Molecular docking and simulation study for synthesis of alternative dapsone derivative as a newer antileprosy drug in multidrug therapy.

Leprosy (causative, Mycobacterium leprae) continues to be the persisting public health problem with stable incidence rates, owing to the emergence of dapsone resistance that being the principal drug in the ongoing multidrug therapy. Hence, to overcome the drug resistance, structural modification through medicinal chemistry was used to design newer dapsone derivative(s) (DDs), against folic acid biosynthesis pathway. The approach included theoretical modeling, molecular docking, and molecular dynamic (MD) simulation as well as binding free energy estimation for validation of newly designed seven DDs, before synthesis. Theoretical modeling, docking, and MD simulation studies were used to understand the mode of binding and efficacy of DDs against the wild-type and mutant dihydropteroate synthases (DHPS). Principal component analysis was performed to understand the conformational dynamics of DHPS-DD complexes. Furthermore, the overall stability and negative-binding free energy of DHPS-DD complexes were deciphered using Molecular Mechanics/Poisson-Boltzmann Surface Area technique. Molecular mechanics study revealed that DD3 possesses higher binding free energy than dapsone against mutant DHPS. Energetic contribution analysis portrayed that van der Waals and electrostatic energy contributes profoundly to the overall negative free energy, whereas polar solvation energy opposes the binding. Finally, DD3 was synthesized and characterized using Fourier-transform infrared spectroscopy, UV, liquid chromatography-mass spectrometry, and proton nuclear magnetic resonance techniques. This study suggested that DD3 could be further promoted as newer antileprosy agent. The principles of medicinal chemistry and bioinformatics tools help to locate effective therapeutics to minimize resources and time in current drug development modules.

A short history of dapsone, or an alternative model of drug development.

From 1936 until 1996, the drug dapsone treated a diverse array of diseases, including tuberculosis, leprosy, malaria, and AIDS-related pneumonia. This article explores how dapsone transformed from a cure for one disease into a treatment for a totally different malady. This process of reinvention in the clinic represents an alternative model of drug development that the historical literature, focused on success in the laboratory, has largely ignored. The core of the paper discusses the reinvention of dapsone as an antimalarial in the Vietnam War through trials led by Robert J. T. Joy, a physician and military officer. As a case study, it offers a fresh perspective on the clinic-as-laboratory approach that other scholars have addressed in a civilian context. Viewing the randomized clinical trial (RCT) through a military prism will demonstrate how a combat environment combined with the regimentation of the armed forces affected the standard methodology of the RCT.

A short history of dapsone, or an alternative model of drug development.

From 1936 until 1996, the drug dapsone treated a diverse array of diseases, including tuberculosis, leprosy, malaria, and AIDS-related pneumonia. This article explores how dapsone transformed from a cure for one disease into a treatment for a totally different malady. This process of reinvention in the clinic represents an alternative model of drug development that the historical literature, focused on success in the laboratory, has largely ignored. The core of the paper discusses the reinvention of dapsone as an antimalarial in the Vietnam War through trials led by Robert J. T. Joy, a physician and military officer. As a case study, it offers a fresh perspective on the clinic-as-laboratory approach that other scholars have addressed in a civilian context. Viewing the randomized clinical trial (RCT) through a military prism will demonstrate how a combat environment combined with the regimentation of the armed forces affected the standard methodology of the RCT.

Effects of H(2)-receptor antagonists on dapsone-induced methaemoglobinaemia in rats.

