Structure-activity relationship and cytotoxicity of the new thiosemicarbazide derivatives and their Cu(II) complexes against prostate and melanoma cancer cells.

In this study, eighteen new ligands (B1-B18) containing a thiosemicarbazide core were synthesized and characterized in terms of physicochemical properties, molecular docking and in vitro biological activity. The structures of eleven ligands were investigated using X-Ray diffraction and Hirschfeld Surface analysis. To study the structure-activity relationship, the organic ligands contained pyridin-2-ylmethyl, pyridin-3-ylmethyl or pyridin-4-ylmethyl moieties and various substituents. Their pharmakokinetic profiles and molecular docking results suggest high potential as new drug candidates. The complexing ability of the selected organic ligands was also evaluated, yielding five new Cu(II) complexes (Cu(B1)Cl2, Cu(B4)Cl2, Cu(B10)Cl2, Cu(B17)Cl2, Cu(B18)Cl2). The obtained results suggest the formation of the polymeric structures. All organic ligands and Cu(II) complexes were tested for anticancer activity against prostate and melanoma cancer cells (PC-3, DU-145, LNCaP, A375, G-361, SK-MEL-28) and normal fibroblasts (BJ), as well as antimicrobial activity against six selected bateria strains. Among B1-B18 compounds, B3, B5, B9, B10, B12 and B14 exhibited cytotoxic activity. The studied Cu(II) complexes were in general more active, with Cu(B1)Cl2 exhibiting antincancer activity agains all three prostate cancer cells and Cu(B10)Cl2 reaching the IC50 value equal to 88 µM against G-361 melanoma cells. Several compounds also exhibited antimicrobial activity against gram-positive and gram-negative bacteria. It was found that the type of specific substituents, especially the presence of -chloro and -dichloro substituents had a greated impact on the cytotoxicity than the position of the nitrogen atom in the pyridylacetyl moiety.

Novel phenoxyacetylthiosemicarbazide derivatives as novel ligands in cancer diseases.

Numerous epidemiological studies report an increased risk of developing prostate cancer in patients with melanoma and an increased risk of developing melanoma in patients with prostate cancer. Based on our previous studies demonstrating the high anticancer activity of thiosemicarbazides with a phenoxy moiety, we designed nineteen phenoxyacetylthiosemicarbazide derivatives and four of them acting as potential dual-ligands for both cancers. All of the compounds were characterized by their melting points and 1H, 13C NMR and IR spectra. For selected compounds, X-ray investigations were carried out to confirm the synthesis pathway, identify the tautomeric form and intra- and intermolecular interaction in the crystalline state. The conformational preferences and electronic structure of molecules were investigated by theoretical calculation method. Lipophilicity of compounds (log kw) was determined using isocratic reversed phase/high pressure liquid chromatography RP-18. For the obtained compounds, in vitro tests were carried out on four melanoma cell lines (A375, G-361, SK-MEL2, SK-MEL28), four prostate cancer cell lines (PC-3, DU-145, LNCaP, VcaP) and a normal human fibroblast cell line (BJ). The most active compounds turned out to be F6. Cell cycle analysis, apoptosis detection, CellROX staining and mitochondrial membrane potential analysis were performed for the most sensitive cancer cells treated with most active compounds. DSC analysis was additionally performed for selected compounds to determine their purity, compatibility, and thermal stability. The process of prooxidation was proposed as a potential mechanism of anticancer activity.

Evaluation of developmental toxicity in zebrafish embryos and antiproliferative potential against human tumor cell lines of new derivatives containing 4-nitrophenyl group.

