How it is administered

Obinutuzumab is given as an intravenous (IV) infusion, meaning it is delivered directly into a vein by a healthcare professional. It is not taken by mouth or injected under the skin. The medication comes as a sterile, clear to slightly brown liquid concentrate that is diluted and infused over several hours.

For chronic lymphocytic leukemia (CLL), the typical schedule is:

• Cycle 1: 100 mg on Day 1, 900 mg on Day 2, 1,000 mg on Days 8 and 15
• Cycles 2–6: 1,000 mg on Day 1 of each 28-day cycle

Premedication with steroids, acetaminophen, and antihistamines is required to reduce the risk of infusion reactions. The infusion rate is started slowly and increased if tolerated.

How it works

Obinutuzumab is a monoclonal antibody that specifically targets the CD20 protein found on the surface of B cells, which are a type of white blood cell often involved in blood cancers like CLL and some lymphomas.

When obinutuzumab binds to CD20, it helps destroy these B cells in several ways:

• It recruits immune cells to attack and kill the B cells (antibody-dependent cellular cytotoxicity and phagocytosis).
• It can directly trigger cell death by activating internal cell death pathways.
• It activates the complement system, a part of the immune system that helps clear out targeted cells.

By depleting abnormal B cells, obinutuzumab helps control the growth and spread of blood cancers. The effects on B cells can last for months after treatment, and B cell recovery may take time.

Who Should take it

Obinutuzumab is indicated for adults with certain blood cancers:

• In combination with chlorambucil for patients with previously untreated chronic lymphocytic leukemia (CLL).
• In combination with bendamustine (and then as a single agent) for follicular lymphoma that has relapsed or is refractory to rituximab-containing regimens.
• In combination with chemotherapy (then as a single agent) for previously untreated stage II bulky, III, or IV follicular lymphoma.

While not specifically approved for B-cell prolymphocytic leukemia (B-PLL), obinutuzumab may be considered in certain cases of B-cell blood cancers where CD20 is present, under the guidance of a hematologist.

Who should not take it

Obinutuzumab should not be used by patients who have had:

• Severe allergic reactions (anaphylaxis) or serum sickness to obinutuzumab or any of its ingredients.
• Active infections at the time of planned treatment.

Caution is needed in patients with a history of hepatitis B, as the virus can reactivate. Live vaccines should be avoided during and after treatment until B-cell recovery. Pregnant women should not use obinutuzumab due to the risk of harm to the unborn baby, and women of childbearing potential should use effective contraception during and for 6 months after treatment.

Commonly used with

Obinutuzumab is most commonly used in combination with other chemotherapy agents, such as:

• Chlorambucil (for CLL)
• Bendamustine, CHOP, or CVP (for follicular lymphoma)

Premedications like steroids, acetaminophen, and antihistamines are routinely used to prevent infusion reactions. Sometimes, medications to prevent tumor lysis syndrome (like allopurinol) or infection (antibiotics, antivirals) are also given.

Commonly tested with

Obinutuzumab has been tested in combination with:

• Chlorambucil (in CLL clinical trials)
• Bendamustine, CHOP, or CVP (in follicular lymphoma trials)
• It is often compared to rituximab, another anti-CD20 antibody, in clinical studies.

Other supportive medications, such as growth factors for low blood counts and prophylactic antimicrobials, may be used in clinical trials and practice.