Sukari, Ammar

Importance The incidence of human papillomavirus type 16 (HPV16–positive) recurrent/metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) is rising. Approved therapies offer a durable response to a minority of patients. Objective To determine the efficacy and safety of a therapeutic HPV16-targeted immunotherapy, PDS0101, in combination with pembrolizumab in participants with HPV16-positive R/M HNSCC, with separate evaluation of immune checkpoint inhibitor (ICI)–naive and ICI-resistant cohorts. Design, Setting, and Participants VERSATILE-002 was a phase 2, open-label, multicenter nonrandomized clinical trial conducted at 26 oncology centers from March 29, 2021, to May 15, 2025, across the US, UK, and Ireland using the Simon 2-stage optimal design. Efficacy analyses were performed on modified intent-to-treat (mITT) population; safety analyses included all participants who received 1 or more doses. Eighty-eight participants with histologically confirmed R/M HPV16-positive HNSCC were enrolled, of whom 87 (98.9%) received treatment and composed the safety population. Seventy five (85.2%) were in the mITT population used for efficacy analyses, of whom 53 (70.7%) were ICI-naive with a programmed cell death ligand 1 combined positive score of 1 or greater and 22 (29.3%) were ICI-resistant. Exposures Pembrolizumab (200 mg, intravenously, every 3 weeks for up to 35 cycles) plus subcutaneous PDS0101 (5 scheduled doses per protocol). Main Outcomes and Measures The primary end point was objective response rate (ORR) per the Response Evaluation Criteria in Solid Tumors , version 1.1, by a masked independent central reviewer. Secondary end points included progression-free survival (PFS), median overall survival (mOS), and safety, with exploratory end points of duration of response, disease control rate, and response rates by programmed cell death ligand 1 status. Results Of the 75 patients in the mITT population, the mean (SD) age was 64.0 (8.3) years; 4 individuals (5%) were female and 71 (95%) were male; and 2 individuals (3%) were Asian, 1 (1%) was Black, 5 (7%) were Hispanic, and 71 (95%) were White. Among 53 ICI-naive participants in the mITT cohort, ORR by the central reviewer was 34.0%, median PFS was 5.3 months (95% CI, 2.10-9.00), and mOS was 39.3 months (95% CI, 23.90 to not evaluable). Among 22 ICI-resistant patients in the mITT cohort, no objective responses were observed and the primary end point (ORR by central reviewer) was not met, but mOS was 14.8 months (95% CI, 8.50-26.00). The treatment was well tolerated, with 13.8% experiencing grade 3 or higher treatment-related adverse events. Conclusions and Relevance The results of this nonrandomized clinical trial suggest that PDS0101 plus pembrolizumab showed antitumor activity in ICI-naive HPV16-positive R/M HNSCC, with favorable safety, response rates, and survival outcomes. The findings support further evaluation in a first-line setting. Trial Registration ClinicalTrials.gov Identifier: NCT04260126

6037 Background: The incidence of HPV-associated head and neck squamous cell carcinoma (HNSCC) continues to rise with over 90% of cases being driven by HPV16. Median overall survival (OS) with pembrolizumab in first-line recurrent/metastatic (R/M) HNSCC is 12.3 months in subjects with CPS ≥1, 10.8 months for CPS ≥1-19, and 14.9 months for CPS ≥20. There is an urgent need to improve survival rates in the growing population of HPV16-positive R/M HNSCC. PDS0101 (Versamune HPV) is an investigational T cell stimulating immunotherapy that unleashes a potent, durable attack against HPV16-positive cancers and is being studied in combination with pembrolizumab. Preliminary results were presented at ASCO 2023. (Price KAR, et al. ASCO 2023. Abstract 6012). Methods: VERSATILE-002 is a single-arm phase 2 study evaluating PDS0101 and pembrolizumab for first-line HPV16-positive R/M HNSCC with CPS ≥1. Subjects received pembrolizumab 200 mg IV Q3W with PDS0101 1 mL SC administered concurrently during Cycles 1, 2, 3, 4, and 12 and pembrolizumab alone for all other Cycles up to Cycle 35 (approx. 2 years). The primary study endpoint is confirmed objective response rate (ORR) per RECIST 1.1. Secondary endpoints include progression-free survival (PFS), OS, and safety. Results: The median follow-up is 18.4 months (range 0.2-42.7 months). The efficacy population consists of 53 subjects: 32 (60%) with CPS ≥1-19 and 21 (40%) with CPS ≥20. The median OS for subjects with CPS ≥1 is 30 months (95% CI 23.9, NE). For the CPS ≥1-19 subgroup, the median OS is 29.5 months (95% CI 15.3, NE). For the CPS ≥20 subgroup, the median OS is 39.3 months (95% CI 18.4, NE). Confirmed response rates by investigator assessment are shown in the Table. Twenty-three subjects are still on study: 3 on treatment and 20 in long-term follow-up. No new safety signals have emerged. The most common TRAEs are injection site reactions, fatigue, headache, and pruritus. Only 19% of subjects experienced Grade ≥3 TRAEs. No subject had a Grade 5 TRAE. Conclusions: These data represent one of the most extended follow-up periods to date of subjects receiving an HPV16-targeted therapy for HPV16-positive R/M HNSCC. The PDS0101 and pembrolizumab combination is well tolerated and has demonstrated deep and durable clinical responses. Median OS is promising in light of historic expectations, both overall and relative to PD-L1 subgroup, and remains durable with continued follow up. The results support further evaluation in a randomized phase 3 study with OS as the primary endpoint. Clinical trial information: NCT04260126 . Summary of results. CPS ≥1-19 (N=32) CPS ≥20 (N=21) CPS ≥1 (N=53) ORR, % 28.1 47.6 35.8 DCR, % 75.0 81.0 77.4 Median DOR, months (95 % CI) 21.8 (4.2, NE) NE (5.6, NE) 21.8 (11.5, NE) Median PFS, months (95% CI) 5.1 (2.4, 8.1) 14.1 (2.1, NE) 6.3 (3.5, 9.0) Median OS, months (95% CI) 29.5 (15.3, NE) 39.3 (18.4, NE) 30.0 (23.9, NE)

