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C. Sousa1
1None - Retired, None, El Dorado Hills, USA
One aspect of finding the right therapeutic for any condition is choosing the most appropriate technology platform. Molecules used as active substances can be divided into two classes: small and large molecules. They differ not only in terms of size, but also in how they are made, how they behave, their mode of action in the body, and their suitability for certain drug forms.
Small, chemically manufactured molecules make up over 90% of the drugs on the market today and, for the most part, act intracellularly. By contrast, large molecules, also known as biologics, are therapeutic proteins that have extracellular targets. Biologic or biological therapy uses portions of the body’s natural immune system to treat
a disease. Therapeutic biologics are proteins derived from biological sources, unlike chemically synthesized “small molecule” pharmaceuticals. Over time veterinary medicine will see development of new therapeutics that are highly targeted, safe, and have minimal or no side effects.
Key Facts
• Some of the oldest forms of biologics are extracted from the bodies of animals, including humans. These include:
o Whole blood and other blood components
o Organs and tissue transplants
o Stem cell therapy
o Antibodies for passive immunization (eg, to treat a virus infection)
o Colostrum
o Fecal microbiota o Reproductive cells
• Some biologics that were previously extracted from animals, such as insulin, are now more commonly produced by recombinant DNA.
• Monoclonal antibodies (mAbs) are laboratory- produced antibodies used to treat many different human inflammatory conditions and cancers, similar to the antibodies that the natural immune system uses to fight off bacteria and viruses.
• Because monoclonal antibodies are “custom designed,” they can be made to target specific proteins, such as cellular receptors or soluble molecules involved in disease pathogenesis.
How Does Biologic Therapy Compare with Conventional Drug Therapy?
Biologic therapy works by targeting proteins that
are a part of the pathophysiology of an inflammatory disease, aid in the growth of cancer cells, or are specific molecules on cancer cells that can destroy the cells. Therapeutic monoclonal antibodies, interferon, interleukin-2 (IL-2), and several types of colony- stimulating factors (CSF, GM- CSF, G-CSF) are forms of biological therapy.
Monoclonal Antibodies
Monoclonal antibodies, or mAbs, are laboratory- produced antibodies. They are a common type of biologic therapy used to treat many different inflammatory conditions and cancers in humans. These are similar to the antibodies that the immune system uses to fight off bacteria and viruses, but they are “custom designed” and can therefore be made specifically to selectively target proteins, such as cellular receptors or soluble molecules involved in disease pathogenesis.
Modes of biologic therapy that involve blocking the action of specific proteins of inflammation (eg, tumor necrosis factor [TNF]) are being used for the treatment of a number of diseases in humans, including rheumatoid arthritis and Crohn’s disease. Adalimumab (Humiraâ) and infliximab (Remicadeâ) are examples of commercially available injectable TNF-blocking treatments for patients with severe rheumatoid arthritis (Figure 1A). Other mAbs, such as dupilumab, target the receptors for cytokines, which modulate the signaling for IL-4 and IL-13 and will be used to treat allergic asthma and atopic dermatitis in humans (Figure 1B).
Figure 1. (A) One mode of monoclonal antibody therapy blocks the proteins that cause inflammation by injection of tumor necrosis factor (TNF), thereby preventing a protein from binding to its receptor. (B) Another mode targets the cytokine receptors to inhibit the signaling of IL-4 and IL-13.
An Urban Experience

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