Pomalidomide in patients with multiple myeloma: potential impact on the reconstitution of a functional T-cell immunity

Abstract

Background: Pomalidomide, a third-generation oral immunomodulatory drug, exhibits efficacy in patients with relapsed multiple myeloma or those refractory to bortezomib and lenalidomide (RRMM).

Methods: In this clinical context, we employed flow cytometry and CDR3 spectratyping to monitor the dynamics of the T-cell repertoire during Pomalidomide treatment, aiming to investigate its potential to reverse the immunological abnormalities characteristic of RRMM.

Results: By flow cytometry at baseline we found a significant decrease in CD4 + frequency in MM patients, while CD8 + frequency were significantly higher in patients when compared to controls. Most T cell populations remained stable across all time points, except for CD4 + frequency, which notably decreased from t1 to subsequent assessments. Our investigation revealed as most relevant finding the notable increase in CD4 + expansions and the growing prevalence of patients manifesting these expansions. This pattern is even more evident in patients receiving their treatment until t3 and therefore still responding to treatment with Pomalidomide. We also conducted a comparison of spectratyping data before and after treatment, substantially demonstrating a relatively stable pattern throughout the course of Pomalidomide treatment.

Conclusions: These observations imply that Pomalidomide treatment influences the T-cell repertoire, particularly in the CD4 + subpopulation during the later stages of treatment, raising speculation about the potential involvement of these lymphocyte expansions in mechanisms related to antitumor immunity.

Keywords: Antitumor immunity; CDR3 spectratyping; Flow cytometry; Pomalidomide; Relapsed/refractory multiple myeloma; T-cell repertoire.

Fig. 1

T-cell frequencies determined by flow cytometry before and during pomalidomide treatment. (A-E) T-cell frequencies of a pool of age- and sex- matched healthy control (ctr) that were compared with MM patients (pts) prior to initiating Pomalidomide treatment. The lymphocytes subpopulations are reported as percentage over total lymphocyte population from peripheral blood samples collected at t = 1. Statistical difference between the two groups (Ctl vs. Pts) is evaluated with the Mann Whitney test (two-tailed, non-parametric test for non-matched samples). (F-M) The percentages of lymphocyte subpopulations in MM patients are shown relative to the total lymphocyte population in peripheral blood samples collected before Pomalidomide treatment and at 3, 6, and 12 months (t1, t2, t3, and t4, respectively). Statistical difference within these groups is evaluated with the Friedman test (non-parametric test for repeated measures)

Fig. 2

Kinetic of expanded T-cell subpopulations in MM patients during Pomalidomide treatment. (A, B) Percentages of BV expansions over total BV examinate from CD4 + subpopulation and from CD8 + subpopulation of MM patients. Peripheral blood samples were collected before Pomalidomide treatment and after 3-, 6- and 12-months therapy including Pomalidomide (t1, t2, t3 and t4 on x-axis, respectively) (C, D) Percentages of MM patient that show none, a single or at least two expansions of BVs from CD4 + subpopulation and from CD8 + subpopulation. Peripheral blood samples were collected before Pomalidomide treatment and after 3-, 6- and 12-months therapy including Pomalidomide (t1, t2, t3 and t4 on the x-axe, respectively)

Fig. 3

Percentages of CDR3 skewing (Skewed) and oligoclonality (oligo) in both CD4 + and CD8 + cells. (A, E) Percentages of skewed and oligo BVs were determined by spectratyping of a pool of age- and sex- matched healthy controls (ctr) with MM patients (pts) before starting Pomalidomide therapy. Statistical difference between groups is calculated with Mann Whitney test (non-parametric test for unpaired measures) (B, C, F, G) Percentages of skewed and oligo BVs were determined by spectratyping of samples before Pomalidomide treatment (t1) and after 3-, 6- and 12-months therapy including Pomalidomide (t2, t3 and t4 on x-axis, respectively). Statistical difference within groups is calculated with Friedman test (non-parametric test for repeated measures) (D, H) Percentages of CDR3 skewing (S), oligoclonality (O) and Gaussian profile (G) were found among BV expanded from both CD4 + and CD8 + cells. Data are reported for samples were collected before Pomalidomide treatment (t1) and after 3, 6 and 12 months of therapy including Pomalidomide (t2, t3 and t4 on x-axis, respectively). Percentages were obtained by formulae: % G on exp: (Number of Gaussian/number of total expanded BVs) * 100; % O on exp: (Number of oligo/number of total expanded BVs) *100; % S on exp: (Number of Skewed/number of total expanded BVs) * 100