groups: (i) the serum sodium level is improved to normal range; (ii) the level is still low, but increase is ≥6 mEq/l and (iii) the level is still low, and increase is <6 mEq/l. And mean sodium concentration after the final administration of the study drug was compared with that of baseline value by paired t-test [2].
In vivo animal experiments for Mozavaptan HCl typically involve the administration of the compound to animal models of water retention or SIADH. The compound is given orally, and its effects on urine output, urine osmolality, and electrolyte levels are measured. In models of SIADH, the ability of Mozavaptan to correct hyponatremia (low blood sodium) is a key endpoint. These studies confirm its in vivo efficacy and its mechanism as an aquaretic agent.

At baseline and at the end of the study, the mean serum sodium concentrations were 122.8 ± 6.7 mEq/L and 133.3 ± 8.3 mEq/L, respectively, which were statistically significant (P = 0.002; Figure 1). Serum sodium concentrations increased 24 hours after the first dose of Mozavaptane and remained elevated for 7 days within ≤24 hours after administration. Serum osmolality gradually increased from 24 hours after the first dose until the end of the study. Cumulative urine volume increased on the first day of treatment, while urine osmolality decreased during the first two days of treatment. [2]
Pharmacokinetic (PK) properties of Mozavaptan HCl are characterized by its oral bioavailability, which makes it suitable for oral administration. As a small molecule, it is likely well-absorbed and has a reasonable half-life for once or twice daily dosing. Its distribution, metabolism, and excretion would be typical of a lipophilic, orally active drug. Specific PK parameters, such as Cmax, Tmax, and AUC, would be determined in preclinical and clinical studies.

Mice were orally administered LDLo 1500 mg/kg. Sensory organs and special senses: ptosis; Behavior: somnolence (reduced overall activity). Journal of Biology and Pharmaceutical Sciences, 23(182), 2000 [PMID:10706381]

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Serum sodium levels were assessed in 16 patients. Serum sodium levels returned to normal in 8 patients, serum sodium levels remained below normal but increased by at least 6 mEq/L in 4 patients, and serum sodium levels increased by less than 6 mEq/L in 4 patients (Table 1).
Of the 8 patients who had at least one ectopic ADH syndrome-related symptom at baseline (such as anorexia, nausea/vomiting, headache, and central nervous system symptoms), these symptoms improved or disappeared in 7 patients. By symptom analysis, of the 8 patients with anorexia at baseline, anorexia disappeared in 3 patients and improved in 2 patients; while in patients who had at least one nausea/vomiting, headache, and central nervous system symptoms at baseline, these symptoms disappeared after treatment. However, one patient developed new anorexia, and another developed new headache. Although some patients experienced slight increases or decreases in plasma antidiuretic hormone (ADH) levels after Mozavaptane treatment, no significant changes were observed overall. Of the 16 patients, 11 experienced 35 adverse events, all of which were minor. The most common adverse event was dry mouth in 5 patients. A total of 15 adverse drug reactions occurred in 6 patients (dry mouth, n=5; elevated serum potassium, n=2; malaise, elevated aspartate aminotransferase (AST), elevated alanine aminotransferase (ALT), decreased serum calcium, elevated serum lactate dehydrogenase, elevated blood urea nitrogen, decreased appetite, and nocturia, 1 case each). One patient withdrew from the study due to anorexia after 3 days of treatment with the study drug. After completion of Mozavaptane treatment, one patient died 30 days later from cancer-related illness (ID 1 in Table 1); this patient had small cell lung cancer, accompanied by myasthenia gravis, diabetes, pneumonia, and hypertension. 146 to 144 days prior to Mozavaptane treatment, the patient received chemotherapy with carboplatin and etoposide, which shrank the tumor and improved syndrome of inappropriate antidiuretic hormone secretion (SIADH). However, chemotherapy was forced to be discontinued due to significant myelosuppression, which subsequently led to rapid tumor growth. 29 days before Mozavaptane treatment, the patient's serum sodium concentration was 132 mEq/L, but it gradually decreased to 119 mEq/L 14 days before treatment. At this point, the patient's condition was no longer suitable for continued chemotherapy, so Mozavaptane treatment was initiated. Despite the effectiveness of Mozavaptane treatment, the patient's condition deteriorated due to rapid tumor progression. The patient died 30 days after completing Mozavaptane treatment, and autopsy showed that the tumor directly invaded the heart and thoracic vertebrae, indicating that the patient died of cancer. No other serious adverse events were reported. [2]
Toxicology data for Mozavaptan HCl would be derived from preclinical safety studies. As a V2 receptor antagonist, its primary on-target effects are related to increased urine output, which could lead to dehydration or electrolyte imbalances if not properly managed. Off-target effects would be minimized by its selectivity for the V2 receptor over the V1 receptor. Preclinical studies would have assessed its safety profile, including acute and chronic toxicity.

