Sandra J. Hofstead

Doxorubicin immunoconjugates containing bivalent, lysosomally-cleavable dipeptide linkages

Bivalent doxorubicin (DOX)-dipeptides (16a-c) were prepared and conjugated to the monoclonal antibody BR96. The dipeptides are cleaved by lysosomal proteases following internalization of the resulting immunoconjugates. Conjugate 18b demonstrated antigen-specific in vitro tumor cell killing activity (IC(50)=0.2 microM) that was equipotent to DOX with a near doubling of drug molecules/MAb. Size exclusion chromatography showed 18b to be a noncovalent dimer that was formed immediately upon conjugation.

Synthesis of an Immunoconjugate of Camptothecin

The first immunoconjugate of camptothecin has been synthesized wherein the drug is attached to the tumor-recognizing antibody BR96 via a Cathepsin B cleavable linker. Endocytosis of the immunoconjugate upon binding to the tumor cell followed by enzymatic cleavage of the linker inside the endosome ensures tumor-specific release of the drug. In this way, it is hoped that the dose-limiting side effects associated with camptothecin can be eliminated while the antitumor activity is preserved.

Targeting the MraY and MurG bacterial enzymes for antimicrobial therapeutic intervention.

Assays for two enzymes from Escherichia coli were developed and validated as antibacterial inhibitor screens. The MraY and MurG enzymes were overexpressed and purified as the membrane fraction or to homogeneity, respectively. The MurG enzyme was expressed with a six-histidine tag using an optimized minimal-medium protocol for subsequent purification. Although traditional assays were established, the enzymes were also assayed via a 96-well membrane plate assay and a 384-well scintillation proximity-based assay developed herein. These assays afford a more economical and high-throughput evaluation of inhibitors. A mureidomycin inhibitor mix was used as a control for the assay development and screen validation. Several inhibitors resulting from a high-throughput screen were found and evaluated for potential therapeutic use.

Synthesis and antitumor activity of the immunoconjugate BR96-Dox

Abstract BR96-Dox is an immunoconjugate (IC) in which doxorubicin (8 equivalents) is linked via an acid-labile hydrazone to the chimeric MAb BR96. It binds to a modified Le y Ag on tumor cells, which then internalize it via endocytosis into lysosomes. There, the acidic milieu hydrolyzes the hydrazone link, releasing free Dox. In vivo, it is more active and less toxic than untargeted Dox, producing complete remissions and many cures of subcutaneous human breast, lung and colon tumors, as well as disseminated lung tumors. In vivo, only BR96 + and not BR96 − tumors respond, and ICs with nonbinding Abs are inactive.

Kedarcidin chromophore: Structure elucidation of the amino sugar kedarosamine

Abstract The structure of kedarosamine, the amino sugar moiety of kedarcidin chromophore, was established by NMR spectroscopy and X-ray crystallography as 2,4 dideoxy-4-(dimethylamino)-L-fucopyranose. bl