Association of autologous AdHER2 dendritic cell vaccination with antitumor activity and number of circulating tumor cells.

Abstract

3089 Background: We achieved cure of large established tumors in syngeneic BALB/c mice using an adenoviral vector vaccine expressing rodent HER2 extracellular (EC) and transmembrane (TM) domains mediated by the induction of anti-HER2 antibodies. We report clinical translation utilizing an autologous adenoviral- transduced dendritic cell (DC) vaccine expressing human HER2 EC and TM domains (AdHER2ECTM) in adults with advanced metastatic tumors with 1-3+ HER2 expression. Methods: In this two-part phase I study (NCT01730118) subjects with HER2+ metastatic solid tumors naïve to HER2-targeted therapies (Part 1) or HER2+ treatment-experienced breast cancer (Part 2) received 5 doses of vaccine at Weeks 0, 4, 8, 16 and 24. Part 1 dose escalation involved 3 cohorts of 6 patients utilizing 5x106, 10x106 and 20x106 viable DCs per dose, respectively. With no DLTs or evidence of cardiac toxicity, dose escalation to 40x106 viable DCs per dose was allowed in the Part 1 Expansion Cohort and Part 2 treatment was begun at a starting dose of 20x106 viable DCs per vaccine. Adjuvant muscle-invasive bladder cancer patients were allowed to enroll with safety documented out to 12 weeks in > 10 treated patients. Re-staging was assessed using immune-related response criteria (irRC). Remaining study accrual: Part 1 (N = 9), Part 2 (N = 24). Results: A total of 27 cancer patients (7 colon, 6 breast, 5 ovarian, 3 bladder, 6 other) have received > 2 vaccine doses (median 4): 19F, 8M, median age 60 yrs, median 3 prior treatment regimens (range 1-11); HER2 IHC 1+ N = 6, 2+ N = 9, 3+ N = 12. Of metastatic patients receiving 10x106viable DCs per dose or higher, 7 of 19 (37%) had evidence of response by irRC: 1 CR (ongoing at 100 weeks), 1 PR (-71% lasting 44 weeks) and 5 SD (median duration 24 weeks, range 8 to 48 weeks). Two adjuvant bladder cancer patients remain without disease at 100 weeks. Adverse events were limited to local injection site reactions < G2. Of patients with paired baseline samples, 40% (8/20), 83% (5/6) and 100% (2/2) exhibited decreases in circulating tumor cells at 12, 28 and 48 weeks, respectively. Conclusions: AdHER2 DC vaccination is safe and is associated with evidence of clinical benefit and anti-tumor activity. Clinical trial information: NCT01730118.