The aim of the studies was to evaluate the antiproliferative potential against human tumor cell lines of newly synthetized derivatives containing 4-nitrophenyl group, as well as its impact on developmental toxicity in zebrafish model. We selected 1-(4-nitrobenzoyl)-4-ethylsemicarbazide (APS-1) and 1-[(4-nitrophenyl)acetyl]-4-hexyl-thiosemicarbazide (APS-18) for research. The antiproliferative properties of semicarbazide derivatives were assessed against human cancer cell lines derived from hepatocellular adenocarcinoma (HepG2), renal cell carcinoma (769-P), non-small cell lung cancer (NCI-H1563) and glioblastoma multiforme (LN229) in comparison to the physiological human embryonic kidney (HEK-293) cell line. The influence of the tested substances on the cell cycle and apoptosis was also evaluated. Fish embryo acute toxicity test (FET) was performed based on OECD Guidelines (Test No. 236), and was carried out for the first 5 days post fertilization. The following concentrations of APS-1 and APS-18 were tested: 125-2000 µM and 0.125-1000 µM, respectively. The presented studies on the antiproliferative properties of the new semicarbazide derivatives showed that the compounds APS-1 and APS-18 reduce the viability of human tumor lines. Particularly noteworthy is the strong and selective antiproliferative activity of APS-18 against all neoplastic cell lines, in particular against glioblastoma. Against this tumor line, the compound APS-1 showed an effective inhibitory effect. In the FET we noted that the direct exposure of zebrafish embryos to APS-1 and APS-18 in used range of concentration did not cause morphological abnormalities, including cardiotoxicity. On basis of obtained outcomes it could be concluded that APS-1 and APS-18 may constitute models for further research, design and synthesis of new, safer drugs with more favorable anticancer properties.

Retention Behavior of Anticancer Thiosemicarbazides in Biomimetic Chromatographic Systems and In Silico Calculations.

Chromatographic methods, apart from in silico ones, are commonly used rapid techniques for the evaluation of certain properties of biologically active compounds used for their prediction of pharmacokinetic processes. Thiosemicarbazides are compounds possessing anticancer, antimicrobial, and other valuable biological activities. The aim of the investigation was to estimate the lipophilicity of 1-aryl-4-(phenoxy)acetylthiosemicarbazides, to predict their oral adsorption and the assessment of their % plasma-protein binding (%PPB). RP-HPLC chromatographic techniques with five diversified HPLC systems, including columns with surface-bonded octadecylsilanes (C-18), phosphatidylcholine (immobilized artificial membrane, IAM), cholesterol (Chol), and α1-acid glycoprotein (AGP) and human serum albumin (HSA), were applied. The measured lipophilicity of all investigated compounds was within the range recommended for potential drug candidates. However, some derivatives are strongly bonded to HSA (%PPB ≈ 100%), which may limit some pharmacokinetic processes. HPLC determined lipophilicity descriptors were compared with those obtained by various computational approaches.

Polymer microspheres modified with pyrazole derivatives as potential agents in anticancer therapy - Preliminary studies.

The methods of fighting cancer are far from ideal, therefore it is necessary to search for innovative and effective drugs. In our work, we present pyrazole derivatives and their modifications with polymer microspheres as potential anticancer agents. Molecular and crystal structures of pyrazole derivatives were determined an X-ray analysis and characterized by theoretical calculations. Modifications of cross-linked polymer microspheres with pyrazole derivatives were made on the basis of divinylbenzene and glycidyl methacrylate. The in vitro antiproliferative activity of the pyrazole derivatives and their modified microspheres was assessed against a normal cell line, namely monkey epithelial renal cells (GMK) and cancer cell lines, such as human hepatocellular carcinoma cell line (HepG2), human breast adenocarcinoma cell line (MCF-7) as well as human lung adenocarcinoma cell line (A549), using the MTT assay. All the tested pyrazole derivatives and the polymer microspheres modified by them showed antiproliferative activity in vitro. Two of the modified substances showed the greatest ability to inhibit divisions of all cancer cells. In order to determine a potential target, molecular docking was performed. In silico studies carried out with the use of the human EphB1 receptor revealed that the analyzed compounds bound to the EphB1 binding site, and the compounds with the highest antiproliferative activity showed a better fit to the active site.

Terminal Phenoxy Group as a Privileged Moiety of the Drug Scaffold-A Short Review of Most Recent Studies 2013-2022.

The terminal phenoxy group is a moiety of many drugs in use today. Numerous literature reports indicated its crucial importance for biological activity; thus, it is a privileged scaffold in medicinal chemistry. This review focuses on the latest achievements in the field of novel potential agents bearing a terminal phenoxy group in 2013-2022. The article provided information on neurological, anticancer, potential lymphoma agent, anti-HIV, antimicrobial, antiparasitic, analgesic, anti-diabetic as well as larvicidal, cholesterol esterase inhibitors, and antithrombotic or agonistic activities towards the adrenergic receptor. Additionally, for selected agents, the Structure-Activity-Relationship (SAR) is also discussed. Thus, this study may help the readers to better understand the nature of the phenoxy group, which will translate into rational drug design and the development of a more efficient drug. To the best of our knowledge, this is the first review devoted to an in-depth analysis of the various activities of compounds bearing terminal phenoxy moiety.

