Efficient Vaccination of Follicular Lymphoma (FL) Patients with Multiple Intradermal (ID) and Intravenous (IV) Administrations of Mature Dendritic Cells (DC) Loaded with Tumor Cell Lysate Ex Vivo.

DCs are the most potent antigen-presenting cells and antigen (Ag) delivery by ex vivo Ag-loaded DC cells may be an effective strategy for FL. The relevant source of tumor Ag, vaccine doses, schedules or routes of administration are still a matter of investigation. Tumor cell lysate (TCL) is an interesting source of multiple tumor Ag. After preclinical study and an acceptation of the “dossier de lot” by the french drug agency (afssaps), we started a phase II study evaluating the feasibility and safety of multiple ID and IV injections of autologous DC-TCL, in 07/04. At this time, 5 FL patients (pts) completed their treatment, with 5 to 7 DC-TCL vaccinations every 2–3 weeks, receiving 5.10⁶ cells IV and 5.10⁶ cells ID per vaccination. All the pts (2F/ 3M, age 44–61; 1 to 8 previous lines of therapy, including autologous transplantion in 2 pts) had measurable disease at inclusion. Tumor lymph node biopsy (for preparing TCL) was followed by rituximab administration in pts with no history of previous infusion of the monoclonal antibody. Cyclophosphamide (2g/m²) and G-CSF (5 mg/kg) were administered to mobilize mononuclear cells including CD14 monocytes. Two pts still had measurable disease at time of vaccination (lymph nodes on CT and Pet scans for the 2 pts, cutaneous localizations and molecular analysis evidence of disease in BM and PB, in 1 pt). Immature DC were obtained from thawed leukapheresis cells cultured for 5 days with GM-CSF and IL-4, pulsed with L, and then induced to mature with TNFalpha and PGE2 for 24 hours. All DC preparations fitted the quality criteria defined by the preclinical study (viability≥60%, ≤20% CD14+ cells, ≥60% CD83+ cells). Vaccinations were safe and well tolerated. One of the 2 pts with prevaccination residual disease entered CR (disappearance of Pet-scan positivity after the 7th vaccination, with sequential Pets, showing an increase of the signal during the first vaccinations linked to an initial lymph node activation), while a PR was observed in the 2nd pt with a regression of both lymph nodes and tumoral subcutaneous lesions. Quantitative PCR for bcl-2 signal were performed in both PB and BM. All pts developed significant delayed-type hypersensitivity responses to DC-TCL (as defined by erythema and induration of more than 5 mm of diameter, lasting 48h at least) after the 4^th or 5^th vaccinations. Analysis of biopsies performed at the site of DC-TCL injections, showed HSR including neutrophils and dense infiltration by T lymphocytes, mainly CD4 cells, as compared to site of injection of unmodified DC. Immunologic tests (Elispot assays) for monitoring vaccine efficacy will be presented. These preliminary results show that DC-TCL might be an efficient immunotherapy in patients with FL and that schedule of administration of the vaccine (especially to perform at least 5 vaccinations in a short period of time) as well as combination of 2 routes of DC administration might be critical points. We are now trying to pursue vaccinations for a longer period of time for every pt, and this study is now a multicenter study from Goelams group.