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A new family of squaramide-based anionophores (L1–L8) have been synthesised and fully characterised with the aim to investigate the effect of indolyl substituents on their anion binding and transmembrane transport properties. L1, L2, L6, and L8, bearing a 7-indolyl/indol-7-yl moiety as the substituent, were found to be the most efficient of the series in binding chloride with high stability constants. L1, L6, and L8 were also found to be the most potent anionophores of the series, able to mediate transmembrane anion transport. In particular, L6 bearing the 3,5-bis(trifluoromethyl)phenyl group was found to be the most active transporter, and its efficiency as an anionophore/anion transporter was favourably compared with that of their symmetrically-substituted squaramide analogues L9 and L10, previously reported in the literature., Consejería de Educación de la Junta de Castilla y León (project BU067P20) and the Ministerio de Ciencia e Innovación (project PID2020-117610RB-I00). I. C.-B. and D. A.-C. thank the Consejería de Educación de la Junta de Castilla y León, the European Social Fund (ESF) and the European Regional Development Fund (ERDF) for their post-doctoral (I. C.-B.) and pre-doctoral (D. A.-C.) contracts. The authors gratefully acknowledge Andrea Sancho-Medina for her contributions to transmembrane anion transport experiments. Financial support from MIUR (PRIN 2017 project 2017EKCS35) is gratefully acknowledged by C. C. and G. P. along with the Università degli Studi di Cagliari (FIR 2016-2019) and the Fondazione di Sardegna (FdS Progetti Biennali di Ateneo, annualità 2020, project F75F21001260007).

Overcoming resistance is one of the most challenging features in current anticancer therapy. Autophagy is a cellular process that confers resistance in some advanced tumors, since it enables cancer cells to adapt to stressful situations, such as anticancer treatments. Hence, the inhibition of this cytoprotective autophagy leads to tumor cells sensitization and death. In this regard, we designed a novel potent anionophore compound that specifically targets lysosomes, called LAI-1 (late-stage autophagy inhibitor-1), and evaluated its role in blocking autophagy and its potential anticancer effects in three lung cancer cell lines from different histological subtypes. Compared to other autophagy inhibitors, such as chloroquine and 3-Methyladenine, the LAI-1 treatment induced more potent anticancer effects in all tested cancer cells. LAI-1 was able to efficiently target and deacidify lysosomes, while acidifying cytoplasmic pH. Consequently, LAI-1 efficiently blocked autophagy, indicated by the increased LC3-II/I ratio and p62/SQSTM1 levels. Moreover, no colocalization was observed between autophagosomes, marked with LC3 or p62/SQSTM1, and lysosomes, stained with LAMP-1, after the LAI-1 treatment, indicating the blockage of autophagolysosome formation. Furthermore, LAI-1 induced cell death by activating apoptosis (enhancing the cleavage of caspase-3 and PARP) or necrosis, depending on the cancer cell line. Finally, LAI-1 sensitized cancer cells to the first-line chemotherapeutic agent cisplatin. Altogether, LAI-1 is a new late-stage autophagy inhibitor that causes lysosomal dysfunction and the blockage of autophagolysosome formation, as well as potently induces cancer cell death and sensitization to conventional treatments at lower concentrations than other known autophagy inhibitors, appearing as a potential new therapeutic approach to overcome cancer resistance., This research was supported by Consejería de Educación de la Junta de Castilla y León (grant BU067P20), MCIN/AEI/10.13039/501100011033 (grant PID2020-117610RB-I00) and Instituto de Salud Carlos III (grant PI18/00441), co-funded by the European Regional Development Fund. ERDF, a way to build Europe. P.F., D.A.-C. and I.C.-B. thank Consejería de Educación de la Junta de Castilla y León, European Social Fund and ERDF for their predoctoral (D.A.-C.) and postdoctoral (P.F. and I.C.-B.) contracts. C.B.-G. thanks the University of Barcelona for a predoctoral fellowship.

The vesicular anion transport activity assay, which uses 8-hydroxypyrene-1,3,6-trisulfonic acid to monitor the internal pH of the vesicles (the HPTS assay), is a widely used technique for analysing the activity of anionophore facilitated transport across a phospholipid membrane. This methods paper describes the stepwise technique to conduct this transport assay, detailing both the perks and pitfalls of using this method to determine the activity of an anionophore and the transport mechanism.

Eight N,N´-diarylisophthalamide/dipicolineamide derivatives have been synthesised and fully characterised, both in solution and in the solid state. The transmembrane anion transport properties of these compounds have been studied by chloride-selective electrode and fluorescence experiments. The substitution pattern of the aromatic moieties determines the transport properties of these systems, with those containing electron-withdrawing groups in their structures being the most active ones of the series., Consejería de Educación de la Junta de Castilla y León (project BU075G19)

Highly active transmembrane anion transporters have demonstrated their activity against antibiotic-resistant and clinically relevant bacterial strains. This type of compound offers promise as a strategy to develop novel antibacterial agents.

A novel class of transmembrane anion carriers, the click-tambjamines, display remarkable anionophoric activities in model liposomes and living cells. The versatility of this building block for the generation of molecular diversity offers promise to develop future drugs based on this design., European Union’s Horizon 2020 research and innovation programme (TAT-CF project, grant agreement 667079), Instituto de Salud Carlos III (Grant PI18/00441) (co-funded by the European Regional Development Fund (ERDF), a way to build Europe) and “La Caixa” Foundation and Caja Burgos Foundation (CAIXAUBU004)