Lastly, Isatuximab reveals direct killing activity when a larger increase in apoptosis is detected in CD38 expressing cancer cells. Furthermore, isatuximab demonstrated a dose dependent inhibition of CD38 enzymatic activity. However, daratumumab with the same experimental conditions shows a more limited inhibition without a dose response. Reactions
Isatuximab binds uniquely to an epitope on the CD38 receptor and is the only CD38 antibody which can start apoptosis directly. Isatuximab binds to a different CD38 epitope amino-acid sequence than does the anti-CD38 monoclonal antibody daratumumab. The binding with the CD38 receptor is mainly via the gamma heavy chains and are more potent than other CD38 antibodies such as daratumumab which can inhibit the enzymatic activity of CD38. Moreover, isatuximab inhibits the hydrolase activity of CD38.The antibodies show signs of improving antitumor immunity by eliminating regulatory T cells, B cells and myeloid-derived suppressor cells. The difference in binding between isatuximab and daratumumab is in the recognition of the different amino acid groups. Isatuximab identifies 23 amino acids of CD38 to the contrary with daratumumab who has 27. The residue of Glu233 has a flexible sidechain and faces the N-terminal of Asp1 residue in the isatuximab light chain. The latter light chain of isatuximab is also flexible which makes the interaction between CD38/Glu233 and the Asp1 weaker than the other interactions between CD38 and isatuximab. The caspase-dependent apoptotic pathway and the lysosomal mediated cell death pathway in MM cells is induced by isatuximab. The MM cell death follows the downstream reactions of the lysosomal activation.
The binding of isatuximab to CD38 on multiple myeloma (MM) cells leads to a trigger to several mechanisms leading to direct apoptosis of target cancer cells. The triggered pathways are the caspase-dependent apoptotic and the lysosome-mediated cell death pathway in MM cells.It is used in a combination with dexamethasone and pomalidomide. The drug is thus to treat patients with multiple myeloma. Restrictions for the use of isatuximab is that the patients have to be adults who have at least received two previous treatments with lenalidomide and a proteasome inhibitor.Isatuximab is currently also being tested in a Phase II trial as a monotherapy against refractory/recurrent systemic light-chain amyloidosis. Efficacy and side effects
Efficacy
A Phase III study of patients with refractory and relapsed MM, who were resistant to lenalidomide and a proteasome inhibitor, and could not have received daratumumab, another anti-CD38 monoclonal antibody was published in 2019 (ICARIA-MM). The addition of isatuximab to pomalidomide and dexamethasone improved progression free survival to 11.5 months compared to 6.5 months, with an overall response rate of 63%. Side effects
Adverse reactions to isatuximab-irfc may include neutropenia, infusion-related reactions and/or secondary primary malignancies. Of these three the most commonly occurring ones are the infusion-related reactions. Examples of the most frequent symptoms of infusion-related reactions are dyspnea, cough, chills, and nausea, while the severest signs and symptoms included hypertension and dyspnea. Effects on animals
The activity of isatuximab has been researched in mouse tumor models. It has been proven that isatuximab leads to antitumor activity in MM cells.