Abstract: Provided are multi-specific antibodies that target both a cellular efflux pump and a cancer-associated antigen as well as pharmaceutical compositions, nucleic acids, recombinant expression vectors, cells, and kits that include or encode such multi-specific antibodies. Methods of treating a subject for a cancer that include administering to the subject a multi-specific antibody that targets both a cellular efflux pump and a cancer-associated antigen are also provided. Provided as well are methods of generating the described multi-specific antibodies and reagents related thereto, including genetically modified cell lines useful in the subject methods and methods of making such genetically modified cell lines.

Abstract: Provided are anti-ABCB 1 antibodies that may be used as multi-specific, including bispecific, antibodies targeting both ABCB 1 and a tumor-associated antigen (TAA), as well as pharmaceutical compositions, nucleic acids, recombinant expression vectors, cells, and kits that include or encode such antibodies and multi-specific antibodies. Further included are uses and methods of treating conditions where inhibition of ABCB 1-mediated efflux transport is desirable, such as, cancer or multi-drug resistance mediated by the ABCB1 transporter, e.g., multi-drug resistant cancer. In particular, the disclosure provides humanized multi-specific, e.g. bispecific, IgG (IgG1) antibodies that bind ABCB1 and a TAA. Multi-specific IgG1 antibody molecules are provided with Fc substitutions in at least one of a first and a second heavy chain constant region.

Abstract: Provided are antibodies that target the cellular efflux pump ABCC4. Also provided are pharmaceutical compositions, nucleic acids, recombinant expression vectors, cells, and kits that include or encode such antibodies. Methods of using the antibodies for detecting presence or absence of ABCC4 expression in cells, e.g., tumor cells, level of ABCC4 expression, and/or inhibiting ABCC4 function are also disclosed. Also provided are methods for treating a subject for a cancer that include administering to the subject an anti-ABCC4 antibody disclosed herein.

Abstract: Provided are antibodies that target the cellular efflux pump ABCC1. Also provided are pharmaceutical compositions, nucleic acids, recombinant expression vectors, cells, and kits that include or encode such antibodies. Methods of using the antibodies for detecting presence or absence of ABCC1 expression in cells, e.g., tumor cells, Level of ABCC1 expression, and/or inhibiting ABCC1 function are also disclosed. Also provided are methods for treating a subject for a cancer that include administering to the subject an anti-ABCC1 antibody disclosed herein. The subject antibody may be a bispecific antibody. The bispecific antibody may bind to ABCC1 and a tumor associated antigen (TAA).

Abstract: Provided are multi-specific antibodies that target both a cellular efflux pump and a cancer-associated antigen as well as pharmaceutical compositions, nucleic acids, recombinant expression vectors, cells, and kits that include or encode such multi-specific antibodies. Methods of treating a subject for a cancer that include administering to the subject a multi-specific antibody that targets both a cellular efflux pump and a cancer-associated antigen are also provided. Provided as well are methods of generating the described multi-specific antibodies and reagents related thereto, including genetically modified cell lines useful in the subject methods and methods of making such genetically modified cell lines.