Influence of Lenalidomide Treatment on Immune Effector Cells From High-Risk Smoldering Multiple Myeloma (SMM) Patients,

Abstract 3944

Lenalidomide is an immunomodulatory agent that enhances T and NK cell activation, being this consideration as a major player in its anti-myeloma effect. However, in MM lenalidomide is usually combined with the immunosuppressant dexamethasone, which has raised questions regarding a potential abrogation of this immunomodulatory effect. In fact, this may be a dilemma upon treating early stage MM patients with lenalidomide +/− dexamethasone. Moreover, our current knowledge of the immune system in SMM is limited.

Herein we evaluated by multiparameter flow cytometry (MFC) immunophenotyping peripheral blood (PB) T and NK cells from high-risk SMM patients (N=33), treated according to the QUIREDEX trial (NCT 00480363): an induction phase of 9 four-week cycles of LenDex followed by maintenance with lenalidomide until disease progression. To evaluate the immune status of T and NK cells of SMM patients, we compared them at baseline vs healthy adults (HA) aged over 60 years (N=10). To assess the effect of LenDex on T and NK cells of SMM patients, we compared baseline samples vs those studied after 3 and 9 cycles of LenDex. To address the question whether dexamethasone antagonizes the immunomodulatory properties of lenalidomide, we compared in 11 of the 33 patients, the PB T and NK cells at the end of induction (9^th cycle of LenDex) vs during maintenance (lenalidomide alone and at least 3 months after dexamethasone discontinuation).

The percentage of PB T cells in high-risk SMM patients at baseline was increased when compared to HA (23% vs 17%; P=.02), mainly due to expansion of CD8 T cells (P=.03). Of note, γδ T cells were also increased in SMM (0.8% vs 0.3%; P=.003). In turn, no differences (P>.05) were noted for both the CD56dim and CD56bright NK cell compartments. However, when a more detailed immunophenotypic characterization was carried out, CD4 and/or CD8 T cells from SMM patients showed decreased expression of activation markers (CD25, P≤.04; CD54, P<.001 and CD154, P=.002), as well as decreased production of the Th1 related cytokines (IFNγ, P=.03; TNFα, P≤.003; and IL-2, P=.02).

We then investigated the effect of LenDex treatment. After 3 and 9 cycles of LenDex both CD4 and/or CD8 T cells showed up-regulation of Th1related chemokines (CCR5; p<.001) and cytokine production (IFNγ, P=.03; TNFα, P=.03 and IL-2, P=.02), as well as increased expression of activation markers (CD69, P≤.005; CD25, P<.001; CD28, P≤.04; CD54, P<.001 and HLA-DR, P<.001). Similarly, CD56dim and CD56bright NK cells showed up-regulation of HLA-DR (P<.001), the antibody-dependent cell-mediated cytotoxicity associated receptor CD16 (p≤.005), and the adhesion molecules CD11a (p≤.001) and CD11b (p≤.005). Concerning cell cycle analysis, the percentage of cells in S-phase was significantly increased from baseline vs. 3 vs. 9 cycles of LenDex for T CD4 (0.04% vs 0.13% vs 0.13%; p<.001), CD8 (0.05% vs 0.13% vs 0.18%; p<.001) and NK cells (0.07% vs 0.16% vs 0.15%; p<.001). Interestingly, an unsupervised cluster analysis of the overall immunophenotypic expression profile obtained after 9 cycles of LenDex was able to discriminate two groups of patients with different activation profiles particularly on T CD8 cells, with differences (P<.05) in both their percentage in PB and expression of activation, Th1 and maturation markers. Patients displaying a higher activation profile showed a trend towards increased depth of response after 9 cycles of LenDex (sCR+CR: 31% vs 15%; p=.229), as well as time-to progression (TTP) to symptomatic MM (TTP at 2-years: 100% vs 79%; P=.177).

Finally, we explored whether the immunomodulatory properties of lenalidomide could be increased when dexamethasone was removed for the maintenance phase. Regarding T and NK cell distribution, only an increase in the percentage of CD4 T cells was found (9% vs. 12%, P=.04), whereas no differences (P>.05) were noted regarding the immunophenotypic expression profile of T and NK cells studied.

In summary, we show that in high-risk SMM patients at baseline CD8 and γδ T cells are increased but overall T cells show an impaired activation profile. Treatment with LenDex induces an activation and proliferation of T and NK cells which may contribute to disease control. Finally, our results do not show an inhibition of the immunomodulatory effects of lenalidomide by the concomitant use of dexamethasone.