Dapsone (DDS) (4,4'diaminodiphenylsulfone), the drug of choice for the treatment of leprosy, frequently induces haemolytic anaemia and methaemoglobinaemia. N-hydroxylation, one of the major pathways of biotransformation, has been constantly related to the methaemoglobinaemia observed with the use of the drug. In order to determine the reversible inhibition of this toxicologic bioactivation pathway without changing the detoxification pathways of the drug or cytosolic acetylation, cimetidine (CIM), ranitidine and famotidine were administered in combination with DDS to male Wistar rats weighing 200-220 g. The animals were divided into nine groups of eight: group 1 received a single dose of 40 mg kg (-1) DDS in dimethylsulfoxide (DMSO) and groups 2-4 received the same treatment as group 1 but after the administration of a single dose of 100, 150 and 200 mg kg (-1) CIM, respectively, injected 2 h prior DDS administration. Groups 5-9 received the same treatment as group 2 but after the treatment of ranitidine (50 and 100 mg kg (-1) intraperitoneally (i.p.) in 200 microl DMSO) and famotidine (10, 50 and 100 mg kg (-1) i.p. in 200 microl DMSO), respectively. The animals were then anaesthetized with ether and blood was collected from the aorta for the determination of plasma DDS and monoacetyldapsone concentrations by HPLC and later for the determination of methaemoglobinaemia by spectrophotometry. CIM showed a higher affinity for cytochrome P-450 than famotidine and ranitidine. The results obtained showed the potentiality of the pharmacological effects of DDS with a low risk of adverse reactions, especially methaemoglobinaemia, which is dose dependent.

Hemolytic drugs aniline and dapsone induce iron release in erythrocytes and increase the free iron pool in spleen and liver.

Incubation of rat erythrocytes with the hydroxylated metabolites of aniline and dapsone (4-4'-diaminodiphenylsulfone), phenylhydroxylamine and dapsone hydroxylamine, respectively, induced marked release of iron and methemoglobin formation. On the contrary, no release of iron nor methemoglobin formation was seen when the erythrocytes were incubated with the parent compounds (aniline and dapsone). The acute intoxication of rats with aniline or dapsone induced a marked increase in the erythrocyte content of free iron and methemoglobin, indicating that the xenobiotics are effective only after biotransformation to toxic metabolites in vivo. Prolonged administration of aniline or dapsone to rats produced continuous release of iron from erythrocytes. Marked iron overload was seen in the spleen and in the liver Kupffer cells, as detected histochemically. The spleen weight in these subchronically treated animals was significantly increased. The free iron pool was markedly increased in the spleen and to a lower extent in the liver. The possible relationships between iron release in erythrocytes, oxidative damage seen in senescent cells, hemolysis, overwhelmed capacity of spleen and liver to keep iron in storage forms and subsequent increase in low molecular weight, catalitically active iron is discussed.

Dapsone hydroxylamine inhibits the LTB4-induced chemotaxis of polymorphonuclear leukocytes into human skin: results of a pilot study.

OBJECTIVE: Dapsone (4,4'diaminodiphenylsulfone) is effective in treating leprosy, chronic inflammatory conditions and opportunistic infections in HIV patients. By the oral route, the sulfone is metabolized to monoacetyldapsone (MADDS) and dapsone hydroxylamine (DDS-NOH). We have addressed the question as to whether these dapsone metabolites have anti-inflammatory properties of their own in vivo. TREATMENT AND METHODS: After two weeks topical pre-treatment with MADDS (1%), DDS-NOH (1%) and clobetasol proprionate (CP; 0.05%) dissolved in acetone, as a reference, 10 ng leukotriene B4 (LTB4) were applied on the upper arms of eight healthy volunteers. After 24 h, biopsies were taken and the polymorphonuclear leukocytes (PMN) were quantified fluorometrically using elastase as marker enzyme. RESULTS: MADDS did not show any inhibitory activity on trafficking of PMN compared to the corresponding control and nontreated area (untreated: 790 +/- 450 PMN/10 micrograms skin; p > 0.05, acetone: 840 +/- 578 PMN/10 micrograms skin; MADDS: 1099 +/- 556 PMN/10 micrograms skin), whereas DDS-NOH caused a statistically significant inhibition of PMN accumulation as did the reference CP (DDS-NOH: 128 +/- 143 PMN/10 micrograms skin; CP: 86 +/- 131 PMN/10 micrograms skin, p < 0.01). CONCLUSIONS: These results indicate that DDS-NOH has anti-inflammatory potential which might contribute to the effectiveness of dapsone therapy.

[Synthesis of promin in Japan and global elimination of Hansen's disease].

