A review of the clinical experience with CMN-001, a tumor RNA loaded dendritic cell immunotherapy for the treatment of metastatic renal cell carcinoma

Abstract

Engineering dendritic cells (DCs) to treat cancer is a long sought-after goal for cell-based immunotherapies. In this review, we focus on the experience with CMN-001, formally AGS-003, a DC-based immunotherapy, employing autologous DC electroporated with autologous tumor RNA to treat subjects with metastatic renal cell carcinoma (mRCC). We will review the early clinical development of CMN-001 up to and including deployment in a multicenter phase 3 study and provide a rationale to continue the development of CMN-001 in an ongoing randomized phase 2 study. The synergy between CMN-001 and everolimus observed in the phase 3 study provides an opportunity to design a phase 2b study building on the mechanism of action of CMN-001 and underlying immune and clinical outcomes revealed in the earlier studies. The design of the phase 2b study combines CMN-001 with first-line checkpoint inhibition therapy and second line lenvatinib/everolimus in poor-risk mRCC subjects.

Keywords: Dendritic cells; cancer vaccines; immunotherapy; mRCC; memory T cells.

Figure 1.

CMN-001 mechanism of action. Signal 1, mature DC expresses human leukocyte antigen (HLA) (a–c) surface molecules. In the CMN-001 manufacturing process, electroporation of autologous DC with amplified autologous tumor RNA enables the surface presentation of autologous tumor antigens in an appropriate HLA context. Signal 2, mature DCs express CD80/86 costimulatory molecules on the cell surface and deliver a costimulatory signal through the CD28 receptor present on T cells. Signal 3, the induction of IL-12 secretion from DC is achieved by cell surface ligation of CD40 by interaction with CD4⁺ helper T cells, which express CD40L on their cell surface. The efficiency of CD40/CD40L ligation is improved by performing it ex vivo in the CMN-001 manufacturing process. Electroporation of the DC with CD40L RNA allows for ectopic expression of CD40L with subsequent ligation with CD40 within the DC. Signaling via the formation of CD40/CD40L complexes within the DC stimulates IL-12 release from the DC, thus bypassing the requirement for a chance CD4⁺ helper T cell encounter in vivo and providing IL-12 for the expansion of cytotoxic T cells.

Figure 2.

CMN-001 manufacturing process. Two cellular components are collected from an mRCC patient. The first is a tumor specimen collected from subjects during nephrectomy or biopsy, and autologous total tumor RNA is extracted and amplified. The second component is monocytes, which are DC precursors isolated from the leukocytes by elutriation from a leukapheresis collection. GM-CSF and IL-4 are used initially to convert the monocytes into immature DC, which are then matured using TNF-α, IFN-γ, and PGE₂. These mature DCs are then co-electroporated with amplified tumor RNA and synthetic CD40L RNA. The resulting RNA-electroporated mature DC is formulated as a single dose and vialed for cryogenic storage.

Figure 3.

Kaplan–Meier survival curves for subjects treated with everolimus in second line. (a) A comparison of survival curves between ADAPT subjects receiving everolimus in second-line therapy in the SOC arm during follow-up (blue line) (n = 20, 30% censored subjects) or in treatment (orange line) (n = 11, 27% censored subjects). Median OS was 17.8 months and 13.4 months for follow-up and treatment, respectively (HR 0.96, CI, 0.40–2.32). (b) A comparison of survival curves between ADAPT subjects receiving everolimus in second-line therapy in the combination arm, during follow-up (blue line) (n = 22, 45% censored) or in treatment (orange line) (n = 38, 31.5% censored). Median OS was 25.7 months and 19.3 months for follow-up and treatment, respectively (HR 0.60, 95% CI, 0.31–1.14). Statistical analysis was performed with GraphPad Prism v9.4 software and hazard ratios were calculated using log-rank test.

Figure 4.

CMN-001 expansion of proliferating CD4⁺CD25⁺FoxP3⁺ T cells in vitro. PBMC collected from mRCC subjects (n = 15) enrolled in the ADAPT study were co-cultured in vitro with autologous CMN-001 product (Stim) or left in culture (No stim) for 6 days, and the expansion of FoxP3⁺CD4⁺ T cells was determined. Intracellular staining detected FoxP3⁺ CD25⁺CD4⁺ T cells on the PD-1 positive and negative cell populations. The number of proliferating cells was determined by Ki67 expression for each population of cells. White bars are unstimulated cells, and gray bars are PBMCs stimulated with CMN-001. Statistical significance was determined by paired T-test ** p value < .05 using GraphPad Prism v9.4 software.

Figure 5.

Everolimus reduces TGF-β secretion and the frequency of CD38⁺ B cells. (a) TGF-β was measured by ELISA in plasma collected from mRCC subjects (n = 8) (gray box) or healthy donors (HD n = 2) (white box). (b) PBMC from mRCC subjects were stimulated (Stim) with the combination of reagents described in the Material and Method section or left unstimulated (Unstim) in the presence of everolimus (⁺everolimus) to induce TGF-β secretion. TGF-β concentrations in the supernatant were measured after 6 days by ELISA. (c) The frequency of CD38⁺ B cells was determined by flow cytometry by gating on the viable CD19⁺ B cells in groups unstimulated or stimulated with everolimus (white bars) or without everolimus (gray bars). Data is from five individual mRCC subject PBMC samples. (d) the number of LAP⁺CD38⁺ B cells was determined by flow cytometry in cultures stimulated without everolimus (gray bar) or with everolimus (white bar). Data are representative of three independent experiments from four individual mRCC subject PBMC samples. Statistical significance was determined by paired T-test * p value < .05 using GraphPad Prism v9.4 software.

Figure 6.

Expansion of CMVpp65-specific CTL after coculture with CMVpp65 antigen-loaded DC and lenvatinib plus everolimus. (a) The number of CMVpp65-specific CTL after 10 days coculture with CMVpp65 antigen-loadedantigen loaded DC (untreated, black bar) or cocultured with the combination of lenvatinib plus everolimus (white bar) was determined by flow cytometry using Trucount tubes to report the number of CMVpp65-specific CTL cells/mL. (b) Day 10 CTL were then restimulated with CMVpp65 antigen-loaded DC for an additional 4 hrs to measure cytokine production and Grb expression without the addition of lenvatinib plus everolimus (black bars) or with lenvatinib plus everolimus (white bars). The number of functional CMVpp65-specific CTL expressing TNF-α, CD107a, IFN-γ, or Grb after 4-hr stimulation was measured by flow cytometry using Trucount tubes to report the number of cells/mL. The data shown are from one of four representative donors with similar results.

Figure 7.

CMN-001-1 study schema. This study is a two-arm trial with the only difference between the arms being the administration of CMN-001 in the combination arm versus SOC alone (Control arm). The study will recruit primarily poor-risk subjects with up to 50% intermediate-risk subjects with metastatic RCC who are eligible for nephrectomy or biopsy (n = 90). Subjects will be randomized 1:1 either to the combination arm, CMN-001 plus SOC or the SOC alone arm. Subjects will receive CPI (checkpoint inhibition therapy) in first line and after first progression will proceed to second line with lenvatinib plus everolimus. First-line CPI therapy will be the combination of ipilimumab and nivolumab. Subjects on the combination arm will continue to receive CMN-001 through a second progression. Any subject not eligible for second-line therapy with lenvatinib plus everolimus will be replaced. The primary end point is OS with secondary end points for PFS, RR, and safety.