A5368

Safety and Immunotherapeutic Activity of Cemiplimab in Participants With HBV on Suppressive Antiviral Therapy: A Phase I/II Ascending Multiple Dose Study

The study consists of up to three cemiplimab dose cohorts (n=10 participants each). The cohorts will open sequentially, based on the safety of the previous cohort. Cohort 1 will open first to examine the lowest dose. When Cohort 1 participants have completed study week 18 visit and there are no safety concerns, Cohort 2 will open for enrollment. A similar assessment will be conducted with Cohort 2 to make a decision on opening Cohort 3. In each cohort, participants enter the study 6 weeks prior to initiation of treatment. The 6-week lead-in period is followed by a 6-week treatment period where two infusions of cemiplimab are administered 6 weeks apart, at study weeks 6 and 12.

The total study duration per participant is 90 weeks, including 78 weeks of follow-up after the treatment period. Study visit schedule includes visits at entry, and weeks 6, 7, 8, 10, 12, 13, 14, 16, 17, 18, 22, 24, 30, 36, 54, 72 and 90. Evaluations include: a medical and medication history; assessment of HBV antiviral therapy adherence; physical exam; blood, urine, and fecal collection; rectal swab; liver biopsy and fine needle aspiration; and optional leukapheresis.