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Obinutuzumab

  • Antineoplastic monoclonal antibodiesAntineoplastic monoclonal antibodies
  • High alertAn error with this medicine can cause serious harm: double checks and protocols are used.

Glycoengineered anti-CD20 antibody with stronger immune killing than rituximab. For CLL and follicular lymphoma; can reactivate hepatitis B.

Updated

Quick facts

Group
Antineoplastic monoclonal antibodies
Target
CD20 (B-lymphocyte surface antigen)
Used for
Follicular lymphoma · Also used for lupus nephritis
Key effects
Infusion reactions · Muscle or joint pain · Tiredness
Monitor
Hepatitis B blood test before starting · Blood count
ATC
L01FA03

No doses: the clinician sets them by the current guideline.

Mechanism of action

The cryo-electron microscopy structure shows full-length human CD20 in the membrane with obinutuzumab Fab arms bound.

Target in 3D: CD20 (B-lymphocyte surface antigen). PDB structure 6Y97 (RCSB PDB, public domain). View the structure at RCSB PDB

Obinutuzumab is a humanised IgG1 antibody against CD20, a protein on the surface of normal and malignant B cells. Once bound, it kills the B cell through complement (CDC) and through immune effector cells (ADCC). The sugar chains on its Fc portion were changed (glycoengineering) so that it binds effector immune cells more strongly; it was the first glycoengineered antibody approved.

  1. Obinutuzumab binds CD20 on B cells
  2. Its modified Fc recruits immune killer cells strongly
  3. B cells, malignant and normal, are destroyed

Indications

  • Previously untreated chronic lymphocytic leukaemia, with chlorambucil. Chronic lymphocytic leukaemia →
  • Follicular lymphoma: with bendamustine after rituximab failure, or with chemotherapy as first line, then alone as maintenance. Non-Hodgkin lymphoma →
  • Also used for lupus nephritis, by blocking immune cells that damage the kidney.

Adverse effects

Common

  • Infusion reactions, mostly with the first infusion
  • Muscle or joint pain, headache, itching
  • Constipation, diarrhoea, decreased appetite
  • Tiredness, trouble sleeping

Contraindications

  • None stated in the sources used; hepatitis B is tested and treated first

Key interactions

Vaccines
No vaccinations are given during treatment without asking the treating doctor.
Chlorambucil or bendamustine (combination regimens)
Intended combinations; they add to low blood counts and infection risk.

What is monitored

  • Hepatitis B blood test before starting, and signs of hepatitis during and for months after treatment
  • Vital signs during each infusion
  • Blood count
  • New confusion, imbalance, speech or vision changes (PML)

Administration and safety

  • Slow intravenous infusion by a doctor or nurse; medicines are given before each infusion to prevent reactions.
  • The patient is watched closely during the infusion; it is slowed or stopped for a reaction.

Pregnancy and breastfeeding

Effective contraception is used during treatment and for months after the last dose, and breastfeeding is avoided for the same period.

Nursing care

  • Confirm the hepatitis B test result before the first dose.
  • Ask about heart, lung, kidney or liver disease and any current or recurring infection.
  • Teach to report fever, cough, yellow skin, leg pain or swelling, bleeding, and any sudden change in thinking, balance, speech or vision.
  • No vaccinations without asking the treating doctor.

Pharmacokinetics

Absorption
Slow intravenous infusion.
Elimination
Broken down like other IgG antibodies, by protein catabolism.

Test yourself

Think of the answer, then tap the question to see it.

What is special about the Fc portion of obinutuzumab?

Its sugars were glycoengineered to bind immune effector cells more strongly, boosting ADCC.

Which two boxed-warning risks does obinutuzumab carry?

Hepatitis B reactivation and progressive multifocal leukoencephalopathy.

With which drug is obinutuzumab combined in untreated CLL?

Chlorambucil.

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More Pharmacology questions →

Connections

← Back to the class: Antineoplastic monoclonal antibodies

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Obinutuzumab Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Obinutuzumab - NCI (National Cancer Institute (U.S.), 2026); Structure of full-length CD20 in complex with Obinutuzumab Fab (RCSB Protein Data Bank, 2020).

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Representative model, for educational purposes only.