The dose for intravenous administration of OPC-61815 achieving tolvaptan exposure equivalent to that for oral administration of tolvaptan 15-mg tablet will be investigated by administering OPC-61815 injection 2 to 16mg or tolvaptan 15-mg oral tablet to subjects with congestive heart failure.

Inclusion Criteria:

1. Subjects who are currently on treatment with any of the following diuretics

   • Loop diuretics equivalent to furosemide tablet or fine granules at a dose of 40 mg/day or higher
   • Concomitant use of a loop diuretic and a thiazide diuretic (including thiazide analogs) at any dose
   • Concomitant use of a loop diuretic and an aldosterone antagonist or potassium-sparing diuretic agent at any dose

2. Subjects with congestive heart failure in whom lower limb edema, pulmonary congestion, and/or jugular venous distension due to volume overload is present

3. Subjects who are currently hospitalized or who are able to be hospitalized during the trial

Exclusion Criteria:

1. Subjects with acute heart failure
2. Subjects with a history of hypersensitivity to any of ingredients of OPC-61815 or tolvaptan
3. Subjects who are unable to sense thirst or who have difficulty with fluid intake

Anonymized Individual participant data (IPD) that underlie the results of this study will be shared with researchers to achieve aims pre-specified in a methodologically sound research proposal.

Data will be available after marketing approval in global markets, or beginning 1-3 years following article Publication. There is no end date to the availability of the data.

Otsuka will share data on an Otsuka-owned remotely accessible data sharing platform with Python and R analytical software. Research requests should be directed to clinicaltransparency@Otsuka-us.com.