Tri-Ad5 vaccine plus bintrafusp alfa for newly diagnosed, advanced-stage head and neck cancer not associated with human papillomavirus infection.

Background: Newly diagnosed, advanced-stage head and neck cancer (HNSCC) not associated with human papillomavirus (HPV) infection has poor survival and functional outcomes despite surgical management. Neoadjuvant immunotherapy is of interest to improve long-term outcomes.

Methods: Individuals with untreated intermediate/high risk, p16-negative (if oropharyngeal) HNSCC were eligible and underwent pre- and post-treatment tumor biopsies. Primary endpoint was pathologic complete response or clinical-to-pathological downstaging (CPD). Treatment regimen: 5 × 1011 viral particles once, subcutaneously of each component of the Tri-Ad5 vaccine (ETBX-011, ETBX-061, and ETBX-051 targeting tumor-associated antigens (TAA): carcinoembryonic antigen [CEA], MUC-1, and brachyury, respectively) plus 1200 mg IV of bintrafusp alfa (anti-PD-L1 and anti-transforming growth factor-β) every 2 weeks for 2 doses. Participants returned to referring physicians for standard surgery ± adjuvant treatment if indicated.

Results: Of 6 HNSCC patients, 2 (33.3%) had CPD. There were no pathologic complete responses. 2-year recurrence free survival (RFS) was 83.3% (95% CI, 27.3%-97.5%). Adverse events were consistent with known safety profiles of each agent. There were no surgical delays.

Conclusions: In this small study, Tri-Ad5 vaccine plus bintrafusp alfa resulted in CPD in 2/6 patients. Participants also had favorable 2-year RFS compared to historical values. Ongoing tissue and peripheral immunome analyses may provide mechanistic insight. (ClincalTrials.gov Identifier: NCT04247282; IRB Approved.).