<div class="\\"page\\"" title="\\"Page" 1"=""><div class="\\"layoutArea\\""><div class="\\"column\\""><span style="\\"font-size:" 10.000000pt;="" font-family:="" 'urwpalladiol'"="">PEGylation of biomolecules is a major approach to increase blood stream half-life, stability<br>and solubility of biotherapeutics and to reduce their immunogenicity, aggregation potential and<br>unspecific interactions with other proteins and tissues. Antibodies have generally long half-lives<br>due to high molecular mass and stability toward proteases, however their size lowers to some extent<br>their potential because of a reduced ability to penetrate tissues, especially those of tumor origin.<br>Fab or otherwise engineered smaller fragments are an alternative but are less stable and are much<br>less well retained in circulation. We have here investigated the effects of various PEGylations on<br>the binding properties and </span><span style="\\"font-size:" 10.000000pt;="" font-family:="" 'urwpalladiol';="" font-style:="" italic"="">in vivo </span><span style="\\"font-size:" 10.000000pt;="" font-family:="" 'urwpalladiol'"="">half-life of Fab fragments derived from the enzymatic splitting of<br>Trastuzumab. We find that PEGylation increases the half-life of the molecules but also strongly affects<br>the ability to recognize the target antigen in a way that is dependent on the extent and position of the<br>chemical modification. Data thus support the concept that polyethylene glycol (PEG) conjugation on<br>Trastuzumab Fabs increases half-life but reduces their affinity and this is a fine balance, which must<br>be carefully considered for the design of strategies based on the use of antibody fragments.<br></span><br>