Prof. Morizo Ishidate synthesized "Promin" for the treatment of leprosy/Hansen's disease which had been considered "incurable" until the discovery of antileprosy effect of that drug by Dr. Faget of U.S.A. in 1941. Prof. Ishidate was the first to synthesize the drug in Japan in 1946 based on a brief news item on a Swiss journal smuggled in during the War. For this achievement, he is known as "father of chemotherapy for leprosy in Japan." Prof. Ishidate also contributed to the global fight against leprosy as the Chairman of the Board of Directors of Sasakawa Memorial Health Foundation, which he helped to establish in May 1974, with a full financial backing of Mr. Ryoichi Sasakawa, President of Japan Shipbuilding Industry Foundation. Prof. Ishidate, with his scientific knowledge as well as christianity based humanitarian concern, advised Mr. Sasakawa how to spend JSIF money wisely for eliminating leprosy and nearly US$200 million was channeled through WHO and SMHF. The successful outcome of global multidrug therapy (MDT) programme in the '80s resulted in the adoptation of resolution by the World Health Assembly, "Elimination of Leprosy, as a public health problem" by the Year 2000. The synthesis of "Promin" in Japan and promoting the global implementation of MDT, both achievement can be attributed to Prof. Ishidate.

Combined dapsone and clofazimine intoxication.

We report clinical findings and pharmacokinetic data regarding a combined dapsone and clofazimine intoxication in a man, who ingested 50 tablets of dapsone (100 mg) 20 capsules of clofazimine (100 mg) and two tablets of rifampicin (600 mg). Oral administration of activated charcoal (50 grams) and sodium sulphate (20 grams) after gastric lavage resulted in an elimination half-life in plasma of 11.1 and 10.8 h for dapsone and its main metabolite, monoacetyldapsone, respectively. A rapid initial decrease of the plasma concentration of clofazimine was observed after gastric lavage and administration of activated charcoal and sodium sulphate. 15 h after this treatment, clofazimine plasma levels remained relatively constant. Dapsone-induced methaemoglobinaemia (48% at admission) was treated successfully with methylene blue.

Metabolism of dapsone to its hydroxylamine by CYP2E1 in vitro and in vivo.

Dapsone toxicity is putatively initiated by formation of a hydroxylamine metabolite by cytochromes P450. In human liver microsomes, the kinetics of P450-catalyzed N-oxidation of dapsone were biphasic, with the Michaelis-Menten constants of 0.14 +/- 0.05 and 0.004 +/- 0.003 mmol/L and the respective maximum velocities of 1.3 +/- 0.1 and 0.13 +/- 0.04 nmol/mg protein/min (mean +/- SEM). Troleandomycin (40 mumol/L) inhibited hydroxylamine formation at 100 mumol/L dapsone by 50%; diethyldithiocarbamate (150 mumol/L) and tolbutamide (400 mumol/L) inhibited at 5 mumol/L dapsone by 50% and 20%, respectively, suggesting that the low-affinity isozyme is CYP3A4 and the high-affinity isozymes are 2E1 and 2C. Disulfiram, 500 mg, 18 hours before a 100 mg oral dose of dapsone in healthy volunteers, diminished area under the hydroxylamine plasma concentration-time curve by 65%, apparent formation clearance of the hydroxylamine by 71%, and clearance of dapsone by 26%. Disulfiram produced a 78% lower concentration of methemoglobin 8 hours after dapsone.

Pharmacokinetics of dapsone in human immunodeficiency virus-infected children.

