Patients with Multiple Myeloma on Anti-CD38 or Anti-BCMA Based Regimens and Patients with Waldenstrom's Macroglobulinemia Under Rituximab or BTK Inhibitors Have a Poor Humoral Response Following COVID-19 Vaccination

Introduction: Recent data suggest a suboptimal antibody response to COVID-19 vaccination in patients with hematological malignancies. Herein, we evaluated the development of neutralizing antibodies (NAbs) against SARS-CoV-2 in patients with plasma cell neoplasms (PCNs) after vaccination with either the mRNA BNT162b2 or viral vector AZD1222 vaccine, up to 50 days post their first vaccine dose.

Methods: This is an ongoing large prospective study (NCT04743388) evaluating the kinetics of anti-SARS-CoV-2 antibodies after COVID-19 vaccination in healthy subjects and in patients with hematological malignancies or solid tumors. Here we present the data on patients with PCNs in comparison to controls of similar age and gender, who were vaccinated during the same time period (January to March 2021) in Athens (Greece). Major exclusion criteria for both patients and controls included the presence of: (i) autoimmune disorder under immunosuppressive therapy or other active malignant disease; (ii) HIV or active hepatitis B and C infection, (iii) end-stage renal disease and (iv) prior diagnosis of COVID-19.

Serum was collected on day 1 (D1; before the first vaccine dose), on day 22 (D22; before the second dose of the BNT162b2 or 3 weeks post the first AZD1222 dose) and on day 50 (D50; 4 weeks post second dose of the BNT162b2 or 7 weeks post the first AZD1222 dose). NAbs against SARS-CoV-2 were measured using an FDA approved-ELISA methodology (cPass™ SARS-CoV-2 NAbs Detection Kit, GenScript, Piscataway, NJ, USA).

Results: We evaluated 382 patients with PCNs after vaccination with either the BNT162b2 or the AZD1222 vaccine. Patients with MM (n=213), WM (n=106), SMM (n=38) and MGUS (n=25) and 226 healthy controls were enrolled in the study. Of MM/SMM/MGUS patients, 215 (77.9%) were vaccinated with the BNT162b2 and 61 (22.1%) with the AZD1222 vaccine, while out of 106 WM patients 90 (84.9%) were vaccinated with the BNT162b2 and 16 (15.1%) with the AZD1222 vaccine. Vaccination with either two doses of the BNT162b2 or one dose of the AZD1222 vaccine led to lower production of NAbs against SARS-CoV-2 in patients compared with controls both on day 22 and on day 50 (P<0.001 for all comparisons).

After the first dose of the vaccine, on D22, the patient group had lower NAb titers compared with controls: the median NAb inhibition titer was 27% (IQR: 15.3-42%) for MM/SMM/MGUS versus 20.5% (IQR: 10-37%) for WM patients versus 38.7% (IQR: 22-54.3%) for controls (P<0.001 for all comparisons). On D50 the median NAb inhibition titer was 62.8% (IQR: 26-88.9%) for MM/SMM/MGUS versus 36% (IQR: 18-78%) for WM patients versus 90% (IQR: 58-96.4%) for controls (P<0.001 for all comparisons). 57.3% MM/SMM/MGUS, 42% WM patients and 81% controls developed NAb titers ≥50% (p<0.001 for patients versus controls). Furthermore, MM patients showed an inferior NAb response compared with MGUS on day 22 (p=0.009) and on day 50 (p=0.003). Importantly, active treatment with either anti-CD38 monoclonal antibodies or belantamab mafodotin and lymphopenia at the time of vaccination were independent prognostic factors for suboptimal antibody response following vaccination in MM (p<0.05). Disease-related immune dysregulation and therapy-related immunosuppression were involved in the low humoral response in patients with WM. Importantly, active treatment with either rituximab or Bruton's Tyrosine Kinase inhibitors (BTKIs) was proven as an independent prognostic factor for suboptimal antibody response following vaccination in WM (p<0.05). Regarding adverse events, 33% and 31.6% patients reported mild reactions after the first and second dose of the BNT162b2 vaccine, respectively; 32.8% patients vaccinated with the first dose of AZD1222 also presented with local reactions.

Conclusion: Patients with MM and WM have a low humoral response following SARS-CoV-2 vaccination, especially those who are under treatment with anti-CD38-, anti-BCMA-, anti-CD20- or BTKIs-based regimens. This result suggest that these patients have to continue the protective measures against SARS-CoV-2 as they are at high risk for COVID-19. Further studies on the kinetics of immune subpopulations following COVID-19 vaccination will elucidate the underlying immune landscape and determine the potential need for additional booster vaccine doses or protective administration of antibodies against SARS-CoV-2 in MM/WM patients with poor response after full vaccination.