• Top-line trial results for this intravenously administered prodrug of oral tolvaptan showed non-inferiority to oral tolvaptan
• If approved in Japan, OPC-61815 is expected to provide a new treatment options to patients who cannot take tolvaptan orally

Otsuka Pharmaceutical Co., Ltd. (Otsuka) announces positive top-line results from the phase 3 program for OPC-61815, under development in Japan for the treatment of cardiac edema. OPC-61815 is a prodrug of oral tolvaptan (tolvaptan sodium phosphate). A prodrug is a medicine that is converted into an active drug in the human body following administration.

Tolvaptan is a novel compound discovered by Otsuka designed as an orally available antagonist of the vasopressin V₂-receptor. It inhibits water reabsorption at the renal collecting duct, thereby enhancing water diuresis (aquaresis) without depletion of electrolytes.

In the non-clinical studies, OPC-61815, has been rapidly hydrolyzed to tolvaptan after intravenous administration, and shown effects. In the clinical phase 3 trial in Japan, the efficacy and safety of this drug were compared with 15 mg tolvaptan tablets in 294 patients with cardiac edema.

The trial outcomes showed non-inferiority of OPC-61815 versus tolvaptan 15mg tablet in the primary endpoint of change in body weight from baseline at the final dose. In addition, the main secondary endpoints were not significantly different from tolvaptan tablets. No safety issues were identified during the trial.

The full dataset from the phase 3 program for OPC-61815 is expected to be communicated at an upcoming medical congress and in medical journals.