New Potential Agents for Malignant Melanoma Treatment-Most Recent Studies 2020-2022.

Malignant melanoma (MM) is the most lethal skin cancer. Despite a 4% reduction in mortality over the past few years, an increasing number of new diagnosed cases appear each year. Long-term therapy and the development of resistance to the drugs used drive the search for more and more new agents with anti-melanoma activity. This review focuses on the most recent synthesized anti-melanoma agents from 2020-2022. For selected agents, apart from the analysis of biological activity, the structure-activity relationship (SAR) is also discussed. To the best of our knowledge, the following literature review delivers the latest achievements in the field of new anti-melanoma agents.

New Derivatives of 5-((1-Methyl-Pyrrol-2-yl) Methyl)-4-(Naphthalen-1-yl)-1,2,4-Triazoline-3-Thione and Its Coordination Compounds with Anticancer Activity.

A new ligand 5-((1-methyl-pyrrol-2-yl) methyl)-4-(naphthalen-1-yl)-1,2,4-triazoline-3-thione (C15) and its metal complexes with formulae: Mn(C15)Cl2MeOH (1), Fe(C15)Cl2MeOH (2), Ni(C15)Cl2MeOH (3), Cu(C15)2Cl2 (4) and Zn(C15)4Cl2 (5) have been synthesized. The C15 ligand and complexes were characterized by NMR, elemental analysis, FT-IR, EPR, magnetic and TGA studies. The anticancer activities of the organic ligand (C15) and complexes (1-5) were evaluated against human colon adenocarcinoma (HT29) and human lung (A549) cancer cell lines. The complex (1) exhibited potential activity at concentration of 794.37 µM (A549) and 654.31 µM (HT29) in both cancer cells. The complex (3) showed significant activity against the HT29 cancer cell line with an IC50 value of 1064.05 µM. This article highlights some of the metals that have become important in the development of new coordination complexes and the treatment of cancer. Additionally, for C15, the toxicity was predicted by ADMET analysis and molecular docking.

Experimental and Computational Structural Studies of 2,3,5-Trisubstituted and 1,2,3,5-Tetrasubstituted Indoles as Non-Competitive Antagonists of GluK1/GluK2 Receptors.

The blockade of kainate receptors, in particular with non-competitive antagonists, has-due to their anticonvulsant and neuroprotective properties-therapeutic potential in many central nervous system (CNS) diseases. Deciphering the structural properties of kainate receptor ligands is crucial to designing medicinal compounds that better fit the receptor binding pockets. In light of that fact, here, we report experimental and computational structural studies of four indole derivatives that are non-competitive antagonists of GluK1/GluK2 receptors. We used X-ray studies and Hirshfeld surface analysis to determine the structure of the compounds in the solid state and quantum chemical calculations to compute HOMO and LUMO orbitals and the electrostatic potential. Moreover, non-covalent interaction maps were also calculated. It is worth emphasizing that compounds 3 and 4 are achiral molecules crystallising in non-centrosymmetric space groups, which is a relatively rare phenomenon.

Antitumor Activity and Physicochemical Properties of New Thiosemicarbazide Derivative and Its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes.

A novel biologically active thiosemicarbazide derivative ligand L (N-[(phenylcarbamothioyl)amino]pyridine-3-carboxamide) and a series of its five metal(II) complexes, namely: [Co(L)Cl2], [Ni(L)Cl2(H2O)], [Cu(L)Cl2(H2O)], [Zn(L)Cl2] and [Cd(L)Cl2(H2O)] have been synthesized and thoroughly investigated. The physicochemical characterization of the newly obtained compounds has been performed using appropriate analytical techniques, such as 1H and l3C nuclear magnetic resonance (NMR), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and magnetic measurements. In order to study the pharmacokinetic profile of the compounds, ADMET analysis was performed. The in vitro studies revealed that the synthesized compounds exhibit potent biological activity against A549 human cancer cell line.

