A Clue to Better Select Chronic Lymphocytic Leukemia Patients with Optimal Response to BNT162b2 mRNA COVID-19 Vaccine

Given the immunosuppression of chronic lymphocytic leukemia (CLL), this disease represents a challenging model for assessing the extent of serologic response to mRNA vaccination against severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). In this perspective, we assessed the efficacy of the BNT162b2 mRNA COVID-19 vaccine in 70 CLL pts followed up at single hematological institution. The study was approved by the Institutional Review Board. Serologic testing for SARS Cov2 IgG was performed using the LIAISON® SARS-CoV-2 S1/S2 IgG test (DiaSorin; Saluggia, Italy), a chemiluminescence immunoassay for the quantitative determination of anti-S1 and anti-S2 specific IgG antibodies to SARS-CoV-2. Clinical sensitivity and specificity of assay were 98.7% and 99.5% respectively. Samples were considered negative for antibody titers below 13 AU/ml. Results were compared with those of an age-matched group of subjects with no hematological malignancy (n=57). Patient samples for serology testing were obtained after median time of 14 days (range, 14-28) from the second vaccine dose. Median age of CLL pts was 72 years (range, 63-88) and 71.4% were males. The median time from CLL diagnosis to vaccination was 82.5 mo. (range, 1-280). Twenty-three pts (32.9%) were treatment naïve (TN), 36 (51.4%) on active therapy (i.e., BTKi, 22; anti-BCL2 12; PI3Ki,1; cyclophosphamide,1) and 11 (15.7%) off-therapy (i.e., 8 in complete [CR] or partial remission [PR], and 3 in CLL relapse). Of note, 9 (25.7%) of 35 pts on therapy with a pathway inhibitor (PI) at the time of vaccination had been given an anti-CD20 antibody. The vaccine elicited an antibody-mediated response in 41 (58.5%) of the 70 CLL pts. An inferior response rate [RR] (58.5% vs 100%, OR, 0.012 [0.0007-0.206];P=0.02) and a lower antibody titers (median, 58 AU/ml; range, 1.8-800 vs. 284 AU/ml; range, 14-800; P< 0.0001) were observed in CLL pts in comparison to age-matched subjects with no hematological malignancy. The RR was higher in TN (87%) or off-therapy pts with sustained clinical response (87.5%) in comparison to pts on therapy at the time of vaccination (41.7%)(<0.0001). Similar results were observed when comparison was performed in terms of antibody titers (P=0.02;Kruskall-Wallis test; Fig 1). In comparison to pts treated with a PI as monotherapy, those who received an anti-CD20 antibody in association to PI had a lower antibody response to SARS-CoV-2 vaccine (11.1% vs 53.8%; OR,0.107 [0.011-0.984];P=0.04). In univariate analysis, the following variables were significantly associated with serological response to SARS-CoV-2 vaccination: early Rai stage (i.e.,0-I) (OR, 0.36 [0.13-0.97];P=0.04), mutated IGHV status (OR,0.30 [0.10-0.88]; P=0.02), lack of active therapy - which comprised TN and off-therapy pts with sustained response - (OR,0.09 [0.03-0.32];P<0.0001), and no anti-CD20 antibody exposure preceding vaccination (OR, 013 [0.01-1.23];P=0.04). Levels of immunoglobulins or absolute values of CD3,CD4,CD8, and CD16/CD56 cells measured before the first COVID-19 vaccination were not associated to vaccine response. Of note, in pts who experienced a serological response a concomitant increase of the absolute of CD16/CD56 positive cells was observed (P=0.02). Finally, Rai stage (OR, 0.19 [0.05-0.79]; P=0.02) and treatment status (OR, 0.06 [0.02-0.27]; P<0.0001) were independent predictors of response in multivariate analysis. We used these factors to build a score that identified pts with different pattern of response to vaccine. Serologic response to SARS-CoV-2 vaccination was 100% in pts with no factor (n=21), 45% in pts. with one factor (n=38) and 36% in pts with two factors (n=11) (P<0.0001). In agreement with results of recent studies (Herishanu et al, Blood 2021; Roeker et al, Leukemia 2021;Perry et al, Blood Cancer J. 2021; Benjamini O et al, Haematologica 2021 ) our findings suggest that antibody-mediated response to COVID-19 vaccination is significantly reduced in CLL and influenced by disease activity and treatment status. The serological response to SARS-CoV-2 vaccination observed in pts. with early disease with no need of therapy may help to identify CLL pts who are expected to achieve an optimal response to COVID-19 vaccine similarly to age- and sex-matched controls. [Figure: see text] DISCLOSURES: Molica: Astrazeneca: Honoraria; Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria.