To evaluate the efficacy of two dose levels of UB-621 administration in reducing the HSV-2 genital shedding rate in patients with recurrent genital HSV-2 infection.

This is a 2-stage, randomized, double-blind, dose-ranging, multi-center phase 2 study designed to evaluate the efficacy, safety, and PK of UB-621 given at 2.5 or 5 mg/kg in adult subjects with recurrent genital HSV-2 infection. The study consists of 2 stages of enrollments, in which 40 subjects will be enrolled in the first stage and randomly assigned to receive placebo or UB-621 at 2.5 mg/kg in a 1:3 ratio into Cohort 1 at Bv6 (Day B57), and another 40 subjects will be enrolled in the second stage and randomly assigned to receive placebo or UB-621 at 5 mg/kg in a 1:3 ratio into Cohort 2 at Bv6 (Day B57) after review by the Data Safety Monitoring Committee (DSMC). The DSMC will review safety data after all subjects of Cohort 1 complete the visit Fv6 (Day F28) and make the recommendation whether to proceed with enrollment for Cohort 2.

Inclusion Criteria:

• Subject must be at least 18 years of age inclusive.
• Subject must be HSV-2 seropositive
• Subjects have a history of recurrent genital herpes in the past year
• Subjects have a negative result on the HIV Ab/Ag assay
• Subjects must agree to use contraception during study participation
• Subjects must be willing NOT to use any topical genital therapy and systemic anti-HSV therapy from the beginning of the study till the end of week 16.
• Subjects must be willing to collect a swab each day from their genital area (non-lesional as well as lesional, if appropriate) during the swabbing periods, which are 8 weeks prior to and upon the administration of study drug.
• Female subjects must have a negative serum β-HCG at Screening and a negative urine pregnancy test prior to study drug administration.

Exclusion Criteria:

• Serious medical conditions, including poorly controlled diabetes, significant autoimmune diseases, co-existing sexually transmitted disease presentation (except HSV) in the anogenital area, etc. that may interfere with the assessment of the efficacy of UB-621.
• Documented HSV resistance to acyclovir, valacyclovir, famciclovir, or penciclovir
• History or current evidence of malignancy except for a localized non-melanoma skin cancer
• Known immunosuppression
• Exposure to HSV vaccine
• Medical history of macular or maculopapular skin reactions to antibody (ie, as evidenced by IgG or plasma administration)
• Any other conditions that in the judgment of the Investigator would preclude successful completion of the clinical study
• Treatment with systemic steroids or other immunomodulating agents within 30 days prior to Screening or planned treatment with systemic steroids or immunomodulators during the study period.
• Renal impairment and/or hepatic impairment
• ECG abnormalities of clinical relevance or cardiovascular conditions