Vaccination with autologous dendritic cells pulsed with multiple tumor antigens for treatment of patients with malignant melanoma: results from a phase I/II trial.

BACKGROUND AND AIM

Dendritic cells are regarded as the most effective antigen presenting cells and coordinators of the immune response and therefore suitable as vaccine basis. Here we present results from a clinical study in which patients with malignant melanoma (MM) with verified progressive disease received vaccination with autologous monocyte-derived mature dendritic cells (DC) pulsed with p53, survivin and telomerase-derived peptides (HLA-A2+ patients) or with autologous/allogeneic tumor lysate (HLA-A2(−) patients) in combination with low-dose interleukin (IL)-2 and interferon (IFN)-alpha2b.

RESULTS

Of 46 patients who initiated treatment, 10 stopped treatment within 1-4 weeks because of rapid disease progression and deterioration. After 8 weeks, 36 patients were evaluable: no patient had an objective response, 11 patients had stable disease (SD); six had continued SD after 4 months, and three patients had prolonged SD for more than 6 months. The mean overall survival time was 9 months, with a significantly longer survival (18.4 months) of patients who attained SD compared with patients with progressive disease (PD) (5 months). Induction of antigen-specific T-cell responses was analyzed by multidimensional encoding of T cells using HLA-A2 major histocompatibility complex (MHC) multimers. Immune responses against five high-affinity vaccine peptides were detectable in the peripheral blood of six out of 10 analyzed HLA-A2+ patients. There was no observed correlation between the induction of immune responses and disease stabilization. A significant lower blood level of regulatory T cells (CD25(high) CD4 T cells) was demonstrable after six vaccinations in patients with SD compared with PD.

CONCLUSIONS

Vaccination was feasible and safe. Treatment-associated SD was observed in 24% of the patients. SD correlated with prolonged survival suggesting a clinical benefit. Differences in the level of regulatory T cells among SD and PD patients could indicate a significant role of these immune suppressive cells.