Less common side effects of obinutuzumab include:

Hypersensitivity reactions, including serum sickness:
Symptoms may include fever, rash, joint pain, and swelling. (drugs.com)
Tumor lysis syndrome:
Rapid breakdown of tumor cells leading to metabolic abnormalities. (drugs.com)
Progressive multifocal leukoencephalopathy (PML):
A rare, serious brain infection leading to neurological symptoms. (drugs.com)
Hepatitis B virus reactivation:
Reactivation of HBV infection, which can lead to serious liver problems. (drugs.com)