In this paper, 26 natural polymyxin components and a new derivative S were synthesized, and their differences in efficacy and toxicity have been investigated. Almost all of the synthesized components showed strong activity against both susceptible and resistant strains of E. coli, K. pneumoniae, P. aeruginosa, and A. baumannii. The toxicities were obviously different between the components. Only some of the components were tested for toxicity in vivo. Compounds E, E-Val, A, M, D, and S showed obviously lower renal cytotoxicity and acute toxicity than polymyxins B and E. The in vivo nephrotoxicity of E, M, and S was similar to that of polymyxin E. Compound S, with four positive charges, was especially interesting as it possessed both increased efficacy and decreased toxicity. The SAR and toxicity studies indicated that further structural modification could concentrate on polymyxin S. The results also indicated that S could be a new drug candidate.

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Epidermal growth factor receptor (EGFR) is a rational target for cancer therapy, because its overexpression plays an important oncogenic role in a variety of solid tumors; however, EGFR‐targeted antibody–drug conjugate (ADC) therapy for esophageal squamous cell carcinoma (ESCC) is exceedingly rare. LR004 is a novel anti‐EGFR antibody with the advantages of improved safety and fewer hypersensitivity reactions. It may be of great value as a carrier in ADCs with high binding affinity and internalization ability. Here, we prepared an EGFR‐targeting ADC, LR004‐VC‐MMAE, and evaluated its antitumor activities against ESCC and EGFR‐positive cells. LR004 was covalently conjugated with monomethyl auristatin E (MMAE) via a VC linker by antibody interchain disulfide bond reduction. VC‐MMAE was conjugated with LR004 with approximately 4.0 MMAE molecules per ADC. LR004‐VC‐MMAE showed a potent antitumor effect against ESCC and other EGFR‐positive cells with IC 50 values of nM concentrations in vitro. The in vivo antitumor effects of LR004‐VC‐MMAE were investigated in ESCC KYSE520 and A431 xenograft nude mice models. Significant activity was seen at 5 mg·kg−1, and complete tumor regression was observed at 15 mg·kg−1 in the KYSE520 xenograft nude mice after four injections, while the naked antibody LR004 had little effect on inhibiting tumor growth. Similar promising results were obtained in the A431 models. In addition, the tumors also remained responsive to LR004‐VC‐MMAE for large tumor experiments (tumor volume 400–500 mm3). The study results demonstrated that LR004‐VC‐MMAE could be a potential therapeutic agent for ESCC and other EGFR‐expressing malignancies. We also evaluated PK profile of LR004‐VC‐MMAE ADC in the mice model, which would provide qualitative guiding significance for the further research.

Twenty-three polymyxin analogs with variations at nine amino acid positions were synthesized and assessed for antimicrobial activity and renal cytotoxicity. Compounds M 2 , 14, S 2 , and 16 (MIC = 0.125−4 μg/mL) had similar or stronger activities against susceptible and drug-resistant strains of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii compared to polymyxin B (MIC = 1−2 μg/mL). Most synthesized compounds (50% cytotoxic concentration, CC 50 ≥ 200 μg/mL) exhibited lower cytotoxicity than polymyxin B (CC 50 = 99 ± 6 μg/mL). Polymyxin S 2 showed high plasma stability in vitro and strong efficacy in a mouse systemic infection model (ED 50 = 0.9 mg/kg) against NDM-1-producing Klebsiella pneumoniae, suggesting that it is a potential candidate for drug development. The activity and cytotoxicity results indicated that the amino acids at positions 2, 3, 6, and 7 might be replaced. Effects on activity and cytotoxicity linked to changes in the number of positively charged amino acids varied among different cyclopeptide skeletons, but the underlying mechanisms are unknown.

Animal models are widely used for biomedical studies and drug evaluation. The small intestine plays key roles in nutrient absorption, hormone secretion, microbiota defense and drug absorption and metabolism. Although the intestinal structure of mammals is conserved, the differences on epithelial cell composition, functional assignments and drug absorption among mammals are largely unknown. Here, cross-species analysis of single-cell transcriptomic atlas of the ileum epithelium from mouse, rat, pig, macaque and human reveals the conserved and differential cell types and functions among species, identifies a new CA7+ cell type in pig, macaque and human ileum, uncovers the distinct expression pattern in enterocytes, enteroendocrine cells and Paneth cells, and defines the conserved and species-specific intestinal stem cell signature genes. The examination of drug absorption across species suggests that drug metabolism in mouse ileum is closer to human while drug transport in macaque ileum is more similar to human. Together, our data provide the comprehensive information about cell composition and functional assignments in five species, and offer the valuable guidance for animal model selection and drug testing.