xbiotech's scientific overview...

What is an Antibody?

Antibodies are proteins normally found in blood or other bodily fluids and are key immune system components that bind and help eliminate foreign substances, such as bacteria, viruses and other toxins. Antibodies function by tagging and neutralizing substances or infectious agents. Once tagged by an antibody, a substance or infectious agent may be further targeted by the immune system for destruction.

The substance bound by an antibody is called an antigen. Antigens, therefore, are by definition able to trigger an antibody response by the immune system. Each antibody has a unique structure that allows it to bind to a specific antigen. Once an antibody has become bound to an antigen, it may act to prevent pathogens from entering or damaging other cells within the body, block or limit growth of tumors or activate and/or block immune or inflammatory responses. Research conducted at XBiotech and elsewhere has shown that antibodies against pro-inflammatory substances are present in the body and may normally function to reduce or down-regulate inflammation.

Monoclonal Antibody Therapy

Since a single (monoclonal) antibody targets a specific antigen, when used as drugs, an antibody is capable as acting as a highly-specific, disease-targeting agent. This notion forms the basis of therapies which harness the potential of a patient’s own immune system to attack or neutralize a specific disease condition. Since a monoclonal antibody only binds a single target, this therapy is considered to be very selective and specific—a highly coveted attribute in drug treatment.

Murine, Chimeric and Fully Human Antibodies

Therapeutic monoclonal antibodies were first developed from gene sequences obtained from mice (murine). These murine antibodies, however, had limited therapeutic value, because mouse antibodies are recognized as foreign substances to the human body and trigger human immune responses against the murine antibodies themselves.

Subsequently, chimeric antibodies (hybrid molecules derived from mouse and human antibodies) and humanized antibodies (hybrid molecules further modified to contain over 80% human sequences) were developed to reduce the immunogenicity of murine sequences.
More recently, research and development efforts in the industry have centered on the production of so called “fully human” antibodies. Despite the reassuring nomenclature, these antibodies are actually engineered or produced in mice that have been genetically modified to carry a portion of human gene sequences. Extensive clinical experience with antibodies now indicates that these “fully human” antibodies are immunogenic. These results were indeed anticipated by XBiotech. Surprisingly, however, it has been reported that these antibodies may even be more immunogenic than the traditional chimeric or humanized antibodies. Nonetheless, highly promoted by developers and eagerly anticipated in the marketplace, fully human antibody therapeutics have achieved significant commercial success.

True Human Antibodies

XBiotech, by contrast, is producing true human monoclonal antibody therapeutics: that is, a monoclonal antibody that was naturally produced by a human immune system and which was cloned from a human body. XBiotech’s true human antibody therapeutics are therefore actually derived directly and entirely from a human gene sequence which produces a molecule that is theoretically non-immunogenic in humans. The Company believes that its monoclonal antibodies represent a minimized immunogenic footprint, and will therefore have better potential safety, efficacy and commercial value compared to earlier generation antibody therapeutics, including fully human antibodies. Accordingly, the Company believes that its true human antibodies represent the first of a next generation of monoclonal antibody therapeutics.

 

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