Fluoroquinolones remain one of the most important kind of antibacterial agents used nowadays. The emergence of more virulent and resistant strains of bacteria by the development of either mutated DNA-binding proteins or efflux pump mechanism for drugs is considered the main problem associated with the therapeutic use of these drugs. This situation participated in pushing researchers to design new fluoroquinolone derivatives, mainly with different substituents at C-7 to withstand these resistant strains of bacteria and to obtain a wider spectrum of activity including activity against anaerobic organisms. Conjugation of fluoroquinolones with substitutions such as 1,2,4-triazoles, alkyl oximes, flavonoids, aryl furans, benzofuroxans, metronidazoles or even other antibiotics such as neomycin-B produced derivatives that have a superior and wider spectrum of activity and better resistance than the classical fluoroquinolone agents. Addition of a hydroxamic acid moiety to fluoroquinolones also increased the activity against Proteus mirabilis, which represents one of the most resistant strains of bacteria in urinary tract infections. This review aims to highlight the recent updates made for fluoroquinolones for broadening the spectrum of activity to become active not only against resistant strains of bacteria but also against anaerobic pathogens.

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Ciprofloxacin-Piperazine C-7 linked quinoline derivatives 6a–c and 8a–c were synthesized and investigated for their antibacterial, antifungal, and anti-proliferative activities. Ciprofloxacin-quinoline-4-yl-1,3,4 oxadiazoles 6a and 6b showed promising anticancer activity against SR- leukemia and UO-31 renal cancer cell lines. The hybrids 8a–c and compound 6b exhibited noticeable antifungal activities against C.Albicans; 8a experienced the most potent antifungal activity compared to Itraconazole with MICs of 21.88 µg/mL and 11.22 µg/mL; respectively. Most of derivatives displayed better antibacterial activity than the parent ciprofloxacin against all the tested strains. Compound 6b was the most potent against the highly resistant Gram-negative K.pneumoniae with MIC 16.96 of µg/mL relative to the parent ciprofloxacin (MIC = 29.51 µg/mL). Docking studies of the tested hydrides in the active site of Topo IV enzyme of K.pneumoniae (5EIX) and S.aureus gyrase (2XCT) indicate that they had stronger binding affinity in both enzymes than ciprofloxacin but have different binding interactions. The hybrid 6b could be considered a promising lead compound for finding new dual antibacterial/anticancer agents. Moreover, Compound 8a could be a lead for discovering new dual antibacterial/antifungal agents. Graphical abstract

New 3-substituted oxindole derivatives were designed and synthesized as antiproliferative agents. The antiproliferative activity of compounds 6a–j was evaluated against 60 NCI cell lines. Among these tested compounds, compounds 6f and 6g showed remarkable antiproliferative activity, specifically against leukemia and breast cancer cell lines. Compound 6f was the most promising antiproliferative agent against MCF-7 (human breast cancer) with an IC50 value of 14.77 µM compared to 5-fluorouracil (5FU) (IC50 = 2.02 µM). Notably, compound 6f hampered receptor tyrosine EGFR fundamentally with an IC50 value of 1.38 µM, compared to the reference sunitinib with an IC50 value of 0.08 µM. Moreover, compound 6f afforded anti-tubulin polymerization activity with an IC50 value of 7.99 µM as an outstanding observable activity compared with the reference combretastatin A4 with an IC50 value of 2.64 µM. In silico molecular-docking results of compound 6f in the ATP-binding site of EGFR agreed with the in vitro results. Besides, the investigation of the physicochemical properties of compound 6f via the egg-boiled method clarified good lipophilicity, GIT absorption, and blood–brain barrier penetration properties.

Fms-like tyrosine kinase 3 (FLT3) mutation mechanisms are among the most common genetic abnormalities detected in about 30% of acute myeloid leukemia (AML) patients. These mutations are accompanied by poor clinical response, although all these progressions in identifying and interpreting biological AML bio-targets. Several small structured FLT3 inhibitors have been ameliorated to struggle against AML. Despite all these developments regarding these inhibitors, the Overall survival rate is about five years or more in less than one-third of diagnosed AML patients. Midostaurin was the first FDA-approved FLT3 inhibitor in 2017 in the United States and Europe for AML remedy. Next, Gilteritinib was an FDA-approved FLT3 inhibitor in 2018 and in the next year, Quizartinib was approved an as FLT3 inhibitor in Japan. Interestingly, indole-based motifs had risen as advantaged scaffolds with unusual multiple kinase inhibitory activity. This review summarises indole-based FLT3 inhibitors and related scaffolds, including FDA-approved drugs, clinical candidates, and other bioactive compounds. Furthermore, their chemotypes, mechanism of action, and interaction mode over both wild and mutated FLT3 target proteins had been judgmentally discussed. Therefore, this review could offer inspiring future perspectives into the finding of new FLT3-related AML therapies.