Correlation between prior therapeutic dendritic cell vaccination and the outcome of patients with metastatic melanoma treated with ipilimumab

Abstract

e20006 Background: Ipilimumab (Ipi) is an anti-cytotoxic T lymphocyte associated antigen 4 (CTLA4) IgG1 monoclonal antibody active against metastatic melanoma. Ipi acts by reinforcement of CTL-activation trough B7/CD28 receptor stimulation. A pre- existing anti-tumor CTL repertoire, induced by dendritic cell (DC) vaccination, could influence the therapeutic effect of Ipi. The influence of prior DC-vaccination on the outcome of melanoma patients (pts) treated with Ipi at a single center was analyzed to evaluate this hypothesis. Methods: Data were obtained from the medical files of pts treated at the UZ Brussel with Ipi in protocols CA184–022, -025, and the BMS Ipi medical need program. Ipi (0.3, 3 or 10 mg/kg) was administered iv q3 wks x4 q12 wks thereafter. Results: 20 pts (10M/10F; med age 51y, range 28–72) were identified. Prior therapy: autologous DC-vaccine loaded with melanoma associated antigens (14 pts) ± IFN-a2b (9/14 pts), cytotoxic agents (17 pts). Baseline characteristics: AJCC st IV melanoma (20 pts); baseline LDH > ULN (16 pts). Ipi dose: 0.3 mg/kg (4 pts), 3 mg/kg (2 pts), 10 mg/kg (14 pts). Serial LDH measurements were available for 17 pts; 4 types of LDH-response following Ipi administration were observed: increase (11 pts), decrease (1 pt), fluctuation (4 pts), stable (1 pt). Objective response according to mWHO or irWHO: 3 PR, 1 SD, 16 PD. One pt received 0.3 mg/kg of Ipi (CA184–022) and had SD but no LDH response; at PD she received DC-vaccine and subsequently 10 mg/kg Ipi (medical need program) resulting in a fluctuating LDH-response and regression of an orbita-metastasis. Increasing LDH values following Ipi were less often observed in pts with prior DC-vaccination (5/6 pts (83%) without prior DC-vaccination had increasing LDH-values vs 6/12 pts (50%) with prior vaccination). DC- vaccination also correlated with regression of metastases and disease control (3/15 pts (20%) who were vaccinated had a PR/SD vs 1/6 (17%) PR for those who had not received prior DC-vaccinations). Conclusions: These data represent a small sample size from a single institution; however, our results suggests a potential correlation between prior therapeutic DC vaccination and outcomes in advanced melanoma patients treated with ipilimumab. [Table: see text]