Abstract CT016: A first in man phase I/II adjuvant dendritic cell vaccine study in high-risk prostate cancer patients following radical surgery reduce the incidence of biochemical relapse

Prostate cancer patients diagnosed with high Gleason score (≥ 8) and large tumors (≥T2c) are considered high-risk patients and >50% will develop an early biochemical relapse following radical surgery. Presently, there is no curative therapy available for patients once when biochemical relapse occur. Based on encouraging clinical results from 6 relapsed prostate cancer patients treated under hospital exemption with dendritic cell (DC) vaccines we started an adjuvant, first in man, phase I/II study using autologous, monocyte derived DCs targeting autologous tumor antigens from primary tumor, combined with hTERT and survivin. Twenty patients were included in the study. All patients had pathological stage pT2-pT3b and Gleason score 7b-10. Following surgery prostate specific antigen (PSA) was < 0,2 µg/L in all patients. Fifteen patients have received 3-days DCs generated according to our standard protocol with a maturation cocktail composed of GM-CSF, IL-4, TNFα, IL1β and PgE2. Five patients were treated with a TLR 7/8 ligand containing maturation cocktail, resulting in DCs with a polarized release of IL-12p70 and no or low IL-10. The patients received 4 weekly vaccinations, then DTH vaccine at week 8 and thereafter-monthly vaccinations the first year, and every third month the second and third year. All patients except of two have completed vaccination. Of the 15 first patients using the standard DCs, three patients developed PSA relapse during vaccination (PSA measured twice >0,5 μg/L with minimum 4 weeks interval) and two additional patients relapsed after completed 3 years of vaccination. From the last 5 patients given the new type of DCs none have experienced PSA relapse. Seventy-five percent of the patients remain without biochemical relapse with a mean observation time of 47,5 (range 29-82) months. We confirm that the study is feasible and safe. Immune responses in the patients are under investigation. Altogether, our clinical results are promising and the use of adjuvant DC vaccines might become a new approach to prevent biochemical relapse in high-risk prostate cancer patients following radical surgery. Citation Format: Anne Merete Tryggestad, Iris Bigalke, Karol Axcrona, Bjørn Brennhovd, T Kirsti Hønnåshagen, Lisbeth Skoge, Lena Tjeldhorn, Lene Mowinckel, Stein Sæbøe-Larsen, Jens A L Jørgensen, Grete S Andreassen, Gjertrud Skorstad, Dag Josefsen, Ulrika Axcrona, Steinar Aamadal, Wolfgang Lilleby, Svein Dueland, Gunnar Kvalheim. A first in man phase I/II adjuvant dendritic cell vaccine study in high-risk prostate cancer patients following radical surgery reduce the incidence of biochemical relapse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT016.