Physico-chemical and technological properties of sodium naproxen granules prepared in a high-shear mixer-granulator.

In the present work, authors produced tablets of anhydrous sodium naproxen by wet granulation using a high-shear mixer-granulator. Drug hydrated to the tetrahydrated form, as observed by X-ray powder diffractometry. After wet granulation, authors then performed two different drying procedures, obtaining granules of different water content and crystallographic characteristics. The first procedure dried granules in the high-shear mixer-granulator by applying vacuum at room temperature (batch A), while the second employed the same apparatus and time, under vacuum at 40 degrees C (batch B). X-ray powder diffractometry revealed that the sodium naproxen (SN) contained in batch A granules was a mixture of dihydrated and tetrahydrated forms (as demonstrated by the coexistence of peaks typical of both hydrated forms), while that of batch B granules was a mixture of monohydrated and tetrahydrated forms. This means that differences in drying procedures could lead to products of different crystallographic properties. The behavior under compression was evaluated, revealing that batch A offered the best tabletability and compressibility. These results make it possible to conclude that differences in the crystallographic properties and water content of SN are such that different hydration/drying processes can alter the drug crystal form and thus the tabletability of the resulting granules.

Validation of an HPLC-MS method for rociverine tablet dissolution analysis.

The aim of this work was to develop and validate a method to assess the dissolution behaviour of rociverine sugar-coated tablets. In our laboratories, an HPLC-MS in reverse phase method of analysis was developed for the dosage of unknown rociverine solution. This analytical method was applied to determine the dissolution rate of rociverine tablets produced by the industrial procedure, because there is no official method description. Dissolution tests were carried out in sink conditions as follows: dissolution medium HCl 0.01 N, paddle rotation speed 50 rpm and vessel volume 1000 ml. The dissolution test gave satisfactory results: 95% of the drug was dissolved within 30 min and drug dissolution was concluded after 60 min. The method was demonstrated to be adequate for Quality Control of rociverine tablets. Validation was inferred from specificity, linearity, precision, accuracy and robustness.

The role of several l-HPCs in preventing tablet capping during direct compression of metronidazole.

Several low-hydroxypropyl cellulose (l-HPC) derivatives (LH-11, 21, 22, 31, and 32) differing in granulometric particle size or in hydroxypropyl content were considered in the present study. The l-HPC grades were characterized as pure powders, in order to determine both compression and densification behavior, in presence or in absence of magnesium stearate as lubricant, and then, were physically mixed in different proportions with metronidazole, which was also previously characterized as pure powder. The tabletability and compressibility of these binary mixtures were then evaluated, in presence or in absence magnesium stearate as lubricant at two different compression speeds (20 and 70 mm/sec). It was observed that both binary mixture compression behavior and capping tendency were influenced by compression speed and by the presence of lubricant. Differences in anti-capping efficiency between the l-HPCs may be related to their hydroxypropyl content. This parameter influences the interaction between the metronidazole and the polymer particles, and consequently the ability of the binary system to undergo densification under compression.

Characterization and compaction behaviour of nimesulide crystal forms.

Nimesulide is a typical nonsteroidal anti-inflammatory drug (NSAID), widely used in solid oral formulations. By crystallizing nimesulide from an ethanol solution a crystalline form was obtained, different from the reference sample, as confirmed by X-ray powder diffraction (XRPD), Differential Scanning Calorimetry (DSC) and solid cross polarization-magic angle spinning ((13)C-CPMAS) NMR. Moreover, when crystallized from dioxane nimesulide forms a solvate. The solvate was characterized by XRPD, IR-spectrometry, DSC, thermo-gravimetric analysis (TGA) and by (13)C-CPMAS NMR. In particular, through this technique, the presence of several conformational isomers was demonstrated. In addition to the physico-chemical characterization, the technological properties of nimesulide, namely densification and tableting, were evaluated. Contrarily to the other forms that are affected by capping phenomena at increasing compression pressures, the form obtained by desolvation of dioxane solvate has positive effect on tableting properties, increasing both compressibility and tabletability of nimesulide.

Influence of metronidazole particle properties on granules prepared in a high-shear mixer-granulator.

