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6081 Background: Treatment selection based on actionable alterations (AAs) is an appealing strategy for pts with R/M SGT. The GEMS-001 study (NCT02069730) at Princess Margaret Cancer Centre (PM) and the Vall D´Hebron Institute of Oncology (VHIO) pre-screening program facilitate the identification of AAs for R/M SGT pts and treatment selection. Methods: We analyzed R/M SGT treated at PM and VHIO from 2015 to 2020. Clinicopathological features, molecular alterations and treatment modalities were correlated with outcomes. The primary endpoint was overall response rate (ORR) by RECIST 1.1. Clinical benefit rate (CBR) was defined by pts with partial response or stable disease ≥4 months. Clinical actionability of multigene panel testing (NGS) and immunohistochemistry (IHC) were assessed as per institutional molecular tumor boards or investigators. Pts were opportunistically matched to available therapies from each center. Results: In total 206 pts were enrolled. On IHC, HER2 overexpression was present in 9%, Androgen Receptor (AR) 33%, Estrogen/Progesterone Receptor (ER/PR) 11% and ALK overexpression 0%. On NGS, PIK3CA mutation (mut) was in 9%, NTRK fusion 6%, NOTCH1-3 mut 5%, HRAS mut 6%, ERBB2/3 alterations (alt) 4% and FGFR1-4 alt 3%. Up to 92 pts (45%) displayed at least 1 AA and 36 pts (18%) had ≥2 AAs. A total of 60 pts (29%) were matched to AAs. Of those matched, median age was 60 years (range 33-84), M:F 21:39, 95% ECOG≤1 with a median number of prior treatment lines 0 (range 0-3), and their AAs included 26 AR, 9 HER2 or ERBB2 overexpression, 9 PIK3CA mut, 3 NTRK fusion, 3 FGFR1-3 alt and 10 other AAs (2 ER/PR overexpression, 2 EGFR mut, 1 c-kit mut, 1 BAP1 mut, 1 Non-V600 BRAF mut, 1 CDKN2A mut, 1 CHEK2 mut and 1 PTCH1 mut). Overall, ORR was 27% for the matched population. See table for outcomes. Conclusions: In our cohort, almost one third of the population received therapies matched to AAs. Our results suggest that targeted therapies have promising activity in pts with R/M SGT supporting comprehensive molecular and IHC profiling in treatment determination.[Table: see text]

6005 Background: Pembrolizumab (P) is approved to treat patients (pts) with recurrent, metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). BCA101 is a first-in-class bifunctional EGFR antibody fused to a TGFβ immune modulating payload which is well tolerated and has clinical activity as monotherapy and in combination with pembrolizumab in advanced solid tumors (ESMO 2022 731MO). Here we report the results from the interim analysis of an expansion cohort combining BCA101+P as first line therapy in R/M HNSCC. Methods: This ongoing single-arm, open-label multicenter dose expansion cohort enrolled pts with R/M HNSCC with a tumor PD-L1 CPS≥1 with no prior systemic therapy for R/M disease, ECOG 0-1, and measurable disease (RECIST v1.1). Pts received BCA101 (1500 mg IV on days 1, 8, 15) with P (200 mg IV on day 1) every 21-days. Primary endpoint: safety; secondary endpoints: overall response rate (ORR), duration of response (DOR), progression-free survival (PFS), overall survival (OS). Exploratory: molecular and immunologic predictors of response. A Simon optimal two-stage design was employed: among 18 evaluable pts in stage 1, >3 pts in response triggered continuation to stage 2 enrolling 21 additional pts targeting an ORR>35%. Results: From 2/2022 to 1/2023, 20 pts enrolled while 18 were evaluable (had first restaging scans) in stage 1. Pts were more often men (n=13, 65%) with a median age of 66 (range: 31-77). Oropharynx (10, 50%) [7/10 (70%) were HPV/p16-pos] and oral cavity (7, 35%) were the most common primary subsites (larynx/hypopharynx: 3). Fifteen (75%) had distant metastatic disease. The ORR in stage 1 was 44% (8 PRs, 4 SD) with a clinical benefit rate (CBR=PR+SD) of 67%; 7/12 (58%) HPV-neg pts achieved a response. Median DOR not reached, but median time on-treatment was 6.7 months (range: 2.7-11.0+) among responders. Ten pts discontinued therapy; all but 1 for PD (n=1 for toxicity). Grade 3+ treatment-related adverse events (TRAEs) were observed in 4 pts (20%, most common: anemia). No treatment-related deaths were observed. Acneiform rash was the most common TRAE of any grade (15, 75%). PFS and OS estimates are forthcoming. Eight (44%) had baseline PD-L1 CPS scores of 0-19, while ten (56%) were ≥20. Stage 2 is actively enrolling with completion of accrual expected by the meeting. Conclusions: Stage 1 of this dose expansion cohort of BCA101+P shows encouraging anti-tumor activity with additive potential, particularly among HPV-neg pts; and the combination is well tolerated among this R/M HNSCC population. Further investigation is warranted. Study funded by Bicara Therapeutics and conducted in collaboration with Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc. USA (NCT04429542). Clinical trial information: NCT04429542 . [Table: see text]

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