CD3 x CD19 bispecific antibodies and CD28 costimulation for locoregional treatment of low-malignancy non-Hodgkin's lymphoma.

In advance of using bispecific antibodies for the treatment of B cell lymphoma in humans, we analysed CD3 x CD19 bispecific antibodies for their capacity to induce T cell activation in cell suspensions from follicular lymphoma lymph nodes. Here, we demonstrate that the lack of costimulatory molecules, such as members of the B7 family, on the tumour cells resulted in insufficient activation of autologous T lymphocytes. However, stimulation and proliferation of T cells could be induced by addition of monospecific CD28 antibodies. Moreover, we show that bispecific CD3 x CD19 antibodies can protect severe combined immunodeficiency (SCID) mice from human Epstein-Barr-virus (EBV)-induced B cell lymphoma growth. In these in vivo studies, CD28 costimulation did not show a significant benefit, possibly because of the high-level expression of CD80 and CD86 on the surface of the lymphoma cells. Furthermore, the treatment of SCID mice with bispecific antibodies, with or without CD28 antibodies, induced tumour-protective effects, as determined by a rechallenging experiment in long-term-surviving animals with the autologous EBV-transformed tumour B cell line. Treatment of a follicular lymphoma patient by intratumoural injection of both antibodies resulted in immunological responses with increases in the T/B ratio of peripheral blood as well as enhanced NK cell activity without toxic systemic side-effects.