Combating Non-hodgkin Lymphoma By Targeting Both CD20and HLA-DR Through CD20-243CrossMab

Non-Hodgkin lymphoma (NHL) is a heterogeneous group of malignancies. thefirst monoclonal antibody (mAb) approved for cancer treatment, has revolutionizedthe management and treatment of B-cell malignancies, increasing the median overallsurvival of patients with many of these diseases. Despite widespread use of rituximab,the efficacy remains variable and often modest, and the pursuit of improved agents toreplace rituximab is intense, with several candidates currently under clinicalevaluation.However, complex diseases are often multifactorial in nature, andinvolveredundant or synergistic action of disease mediators or upregulation of differentreceptors, including crosstalk between their signaling networks.Thus, simultaneousblockade of these effector molecules is likely to provide better clinical efficacyand/or reach a broader patient population than inhibition of a single target. However,combination therapy of several mAbs increases health-care costs and the financialburden to families and societies, and the option of using several approved mAbs forcombination therapy is limited because of the small number of therapeutic mAbscurrently on the market. These data show the urgent need to design bispecificantibody with potent anti-tumor activities against NHL.Acquired therapy resistance is one of the prime obstacles for successful cancertreatment. Resistance is often acquired already during an early phase of tumordevelopment when genetic changes cause defects in caspase-dependent apoptosispathways and provide transformed cells with higher growth and survival potential.Thus, alternative cell death pathways capable of killing apoptosis andtherapy-resistant cancer cells have attracted vast interest among cancer researchers.Growing evidence indicated that lysosomes can be considered as an “Achilles heel”for selectively destroying cancer cells, which has been demonstrated as an effective way to kill apoptosis-resistant cancer cells and re-sensitize MDR cells to classicalchemotherapy. Previous studies demonstrated that, although HLA-DR is expressedat high levels on a range of hematologic malignancies, it is constitutively expressedon normal B cells, monocytes/macrophages and dendritic cells. Due to the fact thatthe antigen is expressed on normal as well as tumor cells, safety concerns have beenraised regarding the clinical use of HLA-DR-directed antibodies. Whileacknowledging that HLA-DR is not a tumor-specific antigen, HLA-DR remains anattractive molecule with potential as a target for a CD20-HLA-DR bispecificantibody.To our knowledge, the classical IgG architecture, as it was selected duringevolution, has many advantages for the therapeutic application of bispecificantibodies. We converted the CD20antibody rituximab and HLA-DR antibodyhL243γ1into an IgG-like bispecific antibody (CD20–243CrossMab) by usingCrossMab technology.Our results indicated that CD20–243CrossMab inducessignificantly high levels of CDC, ADCC and cell death in NHL, and has potentanti-tumor capacities against both B-lymphoma cells and rituximab-resistant (RR)B-lymphoma cells. More importantly, although HLA-DR is not specificallyexpressed on malignant cells, CD20–243CrossMab exhibits specific anti-tumoractivities against both CD20and HLA-DR positive malignant cells.