Figure 1.

EC0746 folate receptor binding affinities. (a) Chemical structure of EC0746. There are four separate functional components to this novel construct: the folate receptor (FR)-targeting moiety folic acid (FA; black), the drug moiety aminopterin (AMT; red), a saccharo-amino acid peptide-based spacer of ((saccharo-γGlu)-γGlu)₂-γCys (blue), and a hydrazide/disulfide-containing linker (green). (b) Relative binding affinities of EC0746 in comparison with AMT and methotrexate (MTX) using FRα-expressing KB cells and FRβ-expressing CHO-FRβ cells. The assays were performed in triplicate at 37°C using each compound as a competitor to displace [³H]FA from binding to FR-expressing cells. Numbers shown next to each test article are relative affinity values with FA itself set at 1.