Anti-CD38 Nanoantibody (JK36) Allows Detection of Minimal Residual Disease in Multiple Myeloma Patients Treated with Daratumumab

Objective: To evaluate the performance of the camel anti-CD38 antibody JK36 by flow cytometry in patients with Multiple Myeloma treated with Daratumumab.

Materials and Methods: 7 bone marrow samples from patients with Multiple Myeloma treated with Daratumumab were evaluated. The immunophenotypic markers studied routinely were: Tube 1 CD38 FITC (T16 - Beckman Coulter), CD56 PE, CD20 PERCP-Cy5.5, CD19 PC7, Kappacy APC, Lambdacy APC-H7, CD45 V450 and CD138 V500; Tube 2 CD38 FITC (T16 - Beckman Coulter), CD28 PE, CD27 PERCP-Cy5.5, CD19 PC7, CD117 APC, CD81 APC-H7, CD45 V450 AND CD138 V500. For the detection of CD38 depletion, a Nano Tube was made with the following markers Kappacy FITC, CD56 PE, CD20 PERCP-Cy5.5, CD19 PC7, CD38 APC (nano antibody from camel JK36 – Beckman Coulter), Lambdacy APC-H7, CD45 V450 and CD138 V500. The samples were analyzed by the immunophenotyping method by flow cytometry, using the CANTO II equipment (Becton Dickinson – BD) and the analysis was performed in the Infinicyt software (Cytognos). The maximum total events acquired was 3,400,000 with merge between tubes 1 and 2. For Tube Nano, the maximum total events acquired was 1,700,000.

Results: In the routinely used panel (Tube 1 and Tube 2) CD38 expression in plasma cells was negative in all samples. However, in all samples, it was possible to identify plasmocytes through expression of CD138 in conjunction with multiple gate strategies that include expressions of aberrant markers. In the Nano Tube containing the marker CD38 Nano Antibody of Camel (JK36) it was possible to visualize the expression of CD38 in the plasmocytes of all analyzed samples. Furthermore, with this marker it was possible to discriminate abnormal plasma cells from normal ones.

Discussion: The expressions of CD38 together with CD138 characterize plasma cells. Anti-CD38 targeted therapy (Daratumumab) induces immune-mediated clearance of cells expressing CD38. The detection of plasma cells by flow cytometry with the use of this conventional antibody on the cell surface is impaired after the use of Daratumumab. Nano antibodies that occur naturally in camelids are capable of recognizing epitopes hidden and not blocked by targeted therapies, allowing the detection of plasma cells in patients with Multiple Myeloma after this treatment. In our study, we demonstrated that the Camel Nano Antibody CD38 antibody (JK36) was able to detect plasma cells in patients after using Daratumumab.

Although it was possible to identify plasmocytes through the expression of CD138, this strategy becomes very risky and difficult to apply since the expression of this marker can often be of low intensity.

The nanoantibody proved to be an additional and useful marker in the detection of MRD in patients after anti-CD38 target therapy (Dartumumab), bringing greater reliability in the analysis.

Conclusion:

The Camel Nano Antibody CD38 antibody (JK36) offers flow cytometry laboratories the opportunity to more accurately monitor response to anti-CD38 therapies. Nano antibody technology enhances the ability of DRM detection by flow cytometry in the era of immunotherapy.