High-quality binding assays to assess the interaction of PROTAC molecule SD-36 — a potent and selective degrader of STAT3 that has shown anti-tumor activity in preclinical models — with STAT3 and with the CRBN ligase were established using Spectral Shift. The affinity in the low nM range was determined with high-quality data, as shown by S/N above 30 for both binary complexes.
When you have to measure interactions that involve covalent ligands, measuring in solution makes it less complicated versus a method that calls for immobilization. Spectral Shift easily shows that covalent PROTAC molecule LC-2 has an affinity 80 times stronger for the E3 ligase complex VCB when it’s forming a binary complex with target KRAS — ternary complex, blue trace — than when it binds to VCB alone — binary complex, purple trace. The tighter binding translates into a high cooperativity value (α) and confirms why LC-2 shows great promise as a KRAS degrader.
Ternary complex formation, cooperativity, and hook effect must be assessed to ensure efficient ubiquitination and degradation of your target protein. Trust Dianthus to measure binding affinities of binary and ternary complexes in solution for easy calculation of cooperativity and to uncover the hook effect with high-quality data.