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Abstract The design of cereblon-binding molecular glues (MGs) that selectively recruit a desired protein while excluding teratogenic SALL4 is an area of significant interest when designing therapeutic agents. Previous studies show that SALL4 is degraded in the presence of IKZF1 degraders pomalidomide, and to a lesser extent by CC-220. To expand our understanding of the molecular basis for the interaction of SALL4 with cereblon, we performed biophysical and structural studies demonstrating that SALL4 zinc finger domains one and two (ZF1-2) interact with cereblon (CRBN) in a unique manner. ZF1 interacts with the N-terminal domain of cereblon and ZF2 binds as expected in the C-terminal IMiD-binding domain. Both ZF1 and ZF2 contribute to the potency of the interaction of ZF1-2 with CRBN:MG complexes and the affinities of SALL4 ZF1-2 for the cereblon:CC-220 complex are less potent than for the corresponding pomalidomide complex. Structural analysis provides a rationale for understanding the reduced affinity of SALL4 for cereblon in the presence of CC-220, which engages both ZF1 and ZF2. These studies further our understanding of the molecular glue-mediated interactions of zinc finger-based proteins with cereblon and may provide structural tools for the prospective design of compounds with reduced binding and degradation of SALL4.

In pursuit of therapeutics for human polyomaviruses, we identified a peptide derived from the BK polyomavirus (BKV) minor structural proteins VP2/3 that is a potent inhibitor of BKV infection with no observable cellular toxicity. The thirteen-residue peptide binds to major structural protein VP1 with single-digit nanomolar affinity. Alanine-scanning of the peptide identified three key residues, substitution of each of which results in ~1000 fold loss of binding affinity with a concomitant reduction in antiviral activity. Structural studies demonstrate specific binding of the peptide to the pore of pentameric VP1. Cell-based assays demonstrate nanomolar inhibition (EC50) of BKV infection and suggest that the peptide acts early in the viral entry pathway. Homologous peptide exhibits similar binding to JC polyomavirus VP1 and inhibits infection with similar potency to BKV in a model cell line. Lastly, these studies validate targeting the VP1 pore as a novel strategy for the development of anti-polyomavirus agents.

Purpose. In order to improve the in vitro and in vivo efficacy of an integrin antagonist (IA) of the extracellular domain of the αvβ3 integrin, a receptor upregulated on tumor neovasculature, the IA was attached to the surface of a dextran-coated liposome (DCL). IA-DCLs were characterized in vitro, and the pharmacokinetic and anti-tumor properties were assessed in vivo. Methods. The in vitro binding properties were measured with purified integrin, endothelial cells, and melanoma cells. The pharmacokinetic parameters were measured in healthy mice with 14C-labeled IA-DCLs and anti-tumor efficacy was assessed with the M21 human melanoma xenograft mouse model. Results. In vitro, IC50 values for IA-DCLs and IA are similar, and IA-DCLs inhibit cell proliferation relative to controls. IA-DCLs are stable in serum, and the pharmacokinetic half-life in mice is 23 h. In the M21/mouse model, statistically significant inhibition of tumor growth was observed for mice treated with IA-DCLs, whereas controls including saline, DCLs lacking IA, and cyclo(RGDfV) were ineffective. Increased apoptosis and a reduction in vessel counts relative to controls were present in tumors from animals treated with IA-DCLs. Conclusions. These results demonstrate that IA-DCLs are potent anti-angiogenic therapeutic agents with superior in vivo activity and pharmacology compared to unmodified IA. [ABSTRACT FROM AUTHOR]