Inclusion Criteria:  Age ≧18 years at the time of signing ICF HSV-2 seropositive when screening A history of recurrent genital herpes and experience 6-12 episodes in the past year Negative result of the HIV assay In baseline period, subject have to present at the site within 72 hours after the occurrence of new lesions Keep daily diary during the study period Female subjects: negative serum β-HCG at screening and no beast-feeding. Use contraception during study participation Understanding and willing to fully comply with study interventions and restrictions.  Exclusion Criteria:  Any medical conditions that may interfere the assessment of UB-621efficacy, or any medical conditions that may present symptoms in the anogenital regions (such as syphilis, genital warts). History of malignancy, diabetes, auto-immune diseases or immunodificiency diseases. Use of systemic steroids or immunomodulators within 30 days prior to the screening Participating any clinical trials within 30 days prior to the screening, or within 5 half-life of any investigational drugs, take the longer. Vaccination within 30 days prior to the screening. Prior exposure to any HSV vaccines Known hypersensitive to monoclonal antibodies ECG abnormalities with clinical relevance or cardiovascular diseases at screening Serum creatinine > 1.5 mg/dL at screening AST and ALT > 2.5 x ULN at screening HBsAg positive or HCT antibody positive at screening Syphilis RPR test positive at screening TB history or documented T-spot positive, or now is under treatment of TB Any other circumstances that are determined to affect the conduct or successful completion of the clinical study