Human anti-CD30 recombinant antibodies by guided phage antibody selection using cell panning

In various clinical studies, Hodgkin's patients have been treated with anti -CD30 immunotherapeutic agents and have shown promising responses. One of t he problems that appeared from these studies is the development of an immun e response against the nonhuman therapeutics, which limits repeated adminis tration and reduces efficacy. We have set out to make a recombinant, human anti-CD30 single-chain variable fragment (scFv) antibody, which may serve a s a targeting moiety with reduced immunogenicity and more rapid tumour pene tration in similar clinical applications. Rather than selecting a naive pha ge antibody library on recombinant CD30 antigen, we used guided selection o f a murine antibody in combination with panning on the CD30-positive cell l ine L540. The murine monoclonal antibody Ki-4 was chosen as starring antibo dy, because it inhibits the shedding of the extracellular part of the CD30 antigen. This makes the antibody better suited for CD30-targeting than most other anti-CD30 antibodies. We have previously isolated the murine Ki-4 sc Fv by selecting a mini-library of hybridoma-derived phage scFv-antibodies v ia panning on L540 cells. Here, we report that phage display technology was successfully used to obtain a human Ki-4 scFv version by guided selection. The murine variable heavy (VH) and light (VL) chain genes of the Ki-4 scFv were sequentially replaced by human V gene repertoires, while retaining on ly the major determinant for epitope-specificity: the heavy-chain complemen tarity determining region 3 (CDR3) of murine Ki-4. After two rounds of chai n shuffling and selection by panning on L540 cells, a fully human anti-CD30 scFv was selected. It competes with the parental monoclonal antibody Ki-4 for binding to CD30, inhibits the shedding of the extracellular part of the CD30 receptor from L540 cells and is thus a promising candidate for the ge neration of anti-CD30 immunotherapeutics. (C) 2000 Cancer Research Campaign .