Design, Synthesis, and Structure–Activity Relationship Studies of a Potent PACE4 Inhibitor

Abstract

PACE4 plays an important role in the progression of prostate cancer and is an attractive target for the development of novel inhibitor-based tumor therapies. We previously reported the design and synthesis of a novel, potent, and relatively selective PACE4 inhibitor known as a Multi-Leu (ML) peptide. In the present work, we examined the ML peptide through detailed structure-activity relationship studies. A variety of ML-peptide analogues modified at the P8-P5 positions with leucine isomers (Nle, DLeu, and DNle) or substituted at the P1 position with arginine mimetics were tested for their inhibitory activity, specificity, stability, and antiproliferative effect. By incorporating d isomers at the P8 position or a decarboxylated arginine mimetic, we obtained analogues with an improved stability profile and excellent antiproliferative properties. The DLeu or DNle residue also has improved specificity toward PACE4, whereas specificity was reduced for a peptide modified with the arginine mimetic, such as 4-amidinobenzylamide.

Novel Furin Inhibitors with Potent Anti‐infectious Activity

“…For best compound 19,aresidual activity of approximately 27 %w as determineda taconcentration of 1 mm,a lthough only am inor improvement was found after incorporation of basic P5 residues. Owing to its preferred potency for furin among the PCs tested, the structure of inhibitor MI-1148 (19) in complex with furin was determined.…”

“…[17] This approach was furthere laborated by other groups using different P1 residues and N-terminal elongations. [18,19] Further improved potencies in the low picomolar range have been achieved by combination with basic P5 residues. [20] Crystal structures of thesei nhibitors in complex with human furin have revealed numerousk ey interactions contributing to the strong in vitro potencyo ft hese analogues.…”

PACE4 Undergoes an Oncogenic Alternative Splicing Switch in Cancer

“…Peptide synthesis and cleavage analysis ML peptide and its derivatives (Peg8-ML and C23) were synthesized as described previously (12). Synthesis and cleavage analysis of the GDF-15 spanning peptide are described in the Supplementary Material.…”

Structure-Based Optimization of a Potent PACE4 Inhibitor Containing a Decarboxylated P1 Arginine Mimetic

“…All peptides were obtained by a combination of solid-phase peptide synthesis and solution synthesis as previously described [3]. The scan of the P5, P6 and P7 (with the exception of the Tle P7 ) position resulted in analogs with reduced inhibitory potency against PACE4 when compared to the initial peptide (MLAmba), revealing that Leu residues at these positions provide higher binding affinity for the enzyme (Figure 2A).…”

“…Moreover, we developed a potent PACE4 inhibitor with considerable selectivity (20-fold over furin) known as the Multi-Leu (ML) peptide [2]. In order to improve its pharmacological profile, we performed structure-activity relationship (SAR) studies and determined that the incorporation of the decarboxylated arginine mimetic (4-amidinobenzylamide, Amba) at the P1 position led to a more potent and stable analog [3]. Unfortunately, this inhibitor suffered from a reduced selectivity towards PACE4.…”