Metronidazole is a good example of high-dose drug substance with poor granulating and tableting properties. Tablets are generally produced by liquid granulation; however, the technological process failure is quite frequent. In order to verify how the metronidazole particle characteristics can influence granule properties, three metronidazole batches differing for crystal habit, mean particle size, BET surface area and wettability were selected, primarily designed according to their different elongation ratio: needle-shaped, stick-shaped, and isodimensional. In the presence of lactose monohydrate and pregelatinized maize starch, respectively as diluent and binder, they were included in a formula for wet granulation in a high-shear mixer-granulator. In order to render the process comparable as far as possible, all parameters and experimental conditions were maintained constant. Four granule batches were obtained: granules from placebo (G-placebo), granules from needle-shaped crystals (G-needle-shaped), granules from stick-shaped crystals (G-stick-shaped), and granules from isodimensional crystals (G-isodimensional). Different granule properties were considered, in particular concerning porosity, friability, loss on drying (LOD), and flowability. In order to study their tabletability and compressibility, the different granules obtained were then compressed in a rotary press. The best tabletability was obtained with the isodimensional batch, while the poorest was exhibited by the stick-shaped one. Differences in tabletability are in good accordance with compressibility results: to a better tabletability corresponds an important granule ability to undergo a volume reduction as a result of an applied pressure. In particular, it was proposed that the greatest compressibility of the G-isodimensional must be related to the greatest granule porosity percentage.

A new tetrahydrated form of sodium naproxen.

The anhydrous sodium naproxen (ASN) can form several hydrated phases if maintained at different relative humidities (RH). The water uptake can promote crystallographic modifications, according to the amount of water. In a previous work, the authors showed that a dihydrated form could be obtained either by crystallization in water or by exposure of the anhydrous form to a RH of 55%. In the present work, the authors report about the formation and characterization of a new tetrahydrated form, obtained by exposing the ASN to RH >or= 75%. All the hydrated compounds were characterized by the combined use of several spectroscopic, thermal, and crystallographic techniques. The thermal stability of both the dihydrated and tetrahydrated compounds was also tested.

Evaluation of rapamycin chemical stability in volatile-organic solvents by HPLC.

Rapamycin or sirolimus is a carboxylic lactone-lactam macrolide with a potent immunosuppressive activity. It can be successfully used to impregnate stents inserted in coronary arteries during surgical applications, preventing fatal infection and rejection adverse effect. The chemical stability of rapamycin in several organic-volatile solvents (acetone, chloroform, dichloromethane, hexane, ethyl alcohol, ethyl acetate, methyl alcohol, pentane and tetrahydrofurane) was established by HPLC-DAD-MS in reverse phase analysis. Results permitted to exclude rapamycin chemical degradation and to reveal a typical chemical isomerization, favoured in accordance to the solvent used. Two typical peaks appear, denominated beta and gamma, the time retention of which are, respectively, 11.3 and 15.0 min. Thanks to data recovered by NMR, spectrophotometric UV and mass analyses, it was possible to establish that both peaks correspond to two different isomeric forms of rapamycin. In addition, it was possible to establish that the relative percentage peak area varies according to the solvent and to the experimental time. The two isomeric forms are in equilibrium and each solvent concurs to differently displace this equilibrium versus one form rather than another, according to their both polarity index and aproticity.

Synthesis of 7-oxo-7H-naphtho[1,2,3-de]quinoline derivatives as potential anticancer agents active on multidrug resistant cell lines.

Following our earlier finding that tetracyclic anthraquinone analogs with a fused pyridone ring exhibit cytotoxic activity toward multidrug resistant tumor cells, a series of new potential antitumor agents, 7-oxo-7H-naphtho[1,2,3-de]quinoline derivatives (3, 6-8, 10-12, 14, 15, and 18), bearing one or two basic side chains and various substituents at the pyridone ring, have been synthesized. The compounds have been obtained from 1-amino-4-chloroanthraquinone or 1-aminoanthraquinone by cyclization with diethyl malonate and the subsequent reactions of the key intermediates 2, 4, and 17. The compounds exhibited cytotoxic activity toward sensitive human leukemia cell line HL-60 and against its resistant sublines HL-60/VINC (MDR1 type) and HL-60/DX (MRP1 type).

