N -alkanol- N -cyclohexanol amine aryl esters: Multidrug resistance (MDR) reversing agents with high potency and efficacy

Cellular uptake of CPX-351 by scavenger receptor class B type 1-mediated nonendocytic pathway

The proper uptake of drugs in liposome formulations into target cells markedly impacts therapeutic efficacy. The protein corona (PC), formed by the adsorption of serum proteins onto the liposome surface, binds to specific surface receptors of target cells, influencing the uptake pathway. We investigated the uptake pathway into leukemia cells based on PC analysis of CPX-351, a liposome containing cytarabine and daunorubicin in a fixed 5:1 synergistic molar ratio. The PC of CPX-351 mixed with fetal bovine serum was analyzed by nanoflow liquid chromatography-tandem mass spectrometry. CPX-351 uptake in HL-60, K562, and THP-1 leukemia cell lines was measured by flow cytometry using daunorubicin fluorescence. The major components of CPX-351 PC include apolipoproteins A-I and A-II, which bind to scavenger receptor class B type 1 (SR-BI), a nonendocytic pathway that takes up only liposome contents. SR-BI was expressed in each cell, and its expression correlated with CPX-351 uptake. The uptake was significantly decreased by the inhibition of clathrin-mediated endocytosis and macropinocytosis. Additionally, blocks lipid transport-1 (BLT-1), a selective inhibitor of SR-BI, decreased the uptake; however, high-dose BLT-1 addition significantly increased the uptake, which was more strongly inhibited by macropinocytosis suppression compared with clathrin-mediated endocytosis. BLT-1 enhances the binding of SR-BI to liposomes in a dose-dependent manner. These findings indicate that the enhancement of binding between SR-BI and CPX-351 activates different pathways, such as macropinocytosis, distinct from CPX-351 alone. SR-BI may be a biomarker for CPX-351 therapy, and the combination of CPX-351 with high-dose BLT-1 may augment therapeutic efficacy.

P-glycoprotein (P-gp)-driven cancer drug resistance: biological profile, non-coding RNAs, drugs and nanomodulators

Drug resistance has compromised the efficacy of chemotherapy. The dysregulation of drug transporters including P-glycoprotein (P-gp) can mediate drug resistance through drug efflux. In this review, we highlight the role of P-gp in cancer drug resistance and the related molecular pathways, including phosphoinositide 3-kinase (PI3K)-Akt, phosphatase and tensin homolog (PTEN) and nuclear factor-κB (NF-κB), along with non-coding RNAs (ncRNAs). Extracellular vesicles secreted by the cells can transport ncRNAs and other proteins to change P-gp activity in cancer drug resistance. P-gp requires ATP to function, and the induction of mitochondrial dysfunction or inhibition of glutamine metabolism can impair P-gp function, thus increasing chemosensitivity. Phytochemicals, small molecules and nanoparticles have been introduced as P-gp inhibitors to increase drug sensitivity in human cancers.

Advances in the structure, mechanism and targeting of chemoresistance-linked ABC transporters

Cancer cells frequently display intrinsic or acquired resistance to chemically diverse anticancer drugs, limiting therapeutic success. Among the main mechanisms of this multidrug resistance is the overexpression of ATP-binding cassette (ABC) transporters that mediate drug efflux, and, specifically, ABCB1, ABCG2 and ABCC1 are known to cause cancer chemoresistance. High-resolution structures, biophysical and in silico studies have led to tremendous progress in understanding the mechanism of drug transport by these ABC transporters, and several promising therapies, including irradiation-based immune and thermal therapies, and nanomedicine have been used to overcome ABC transporter-mediated cancer chemoresistance. In this Review, we highlight the progress achieved in the past 5 years on the three transporters, ABCB1, ABCG2 and ABCC1, that are known to be of clinical importance. We address the molecular basis of their broad substrate specificity gleaned from structural information and discuss novel approaches to block the function of ABC transporters. Furthermore, genetic modification of ABC transporters by CRISPR-Cas9 and approaches to re-engineer amino acid sequences to change the direction of transport from efflux to import are briefly discussed. We suggest that current information regarding the structure, mechanism and regulation of ABC transporters should be used in clinical trials to improve the efficiency of chemotherapeutics for patients with cancer.

