How Do Immunostimulants Work?

Immunostimulants (immunostimulators) are drugs that stimulate the immune system by increasing the activity of any of its components. The immune system is a complex network of cells, tissues, and organs. Together, they help the body fight infections and diseases. Sipuleucel-T (an immunosuppressant) is used to treat certain types of advanced prostate cancer. Another immunostimulant (human immunodeficiency virus [HIV] vaccine) is currently in clinical trials and awaiting the United States Food and Drug Administration (FDA) approval for therapeutic vaccination to elicit immune responses against a wide variety of HIV antigens. These medications are also called personalized autologous cellular immunotherapy (a type of medication prepared using cells from the patient's own blood).

The two main categories of immunostimulants are:

• Specific immunostimulants: stimulate an immune response to a specific antigen (a toxin or other foreign substance which induces an immune response in the body) such as vaccines.
• Nonspecific immunostimulants: act irrespective of antigenic specificity and are used in immunodeficiency and chronic infections.
• Immunostimulants are prescription-only medicines and are administered as a suspension (liquid) to be injected over about 60 minutes into a vein once every two weeks for a total of three doses. About three days before each dose of sipuleucel-T injection is to be given, a sample of white blood cells is collected at a cell collection center using a procedure called leukapheresis (a process that removes the white blood cells from the body). This sample is then sent to the manufacturer and combined with a protein to prepare a dose of sipuleucel-T injection. 

Immunostimulants work in the following ways:

• They cause the body's immune system to fight cancer cells.
• Sipuleucel-T selectively targets the prostate-specific antigen known as prostatic acid phosphatase (PAP), an antigen that is expressed in around 95% of prostate cancers.
• Sipuleucel-T vaccine is based on the concept of antigen-presenting cells (APCs). These cells present antigens in a form that T cells can recognize.
• It works through APCs to stimulate T-cell immune response targeted against PAP.

• Immunostimulant drug sipuleucel-T was approved by the FDA to treat asymptomatic or minimally symptomatic metastatic hormone-refractory prostate cancer.
• HIV vaccine is awaiting FDA approval to treat HIV antigens.

Common side effects include:

• Nausea
• Chills
• Fatigue
• Headache
• Back/joint pain
• Fever
• Vomiting
• Constipation
• Asthenia (physical weakness or lack of energy)

Other rare side effects include:

• Paresthesia (an abnormal sensation, typically tingling or pricking [pins and needles], caused chiefly by pressure on or damage to peripheral nerves)
• Anemia (low red blood cells)
• Pain in extremity
• Dizziness
• Hematuria (blood in the urine)
• Dyspnea (shortness of breath)
• Peripheral edema (swelling of lower legs or hands)
• Insomnia (trouble falling and/or staying asleep)
• Urinary tract infection
• Rash
• Sweating
• Tremor (an involuntary, rhythmic muscle contraction leading to shaking movement in one or more parts of the body)

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of immunostimulants include:

• HIV vaccine
• Provenge
• Remune
• Sipuleucel-T