Figure 1.

Diagram of generic folate receptor–target conjugate.

Notes: Folate (element 1) acts as a targeting moiety to deliver a therapeutically active molecule (element 4), identified here as “drug”; however, element 4 could also be an imaging agent, a hapten, or another chemical entity, depending on the desired endpoint or function. Elements 1 and 4 are separated by a spacer (element 2) and a cleavable bond (element 3). The spacer may be used to confer desirable chemical characteristics (hydrophilicity, hydrophobicity, acid stability, lability, etc) to the overall conjugate, and element 3 is formulated as either a cleavable or a stable bond depending, again, on the ultimate function of element 4.