Total synthesis of apratoxin C, a cyanobacterial cyclodepsipeptide with highly potent cytotoxicity against some cancer cell lines, was achieved using the apratoxin A synthetic strategy developed by us. To elucidate the relationship between conformation and activity, the tertiary structure of apratoxin C was analyzed by NMR spectroscopy. We obtained 37 ROEs and five (3)JH,H values, which were translated into distance and dihedral angle constraints, respectively. Molecular modeling was performed with a restrained conformational search by a distance geometry method. The lowest energy structure indicated that the methyl group at C37 and the isopropyl group at C39 play critical roles in maintaining the conformation, whereas the methyl group at C34 does not. Moreover, we confirmed that apratoxin A and C possess similar conformations, providing a likely explanation for their nearly equivalent cytotoxicities.

The synthesis and characterization of an ovel DNA-encodedl ibraryo fm acrocyclic peptided erivatives are described;t he macrocyclesa re based on three sets of proteinogenic and non-proteinogenic amino acid building blocks and featuring the use of copper(I)-catalyzeda lkyneazide cycloaddition (CuAAC) reactionf or ring closure. The library (termedY O-DEL) whichc ontains1254 838 compounds, was encoded with DNA in single-stranded format andw as screened against target proteins of interest using affinity capturep rocedures and photocrosslinking. YO-DEL selections yieldeds pecific binders against serum albumins, carbonic anhydrases and NKp46, am arker of activated Natural Killer cells.

We have demonstrated design, synthesis, and biological evaluation of apratoxin A mimetics. In the first generation, the moCys moiety was replaced with seven simple amino acids as their 3D structures can be similar to that of apratoxin A. Apratoxins M1-M7 were synthesized using solid-phase peptide synthesis and solution-phase macrolactamization. Apratoxin M7, which contains a piperidinecarboxylic acid moiety, exhibited potent cytotoxicity against HCT-116 cells. In the second generation, substitution of each amino acid residue in the tripeptide Tyr(Me)-MeAla-MeIle moiety in apratoxin M7 led to the development of the highly potent apratoxin M16 possessing biphenylalanine (Bph) instead of Tyr(Me), which exhibited an IC value of 1.1 nM against HCT-116 cells. Moreover, compared to apratoxin A, apratoxin M16 exhibited a similarly high level of growth inhibitory activity against various cancer cell lines. The results indicate that apratoxin M16 could be a potential candidate as an anticancer agent.

Placental alkaline phosphatase (PLAP) is an abundant surface antigen in the malignancies of the female reproductive tract. Nevertheless, the discovery of PLAP-specific small organic ligands for targeting applications has been hindered by ligand cross-reactivity with the ubiquitous tissue non-specific alkaline phosphatase (TNAP). In this study, we used DNAencoded chemical libraries to discover a potent (IC 50 = 32 nM) and selective PLAP inhibitor, with no detectable inhibition of TNAP activity. Subsequently, the PLAP ligand was conjugated to fluorescein; it specifically bound to PLAP-positive tumors in vitro and targeted cervical cancer in vivo in a mouse model of the disease. Ultimately, the fluorescent derivative of the PLAP inhibitor functioned as a bispecific engager redirecting the killing of chimeric antigen receptor-T cells specific to fluorescein on PLAP-positive tumor cells.

It is necessary for aldosterone synthase (CYP11B2) inhibitors to have both high potency and high selectivity over 11β-hydroxylase (CYP11B1), a critical enzyme for cortisol synthesis. Previous studies have reported a number of CYP11B2 inhibitors, most of which have an imidazole or pyridine ring to coordinate the heme-iron motif of CYP11B2; however, highly selective inhibitors of human CYP11B2 are still needed. To expand the selectivity in humans, we explored alternative templates and found that pyrazoles were suitable templates for CYP11B2 inhibitors. Investigation of pyrazoles, especially N-alkyl pyrazoles, as a new template to coordinate the heme-iron motif led to a potent and highly selective CYP11B2 inhibitor 28 with an aldosterone-lowering effect at 1 mg/kg dosing in cynomolgus monkeys.