Applications for Escherichia coli-Derived Humanized Fab’ Fragments: Efficient Construction of Bispecific Antibodies

The potential benefits of bispecific antibodies (BsAbs) for the diagnosis and therapy of human disease have long been appreciated (reviewed by Clark et al. 1988; Songsivilai and Lachmann 1990; Nolan and O’Kennedy 1990; Nelson 1991). Unfortunately it has proved very difficult to generate clinically relevant amounts of highly purified BsAbs using traditional hybrid hybridoma technology (Milstein and Cuello 1983) or via directed chemical coupling of Fab’ fragments derived from murine monoclonal antibodies (MAbs) (Brennan et al. 1985; Glennie et al. 1987). Nevertheless, in spite of the limited availability of BsAb a few small scale clinical studies have been undertaken (Table 1). For example, BsF(ab’)2 have proved useful for retargeting lymphokine-activated killer cells (Nitta et al. 1990; Bolhuis et al. 1992), toxins (Bonardi et al. 1992) and also radionuclides (Stickney et al. 1989, 1991; Le Doussal et al. 1992) to tumor targets in patients. This motivated us to develop an efficient and general route to the construction of BsF(ab’)2 fragments (Shalaby et al. 1992; Rodrigues et al. 1992a). Our strategy relies upon separate Escherichia coli expression of each Fab’ arm (Carter et al. 1992a) followed by traditional directed chemical coupling to form the BsF(ab’)2.