Evaluation of different fast melting disintegrants by means of a central composite design.

Fast-disintegration technologies have encountered increased interest from industries in the past decades. In order to orientate the formulators to the choice of the best disintegrating agent, the most common disintegrants were selected and their ability to quickly disintegrate direct compressed tablets was evaluated. For this study, a central composite design was used. The main factors included were the concentration of disintegrant (X1) and the compression force (X2). These factors were studied for tablets containing either Zeparox or Pearlitol 200 as soluble diluents and six different disintegrants: L-HPC LH11 and LH31, Lycatab PGS, Vivasol, Kollidon CL, and Explotab. Their micromeritics properties were previously determined. The response variables were disintegration time (Y1), tensile strength (Y2), and porosity (Y3). Whatever the diluent, the longest disintegration time is obtained with Vivasol as the disintegrant, while Kollidon CL leads to the shortest disintegration times. Exception for Lycatab PGS and L-HPC LH11, formulations with Pearlitol 200 disintegrate faster. Almost the same results are obtained with porosity: no relevant effect of disintegrant concentration is observed, since porosity is mainly correlated to the compression force. In particular, highest values are obtained with Zeparox as the diluent when compared to Pearlitol 200 and, as the type of disintegrant is concerned, no difference is observed. Tensile strength models have been all statistically validated and are all highly dependent on the compression force. Lycatab PGS concentration does not affect disintegration time, mainly increased by the increase of compression pressure. When Pearlitol 200 is used with Vivasol, disintegration time is more influenced by the disintegrant concentration than by the compression pressure, an increase in concentration leading to a significant and relevant increase of the disintegration time. With Zeparox, the interaction between the two controlled variables is more complex: there is no effect of compression force on the disintegration time for a small amount of disintegrant, but a significant increase for higher concentrations. With Kollidon CL, the main factor influencing the disintegration time is the compression force, rather than the disintegrant concentration. Increasing both the compression force and the disintegrant concentration leads to an increase of the disintegration time. For lower Kollidon CL percentages, the compression pressure increases dramatically the tablet disintegration. With the Explotab, whatever the increase of compression force, the disintegrant concentration leads to an increase of the disintegration time. According to Student's t-test, only the compression force significantly and strongly influences the disintegration time when Pearlitol 200 is used. A slight interaction and some trends nevertheless appear: above 150 MPa, increasing the disintegrant concentration leads to a shortened disintegration time, below this limit the opposite effect is observed.

2,7-Dihydro-3H-pyridazino[5,4,3-kl]acridin-3-one derivatives, novel type of cytotoxic agents active on multidrug-resistant cell lines. Synthesis and biological evaluation.

We have earlier postulated that the presence of a pyridazone ring fused with an anthracenedione moiety resulted in the analog's ability to overcome multidrug resistance of tumor cells [J. Med. Chem.1999, 42, 3494]. High cytotoxic activity of obtained anthrapyridazones [Bioorg. Med. Chem.2003, 11, 561] toward the resistant cell lines, prompted us to synthesize the similarly modified acridine compounds. A series of pyridazinoacridin-3-one derivatives (2b-h) were prepared from the reaction of 9-oxo-9,10-dihydroacridine-1-carboxylate with POCl(3), followed by addition of the appropriate (alkylamino)alkylhydrazines. In vitro cytotoxic activity toward sensitive and resistant leukemia cell lines: L1210, K562, K562/DX, HL-60, HL-60/VINC, and HL-60/DX, with various type of multidrug resistance (MDR and MRP) was determined. The compounds studied exhibited in comparison to the reference cytostatics (DX, MIT) desirable very low resistance indexes (RI). Variations have been observed depending upon the substituent and the type of drug exporting pump. The cytotoxic activities of examined compounds, as well as of model anthrapyridazone derivative PDZ, were lower than those of reference drugs (DX, MIT) due to their diminished affinity to DNA.

Rational design, synthesis, and biological evaluation of bis(pyrimido[5,6,1-de]acridines) and bis(pyrazolo[3,4,5-kl]acridine-5-carboxamides) as new anticancer agents.