6,7-Dimethoxy-2-phenethyl-1,2,3,4-tetrahydroisoquinoline amides and corresponding ester isosteres as multidrug resistance reversers

Aiming to deepen the structure-activity relationships of the two P-glycoprotein (P-gp) modulators elacridar and tariquidar, a new series of amide and ester derivatives carrying a 6,7-dimethoxy-2-phenethyl-1,2,3,4-tetrahydroisoquinoline scaffold linked to different methoxy-substituted aryl moieties were synthesised. The obtained compounds were evaluated for their P-gp interaction profile and selectivity towards the two other ABC transporters, multidrug-resistance-associated protein-1 and breast cancer resistance protein, showing to be very active and selective versus P-gp. Two amide derivatives, displaying the best P-gp activity, were tested in co-administration with the antineoplastic drug doxorubicin in different cancer cell lines, showing a significant sensitising activity towards doxorubicin. The investigation on the chemical stability of the derivatives towards spontaneous or enzymatic hydrolysis, showed that amides are stable in both models while some ester compounds were hydrolysed in human plasma. This study allowed us to identify two chemosensitizers that behave as non-transported substrates and are characterised by different selectivity profiles.

Chemical molecular-based approach to overcome multidrug resistance in cancer by targeting P-glycoprotein (P-gp)

Multidrug resistance (MDR) remains one of the major impediments for efficacious cancer chemotherapy. Increased efflux of multiple chemotherapeutic drugs by transmembrane ATP-binding cassette (ABC) transporter superfamily is considered one of the primary causes for cancer MDR, in which the role of P-glycoprotein (P-gp/ABCB1) has been most well-established. The clinical co-administration of P-gp drug efflux inhibitors, in combination with anticancer drugs which are P-gp transport substrates, was considered to be a treatment modality to surmount MDR in anticancer therapy by blocking P-gp-mediated multidrug efflux. Extensive attempts have been carried out to screen for sets of nontoxic, selective, and efficacious P-gp efflux inhibitors. In this review, we highlight the recent achievements in drug design, characterization, structure-activity relationship (SAR) studies, and mechanisms of action of the newly synthetic, potent small molecules P-gp inhibitors in the past 5 years. The development of P-gp inhibitors will increase our knowledge of the mechanisms and functions of P-gp-mediated drug efflux which will benefit drug discovery and clinical cancer therapeutics where P-gp transporter overexpression has been implicated in MDR.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

Resolution of co-eluting isomers of anti-inflammatory drugs conjugated to carbonic anhydrase inhibitors from plasma in liquid chromatography by energy-resolved tandem mass spectrometry

Rheumatoid arthritis (RA) is a chronic inflammatory disease caused by a faulty autoimmune response. Recently, it was reported that some human carbonic anhydrases (CAs) isoforms are overexpressed in inflamed synovium of RA patients. New CA inhibitors (CAIs) incorporating CA-binding moiety and the cyclooxygenase inhibitor tail (nonsteroidal anti-inflammatory drug [NSAID] type) were studied. The aim of this work is the evaluation of the chemical stability of NSAID - CAI hybrids towards spontaneous or enzymatic hydrolysis by LC-MS/MS. The analytes are isomer pairs of 6- or 7-hydroxycoumarin, their different fragment ions abundances allowed the development of a mathematical tool (LEDA) to distinguish them. LEDA reliability at ng mL-1 level was checked (>90%), being proved the effectiveness in the correct assignment of the isomer present in the sample. The hybrids resulted stable in all tested matrices allowing us to conclude that these compounds reach the target tissues unmodified, opening perspectives for their development in the treatment of inflammation.

Exploration of 1,2,3-triazole-pyrimidine hybrids as potent reversal agents against ABCB1-mediated multidrug resistance

ABCB1-mediated multidrug resistance (MDR) is a principal obstacle for successful cancer chemotherapy. A series of pyrimidine-based hybrid molecules containing 1,2,3-triazole moiety were evaluated for their reversal activities against MDR. The majority of target compounds displayed moderate to great reversal potency. Among these compounds, compound 25 displayed the most potent reversal activity, about 7-fold more potent than Verapamil (VRP). Further mechanism studies revealed that compound 25 could obviously reverse paclitaxel (PTX) resistance in SW620/AD300 cells by increasing accumulation and extending maintenance of PTX. Our findings indicate that the 1,2,3-triazole-pyrimidine-based derivatives may serve as an interesting lead for the development of new potent and efficacious ABCB1-dependent MDR modulators.