Abstract: A group of functionalized linking agents are disclosed. The linking agents contain thiol reactive functionalities for the covalent reaction with sulfhydryl groups from the hinge-region of antibody fragments. The linking agents also contain masked aldehyde functionalities for covalent attachment of amine-containing therapeutic agents by Schiff base formation. Carrier systems capable of delivering compounds to targeted sites in vivo based on antigen-antibody interactions are constructed from these linking agents.

Abstract: This invention discloses a molecule bearing a biologically active group (a phenanthridinium moiety) joined covalently to an oligonucleotide recognition system (a phosphorus nucleoside group) by a linker that permits intercalation of the active group in the pocket formed by the nucleotide and complementary bases in another polynucleotide strand. This class of compounds is illustrated by the following: ##STR1## where R is selected from the group consisting of --NH.sub.2, methylamino, or ethylamino or hydrogen;where R' is selected from the group consisting of --NH.sub.2, methylamino, or ethylamino or hydrogen;where the chain linking the linker group to the phenanthridinium group (R") consists of 2-8 --CH.sub.2 -- groups.