Dendritic cell vaccination as postremission treatment to prevent or delay relapse in acute myeloid leukemia

Abstract

Relapse is a major problem in acute myeloid leukemia (AML) and adversely affects survival. In this phase 2 study, we investigated the effect of vaccination with dendritic cells (DCs) electroporated with Wilms' tumor 1 (WT1) messenger RNA (mRNA) as postremission treatment in 30 patients with AML at very high risk of relapse. There was a demonstrable antileukemic response in 13 patients. Nine patients achieved molecular remission as demonstrated by normalization of WT1 transcript levels, 5 of which were sustained after a median follow-up of 109.4 months. Disease stabilization was achieved in 4 other patients. Five-year overall survival (OS) was higher in responders than in nonresponders (53.8% vs 25.0%; P = .01). In patients receiving DCs in first complete remission (CR1), there was a vaccine-induced relapse reduction rate of 25%, and 5-year relapse-free survival was higher in responders than in nonresponders (50% vs 7.7%; P < .0001). In patients age ≤65 and >65 years who received DCs in CR1, 5-year OS was 69.2% and 30.8% respectively, as compared with 51.7% and 18% in the Swedish Acute Leukemia Registry. Long-term clinical response was correlated with increased circulating frequencies of polyepitope WT1-specific CD8⁺ T cells. Long-term OS was correlated with interferon-γ⁺ and tumor necrosis factor-α⁺ WT1-specific responses in delayed-type hypersensitivity-infiltrating CD8⁺ T lymphocytes. In conclusion, vaccination of patients with AML with WT1 mRNA-electroporated DCs can be an effective strategy to prevent or delay relapse after standard chemotherapy, translating into improved OS rates, which are correlated with the induction of WT1-specific CD8⁺ T-cell response. This trial was registered at www.clinicaltrials.gov as #NCT00965224.

Figure 1.

The 3 different WT1 constructs used to generate mRNA for electroporation into DCs and their corresponding clinical responses and survival outcomes. Construct 1, WT1 (A); construct 2, WT1-DC-LAMP (B); and construct 3, WT1-DC-LAMP-OPT (C). Additional details have been reported by Benteyn et al. Median OS and 5-year OS percentage were calculated from the start of WT1/DC vaccination; values in brackets represent median follow-up. Full-color blue bars represent the remaining coding sequence of WT1 in constructs 2 and 3. The stable disease (SD) phase in UPN35 started during the administration of DCs electroporated with construct 3 (supplemental Table 1). MR, molecular remission; NLS, nuclear localization signal; undef, undefinable; UTR, untranslated region.

Figure 2.

SD in patient UPN33 during (arrows) and after WT1/DC vaccination. WT1 transcript levels (determined by the Ipsogen WT1 ProfileQuant Kit) in blood (A) and bone marrow (B) were above background (indicated by the dotted blue line) but remained stable, and the bone marrow blast count normalized (normal value indicated by the dotted pink line). (C) Blood values showed pancytopenia at the start of DC vaccination but a normal hemoglobin level (without transfusions) at the end of the SD period (at 19 months); neutropenia was treated with granulocyte colony-stimulating factor. 4 × biw + DTH, period of the first 4 biweekly WT1/DC vaccinations and DTH; ANC, absolute neutrophil count; CTx (I + C), polychemotherapy (induction + 2 consolidations).

Figure 3.

Kaplan-Meier curves of the OS data. The values on the curves are 5-year relative survival from the start of WT1/DC vaccination; the values underneath in gray (A-C) are 5-year relative survival data from SEER (observed survival of newly diagnosed patients with AML included in SEER*Stat database, whereby the following case selection criteria were applied: age [minimum age, 30 years; maximum age, 79 years], race [white], and year of diagnosis [2005-2012]; the patient with an undefinable response [UPN22] was not included in panel D). For median OS (mOS), values in brackets represent median follow-up. n.r., not reached.

Figure 4.

Intracellular cytokine staining of CD8⁺DILs after restimulation with mature DCs alone (mDC) or WT1 mRNA-electroporated DCs (mDC WT1). The WT1-specific T-cell cytokine response was evaluated by comparing mDC WT1 with mDC (all patients examined: UPN03, 05, 06, 08, 14, 17, 21, 22, 29, 30, 34, 35, and 47; long-term [LT] survivors: UPN06, 08, 14, 17, 21, 22, 29, 34, and 35; non-LT survivors: UPN03, 05, 30, and 47). IFN-γ⁺, interleukin-5⁺ (IL-5⁺), or TNF-α⁺ CD8⁺ T cells are shown for all patients (A), LT survivors (B), and non-LT survivors (C). Polyfunctional TNF-α⁺/IFN-γ⁺ CD8⁺ T cells are shown in the same patients (D).