Cytotoxic Activity against A549 Human Lung Cancer Cells and ADMET Analysis of New Pyrazole Derivatives.

Two new pyrazole derivatives, namely compound 1 and compound 2, have been synthesized, and their biological activity has been evaluated. Monocrystals of the obtained compounds were thoroughly investigated using single-crystal X-ray diffraction analysis, FTIR spectroscopy, and NMR spectroscopy. The results gathered from all three techniques are in good agreement, provide complete information about the structures of 1 and 2, and confirm their high purity. Thermal properties were studied using thermogravimetric analysis; both 1 and 2 are stable at room temperature. In order to better characterize 1 and 2, some physicochemical and biological properties have been evaluated using ADMET analysis. The cytotoxic activity of both compounds was determined using the MTT assay on the A549 cell line in comparison with etoposide. It was determined that compound 2 was effective in the inhibition of human lung adenocarcinoma cell growth and may be a promising compound for the treatment of lung cancer.

Influence of Complexation of Thiosemicarbazone Derivatives with Cu (II) Ions on Their Antitumor Activity against Melanoma Cells.

A series of thiosemicarbazone derivatives was prepared and their anti-tumor activity in vitro was tested. The X-ray investigation performed for compounds T2, T3 and T5 confirmed the synthesis pathway and assumed molecular structures of analyzed thiosemicarbazones. The conformational preferences of the thiosemicarbazone system were characterized using theoretical calculations by AM1 method. Selected compounds were converted into complexes of Cu (II) ions. The effect of complexing on anti-tumor activity has been investigated. The copper(II) complexes, with Schiff bases T1, T10, T12, T13, and T16 have been synthesized and characterized by chemical and elemental analysis, FTIR spectroscopy and TGA method. Thermal properties of coordination compounds were studied using TG-DTG techniques under dry air atmosphere. G361, A375, and SK-MEL-28 human melanoma cells and BJ human normal fibroblast cells were treated with tested compounds and their cytotoxicity was evaluated with MTT test. The compounds with the most promising anti-tumour activity were then selected and their cytotoxicity was verified with cell cycle analysis and apoptosis/necrosis detection. Additionally, DNA damages in the form of a basic sites presence and the expression of oxidative stress and DNA damage response genes were evaluated. The obtained results indicate that complexation of thiosemicarbazone derivatives with Cu (II) ions improves their antitumor activity against melanoma cells. The observed cytotoxic effect is associated with DNA damage and G2/M phase of cell cycle arrest as well as disorders of the antioxidant enzymes expression.

Spectroscopic Study of the Molecular Structure of the New Hybrid with a Potential Two-Way Antibacterial Effect.

Bacterial strains become resistant to almost all classes of antibiotics, which makes it necessary to look for new substitutes. The non-absorbable ciprofloxacin-biguanide bismuth complex, used locally, may be a good alternative to a conventional therapy. The purpose of this study was to study the structure of the proposed ciprofloxacin (CIP) -bismuth(III)-chlorhexidine (CHX) composite (CIP-Bi-CHX). The spectroscopic techniques such as UV-VIS (ultraviolet-visible) spectroscopy, FTIR (Fourier-transform infrared) spectroscopy and NMR (Nuclear Magnetic Resonance) spectroscopy were used for structure characterization of the hybrid compound. The performed analysis confirmed the presence of the two active components-CIP and CHX and revealed the possible coordination sites of the ligands with bismuth ion in the metallo-organic structure. Spectroscopic study showed that the complexation between Bi(III) and CIP occurs through the carboxylate and ketone groups of the quinolone ring, while CHX combines with the central ion via the biguanide moieties.

1,2,4-Triazolin-5-thione derivatives with anticancer activity as CK1γ kinase inhibitors.

