Tumor-directed radiation and the immunotoxin SS1P in the treatment of mesothelin-expressing tumor xenografts.

Purpose: Mesothelin is a cell surface protein overexpressed in mesotheliomas and pancreatic and ovarian cancers. The goal of this study was to determine if radiation therapy in combination with the antimesothelin immunotoxin SS1(dsFv)PE38 (SS1P) would result in enhanced antitumor activity against mesothelin-expressing xenografts in nude mice.

Experimental Design: Female athymic nude mice bearing s.

Pretreatment with rituximab does not inhibit the human immune response against the immunogenic protein LMB-1.

Purpose: Rituximab, a humanized monoclonal antibody directed to the CD20 antigen present on B lymphocytes, could potentially abrogate the humoral immune response to murine monoclonal antibodies or immunotoxins by depleting antibody-producing B cells.

Experimental Design: A Phase II study of LMB-1, an immunotoxin targeting the Lewis Y tumor antigen, in combination with rituximab was conducted to test the hypothesis that rituximab could abolish or diminish the development of human antibodies to LMB-1. Five patients were treated in this study and received 375 mg/m(2) rituximab on days 1 and 7 followed by 45 micro g/kg/day LMB-1 on days 10, 12, and 14.