A pilot study of vaccination with sialyl Lewisa (sLea)–keyhole limpet hemocyanin (KLH) conjugate plus the immunologic adjuvant QS-21 in metastatic breast cancer patients (pts).

2599 Background: The carbohydrate antigen sLea, recognized by the monoclonal antibody (mAb), CA19-9, is commonly expressed on breast cancer cells and is a potential target for vaccine therapy. Methods: The primary endpoints were safety and immunogenicity. Secondary endpoint was presence of circulating tumor cells (CTC) pre and post injection. Pts received sLea (10 or 30 mcg) conjugated to KLH + 100 mcg QS-21 via subcutaneous vaccination during weeks 1, 2, 3, 7, and 19. Pts with metastatic breast cancer with no evidence of disease or stable disease were eligible. Results: Seven pts were treated (10 mcg n=3, 30 mcg n=4), median age 45 years (range 31-65). Six pts were on hormone therapy during the study; 2 pts with no disease and 5 pts with stable disease. Six pts completed 5/5 planned injections. One pt received 4/5 injections. Overall the injections were well tolerated, with grade 1-2 local skin injection site reactions and grade 1 flu-like symptoms the most common toxicities. In 5/7 pts there were no CTC...