The optimization and synthesis of new CK2 and CK1 inhibitors are the basis for the development of new therapeutic strategies for the treatment of cancer and neurodegenerative disorders associated with overexpression and abnormal functioning of these enzymes. Triazole derivatives appear to be especially interesting as potential kinase inhibitors. In this context we synthesized a series of 1,2,4-triazolin-5-thione derivatives as CK1γ kinase inhibitors. The antiproliferative activity of synthesized compounds was assessed against cancer cells: human lung adenocarcinoma (A549), human hepatoma (HepG2), and human breast adenocarcinoma (MCF-7). Compound 1 exhibited antiproliferative potency against A549 cancer cells and was characterized by a selective antiproliferative effect. Additionally, this compound has high apoptotic activity against A549, HepG2, MCF-7 cells and induced only slight amount of necrotic cells in these cell lines. In order to decipher the mechanism of anticancer activity of the studied compounds PASS software was used and these compounds were assayed for the inhibition of CK1γ and CK2α kinases. The reported series of 1,2,4-triazolin-5-thiones inhibits CK1γ and CK2α kinases in micromolar range. The most active compound shows activity against isoform γ3 which at concentration of 50 µM reduced the kinase activity by 69% while at 100 µM by 80%. CK2α was found to be less susceptible to the effects of the triazoles tested, as the reduction in kinase activity by 29% was observed for compound 15, and by 27% for compound 1 only at the concentration of 100 µM. The inhibition of CK1γ and CK2α kinases was rationalized using molecular docking.

New Application of 1,2,4-Triazole Derivatives as Antitubercular Agents. Structure, In Vitro Screening and Docking Studies.

A series of 1,2,4-triazole derivatives were synthesized and assigned as potential anti-tuberculosis substances. The molecular and crystal structures for the model compounds C1, C12, and C13 were determined using X-ray analysis. The X-ray investigation confirmed the synthesis pathway and the assumed molecular structures for analyzed 1,2,4-triazol-5-thione derivatives. The conformational preferences resulting from rotational degrees of freedom of the 1,2,4-triazole ring substituents were characterized. The lipophilicity (logP) and electronic parameters as the energy of frontier orbitals, dipole moments, NBO net charge distribution on the atoms, and electrostatic potential distribution for all structures were calculated at AM1 and DFT/B3LYP/6-311++G(d,p) level. The in vitro test was done against M. tuberculosis H37Ra, M. phlei, M. smegmatis, and M. timereck. The obtained results clearly confirmed the antituberculosis potential of compound C4, which turned out to be the most active against Mycobacterium H37Ra (MIC = 0.976 µg/mL), Mycobaterium pheli (MIC = 7.81 µg/mL) and Mycobacerium timereck (62.6 µg/mL). Satisfactory results were obtained with compounds C8, C11, C14 versus Myc. H37Ra, Myc. pheli, Myc. timereck (MIC = 31.25-62.5 µg/mL). The molecular docking studies were carried out for all investigated compounds using the Mycobacterium tuberculosis cytochrome P450 CYP121 enzyme as molecular a target connected with antimycobacterial activity.

Synthesis and Antioxidant Activity of New Norcantharidin Analogs.

New norcantharidin analogs were designed and obtained as compounds with biological activity. As a starting material, exo-7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid anhydride was used. Three groups of compounds: dicarboximides, triazoles and thiazolidines were obtained in multistep reactions. The 1 H- and 13 C-NMR spectra were used to confirm the structures of all obtained products and they were in agreement with the proposed structure of substances. All derivatives were screened for their antioxidant activity. The most promising group was dicarboximides (1-4, 6). Derivatives 2-4 displayed antioxidant activity with EC50 =7.75-10.89 µg/ml, which may be comparable to strong antioxidant Trolox (EC50 =6.13 µg/ml). Excellent activity with EC50 =10.75 µg/ml also presented norcantharidin analog with 1,2,4-triazole system (12).

Synthesis, In Vitro Screening and Docking Studies of New Thiosemicarbazide Derivatives as Antitubercular Agents.

A series of thiosemicarbazide derivatives was designed and synthesized by reaction of carboxylic acid hydrazide with isothiocyanates. The molecular structures of the investigated thiosemicarbazides were confirmed and characterized by spectroscopic analysis. The conformational preference of carbonylthiosemicarbazide chain and intra- and intermolecular interactions in the crystalline state were characterized using X-ray analysis. The antituberculosis activity of the target compounds were tested in vitro against four Mycobacterium strains: M. H37Ra, M. phlei, M. smegmatis, M. timereck. The most active compounds were those with 2-pyridine ring. They exhibited lower minimal inhibitory concentration (MIC) values in the range 7.81⁻31.25 µg/mL in comparison to the other isomers. Compound 5 had activity against M. smegmatis at a concentration of 7.81 µg/mL whereas compound 2 had activity against all tested strains at a concentration of 15.625 µg/mL. The molecular docking studies were performed for investigated compounds using the Mycobacterium tuberculosis glutamine synthetase MtGS as their molecular target.