[1]. Characterization of a novel aquaretic agent, OPC-31260, as an orally effective, nonpeptide vasopressin V2 receptor antagonist. Br J Pharmacol. 1992 Apr;105(4):787-91.

[2]. Clinical implication of the antidiuretic hormone (ADH) receptor antagonist mozavaptan hydrochloride in patients with ectopic ADH syndrome. Jpn J Clin Oncol. 2011 Jan;41(1):148-52.

Mozavaptane hydrochloride belongs to the benzamide class of drugs and has a diuretic effect. Based on these research results, Mozavaptane (Physuline®) was approved as an orphan drug in Japan in 2006 for the treatment of ectopic antidiuretic hormone (ADH) syndrome. It is worth noting that while demeclocycline, lithium chloride, or urea have been reported to be effective for ectopic ADH syndrome, clinical experience indicates that these drugs have limited efficacy. In the United States and the European Union, there are two V2 receptor antagonists on the market—cannivatan (injection) and tolvaptan (oral tablets). Cannivatan is a dual antagonist of both V1a and V2 receptors, and its indication in the United States is "treatment of normovolemic hyponatremia and hypervolemic hyponatremia in hospitalized patients." Tolvaptan, through structural modifications, has a higher affinity for the V2 receptor than its parent drug, mozavaptan. Tolvaptan is indicated in the United States for the treatment of clinically significant hypervolemic and normovolemic hyponatremia, including in patients with heart failure, cirrhosis, and syndrome of inappropriate antidiuretic hormone secretion (SIADH). In the European Union, it is indicated for the treatment of hyponatremia in adults secondary to SIADH. Mozavaptan is currently the only drug approved in Japan for the treatment of ectopic ADH syndrome, but it has not yet been approved or is under development outside of Japan. In the 43 months since its market launch, 100 patients have received treatment with this drug. According to post-marketing outcomes, the overall clinical efficacy of the drug is similar to that of clinical trials. Mozavaptan has made two important contributions to the treatment of ectopic ADH syndrome. First, short-term use of mozavaptan may enable patients with hyponatremia who would otherwise be unsuitable for intensive platinum-based chemotherapy to receive treatment. Second, mozavaptan may allow patients to be freed from strict fluid intake restrictions, thereby improving their quality of life. Therefore, Mozavaptane provides a new treatment option for patients with ectopic ADH syndrome, offering both potent chemotherapy and palliative care. [2]
In summary, Mozavaptan HCl (OPC 31260) is a potent, selective, and orally active vasopressin V2 receptor antagonist. It has an IC₅₀ of 14 nM for the V2 receptor and shows approximately 85-fold selectivity over the V1 receptor. Its mechanism of action involves blocking AVP-mediated water reabsorption in the kidney, leading to aquaresis. It has been investigated for the treatment of hyponatremia and SIADH. The compound is a well-established pharmacological tool and has been advanced into clinical studies.

C27H30CLN3O2

464.006

463.202

C, 69.89; H, 6.52; Cl, 7.64; N, 9.06; O, 6.90

138470-70-9

Mozavaptan;137975-06-5

636389

White to off-white solid powder

543ºC at 760mmHg

282.2ºC

7.49E-12mmHg at 25°C

6.23

2

3

4

33

643

0

MOROBKPIULFQDC-UHFFFAOYSA-N

InChI=1S/C27H29N3O2.ClH/c1-19-9-4-5-10-22(19)26(31)28-21-16-14-20(15-17-21)27(32)30-18-8-13-24(29(2)3)23-11-6-7-12-25(23)30;/h4-7,9-12,14-17,24H,8,13,18H2,1-3H3,(H,28,31);1H

N-[4-[5-(dimethylamino)-2,3,4,5-tetrahydro-1-benzazepine-1-carbonyl]phenyl]-2-methylbenzamide;hydrochloride

OPC31260l; OPC31260; Mozavaptan hydrochloride; 138470-70-9; Physuline; mozavaptan HCl; Mozavaptan (hydrochloride); OPC 31260

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~20.83 mg/mL (~44.89 mM)
H2O : ~10 mg/mL (~21.55 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.48 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (4.48 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (4.48 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)