Peptide Multimerization as Leads for Therapeutic Development

Exploring Multivalency in the Development of Anti-PD-L1 Peptides for Cancer Immunotherapy

PURPOSE

The PD-1/PD-L1 pathway is one of the most effective immune checkpoint pathways utilized for cancer immunotherapy. Despite the success of anti-PD-1/PD-L1 mAbs, there is growing interest in developing low molecular weight anti-PD-1/PD-1 agents, such as peptides, because of their improved tumor penetration. We recently developed a small anti-PD-L1 peptide and demonstrated its promising anti-tumor activity. In this study, we investigate multivalency as a strategy to increase the binding avidity and blocking efficiency of the anti-PD-L1 peptide.

METHODS

Multivalent peptide inhibitors are designed with multiple copies of a peptide inhibitor in a single molecule. We synthesized peptides with different valences and examined their activity. We also investigated how spacer length affects the activity of these multivalent peptides.

RESULTS

Using this strategy, we developed a multivalent peptide that demonstrated approximately 40 times higher blocking efficiency and improved stability compared to the original peptide. Increasing the valency enhanced the peptide's specificity, which is essential for minimizing side effects.

CONCLUSIONS

Multivalency approach represents a promising platform for improving the efficacy of peptide-based checkpoint inhibitors.

68Ga-Labeled TRAP-Based Glycoside Trimers for Imaging of the Functional Liver Reserve

The exclusive asialoglycoprotein receptor (ASGR) expression on hepatocytes makes it an attractive target for imaging of the functional liver reserve. Here, we present a set of TRAP-based glycoside trimers and evaluate their imaging properties compared to the gold standard [99mTc]Tc-GSA. The click-chemistry-based synthesis approach provided easy access to trimeric low-molecular-weight compounds. Labeling with 68Ga was carried out in high radiochemical yields (>99%). Complexes showed high stability and hydrophilicity. Protein binding ranged between 10 and 25%. Highest binding affinity (IC50) and best liver accumulation were found for [68Ga]Ga-T3N3, followed by [68Ga]Ga-T3G3 and [68Ga]Ga-T0G3. Rapid elimination from the rest of the body resulted in excellent target-to-background ratios. Our studies confirmed that high ASGR uptake depends on the correct spacer design and that N-acetylgalactosamine improves targeting properties in vivo. Thus, [68Ga]Ga-T3N3 represents a new low-molecular-weight radiopharmaceutical with pharmacokinetics similar to those of [99mTc]Tc-GSA.

Detection of Hepatocellular Carcinoma in an Orthotopic Patient-Derived Xenograft with an Epithelial Cell Adhesion Molecule-Specific Peptide

Hepatocellular carcinoma (HCC) has emerged as a major contributor to the worldwide cancer burden. Improved methods are needed for early cancer detection and image-guided surgery. Peptides have small dimensions that can overcome delivery challenges to achieve high tumor concentrations and deep penetration. We used phage display methods to biopan against the extra-cellular domain of the purified EpCAM protein, and used IRDye800 as a near-infrared (NIR) fluorophore. The 12-mer sequence HPDMFTRTHSHN was identified, and specific binding to EpCAM was validated with HCC cells in vitro. A binding affinity of kd = 67 nM and onset of k = 0.136 min-1 (7.35 min) were determined. Serum stability was measured with a half-life of T1/2 = 2.6 h. NIR fluorescence images showed peak uptake in vivo by human HCC patient-derived xenograft (PDX) tumors at 1.5 h post-injection. Also, the peptide was able to bind to foci of local and distant metastases in liver and lung. Peptide biodistribution showed high uptake in tumor versus other organs. No signs of acute toxicity were detected during animal necropsy. Immunofluorescence staining of human liver showed specific binding to HCC compared with cirrhosis, adenoma, and normal specimens.

Molecular Complementarity of Proteomimetic Materials for Target-Specific Recognition and Recognition-Mediated Complex Functions

As biomolecules essential for sustaining life, proteins are generated from long chains of 20 different α-amino acids that are folded into unique 3D structures. In particular, many proteins have molecular recognition functions owing to their binding pockets, which have complementary shapes, charges, and polarities for specific targets, making these biopolymers unique and highly valuable for biomedical and biocatalytic applications. Based on the understanding of protein structures and microenvironments, molecular complementarity can be exhibited by synthesizable and modifiable materials. This has prompted researchers to explore the proteomimetic potentials of a diverse range of materials, including biologically available peptides and oligonucleotides, synthetic supramolecules, inorganic molecules, and related coordination networks. To fully resemble a protein, proteomimetic materials perform the molecular recognition to mediate complex molecular functions, such as allosteric regulation, signal transduction, enzymatic reactions, and stimuli-responsive motions; this can also expand the landscape of their potential bio-applications. This review focuses on the recognitive aspects of proteomimetic designs derived for individual materials and their conformations. Recent progress provides insights to help guide the development of advanced protein mimicry with material heterogeneity, design modularity, and tailored functionality. The perspectives and challenges of current proteomimetic designs and tools are also discussed in relation to future applications.

Modulating Lysosomal pH through Innovative Multimerized Succinic Acid-Based Nucleolipid Derivatives

The multimerization of active compounds has emerged as a successful approach, mainly to address the multivalency of numerous biological targets. Regarding the pharmaceutical prospect, carrying several active ingredient units on the same synthetic scaffold was a practical approach to enhance drug delivery or biological activity with a lower global concentration. Various examples have highlighted better in vivo stability and therapeutic efficiency through sustained action over monomeric molecules. The synthesis strategy aims to covalently connect biologically active monomers to a central core using simple and efficient reaction steps. Despite extensive studies reporting carbohydrate or even peptide multimerization developed for therapeutic activities, very few are concerned with nucleic acid derivatives. In the context of our efforts to build non-viral nucleolipid (NL)-based nanocarriers to restore lysosomal acidification defects, we report here a straightforward synthesis of tetrameric NLs, designed as prodrugs that are able to release no more than one but four biocompatible succinic acid units. The use of oil-in-water nanoemulsion-type vehicles allowed the development of lipid nanosystems crossing the membranes of human neuroblastoma cells. Biological evaluations have proved the effective release of the acid within the lysosome of a genetic and cellular model of Parkinson's disease through the recovery of an optimal lysosomal pH associated with a remarkably fourfold lower concentration of active ingredients than with the corresponding monomers. Overall, these results suggest the feasibility, the therapeutic opportunity, and the better tolerance of multimeric compounds compared to only monomer molecules.