Dapsone, administered at various doses and schedules, has been proven to be a safe and effective alternative to trimethoprim-sulfamethoxazole for prevention of Pneumocystis carinii pneumonia (PCP) in adults with human immunodeficiency virus (HIV) infection. Dapsone is also recommended by the Centers for Disease Control for PCP prophylaxis in HIV-infected children. However, the suggested dosage regimen is based upon clinical experience with children with leprosy and dermatitis herpetiformis rather than pharmacokinetic and pharmacodynamic data obtained from the target patient population. In order to determine a rational dosage regimen that could be tested in clinical studies aimed at the evaluation of dapsone for the prevention of PCP in HIV-infected children, we studied the pharmacokinetics of dapsone following a 2-mg/kg of body weight oral dose in twelve HIV-positive children aged 9 months to 9 years. Plasma was collected at the following times after dapsone administration: 0, 2, 4, 6, 12, 24, 48, 72, and 96 h. The levels of dapsone in plasma were determined by high-performance liquid chromatography. Data were analyzed by noncompartmental methods. Expressed as means +/- standard deviations (ranges), the pharmacokinetic parameters were as follows: peak concentration in plasma, 1.12 +/- 0.48 (0.44 to 1.81) mg/liter; time to peak concentration in plasma, 3.8 +/- 1.3 (2 to 6) h; half-life at elimination phase, 24.2 +/- 7.1 (14.4 to 35.0) h; clearance from plasma divided by bioavailability (CL/F), 1.15 +/- 0.67 (0.37 to 2.63) ml/min/kg; and volume of distribution divided by bioavailability (V/F), 2.25 +/- 1.20 (1.00 to 4.57) liters/kg. Oral CL correlated negatively with age (r = 0.614 and P = 0.034), as did V (r = 0.631 and P = 0.028). As a consequence of the high interindividual variability in growth retardation, pharmacokinetic parameters correlated with measures of body development better than they did with age (e.g., for CL/F to height, r = 0.765 and P = 0.004, and for V/F to height, r = 0.748 and P = 0.005). Since oral CL from plasma and V were positively and highly correlated (r = 0.898 and P = 0.0001), a lower absolute F may be the cause, in part, of higher values for CL/F and V/F in smaller children. The results of this study warrant the testing of a 2-mg/kg dose of dapsone administered twice or thrice weekly to HIV-infected children. The monitoring of drug levels in plasma and dosage adjustment may be necessary for smaller children.

Dapsone-induced hemolytic anemia.

Dapsone, an old drug introduced and used almost exclusively for the treatment of leprosy, is now utilized in an increasing number of therapeutic situations. However, its hemotoxicity is potentially severe and is often dose limiting. Effective countermeasures, based on resolution of the mechanisms underlying dapsone-induced hemotoxicity, could significantly enhance the therapeutic value of the drug. In studies on rat red cells, we have established that the N-hydroxy metabolites of dapsone, DDS-NOH and MADDS-NOH, are direct-acting hemolytic agents, that they are formed in amounts sufficient to account for the hemotoxicity of the parent drug, and that the action of these toxic metabolites in the red cell induces premature sequestration by the spleen. Incubation of rat red cells with hemolytic concentrations of arylhydroxylamines leads to the generation of hydroxyl, glutathiyl, and hemoglobinthiyl radicals, and the formation of protein-glutathione mixed disulfides. Disulfide-linked adducts are also formed between membrane skeletal proteins and hemoglobin monomers, as well as between the monomeric hemoglobin units forming dimers, trimers, tetramers, and pentamers. Profound morphological changes are seen with change from normal discoidocity to an extreme nonspherocytic enchinocyte shape. Parallel studies with human red cells indicate that the response of human cells is qualitatively similar but that there are notable differences in regard to skeletal membrane effects. A working hypothesis for the mechanism underlying dapsone hemolytic activity is proposed.

Stimulation of K-C1 cotransport in rat red cells by a hemolytic anemia-producing metabolite of dapsone.

