The present application provides PEI compounds comprising a linker, PEI-polypeptide conjugates (e.g., PEI-antibody conjugates), and complexes thereof comprising a biologically active molecule. Methods of preparing and using the compounds, conjugates and complexes are further provided. The PEI-polypeptide conjugates and complexes are useful for delivering biologically active molecules to the cytoplasm of cells and promoting release of the biologically active molecules from the endo-lysosomal pathway.

The invention relates to cytosol penetrating antigen binding molecules containing cell surface antigen binding domains, cytosolic antigen binding domains and cytosol penetrating domains; pharmaceutical compositions comprising said antigen binding molecules; methods of delivering said antigen binding molecules specifically into cytosols of target cells; methods of depleting, suppressing or activating cytosolic antigens specifically in target cells by using said antigen binding molecules; and pharmaceutical compositions for preventing or treating diseases in patients comprising said antigen binding molecules. The invention also relates to cytosol penetrating antigen binding molecules containing cytosol penetrating domains and Fc regions, wherein the Fc regions comprising one or more amino acid modifications that enhance multimerization of said cytosol penetrating antigen binding molecules. The invention also relates to an antigen-binding molecule comprising a cell surface antigen-binding domain, a cytosol-penetrating domain, which is conjugated to a heterologous moiety. Further, the invention relates to a method for detecting a cytosol-penetrating ability of a molecule comprising split fluorescent proteins.

In a non-limiting embodiment, the present invention relates to antigen-binding molecules containing an altered TRIM21-binding domain and having an altered cytosolic half-life; pharmaceutical compositions containing such an antigen-binding molecule; methods for using such an antigen-binding molecule; methods for increasing or decreasing the cytosolic half-life of an antigen-binding molecule containing a TRIM21-binding domain; and methods for producing an antigen-binding molecule containing an altered TRIM21-binding domain and having an increased or decreased cytosolic half-life. The present invention also relates to substitutions at specific positions in a TRIM21-binding domain that increase or decrease the cytosolic half-life of an antigen-binding molecule containing a TRIM21-binding domain.

The present invention relates to active form specific anti-Rho GTPase conformational single domain antibodies and their uses in particular in the therapeutic and diagnostic fields. In particular, the present invention relates to a single domain antibody wherein the amino acid sequences of CDR1-IMGT, CDR2-IMGT and CDR3-IMGT have at least 90% of identity with the amino acid sequences of the CDR1-IMGT, CDR2-IMGT and CDR3-IMGT of the H12, B6, 4P75, 4SP1, 4SNP36, 4SNP61, 5SP10, 5SP11, 5SP58, 5SNP47, 5SNP48, 5SNP65, B20, B15, B5, B71, E3, A6, G12, NB61, 212B, 111B or 404F (hs2dAb) single domain antibody which are defined in Table B.

Provided herein are, inter alia, antibodies, antigen-binding antibody fragments, cells, polynucleotides, compositions, kits, and methods relating to the detection of HBV protein X (HBx), e.g., in vitro and in vivo. Included are antibodies and fragments thereof that bind HBx, as well as kits, cells, and compositions comprising such antibodies and fragments.

The present disclosure relates to cell penetrating anti-DNA binding proteins. Compositions comprising these binding proteins may be may be useful for delivering agents to cells and treating diseases such as cancer.

Amino acid sequences capable of enhancing nuclear translocation are provided. Also referred to a nuclear localization signals (NLS) the sequences can be linked to or grafted into antibodies or fragments or fusion proteins thereof to enhance nuclear translocation of the antibody. Compositions and antibodies including an NLS conjugated or otherwise linked directly or indirectly to an active agent cargo are also provided. Exemplary cargo includes proteins, peptides, carbohydrates, polysaccharides, nucleic acid molecules, inorganic molecules, organic molecules, and diagnostic agents. Pharmaceutical compositions further including a pharmaceutically acceptable carrier are also provided. Methods of delivering the composition or antibody alone or with a cargo linked thereto to the nucleus of cell, methods of selecting or screening for compositions having a desired cellular activity, and methods of treating diseases and disorders are also provided.

Provided herein are, inter alia, antibodies, antigen-binding antibody fragments, cells, polynucleotides, compositions, kits, and methods relating to the detection of HBV protein X (HBx), e.g., in vitro and in vivo. Included are antibodies and fragments thereof that bind HBx, as well as kits, cells, and compositions comprising such antibodies and fragments.

A method is described of localizing an intact immunoglobulin-format antibody in cytosol by permeating the cell membrane, thereby avoiding the necessity to use a special external protein delivery system. The method achieves high effects on the treatment and diagnosis of tumor and disease-related factors that show structurally complex interactions through a wide and flat surface between protein and protein.

A tumor-specific cytosol-internalized RAS-inhibiting antibody, in which modified heavy-chain variable region and a light-chain variable region are combined, according to the present disclosure facilitates development into a therapeutic drug due to a high production yield, and can effectively suppress mutant RAS by means of tumor-specific internalization into the cytosol, and thus effective anti-cancer activity can be expected as a stand-alone drug or in combination treatment with existing medicine.