Phase 2 study of bintrafusp alfa in recurrent/metastatic olfactory neuroblastoma

TPS6116 Background: Olfactory neuroblastoma (ONB, esthesioneuroblastoma) is a rare malignant tumor of the nasal cavity, believed to arise from the basal cells of the olfactory neurosensory epithelium. ONB is often locally advanced at diagnosis with high rates of spread both locoregionally and systemically. Current therapy for locoregional disease is local resection with adjuvant (chemo-) radiotherapy. Actionable mutations are rare, and treatment options for recurrent or advanced, non-resectable, disease are limited and include off-label combination chemotherapy (most frequently platinum-containing) and somatostatin-directed therapies (ONB expresses somatostatin receptors). These are based on limited data, with response rates poorly characterized. Bintrafusp alfa is a first-in-class, bifunctional TGF-β “trap”/anti-PD-L1 fusion protein. Analysis of ONB has demonstrated both PD-1/PD-L1 (London et al, 2018) and TGF-β ligand expression (Romani et al, 2021). Pre-clinical and clinical data in advanced solid tumors demonstrate enhanced antitumor activity with combination PD-L1/TGF-β blockade, with responses observed independently of high PD-L1 levels (Strauss et al, 2020). Thus, combination PD-L1/TGF-β blockade in ONB is a rational approach in a setting of unmet clinical need. Methods: This study is a Phase 2 single-site, single-arm clinical trial of bintrafusp alfa (1200mg IV every 2 weeks for up to 26 doses) for patients with recurrent or metastatic ONB. Participants must co-enroll to the ONB Natural History study at the NCI (NCT4755205). Patients must not be candidates for local therapy, have received at least 1 line of systemic therapy (including a platinum salt), have RECIST 1.1 measurable disease and have adequate organ function. Prior checkpoint inhibitor therapy is permitted with patients cohorted according to checkpoint exposure; up to 21 checkpoint-naïve and 8 checkpoint-resistant patients will be enrolled. The primary objective is objective response rate by RECIST 1.1 with secondary endpoints including safety and tolerability, duration of response and overall survival; exploratory endpoints include pharmacokinetic analyses, PD-L1 and immune cell correlative analyses. The trial follows a Simon two-stage design, requiring ≥1 response in the first 12 patients. Tumor biopsy at enrollment is optional. Imaging for response assessment is planned for 8-week intervals and PET scan (preferably 68 Ga-DOTATATE) will be obtained for all patients at baseline and first restaging, then on an individualized basis per radiology advice. This study is presently open at the NCI with 5 patients enrolled as of January 2023. Clinical trial registry:NCT05012098. Clinical trial information: NCT05012098 .