Isatuximab

Multiple myeloma is a blood cancer characterized by an overproduction of malignant plasma cells in the bone marrow. A unique characteristic of myeloma cells is their dense and uniform expression of CD38 surface glycoproteins - these proteins, also expressed in relatively minor quantities on other lymphoid and myeloid cells, have been identified as performing several critical cellular functions, and this, along with their relative abundance on myeloma cells, has made them an attractive target for multiple myeloma treatment. CD38 was first identified as an activation marker, but has subsequently demonstrated roles in adhesion to endothelial CD31 proteins, as an accessory component of the synapse complex, and as an ectoenzyme involved in the metabolism of extracellular NAD+ and cytoplasmic NADP. The products of CD38’s ectoenzymatic activity include the calcium-mobilizing compound adenosine diphosphate ribose (ADPR), which can be further metabolized by CD203a/PC-1 and CD73 to adenosine, an immunosuppressive molecule that may play a role in tumour cell evasion of the immune system.

Isatuximab is an IgG1-derived monoclonal antibody targeted against CD38 proteins. Its activity against CD38 results in a number of downstream effects, including direct apoptosis of the affected cell and activation of immune mechanisms including antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and complement dependent cytotoxicity (CDC), all of which result in potent anti-tumour activity. Via allosteric antagonism, isatuximab also inhibits CD38 ectoenzymatic activity, preventing the immunosuppressive effects of its downstream products.

Isatuximab may also exert its effects via downstream promotion of lysosome-dependent cell death, upregulation of reactive oxygen species, and restoration of antitumor immune effector cell functions.