The good results obtained with pyrimido[5,6,1-de]acridines 7 and with pyrazolo[3,4,5-kl]acridinecarboxamides 8 prompted us to the synthesis of two new series of bis acridine derivatives: the bis(pyrimidoacridines) 5 and the bis(pyrazoloacridinecarboxamides) 6. Compounds 5 can be regarded also as cyclized derivatives of bis(acridine-4-carboxamides) 3 and compounds 6 as cyclized derivatives of bis(acridine-4-carboxamides) 4. The noncovalent DNA-binding properties of these compounds have been examined using fluorometric techniques. The results indicate that (i) the target compounds are excellent DNA ligands; (ii) the bis derivatives 5 and 6 are more DNA-affinic than corresponding monomers 7 and 8; (iii) the new bis 5 and 6 result always less efficient in binding than related bis(acridine-4-carboxamides) 3 and 4; and (iv) in both series 5 and 6 a clear, remarkable in some cases, preference for binding to AT rich duplexes can be noted. In vitro cytotoxic potency of these derivatives toward the human colon adenocarcinoma cell line (HT29) is described and compared to that of reference drugs. Structure-activity relationships are discussed. We could identify six very potent cytotoxic compounds for further in vitro studies: a cytotoxic screening against six human cancer cell lines and the National Cancer Institute (NCI) screening on 60 human tumor cell lines. Finally, compound 6a was selected for evaluation in a NCI in vivo hollow fiber assay.

Rheological, mucoadhesive and release properties of Carbopol gels in hydrophilic cosolvents.

Carbopol is one of the most common thickening agent for water phases. It is used after neutralisation and its rheological properties in the aqueous medium are well known. The aim of this work was to investigate the gelation properties of Carbopol 971 e 974 polymeric systems in water-miscible cosolvents such as glycerine and PEG 400. Since in these cosolvents, carboxypolymethylene precipitates after neutralisation with a base, then the attention was pointed out of the gelation properties of the different systems at increasing temperature, in order to obtain Carbopols gels avoiding neutralisation and, at the same time, making possible the dissolution in these gels of insoluble or poorly soluble water drugs. Rheological properties of PEG 400 and glycerine samples were compared with similar systems in water by performing oscillatory analyses and measuring the main rheological parameters, G', G" and delta. The results obtained showed that Carbopol 971 and 974 in PEG 400 gave rise after heating to gels that show a satisfactory rheological behaviour. The elastic modulus is greater than the viscous one showing a remarkable elastic character of these samples and the performed frequency sweeps show a typical spectrum of a "gel-like" structure. Being Carbopols well-known mucoadhesive polymers, gels adhesive properties were studied using the ex vivo method. Then, the possible cutaneous irritation were also tested using the in vivo method (Draize test). No signs of cutaneous irritation and good mucoadhesive properties were obtained for the PEG 400 and water gels of Carbopol 974 prepared by heating. After rheological and mucoadhesive properties were set, paracetamol as a model drug was then inserted in the composition of the gels and the release characteristics were defined. Dissolution tests pointed out the greater release control properties of PEG 400-Carbopol 971 samples. These studies showed PEG 400-Carbopol systems as a first-rate alternative to traditional water gels.

Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism.

The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The mix of either nitrofurantoine large crystals or fine crystals with cellulose microcrystalline showed a negative interaction in all proportions, whatever particle sizes. The lubricant addition induced a positive interaction with Vivapur of greater particle size distribution (200, 102 and 101) favouring higher particle adhesivity, while it maintained unaltered that of Vivapurs of lower particle size (105 and 99). Definitely, when cohesive forces are predominant (Vivapur 105 and 99), the establishment of adhesive bonds between nitrofurantoine and Vivapur remain unnoticed; on the contrary, when cohesion bonds between microcrystalline cellulose particles are weakened by the presence of magnesium stearate, the existence of adhesion bonds between particles of different nature is in evidence, leading to a positive interaction.

Design, synthesis, and biological properties of new bis(acridine-4-carboxamides) as anticancer agents.