3584 Background: Patients (pts) with microsatellite stable (MSS) metastatic colorectal cancer (mCRC) that progressed on ≥2 prior therapies have limited treatment options, with median OS ranging from 6-9 months (mo). In the dose-escalation phase of this first-in-human multicohort study (NCT02720068), the anti-lymphocyte activation gene (LAG)-3 antibody favezelimab (fave) was well tolerated alone and with pembrolizumab (pembro) across all dose levels (Lakhani, SITC, 2018, abstract O26). Here, we evaluate the safety and efficacy of fave alone or in combination with pembro in pts with advanced MSS CRC from the dose confirmation phase. Methods: Eligible pts with MSS PD-1/PD-L1-treatment-naïve mCRC that progressed on prior standard-of-care (3L+) were enrolled (cohort A) to receive the RP2D of 800 mg fave alone (Arm 1), 800 mg fave + 200 mg pembro (Arm 2C), or 800 mg fave + 200 mg pembro (MK-4280A) co-formulation (Arm 5), all Q3W. Treatment continued for 35 cycles or until progression, unacceptable toxicity, or investigator/pt decision. Pts with confirmed progression per irRECIST v1.1 on fave alone could crossover to 800 mg fave + pembro. Safety was assessed in all treated pts; efficacy in the full analysis set (FAS) of all treated pts with baseline scan. Objectives included safety (primary), ORR (RECIST v1.1 by investigator [secondary]), and DOR, PFS, and OS (exploratory). Interim analysis data cut-off was: Oct. 23, 2020. Results: A total of 20 pts received fave (Arm 1); 89 pts (including 9 crossover) received fave + pembro (Arms 2C+5); 12 pts (Arm 1) and 36 pts (Arms 2C+5), had PD-L1 CPS ≥1 tumors. At data cut-off, median follow-up was 5.8 months (mo) in Arm 1 and 6.2 mo in Arms 2C+5. Treatment-related adverse events (TRAEs) were 65% with fave (Arm 1) and 65.2% with fave + pembro (Arms 2C+5). Grade ≥3 TRAEs were 15% (Arm 1), and 20% [Arms 2C+5]). No grade 5 TRAEs were reported. Common TRAEs (≥15%) included fatigue (20.0%), nausea (15%) with fave, and fatigue (16.9%) with fave + pembro. Confirmed ORR was 6.3% (4PR, 1CR) with fave + pembro (Arms 2C+5). No pt receiving fave alone responded. In Arms 2C+5, median DOR was 10.6 mo (range, 5.6-12.7). ORR, OS and PFS by PD-L1 status are reported in the Table. Conclusions: Favezelimab alone or in combination with pembrolizumab had a manageable safety profile, with no treatment-related deaths. Promising antitumor activity was observed with combination therapy, including with MK-4280A, compared with monotherapy most notably in pts with PD-L1 CPS ≥1 tumors. Clinical trial information: NCT02720068. [Table: see text]