Preliminary phase 1/1b dose expansion results of the bifunctional EGFR/TGFβ inhibitor ficerafusp alfa (BCA101) with pembrolizumab in patients with squamous cell carcinoma of the anal canal.

4 Background: Anti-PD-1 monotherapy has limited efficacy in patients (pts) with advanced squamous cell cancer of the anal canal (SCAC). In KN-158, pembrolizumab (P) was reported to have an ORR of 10%, DCR of 25%, and a 12-month PFS rate of 15% in patients with incurable SCAC. TGFβ promotes immunosuppression within the tumor microenvironment, and inhibition of this pathway may improve tumor susceptibility to immune checkpoint blockade.Ficerafusp alfa (F)is a bifunctional EGFR/TGFβ inhibitor with manageable safety and favorable preliminary anti-tumor efficacy in advanced solid tumors (ESMO 2022 731MO). We evaluated the combination of F+P in pts with chemotherapy-refractory locally advanced/unresectable or metastatic SCAC. Methods: This single-arm, multicenter dose expansion from an ongoing phase I/Ib trial enrolled pts with ICI-naïve SCAC that was locally advanced/unresectable or metastatic, who had received 1-2 prior lines of chemotherapy. Pts received ficerafusp alfa (1500 mg IV on days 1, 8, 15) and pembrolizumab (200 mg IV on day 1) every 21-day cycle. The primary endpoint was safety (CTCAE v5), and secondary endpoints were radiographic response (RECIST 1.1), duration of response, progression-free survival, and overall survival. Results: Among 26 pts treated, 21 (81%) were female, and median age was 61 (range: 43-82). As of 7/2024, 22 pts are evaluable for efficacy. ORR was 32% (95% CI 13.9-54.9%). Six of the seven responses were confirmed, including one pt with a radiographic PR with pathologic CR to F+P. Seven pts (32%) achieved SD as best response, resulting in DCR of 64%. Median PFS was 2.8 months (95% CI 1.4-14.8) and the PFS rate at 12 months was 36%. G3 treatment-related adverse events were observed in 10/26 pts (38%, most common: Anemia (19%) and acneiform rash (12%)). TRAEs led to permanent discontinuation of study treatment in 2 pts (8%). The most common TRAEs of any grade were acneiform rash (13/26, 50%), epistaxis (46%) and headache (38%). Conclusions: The addition of ficerafusp alfa demonstrated encouraging efficacy, with increased ORR, DCR, and 12-month PFS relative to historical precedent with pembrolizumab alone. Safety and tolerability were acceptable. Further investigation of this combination in pts with advanced SCAC is warranted. Updated data will be presented. Study funded by Bicara Therapeutics Inc. with access to pembrolizumab in collaboration with Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA (NCT04429542). Clinical trial information: NCT04429542 .