To enhance the outstanding biological response shown by the corresponding monomers 4 and 5, two classes of bis-acridine-4-carboxamides, 9, with a linker between the 4,4' positions, and 13, with a linker between the 1,1' positions, have been prepared as DNA-binding and potential antitumor agents. The noncovalent DNA-binding properties of these compounds have been examined using gel-electrophoresis and fluorometric techniques. The results indicate that (i). target compounds intercalate DNA; (ii). the bis derivatives with the optimal linker are considerably more DNA-affinic than corresponding monomers; (iii). overall affinity is sensitive to the nature of the linker, of the chromophores, and of the substituents at 7,7'; (iv). often, the bis derivatives show a marked AT-preferential binding. In vitro cytotoxic potency of these derivatives toward the human colon adenocarcinoma cell line (HT29) is described and compared to that of reference drugs. Structure-activity relationships are discussed. Some highly DNA-affinic and potent cytotoxic compounds, 9b,f and 13b,c, have been selected for the National Cancer Institute (NCI) screening on 60 human tumor cell lines and identified as new leads in the antitumor strategies.

Synthesis and biological evaluation of 2,7-Dihydro-3H-dibenzo[de,h]cinnoline-3,7-dione derivatives, a novel group of anticancer agents active on a multidrug resistant cell line.

A series of anthrapyridazone derivatives with one or two basic side chains at various positions in the tetracyclic chromophore have been synthesized. The key intermediates in the synthesis are 2,7-dihydro-3H-dibenzo[de,h]cinnoline-3,7-diones 1, 12 and 15 monosubstituted at position 2 (4d, 16a-e), or 6 (2a-f) or disubstituted at positions 2 and 6 (4a-c) or 2 and 8 (17a-e) with appropriate alkylaminoalkylamines. All analogues showed in vitro cytotoxic activity against murine leukemia (L1210) and human leukemia (K562) cell lines. The compounds were also active against human leukemia multidrug resistant (K562/DX) cell line with resistance index (RI) in the range 1-3 depending on the compound's structure. Two of the most active in vitro compounds 4a and 11 were tested in vivo against murine P388 leukemia and displayed antileukemic activity comparable with that of Mitoxantrone. DNA-binding assays were performed and DNA affinity data were correlated with the structures of the compounds. The cytoplasmatic membrane affinity values (log k'(IAM)) have also been determined and the correlation with the resistance indexes discussed. The anthrapyridazones constitute a novel group of antitumor compounds that can overcome multidrug resistance.

Rational design, synthesis and biological evaluation of thiadiazinoacridines: a new class of antitumor agents.

A series of potential DNA-binding antitumor agents, 3-[omega-(alkylamino)alkyl]-6-nitro-thiadiazino[3,4,5-kl]acridines 12 and 1,3-di[omega-(alkylamino)alkyl]-6-nitro-thiadiazino[3,4,5-kl]acridines 13, has been prepared by cyclization with SOCl(2) of 1-[[omega-(alkylamino)alkyl]amino]-9-imino-4-nitro-9,10-dihydroacridines 16 or 1-[[omega-(alkylamino)alkyl]amino]-9-[omega-(alkylamino)alkyl]imino-4-nitro-9,10-dihydroacridines 17, respectively. The non-covalent DNA-binding properties of 12, 13 have been examined using a fluorometric technique. In vitro cytotoxic potencies of these derivatives toward six tumor cell lines, including human colon adenocarcinoma (HT29) and human ovarian carcinoma (A2780 sensitive, A2780cisR cisplatin-resistant, CH1, CH1cisR cisplatin-resistant, and SKOV-3) cells, are described and compared to that of reference drugs. In vivo antitumor activity of some selected derivatives, endowed with relevant cytotoxic activity against murine leukemia P388 are reported. The 3-[2-(dimethylamino)ethyl]-6-nitro-2,7-dihydro-3H-2 lambda(4)-thiadiazino[3,4,5-kl]acridin-2-one (12d) has been identified as a new lead in the development of anticancer tetracyclic acridine derivatives.

Lonidamine solid dispersions: in vitro and in vivo evaluation.

