Further Species of mAbs

In addition to these four types of mAbs, several further species of mAbs have been developed by new engineering technologies, predominantly during the past decade. The production of these mAbs is based on the ability to generate human (or at least human-like) binding sites from a number of starting positions and to link them genetically or chemically to a wide variety of effector elements (see Section 3.5). 

One very new and powerful area of research is that of monoclonal intrabodies (also called intracellular antibodies), which represent a new class of targeting molecules with potential use in gene therapy. Due to their totally different targets, namely inside a cell, and thus different effector functions, they may have a high potential in the treatment of human diseases [6]. 

In an attempt to increase efficacy in therapy, the production of bivalent or multivalent species by linking subunits (non-covalently, covalently, or by disulfide bonds) has been proposed. For example, a bispecific single-chain antibody fragment has been investigated for malaria therapy. This is a combination of two scFv, one directed against the CD3 molecule on human T lymphocytes, and the other against an epitope of a surface protein of Plasmodium falciparum, the parasite which causes malaria [8]. 

In summary, only a few therapeutic polyclonal antibodies are still marketed today. The main advantages of mAbs are their high specificity towards the target and the capability of an unlimited production of these homogeneous biological molecules. In future, new antibody or antibody-derived pharmaceuticals will be developed and can be expected to have favorable efficacy, a lack of immunogeni-city, and appropriate pharmacokinetics such that they can be used to treat intracellular medical disorders. 

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