Rituxan/Rituxamab is an IV B-cell therapy (also called B-cell depletion therapy) used for people with autoimmune encephalitis (AE).  AE is caused by auto-antibodies malfunctioning and attacking the brain. Auto-antibodies are made by plasma cells, b cells are plasma cells. These are cells of your immune system.

If the first-line therapies don’t provide sufficient relief for a patient with AE, the most common second-line therapy is a drug called rituximab. Rituximab is actually an antibody that targets and destroys B cells, which normally go on to become antibody-producing cells. B cells can cross the blood-brain barrier (BBB) and seep into the brain and become antibody-producing cells. Rituximab cannot cross the BBB, therefore, its effects may be limited in patients where this occurs. Also, it should be taken into consideration that there are long-lived plasma cells (half-life of >6 months) refractory to conventional immunosuppressive treatments and treatments targeting B or T cells leading to the continuation of autoimmunity with persistent autoantibodies. Long-lived plasma cells may reside in the bone marrow and intrathecal compartment and contribute to a resistance to treatment, and relapses.

Rituximab, which was initially designed to treat cancer, is, itself, an antibody. But, interestingly, its job is to “tag” the cells in the body’s own immune system that make other antibodies. This causes the body’s immune system to kill its own antibody-producing cells, ultimately halting the production of antibodies. This means that rituximab can stop the immune system from making the harmful brain targeting autoantibodies that cause AE symptoms. But Rituximab doesn’t just suppress the production of the AE-causing antibodies – it suppresses the production of all antibodies, including those necessary for fighting infections. This can leave patients vulnerable to bacterial and viral invaders that they would normally be able to fight off. Additionally, rituximab is known to cause other side effects like fevers, fatigue, and nausea. Nevertheless, rituximab has been shown to be an effective at restoring functioning for patients with AE who need additional treatment on top of first-line therapies.

How B-Cell Therapy (Treatment) Works

B cells are a type of white blood cell. They make antibodies — proteins that fight viruses and bacteria. B cells normally can’t cross from your blood into your brain or spinal cord. If you have AE, some B cells enter your brain and spinal cord and attack healthy cells thinking they are foreign invaders.

B-cell therapy uses drugs called monoclonal antibodies to attack these cells. These meds stick to the surface of B cells. This kills the cells, helps ease inflammation, and plays a part in slowing down nerve damage.

B-cell therapy might affect other parts of your immune system as they fight AE. That’s because B cells affect other immune cells called T cells. T cells usually kill viruses and bacteria. But when you have AE, B cells recruit T cells into your brain. There, they cause inflammation.

When your number of B cells goes down, your amount of T cells that cause inflammation goes down, too. At the same time, your level of something called regulatory T cells goes up. Regulatory T cells turn off inflammation. They may even help slow your immune system’s attacks on your body.

If you don’t have any b cells, then the attacking auto-antibody can-not be made.

The doctor will monitor the patient by taking blood labs to see if the Rituxan has reached its’ full affect. This is when the B cells are at zero. The doctor evaluates their  patient’s symptoms and presentation when the b cells are at zero and the treatment is having its full effect.  It can take around 6 weeks after the patient has received their second dose (full dose) of Rituxan treatment to show effectiveness as it is slow acting. Rituxan can last around 6 months. Some patients require more than one round of this treatment and will receive repeated Rituxan treatments. The doctor continues to re-evaluate how the patient is doing throughout the treatment process.

When the B cells come back, the hope is that they will not make these attacking antibodies anymore. AE is treated with a combination of treatments. Each treatment addresses a different aspect of what the disease is doing.

In AE, Rituxan is a second line treatment after steroids, plasmapheresis, and IVIG. Although some physicians have used Rituxan as a first line treatment, depending on the patient’s presentation.

Remember timing is everything! Once a work up is complete and AE is determined by the physician immediate treatment is crucial.

Side Effects

Infusions sometimes cause an allergic reaction. Your doctor might call it an infusion reaction. If it happens, it’s usually during your first dose.

You might have:

• Itching
• Rash
• Nausea
• Hives
• Headache

These symptoms are often mild but can be severe. You usually get your first dose of these medicines across two sessions to make it less likely that you’ll have a reaction. With any of these treatments, you could be more prone to infections like colds, bronchitis, and herpes. So it’s important to take steps to stay healthy.

Some researchers believe that these treatments can also give you a slightly higher chance of some cancers, especially breast cancer. But experts aren’t sure of the connection. In very rare cases, they may lead to progressive multifocal leukoencephalopathy (PML), a rare brain infection that can be fatal.

Before you begin Rituxan, your doctor will go over all the possible side effects to make sure you know the risks and benefits of treatment.

Key to Treatment the Physician Follows

-The Doctor completes their work up first!
-Immunotherapy takes time to work – weeks to months with continued recovery for 18-24 months
-Need to treat both inflammation and symptoms
-Goal is to Maximize functionality – symptomatic treat also essential

• Timing is everything…
  -Timeline of symptom “control” vs “relapse”
  -Post IVIG?
  Lasts up to 120 days
  -Post IV steroids?
  “self-tapering” (as instructed by physician)
  -Post Rituxmab?
  2-4 months to “sweet spot” for B cell depletion
  -Plasmapheresis?
  Quick improvements but quick declines
• Second Line
  -Rituximab (Antibody to CD20)
  Removes B cells and plasmablasts but not plasma cells (antibody factory)
  Does not work immediately- delayed onset of action, improvements usually 2-3 months later
  Need to continue bridging with IVIG, steroids, and symptomatic therapy
• Maintenance
  – Rituximab
  Standard dosing every 6 months
  Follow B cell repopulation and response to determine ultimate dosing frequency if responsive
  -Mycophenolate mofetil
  -Azathioprine

References: Treatment of Autoimmune Brain Disorders by: Heather Van Mater, MD, MS Pediatric Rheumatology Duke Children’s Hospital Director, Duke Autoimmune Brain Disorders Program