Solid dispersions of lonidamine in PEG 4000 and PVP K 29/32 were prepared by the spray-drying method. Then, the binary systems were studied and characterized using differential scanning calorimetry, hot stage microscopy, and x-ray diffractometry. In vitro dissolution studies of the solid dispersed powders were performed to verify if any lonidamine dissolution rate or water solubility improvement occurred. In vivo tests were carried out on the solid dispersions and on the cyclodextrin inclusion complexes to verify if this lonidamine water solubility increase was really able to improve the in vivo drug plasma levels. Drug water solubility was increased by the solid dispersion formation, and the extent of increase depended on the polymer content of the powder. The greater increase of solubility corresponded to the highest content of polymer. Both the solid dispersions and the cyclodextrin complexes were able to improve the in vivo bioavailability of the lonidamine when administered per os. Particularly, the AUC of the drug plasma levels was increased from 1.5 to 1.9-fold depending on the type of carrier.

Microencapsulation of semisolid ketoprofen/polymer microspheres.

Ketoprofen controlled release microspheres were prepared, by emulsion/solvent evaporation, at 15 degrees C, in order to avoid the formation of semisolid particles. An identical procedure was carried out at 60 degrees C to speed up the solvent evaporation and the formed semisolid microspheres were directly microencapsulated by complex coacervation and spray-dried in order to recover them as free flowing powder. Microspheres and microcapsules were characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffractometry, in vitro dissolution studies, and then used for the preparation of tablets. During this step, the compressibility of the prepared powders was measured. Microspheres and microcapsules showed compaction abilities by far better than those of the corresponding physical mixtures. In fact, it was impossible to obtain tablets by direct compressing drug and polymer physical mixtures, but microspheres and microcapsules were easily transformed into tablets. Finally, in vitro dissolution studies were performed and the release control of the tablets was pointed out. Microspheres were able to control ketoprofen release only after their transformation into tablets. Tablets containing eudragit RS were the most effective in slowing down drug release.

Binding free energy of selected anticancer compounds to DNA--theoretical calculations.

Many studies have elucidated structures and thermodynamics of complexes formed by different ligands with DNA. However, in most cases structural and free energy binding studies were not correlated with each other because of the problem of identifying which experimental free energy of binding corresponds to which experimental DNA-ligand structure. In the present work, Poisson-Boltzmann and solvent-accessible surface area methods were used to predict unknown modes of interaction between DNA and three different ligands: mitoxantrone and two pyrimidoacridine derivatives. In parallel, experimental measurements of binding free energy for the studied complexes were performed to compare experimental and calculated values. Our studies showed that the calculated values of free energy are only close to experimental data for some models of interaction between ligands and DNA. Based on this correlation, the most likely models of DNA-ligand complexes were postulated: (i) mitoxantrone and one derivative of pyrimidoacridine, both with two charged side chains, intercalate from the minor groove of DNA and bind with both chains in this groove; (ii) pyrimidoacridine, with only one side chain, very likely does not intercalate into DNA at all. Additionally, the non-electrostatic and electrostatic parts of the calculated binding free energy for the DNA-ligands studied are discussed.

Effect of modification of 6-[(aminoalkyl)amino]-7H-benzo[e]-perimidin-7-ones on their cytotoxic activity toward sensitive and multidrug resistant tumor cell lines. Synthesis and biological evaluation.

Benzoperimidines, a novel group of antitumor anthracenedione analogues, are of interest due to their ability to overcome multidrug resistance of tumor cells (Stefanska, B., Dzieduszycka, M., Bontemps-Gracz, M. M., Borowski, E., Martelli, S., Supino, R., Pratesi, G., De Cesare, MA., Zunino, F., Kusnierczyk, H., Radzikowski, Cz. J. Med. Chem. 1999, 42, 3494). Although the structural factor essential for exhibiting this desirable property is the presence in the molecule of a fused heterocyclic ring, the cytotoxicity against resistant cells is highly influenced by the nature and location of the substituents. A series of novel synthetic derivatives, comprising monohydroxylated benzoperimidines and 2-aminobenzoperimidines, allowed the establishment of an in vitro structure-activity relationship for a panel of leukemia sensitive, as well as P-gp dependent multidrug resistance (MDR) and multidrug resistance associated protein dependent resistance (MRP) resistant cell lines. The membrane affinity for the compounds has also been determined.