Combination of cemiplimab and ISA101b vaccine for the treatment of recurrent/metastatic HPV16 cervical cancer.

5522 Background: Cemiplimab + ISA101b vaccine is being studied in HPV16-positive cancers in several phase 2 clinical trials. Here, we present the clinical efficacy and safety results of a phase 2 study of cemiplimab + ISA101b vaccine in patients with recurrent HPV16 cervical cancer who had disease progression after first-line chemotherapy (NCT04646005). Methods: Patients received cemiplimab 350 mg administered intravenously every 3 weeks + 3 doses of ISA101b vaccine 100 µg/peptide administered by subcutaneous injection on Days 1, 29, and 50. The primary endpoint was objective response rate (ORR) as measured by RECIST version 1.1. Secondary endpoints included duration of response (DOR), overall survival (OS), progression-free survival (PFS), and safety. Efficacy and safety endpoints were assessed in the full analysis set (patients who received ≥1 dose). Baseline PD-L1 expression was assessed by immunohistochemistry using anti–PD-L1 clone SP263. Results: This single arm study included 113 patients (Table). Median duration of follow-up was 4.9 months (interquartile range [IQR]: 3.0–7.5); median duration of treatment exposure was 10.0 weeks (IQR: 9.7–10.3) for ISA101b and 18.2 weeks (IQR: 9.0–27.6) for cemiplimab. At data cutoff (May 22, 2023), 90 patients discontinued treatment for reasons including disease progression (66.4%), death (7.1%), and an adverse event (AE; 3.5%) and 20.4% of patients were still on treatment. ORR (95% CI) was 16.8% (9.9–23.7). ORR by PD-L1 expression in tumor cells was 12.5% for patients with PD-L1 <1% and 22.4% for patients with PD-L1 ≥1%, per investigator assessment. Median (95% CI) DOR was 5.6 (3.5–not estimable) months. Median (95% CI) OS and PFS were 13.3 (10.8–16.3) months and 3.0 (1.7–4.0) months, respectively. At 6 and 12 months, the estimated survival probabilities (95% CI) were 80.5% (71.7–86.9) and 54.5% (42.1–65.3), respectively, for OS, and 20.5% (13.4–28.6) and 7.8% (3.3–15.0), respectively, for PFS. Treatment-emergent AEs occurred in 92.9% of patients, with the most common being injection-site reaction (38.9%), anemia (25.7%) and nausea (22.1%). Six (5.3%) patients died due to a treatment-emergent AE. Conclusions: Results from this phase 2 study of cemiplimab + ISA101b in patients with recurrent HPV16 cervical cancer show clinical benefit, especially in patients with high PD-L1 expression, and no unexpected safety signals, supporting further research. Clinical trial information: NCT04646005 . [Table: see text]