Additional validation of Osaka method (0.01 mol/L dithiothreitol) for negating the daratumumab interference

Efficient neutralization of daratumumab in pretransfusion samples using a novel recombinant monoclonal anti-idiotype antibody

BACKGROUND

Anti-CD38 antibodies such as daratumumab (DARA) are critical therapies for multiple myeloma and other diseases. Unfortunately, anti-CD38 antibodies cause panreactivity in indirect antiglobulin tests (IATs), complicating blood compatibility testing. The anti-CD38 interference is most often mitigated by treating reagent red blood cells (RBCs) with dithiothreitol (DTT). However, when using the DTT method, not all RBC antibody specificities can be detected (e.g., anti-K), and the DTT method is impractical for some transfusion services. We evaluated the ability of a new anti-idiotype antibody to neutralize DARA in vitro and eliminate the anti-CD38 interference.

STUDY DESIGN AND METHODS

A recombinant monoclonal rabbit anti-DARA idiotype antibody ("anti-DARA") was generated. The ratio of anti-DARA required to neutralize DARA in spiked samples was evaluated in IATs performed in gel. IATs performed in tube were used to demonstrate that anti-DARA allows alloantibody detection in the presence of DARA. Plasma samples from 29 patients receiving DARA were treated with a fixed quantity of anti-DARA (120 μg) before performing antibody detection tests (screens) in tube.

RESULTS

Anti-DARA used at or above a 1:1 ratio with DARA eliminated the DARA interference with IATs. Anti-DARA allowed detection of both alloanti-E and alloanti-K in the presence of DARA. In 27/29 (93.1%) clinical samples, 120 μg anti-DARA was sufficient to neutralize the DARA in 100 μl patient plasma.

DISCUSSION

An anti-DARA:DARA ratio as low as 1:1 is sufficient to neutralize DARA in solution. A fixed amount of anti-DARA eliminates the anti-CD38 interference in most patient samples.

Overcoming Drug Interference in Transfusion Testing: A Spotlight on Daratumumab

Daratumumab, a monoclonal antibody therapeutic, is highly efficacious and widely used in all stages of multiple myeloma and amyloidosis and has promising activity in other hematologic disorders. Daratumumab interacts with red blood cells, interfering with pre-transfusion testing. This interference can lead to compromising transfusion safety, extensive blood bank work ups and delays in provision of compatible units. Several methods have been developed to negate daratumumab interference with indirect antiglobulin testing. They are based on i) standard blood bank techniques including dithiothreitol and enzymatic treatment of reagent cells, using reagent red blood cells negative for CD38, ii) blocking CD38 antigens on reagent or donor cells, iii) neutralization of anti-CD38 antibody in patient plasma prior to testing, and iv) extended antigen typing of patient red blood cells in conjunction with provision of phenotypically matched units for transfusion. Implementation of those methods by the blood bank should be a planned effort coordinated with the patient’s clinical team. Timely involvement of blood bank and transfusion services and educational efforts by both blood banks and clinical providers can improve the overall daratumumab safety profile in regard to blood transfusion.

Impact of new myeloma agents on the transfusion laboratory

Monoclonal antibody (mAb) therapy targeting CD38 and CD47 antigens expressed on cancer cells has transformed therapy options for patients with multiple myeloma as well as other haematological and non-haematological malignancies. While the on target effects of these new drugs highlight the promise of precision cancer therapeutics, the unintended, off target binding of drugs to red blood cells (RBCs) and platelets has required transfusion service laboratories (TSL) and immunohaematology reference laboratories (IRL) to innovate and rapidly set up processes and testing protocols to overcome the significant interference in routine pre-transfusion tests caused by these agents. Binding of anti-CD38 and anti-CD47 drugs to reagent RBCs leads to false positive pan-agglutination during the antihuman globulin phase of testing, making it difficult to rule out underlying alloantibodies, and leading to delays in setting up compatible units for RBC transfusion. Anti-CD47 agents can also interfere with ABO/Rh typing studies. Several methods to successfully mitigate interference have been described, such as treatment of reagent RBCs with reducing agents or enzymes, allogeneic RBC adsorption studies and drug specific neutralisation assays; all methods have limitations. TSLs should select an approach that best fits their workflow and expertise and takes into consideration their level of access to specialised outside testing, local blood supplier capabilities, and the type of patient population served. For platelet refractory patients, samples should be tested by platelet antibody assays that are known to be unaffected by drug therapy. RBC transfusion support for multiple myeloma patients receiving anti-CD38 or anti-CD47 drugs can be optimised by establishing good communication between the clinical teams and TSLs, building electronic notification processes, and ensuring timely completion of baseline pre-transfusion testing and RBC phenotype/genotype prior to starting therapy. Staff education, standardisation of laboratory mitigation measures, and implementation of testing algorithms that consider mAb-induced interference when working up a pan-agglutinin help to significantly decrease delays that would otherwise result if standard methods were employed to complete antibody identification studies.

Daudi cell stroma: An alternative to dithiothreitol to resolve daratumumab interference in pretransfusion testing

Treatment of red blood cells with dithiothreitol (DTT) or trypsin effectively denatures CD38; however, this treatment damages other antigens, some of which are of clinical importance. Thus, other avenues to deplete daratumumab (DARA) from plasma samples should be explored.

STUDY DESIGN AND METHODS

The Daudi B-cell line was found to express high levels of CD38 and was sonicated in a sonication buffer to achieve complete cell lysis. The resulting stroma preparation was centrifuged at 20 000g for 20 minutes and then mixed with 250 μL of DARA-plasma and incubated for 10 minutes at 37°C. The stroma-DARA-plasma mixture was centrifuged again, and the supernatant was collected and subjected to four additional rounds of adsorption with fresh stroma. DARA-depleted plasma was tested by gel indirect antiglobulin test (IAT).

RESULTS

CD38 expression on Daudi cells was confirmed by flow cytometry. Gel IAT analysis showed that the incubation of plasma from DARA-treated patients with Daudi cells stroma resulted in a significant depletion of DARA but allowing detection of other alloantibodies of interest such as anti-K, anti-Yt^a , and anti-Gy^a .

CONCLUSIONS

Daudi cell stroma is inexpensive, easy to prepare in large batches, and can be used as an off-the-shelf reagent. Incubation of plasma from DARA-treated patients with Daudi cell stroma can efficiently overcome DARA interference in serologic testing without affecting DTT- or trypsin-sensitive antigens.