Immune checkpoint inhibitor in high-risk oral potentially malignant disorders (IMPEDE study): An interim analysis on safety

2595 Background: Oral Potentially Malignant Disorders (OPMD) represent the most common oral precancerous condition, with a variable risk of malignant transformation. The most effective biomarker in predicting malignant transformation risk is loss of heterozygosity (LOH). Patients (pts) carrying OPMD with LOH at 3p14 and/or 9p21 plus LOH at another locus have an expected 3-year risk of developing oral cancer of 35%. This chromosomal profile is found in about 30% of OPMD. IMPEDE is a phase II, open-label, single-arm trial designed to evaluate the efficacy of PD-L1 inhibitor avelumab in reverting cancer transformation risk in OPMD with LOH. In this analysis, we report the first safety results, while data about treatment activity need longer follow up. Methods: During the screening period, pts undergo OPMD biopsy. If pathological diagnosis of dysplasia is confirmed, LOH valuation is performed and in case of positivity of this biomarker, subjects receive a short course of immunotherapy with avelumab 800 mg every 2 weeks for 4 total administrations. Follow-up after last avelumab dose is performed monthly and adverse event data are collected at every visit. Six months after treatment start, surgery and LOH re-assessment are performed. Results: Between November 2020 and December 2022, 49 pts were screened in 8 Italian centers. Of these, 16 pts (33%) had a LOH and 12 received the treatment (3 males, median age 65.5 years, range 49-81). Nine out of 12 treated patients had a previous oral cancer. After a median follow up of 14 months, 39 adverse events (AE) of any grade were reported, of these 18 were considered as immune related AEs (irAE). The most frequent AEs was grade 1 (G1) oral pain (4/12 pts), managed with local painkillers. Only three G2 irAEs were reported, namely amylase/lipase increase, psoriasis and fever. No grade 3-4 AEs were described, and no patient had to stop immunotherapy because of toxicities. Local excision after immunotherapy was not delayed by any treatment toxicities. Conclusions: This is the first trial with immunotherapy in an enriched population of OPMD selected according to LOH. First results support the feasibility of this approach, showing that immunotherapy with avelumab is safe and does not compromise subsequent local surgery. Clinical trial information: NCT04504552 .