Repurposing of Tamoxifen Against the Oral Bacteria

Tooth loss in breast cancer patients: A comparison between tamoxifen-treated and non-treated patients

BACKGROUND

Tooth loss (TL) affects quality of life and general health. The literature suggesting that tamoxifen treatment in patients with breast cancer (BC) could be associated with alterations in oral health, increasing the risk of TL, is still scarce. This work aimed to determine the relationship between TL and tamoxifen consumption in patients with BC.

MATERIAL AND METHODS

This cross-sectional observational study was carried out from July to September 2023 in the medical oncology services of the "Virgen de la Puerta" - ESSALUD High Complexity Hospital and "Dr. Luis Pinillos Ganoza" - IREN Norte - Regional Institute of Neoplastic Diseases, in Trujillo - Peru. Overall, 200 adult patients diagnosed with BC were evaluated, of which 100 consumed tamoxifen and 100 did not. Inter- and intra-rater reliability was determined with respect to TL, resulting in intra-class correlation values RHO = 0.971 and interclass RHO = 0.938. The oncologist of the corresponding service performed BC diagnosis and stage. Poisson regression was used to analyze results with a significance level of p<0.05.

RESULTS

No relationship was found between TL and tamoxifen consumption in patients with breast cancer (p= 0.221); however, greater TL was observed in women who consumed tamoxifen for more than one year compared to those who did not use it (p=0.025) and in older adult women compared to young women (p=0.030).

CONCLUSIONS

There is a relationship between TL and time of use of tamoxifen in patients with BC, concluding that patients who consumed tamoxifen for more than one year had greater TL than those who did not. Furthermore, no relationship was found between TL and cancer stages, but there was greater TL in older adult patients and also in those who consumed tamoxifen and did not receive chemotherapy or radiotherapy.

Efficacy of Tamoxifen Metabolites in Combination with Colistin and Tigecycline in Experimental Murine Models of Escherichia coli and Acinetobacter baumannii

This study aimed to evaluate the potential of tamoxifen and N-desmethyltamoxifen metabolites as therapeutic agents against multidrug-resistant Escherichia coli and Acinetobacter baumannii, using a repurposing approach to shorten the time required to obtain a new effective treatment against multidrug-resistant bacterial infections. Characterisation and virulence studies were conducted on E. coli (colistin-susceptible C1-7-LE and colistin-resistant MCR-1+) and A. baumannii (tigecycline-susceptible Ab#9 and tigecycline-resistant Ab#186) strains. The efficacy of the metabolite mix (33.3% each) and N-desmethyltamoxifen in combination with colistimethate sodium (CMS) or tigecycline was evaluated in experimental models in mice. In the pneumonia model, N-desmethyltamoxifen exhibited significant efficacy against Ab#9 and both E. coli strains, especially E. coli MCR-1+ (-2.86 log10 CFU/g lungs, -5.88 log10 CFU/mL blood, and -50% mortality), and against the Ab#186 strain when combined with CMS (-2.27 log10 CFU/g lungs, -2.73 log10 CFU/mL blood, and -40% mortality) or tigecycline (-3.27 log10 CFU/g lungs, -4.95 log10 CFU/mL blood, and -50% mortality). Moreover, the metabolite mix in combination with both antibiotics decreased the bacterial concentrations in the lungs and blood for both A. baumannii strains. In the sepsis model, the significant efficacy of the metabolite mix was restricted to the colistin-susceptible E. coli C1-7-LE strain (-3.32 log10 CFU/g lung, -6.06 log10 CFU/mL blood, and -79% mortality). N-desmethyltamoxifen could be a new therapeutic option in combination with CMS or tigecycline for combating multidrug-resistant GNB, specifically A. baumannii.

Improving the antimicrobial activity of old antibacterial drug mafenide: Schiff bases and their bioactivity targeting resistant pathogens

Background: Increasing rates of acquired resistance have justified the critical need for novel antimicrobial drugs. One viable concept is the modification of known drugs. Methods & results: 21 mafenide-based compounds were prepared via condensation reactions and screened for antimicrobial efficacy, which demonstrated promising activity against both Gram-positive and Gram-negative pathogens, pathogenic fungi and mycobacterial strains (minimum inhibitory concentrations from 3.91 μM). Importantly, they retained activity against a panel of superbugs (methicillin- and vancomycin-resistant staphylococci, enterococci, multidrug-resistant Mycobacterium tuberculosis) without any cross-resistance. Unlike mafenide, most of its imines were bactericidal. Toxicity to HepG2 cells was also investigated. Conclusion: Schiff bases were significantly more active than the parent drug, with iodinated salicylidene and 5-nitrofuran/thiophene-methylidene scaffolds being preferred in identifying the most promising drug candidates.

Drug Repurposing Approaches towards Defeating Multidrug-Resistant Gram-Negative Pathogens: Novel Polymyxin/Non-Antibiotic Combinations

Multidrug-resistant (MDR) Gram-negative pathogens remain an unmet public health threat. In recent times, increased rates of resistance have been reported not only to commonly used antibiotics, but also to the last-resort antibiotics, such as polymyxins. More worryingly, despite the current trends in resistance, there is a lack of new antibiotics in the drug-discovery pipeline. Hence, it is imperative that new strategies are developed to preserve the clinical efficacy of the current antibiotics, particularly the last-line agents. Combining conventional antibiotics such as polymyxins with non-antibiotics (or adjuvants), has emerged as a novel and effective strategy against otherwise untreatable MDR pathogens. This review explores the available literature detailing the latest polymyxin/non-antibiotic combinations, their mechanisms of action, and potential avenues to advance their clinical application.