Effects of Hydrophobic Tail Length Variation on Surfactant-Mediated Protein Stabilization.

Recently, protein therapeutics have gained significant attention as a result of their enhanced selectivity and diminished side effects compared to traditional small-molecule drugs. Despite their advantages, protein formulations typically suffer from stability issues because of aggregation and denaturation during production and storage, often resulting in detrimental immune responses. Surfactants can be used to stabilize and protect proteins in solution by preventing protein adsorption onto interfaces or by forming protective structures in solution. Herein, a detailed structure-activity relationship study is described, demonstrating the role that hydrophobic tail length plays in surfactant-mediated stabilization of the model therapeutic protein IgG. The FM1000 series, originating from a surfactant scaffold that allows for easy structure modulation, was synthesized by a simple 2-step procedure. First, phenylalanine was acylated with a variety of acyl chlorides of differing lengths to yield n-acyl phenylalanine, which was then coupled to Jeffamine M1000, a polyethylene glycol-based amine, to yield the final surfactant. With this FM1000 series, it was observed that the 14 carbon-long tail surfactant (14FM1000) was optimal at preventing IgG aggregation compared to surfactants with tails that were longer or shorter. Using a combination of dynamic surface tensiometry and quartz crystal microbalance with dissipation, it was hypothesized that 14FM1000 was able to prevent IgG adsorption, and therefore aggregation, by adsorbing appreciably onto surfaces quickly. 14FM1000 had the fastest rate of initial adsorption compared to the other surfactants studied. Short-tail surfactants were slow to and did not adsorb appreciably onto surfaces, allowing IgG adsorption. Although long-tail surfactants were also slow to adsorb, allowing IgG to adsorb and aggregate, their equilibrium adsorption was strong. Additionally, 14FM1000 was the most reversibly adsorbed surfactant, likely improving its ability to desorb and adsorb quickly to transient surfaces, therefore protecting the IgG at each new hydrophobic surface and preventing aggregation. By understanding the structure-activity relationship between surfactants and protein stabilization, we move toward more efficient design of future surfactants increasing the stability and utility of important protein therapeutics.

Publisher Correction: BAF complex vulnerabilities in cancer demonstrated via structure-based PROTAC design.

In the version of this article originally published, several lines of text in the last paragraph of the right column on page 1 of the PDF were transposed into the bottom paragraph of the left column. The affected text of the left column should read "The ATP-dependent activities of the BAF (SWI/SNF) chromatin remodeling complexes affect the positioning of nucleosomes on DNA and thereby many cellular processes related to chromatin structure, including transcription, DNA repair and decatenation of chromosomes during mitosis12,13." The affected text of the right column should read "SMARCA2/4BD inhibitors are thus precluded from use for the treatment of SMARCA4 mutant cancers but could provide attractive ligands for PROTAC conjugation. Small molecules binding to other bromodomains have been successfully converted into PROTACs by conjugating them with structures capable of binding to the E3 ligases von Hippel-Lindau (VHL) or cereblon5,6,10,11,25,26,27." The errors have been corrected in the PDF version of the paper.

BAF complex vulnerabilities in cancer demonstrated via structure-based PROTAC design.

Targeting subunits of BAF/PBAF chromatin remodeling complexes has been proposed as an approach to exploit cancer vulnerabilities. Here, we develop proteolysis targeting chimera (PROTAC) degraders of the BAF ATPase subunits SMARCA2 and SMARCA4 using a bromodomain ligand and recruitment of the E3 ubiquitin ligase VHL. High-resolution ternary complex crystal structures and biophysical investigation guided rational and efficient optimization toward ACBI1, a potent and cooperative degrader of SMARCA2, SMARCA4 and PBRM1. ACBI1 induced anti-proliferative effects and cell death caused by SMARCA2 depletion in SMARCA4 mutant cancer cells, and in acute myeloid leukemia cells dependent on SMARCA4 ATPase activity. These findings exemplify a successful biophysics- and structure-based PROTAC design approach to degrade high profile drug targets, and pave the way toward new therapeutics for the treatment of tumors sensitive to the loss of BAF complex ATPases.

Chemically Induced Degradation of the Oncogenic Transcription Factor BCL6.

The transcription factor BCL6 is a known driver of oncogenesis in lymphoid malignancies, including diffuse large B cell lymphoma (DLBCL). Disruption of its interaction with transcriptional repressors interferes with the oncogenic effects of BCL6. We used a structure-based drug design to develop highly potent compounds that block this interaction. A subset of these inhibitors also causes rapid ubiquitylation and degradation of BCL6 in cells. These compounds display significantly stronger induction of expression of BCL6-repressed genes and anti-proliferative effects than compounds that merely inhibit co-repressor interactions. This work establishes the BTB domain as a highly druggable structure, paving the way for the use of other members of this protein family as drug targets. The magnitude of effects elicited by this class of BCL6-degrading compounds exceeds that of our equipotent non-degrading inhibitors, suggesting opportunities for the development of BCL6-based lymphoma therapeutics.

Multiblock copolymers of L-lactide and trimethylene carbonate.

Sequential copolymerizations of trimethylene carbonate (TMC) and l-lactide (LLA) were performed with 2,2-dibutyl-2-stanna-1,3-oxepane as a bifunctional cyclic initiator. The block lengths were varied via the monomer/initiator and via the TMC/l-lactide ratio. The cyclic triblock copolymers were transformed in situ into multiblock copolymers by ring-opening polycondensation with sebacoyl chloride. The chemical compositions of the block copolymers were determined from (1)H NMR spectra. The formation of multiblock structures and the absence of transesterification were proven by (13)C NMR spectroscopy. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and dynamic mechanical analysis (DMA) measurements confirmed the existence of a microphase-separated structure in the multiblock copolymers consisting of a crystalline phase of poly(LLA) blocks and an amorphous phase formed by the poly(TMC) blocks. Stress-strain measurements showed the elastomeric character of these biodegradable multiblock copolymers, particularly in copolymers having epsilon-caprolactone as comonomer in the poly(TMC) blocks.