Synthesis, Structural and Thermal Studies of 3-(1-Benzyl-1,2,3,6-tetrahydropyridin-4-yl)-5-ethoxy-1H-indole (D2AAK1_3) as Dopamine D2 Receptor Ligand.

Compound D2AAK1_3 was designed as a modification of the lead structure D2AAK1 (an in vivo active multi-target compound with nanomolar affinity to a number of aminergic GPCRs) and synthesized in the reaction of 5-ethoxyindole and 1-benzyl-4-piperidone. This compound has an affinity to the human dopamine D2 receptor with Ki of 151 nM. The aim of these studies was the structural and thermal characterization of the compound D2AAK1_3. In particular; X-ray studies; molecular docking and molecular dynamics as well as thermal analysis were performed. The studied compound crystallizes in orthorhombic system; in chiral space group P212121. The compound has a non-planar conformation. The studied compound was docked to the novel X-ray structure of the human dopamine D2 receptor in the inactive state (PDB ID: 6CM4) and established the main contact between its protonatable nitrogen atom and Asp (3.32) of the receptor. The obtained binding pose was stable in molecular dynamics simulations. Thermal stability of the compound was investigated using the TG-DSC technique in the air atmosphere, while TG-FTIR analyses in air and nitrogen atmospheres were also performed. The studied compound is characterized by good thermal stability. The main volatile products of combustion are the following gases: CO2; H2O toluene and CO while in the case of pyrolysis process in the FTIR spectra; the characteristic bands of NH3; piperidine and indole are additionally observed.

Synthesis, antibacterial and antiproliferative potential of some new 1-pyridinecarbonyl-4-substituted thiosemicarbazide derivatives.

In this study, the antibacterial, cytotoxic and antiproliferative activities of novel thiosemicarbazide derivatives were assessed. Our results demonstrated that some of the novel compounds possess good antibacterial properties against Staphylococcus epidermidis, Streptococcus mutans and Streptococcussanguinis and are only slightly cytotoxic; thus, they exhibit an excellent therapeutic index, which is higher than that of ethacridine lactate. Moreover, our data showed that compounds 2 and 4 have an antiproliferative activity against human breast adenocarcinoma and human hepatocellular carcinoma cell lines. We expect that the novel thiosemicarbazide derivatives can be used as agents for treatment of dental caries and also for chemotherapy support.

Inhibitory effect of N-ethyl-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide on Haemophilus spp. planktonic or biofilm-forming cells.

During this study, we have investigated in vitro activity of N-substituted-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide derivatives with N-ethyl, N-(4-metoxyphenyl) and N-cyclohexyl substituents against Gram-negative Haemophilus influenzae and H. parainfluenzae bacteria. A spectrophotometric assay was used in order to determine the bacterial growth and biofilm formation using a microtiter plate to estimate minimal inhibitory concentration (MIC) and minimal biofilm inhibitory concentration (MBIC). Among the tested N-substituted pyrazole derivatives, only N-ethyl-3-amino-5-oxo-4-phenyl-2,5-dihydro-1H-pyrazole-1-carbothioamide showed a significant in vitro activity against both planktonic cells of H. parainfluenzae (MIC = 0.49-31.25 µg ml-1) and H. influenzae (MIC = 0.24-31.25 µg ml-1) as well as biofilm-forming cells of H. parainfluenzae (MBIC = 0.24-31.25 µg ml-1) and H. influenzae (MBIC = 0.49 to ≥31.25 µg ml-1). The pyrazole compound exerted higher inhibitory effect both on the growth of planktonic cells and biofilm formation by penicillinase-positive and penicillinase-negative isolates of H. parainfluenzae than the activity of commonly used antibiotics such as ampicillin. No cytotoxicity of the tested compound in vitro at concentrations used was found. The tested pyrazole N-ethyl derivative could be considered as a compound for the design of agents active against both pathogenic H. influenzae and opportunistic H. parainfluenzae, showing also anti-biofilm activity. This appears important because biofilms are determinants of bacterial persistence in long-term and recurrent infections recalcitrant to standard therapy.