Cyclization of RGD Peptides by Suzuki-Miyaura Cross-Coupling

Kemker I, Schnepel C, Schröder DC, Marion A, Sewald N. Cyclization of RGD Peptides by Suzuki-Miyaura Cross-Coupling. Journal of Medicinal Chemistry. 2019;62(16):7417-7430.Halogenated L- or D-tryptophan obtained by biocatalytic halogenation was incorporated into RGD peptides together with a variety of alkyl or aryl boronic acids. Suzuki-Miyaura cross-coupling either in solution or on-resin results in side chain-to-tail-cyclized RGD peptides, for example, with biaryl moieties, providing a new dimension of structure-activity relationships. An array of RGD peptides differing in macrocycle size, the presence of D-amino acid, N-methylation, or connectivity between the indole moiety and the boronic acid showed that, in particular, connectivity exhibits a major impact on affinities toward integrins, for example, a(v)beta(3). Structure-activity relationship studies yielded peptides with affinities toward a(v)beta(3) in the low nanomolar range, good selectivity, and high plasma stability. Structural characteristics of representative molecules have been investigated by molecular dynamics simulations, which allowed understanding the observed activity differences

Cyclization of RGD Peptides by Suzuki-Miyaura Cross-Coupling

Halogenated L- or D-tryptophan obtained by biocatalytic halogenation was incorporated into RGD peptides together with a variety of alkyl or aryl boronic acids. Suzuki-Miyaura cross-coupling either in solution or on-resin results in side chain-to-tail-cyclized RGD peptides, for example, with biaryl moieties, providing a new dimension of structure-activity relationships. An array of RGD peptides differing in macrocycle size, the presence of D-amino acid, N-methylation, or connectivity between the indole moiety and the boronic acid showed that, in particular, connectivity exhibits a major impact on affinities toward integrins, for example, a(v)beta(3). Structure-activity relationship studies yielded peptides with affinities toward a(v)beta(3) in the low nanomolar range, good selectivity, and high plasma stability. Structural characteristics of representative molecules have been investigated by molecular dynamics simulations, which allowed understanding the observed activity differences

Tuning the Biological Activity of RGD Peptides with Halotryptophanst

An array of L- and D-halotryptophans with different substituents at the indole moiety was synthesized employing either enzymatic halogenation by halogenases or incorporation of haloindoles using tryptophan synthase. Introduction of these Trp derivatives into RGD peptides as a benchmark system was performed to investigate their influence on bioactivity. Halotryptophan-containing RGD peptides display increased affinity toward integrin alpha(nu)beta(3) and enhanced selectivity over integrin alpha(5)beta(1). In addition, bromotryptophan was exploited as a platform for latestage diversification by Suzuki-Miyaura cross-coupling (SMC), resulting in new-to-nature biaryl motifs. These peptides show enhanced affinity toward alpha(nu)beta(3), good affinity to alpha(nu)beta(8), and remarkable selectivity over alpha(5)beta(1) and alpha(IIb)beta(3) while featuring fluorogenic properties. Their feasibility as a probe was demonstrated in vitro. Extensive molecular dynamics simulations were undertaken to elucidate NMR and high-performance liquid chromatography (HPLC) data for these late-stage diversified cyclic RGD peptides and to further characterize their conformational preferences

Linker Hydrophilicity Modulates the Anticancer Activity of RGD\u2013Cryptophycin Conjugates

Most anticancer agents are hydrophobic and can easily penetrate the tumor cell membrane by passive diffusion. This may impede the development of highly effective and tumor-selective treatment options. A hydrophilic \u3b2-glucuronidase-cleavable linker was used to connect the highly potent antimitotic agent cryptophycin-55 glycinate with the \u3b1v\u3b23 integrin ligand c(RGDfK). Incorporation of the self-immolative linker containing glucuronic acid results in lower cytotoxicity than that of the free payload, suggesting that hydrophilic sugar linkers can preclude passive cellular uptake. In vitro drug-release studies and cytotoxicity assays demonstrated the potential of this small molecule\u2013drug conjugate, providing guidance for the development of therapeutics containing hydrophobic anticancer drugs

Tuning the Biological Activity of RGD Peptides with Halotryptophans

Kemker I, Schröder DC, Feiner R, Müller K, Marion A, Sewald N. Tuning the Biological Activity of RGD Peptides with Halotryptophans. Journal of Medicinal Chemistry. 2021;64(1):586–601.An array of l- and d-halotryptophans with different substituents at the indole moiety was synthesized employing either enzymatic halogenation by halogenases or incorporation of haloindoles using tryptophan synthase. Introduction of these Trp derivatives into RGD peptides as a benchmark system was performed to investigate their influence on bioactivity. Halotryptophan-containing RGD peptides display increased affinity toward integrin αvβ3 and enhanced selectivity over integrin α5β1. In addition, bromotryptophan was exploited as a platform for late-stage diversification by Suzuki–Miyaura cross-coupling (SMC), resulting in new-to-nature biaryl motifs. These peptides show enhanced affinity toward αvβ3, good affinity to αvβ8, and remarkable selectivity over α5β1 and αIIbβ3 while featuring fluorogenic properties. Their feasibility as a probe was demonstrated in vitro. Extensive molecular dynamics simulations were undertaken to elucidate NMR and high-performance liquid chromatography (HPLC) data for these late-stage diversified cyclic RGD peptides and to further characterize their conformational preferences

EGFR-Binding Peptides: From Computational Design towards Tumor-Targeting of Adeno-Associated Virus Capsids

The epidermal growth factor receptor (EGFR) plays a central role in the progression of many solid tumors. We used this validated target to analyze the de novo design of EGFR-binding peptides and their application for the delivery of complex payloads via rational design of a viral vector. Peptides were computationally designed to interact with the EGFR dimerization interface. Two new peptides and a reference (EDA peptide) were chemically synthesized, and their binding ability characterized. Presentation of these peptides in each of the 60 capsid proteins of recombinant adeno-associated viruses (rAAV) via a genetic based loop insertion enabled targeting of EGFR overexpressing tumor cell lines. Furthermore, tissue distribution and tumor xenograft specificity were analyzed with systemic injection in chicken egg chorioallantoic membrane (CAM) assays. Complex correlations between the targeting of the synthetic peptides and the viral vectors to cells and in ovo were observed. Overall, these data demonstrate the potential of computational design in combination with rational capsid modification for viral vector targeting opening new avenues for viral vector delivery and specifically suicide gene therapy