Dose-escalation Study to Investigate the Safety, PK, and PD of ISU304/CB2679d in Hemophilia B Patients

Inclusion Criteria: 1. Previously treated male patients with moderate or severe hemophilia B (documented FIX activity ≤ 2% and exposed to any FIX product for ≥ 150 exposure days (estimated) at the time of screening) 2. Patients must be 12 to 65 years old at the time of screening 3. Patients who have discontinued a previously treated FIX product at least 4 days prior to the administration of investigational product 4. HIV negative, or if HIV positive with a CD4 count \> 200/μL (documented \< 200 particles/μL or ≤ 400,000 copies/mL) at the time of screening 5. Voluntary consent to participate in the study Exclusion Criteria: 1. Patients with a history or a family history of FIX inhibitors 2. Patients with FIX inhibitors (positive result for BeneFIX or ISU304 from inhibitor tests) at the time of screening 3. Patients who have a history of thromboembolic events (myocardial infarction, cerebrovascular disease, venous thrombosis, etc.) 4. Patients with known hypersensitivity, allergy, or anaphylaxis to any FIX product or hamster protein 5. Patients receiving treatment with a FIX product or a bypass agent within 4 half-lives for the agent used (at least 96 hours) prior to the administration of the investigational product 6. Patients who have been exposed to long-term administration of immunomodulating agents or immunosuppressants such as α-INF or adrenocortical hormones over the past 3 months or who are currently receiving or planning to receive such treatment during the study period 7. Patients who have been administered vaccines during the period of 6 months prior to the administration of the investigational product or plan to receive vaccines during the study period 8. Patients with any other co-existing bleeding disorder (Von Willebrand disease, etc.) 9. Patients with positive D-dimer results (≥ 0.5 μg/mL) at the time of screening 10. Patients with platelet counts less than 100,000/μL at the time of screening 11. Patients with ALT, AST levels 5 times greater than upper normal limit or total bilirubin, serum creatinine levels 2 times greater than upper normal limit at the time of screening 12. Active hepatitis patients who are HBs Ag positive or anti-HCV Ab positive at the time of screening 13. Patients scheduled for surgery during the study period 14. Patients participated in another study within 30 days before screening or scheduled to participate in any other study during the study period