On November 1, 2013 the FDA approved obinutuzumab (GazyvaTM) for use in combination with chlorambucil (a nitrogen mustard alkylating agent) for the treatment of patients with previously untreated chronic lymphocytic leukemia (CLL). CLL is the most common type of Leukaemia accounting for 35% of all reported Leukaemias (See CRUK CLL page). In a randomized three-arm clinical study, the combination of obinutuzumab (in combination with chlorambucil) improved the progression-free survival (PFS) of patients to 23.0 months compared to 11.1 months for chlorambucil alone.
Obinutuzumab (CHEMBL1743048) is a humanized anti-CD20 monoclonal antibody of ca. 150 kDa molecular weight. Its target, the B-lymphicyte antigen CD20, is the product of the gene MS4A1 (Uniprot: P11836; ChEMBL: CHEMBL2058; canSAR target synopsis. The CD20 antigen is expressed on the surface of pre B- and mature B-lymphocytes. Obinutuzumab mediates B-cell lysis through three main routes:
- Engagement of immune effector cells, resulting in antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis
- Direct activation of intracellular death signaling pathways
- Activation of the complement cascade.
Obinutuzumab has been issued with a boxed warning because of the following observed events: Reactivation of Hepatitis B Virus (HBV), in some cases resulting in fulminant hepatitis, hepatic failure, and death; and causing Progressive Multifocal Leukoencephalopathy (PML) resulting in death.
GazyvaTM is produced by Genentech, Inc. The full Prescribing Information is here.