Dapsone, a sulfone compound used in the treatment of leprosy and, more recently, Pneumocystis carinii pneumonia, produces as a major side effect a hemolytic anemia. This anemia is characterized by oxidation of hemoglobin to methemoglobin and increased splenic uptake of red blood cells. Using a rat model, Grossman and Jollow (J. Pharmacol. Exp. Ther. 244: 118-125, 1988) found that dapsone hydroxylamine (DDS-NOH), a dapsone metabolite, is responsible for its hemolytic effect in vivo. DDS-NOH also promotes hemoglobin binding to SH groups on rat red cell membrane proteins (Budinsky et al., FASEB J. 2: A801, 1988). Since the binding of hemoglobin and other reagents (e.g., N-ethylmaleimide) to membrane SH groups has been associated with increased K transport in red blood cells, we examined the effect of DDS-NOH on K efflux from rat red blood cells in vitro. Cells shrink when exposed to DDS-NOH (100 microM) in media with plasma-like ionic composition. This shrinkage is prevented if extracellular K is raised to 110 mM or if intra- and extracellular Cl are replaced by methylsulfate (MeSO4), suggesting involvement of a K-Cl cotransport pathway. Indeed, 100 microM DDS-NOH produces a 4- to 5-fold increase in K efflux in cells containing Cl but less than a 2-fold increase in cells containing MeSO4. This stimulatory effect is specific for K; Na efflux is slightly inhibited by 100 microM DDS-NOH. The concentrations of DDS-NOH required for half-maximal stimulation of Cl-dependent K efflux (53 microM) is similar to its half-maximal hemolytic concentration in rats (approximately 100 microM). Furthermore, the stimulation of Cl-dependent K efflux by DDS-NOH is greater than 80% reversed by subsequent treatment of the cells with dithiothreitol, suggesting involvement of SH groups. Our results indicate that DDS-NOH exposure stimulates an apparent K-Cl cotransport in rat red blood cells, resulting in cell shrinkage under physiological ionic conditions. Since shrinkage of red blood cells renders them less deformable (Mohandas et al., J. Clin. Invest. 66: 563-573, 1980), this suggests a pathophysiological mechanism whereby DDS-NOH exposure in vivo could promote increased splenic uptake of red blood cells and hemolytic anemia.

Plasma dapsone and its metabolite monoacetyldapsone levels in leprotic patients.

Dapsone (DDS) is a drug of choice in the treatment of leprosy. The DDS and MADDS levels and different pharmacokinetic parameters after a single dose of dapsone and at steady state in leprotic patients have been studied. At steady state, all the patients showed plasma DDS and MADDS levels above 0.5 micrograms/ml throughout the 24-h duration. There was no significant difference in the elimination half-lives of DDS and MADDS after a single dose as compared to at steady state, but AUC0-alpha for both DDS and MADDS were significantly increased at steady state. From these results, it could be concluded that 100 mg daily dose is sufficient to maintain plasma therapeutic concentration in leprotic patients in Indian population.

Influence of acetylator phenotype of the leprosy patient on the emergence of dapsone resistant leprosy.

The half time of disappearance of dapsone and monoacetyl dapsone and the acetylator phenotype of the leprosy patients who harboured dapsone sensitive and dapsone resistant M. leprae was assessed in 27 subjects. Sixteen patients were rapid acetylators, five were slow and six were intermediate acetylators. The mean T 1 1/2 lives of dapsone (30.26 +/- 11.0) and monoacetyl dapsone (31.11 +/- 12.0) were also studied in the above patients. The percentage of different acetylators in both resistant and sensitive groups were similar showing no correlation between the emergence of drug resistance and the phenotype of the patient. The mean time of disappearance of DDS and MAD in the different acetylators did not show significant difference. The ratios of MAD/DDS in an individual at 3, 6 or 24 hours after the dose were similar. The mean T 1 1/2 lives of DDS and MAD in resistant and sensitive patients also showed no difference. Neither T 1 1/2 lives of DDS or MAD nor the acetylator phenotype seem to influence the emergence of dapsone resistance.

A field trial among leprosy patients in Nigeria with depot injections of dapsone and monoacetyldapsone.

