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Pharma Tech Outlook | Monday, March 09, 2020
Analyzing biologics on a multispecific level is a complex undertaking that requires adequate methodologies.
FREMONT, CA: Drugmakers are interested in multispecific antibodies because they open the door to developing more effective or safer treatments for a broader spectrum of disorders. These characteristics result from their ability to target or interact with different proteins simultaneously. Regrettably, this increased capability results in increased structural complexity, frequently accompanied by an increase in the number of charges and structural variants and, possibly, a broader spectrum of post-translational modifications (PTMs). Drug developers must gain a thorough grasp of these highly complex proteins as early in the drug development process as feasible to prevent wasting time and money on unviable options. Analytical techniques that offer more information more quickly are required to facilitate the development of multispecific drugs.
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More complicated than traditional monoclonal antibodies
Multispecific antibodies have a domain structure comparable to that of monoclonal antibodies (mAbs). They are, however, more complex, and this intricacy is growing as antibody developers strive to tailor binding and half-life to distinct biological requirements while also taking into account steric constraints associated with multiple target engagement.
While standard monoclonal antibodies have identical heavy and light chains, charge and sequence differences and several post-translational modifications result in a large number of isoforms. For multispecific, the number of structural variants is more prominent and is dependent on the number of different components joined. Each of these structural variations has a distinct family of isoforms. This significantly complicates the investigation of multispecific.
When multispecific are synthesized using stochastic expression methods, an improper association of the several chains is possible. This renders even size assays ineffective for identifying intact mAbs, as multiple structural combinations may be identical in size, but only the appropriately constructed molecule will demonstrate the necessary activity. The remainder is considered impurities. Additionally, multispecifics' greater structural complexity may have a greater propensity for misfolding and aggregate formation.
Even if a strategy such as the "knob-in-hole" approach is employed to forge multispecific with the correct structures, the bioengineering process typically introduces additional characteristics to these proteins, such as different modifications, which makes these biologics more complex not only structurally, but also affinity-wise.
The increasing quantity of undesirable side products may make it more difficult to purify the needed treatment using conventional chromatography procedures. Multiple chromatography processes and mass spectrometry (MS) are required to characterize the multispecific completely. Additionally, evaluating multiple target binding will be more challenging when the geometry of multispecific and the accessibility of each binding domain are strongly reliant on assay formats.
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