In targeted protein degradation (TPD), species specificity is a critical determinant of translational success. Sequence differences between human and preclinical animal orthologs—either in the target protein or the E3 ligase—can drastically alter the formation of the ternary complex, leading to false-negative pharmacology or misinterpreted toxicity profiles in vivo.

Recent studies of CRBN- and VHL-based degraders highlight how even subtle amino-acid substitutions can abrogate degradation activity in rodents while maintaining potency in primates or humans. Therefore, early quantitative evaluation of cross-species binding and ternary complex formation is essential before animal model selection.

High-quality recombinant protein production is the cornerstone of ICE Bioscience’s TPD assay capability. Our integrated protein expression and purification platform supports rapid, in-house generation of both target and E3-ligase complexes at assay-grade purity.

Equipped with state-of-the-art instruments including AKTA chromatography systems, Prometheus Panta for thermal stability profiling, and Biacore 8K for label-free kinetic analysis, the platform enables seamless transition from protein production to quantitative binding and ternary-complex characterization.

ICE Bioscience can typically deliver new recombinant proteins within five weeks, followed by SPR or TR-FRET binary/ternary assay setup within one week, allowing partners to quickly validate ligand engagement, cooperativity, and degradation potential. This integrated workflow ensures reliable, reproducible data to accelerate TPD lead optimization and mechanism elucidation.

1. Cross-species Binding by SPR

2. Ternary Complex Formation (TR-FRET)

3. Degradation Correlation (Western Blot and Quantification)

These findings indicate that rabbit STAT6 exhibited reduced SPR binary binding and dog STAT6 looks biophysically fine (binary/ternary), but the cellular context is likely limiting degradation, so DC50 is the highest.

To confirm that the biochemical/biophysical findings translate into cellular outcomes, degradation of STAT6 was examined by western blot in primary cells from each species. The results demonstrated clear, concentration-dependent reduction of STAT6 protein levels. While all species showed measurable degradation, the extent and potency (DC₅₀ and Dₘₐₓ) varied, with human and monkey cells displaying the most efficient turnover. This cell-based confirmation is essential, as it reflects the combined influence of intracellular drug exposure, E3-ligase abundance, and proteasomal processing that cannot be inferred from biophysical assays alone.

Integrating WB verification with SPR and TR-FRET therefore provides a more complete, translatable picture of species-dependent degradation efficiency and supports rational selection of relevant animal models for downstream studies.