In two field trials in Nigeria, 74 male and female leprosy outpatients received intra-adipose depot injections of either dapsone (DDS) or monoacetyldapsone (MADDS) at 4-week intervals. Blood samples were taken regularly and sent to Amsterdam to determine the DDS and MADDS concentrations in serum using high-pressure liquid chromatography (HPLC). The DDS injection yielded a good sustained drug release. After repeated administration accumulation occurred, demonstrated by a statistically significant increase in the area under the curve (AUC) in time: until 28 days after the first injection, the mean AUC (+/- S.D.) amounted to 19.3 +/- 5.6 mg d/l in males and 15.1 +/- 5.2 in females; after the fourth injection, 26.4 +/- 7.5 and 24.6 +/- 9.0 mg d/l, respectively (p less than 0.001). One male patient developed an abscess at the injection site; otherwise no side effects were observed. Even better sustained-release results were observed with the MADDS injection. Unfortunately, the injection caused a number of abscesses. Consequently, the DDS injection was very well received by the patients of the DDS study, while half of the patients in the MADDS study would prefer tablets to the MADDS injection. Further investigations are required to find the cause of the abscesses before one of the injections, or possibly a combination of both, could be implemented in the multi-drug treatment regimen proposed by WHO to provide a valuable tool to combat noncompliance among leprosy patients.

Intra-adipose administration of monoacetyldapsone to healthy volunteers.

The pharmacokinetics of intra-adiposely administered monoacetyldapsone (particle size less than 20 micron) were investigated in 11 male and 11 female healthy volunteers. Dapsone and monoacetyldapsone concentrations in serum were determined by high-pressure liquid chromatography (HPLC). Injection of 1175 mg monoacetyldapsone, which is equivalent to 1000 mg dapsone, resulted in dapsone concentration/time profiles in all the volunteers characterized by peak concentrations ranging from 0.14 to 0.85 mg/l, and by averaged dapsone concentrations after 28, 42, and 56 days of 0.33, 0.19, and 0.10 mg/l, respectively. Areas under the curves ranged from 6.7 to 25.3 mg X day/l. Detectable concentrations (greater than 6 ng/ml) of dapsone were achieved for 56 days in most of the subjects. An estimation of the mean concentration after repeated injection every 4 weeks ranged from 0.24 to 0.90 mg/l. No differences in dapsone concentration/time course were detectable between men and women or between rapid and slow acetylators. The injection was generally well tolerated by the subjects. This, combined with the excellent sustained release properties, makes it a promising injection. In the future, it might contribute to combat noncompliance among leprosy patients, which is believed to be one of the main causes of dapsone resistance.

Blood dapsone levels in leprosy patients treated with acedapsone.

The metabolism of the repository drug acedapsone (DADDS,4,4'-diacetyldiaminodiphenyl sulfone) was studied in 15 individuals receiving 225 mg of DADDS, intramuscularly for a period of 75 days. Plasma levels of DDS were determined on the 2nd, 7th, 15th, 30th, 60th and 75th day after administration of the drug by spectrophoto-fluorometric technique. The mean peak levels of DDS (85.36 ng/ml) were noticed on 7th day followed by a gradual decrease in DDS concentration. The mean half-life level (44.53 ng/ml) of DDS were observed around the 15th day. The mean DDS level for the entire period of observation after one dose was 41.95 ng/ml. On the 75th day, the DDS level reached the minimum value of 14.76 ng/ml which was still about 5 times more than the minimal inhibitory concentration (MIC) level of DDS against M. leprae (3 ng/ml). The results are discussed.

Limited duration acedapsone prophylaxis in leprosy.

A randomized controlled chemoprophylaxis trial was carried out in Madras city using 560 disease-free household child contacts of 264 multibacillary cases as study subjects. In the study, 13 cases were diagnosed among 280 contacts who received 3 injections of acedapsone at 10 weeks interval as against 30 cases among 280 contacts who had the same number of placebo injections, during the follow-up period of 225 weeks. The difference in the incidences in the two groups was statistically significant. (X2 6.45; P less than 0.02). The protection due to the limited duration of acedapsone prophylaxis was 56.7 percent. There were no cases of multi-bacillary leprosy in either group. The efficacy of prophylaxis was significant in male children over 9 years of age and female children in the age-group 1-8 years. The other prognostic factors like the infectivity status of the index cases in the household and the duration of exposure to them could have possibly influenced the effectiveness of prophylaxis in preventing progression from infection to clinical disease among the subjects studied. Their effects could not be assessed in this study.