In silico repositioning of approved drugs against Schistosoma mansoni energy metabolism targets

Schistosomiasis is a neglected parasitosis caused by Schistosoma spp. Praziquantel is used for the chemoprophylaxis and treatment of this disease. Although this monotherapy is effective, the risk of resistance and its low efficiency against immature worms compromises its effectiveness. Therefore, it is necessary to develop new schistosomicide drugs. However, the development of new drugs is a long and expensive process. The repositioning of approved drugs has been proposed as a quick, cheap, and effective alternative to solve this problem. This study employs chemogenomic analysis with use of bioinformatics tools to search, identify, and analyze data on approved drugs with the potential to inhibit Schistosoma mansoni energy metabolism enzymes. The TDR Targets Database, Gene DB, Protein, DrugBank, Therapeutic Targets Database (TTD), Promiscuous, and PubMed databases were used. Fifty-nine target proteins were identified, of which 18 had one or more approved drugs. The results identified 20 potential drugs for schistosomiasis treatment; all approved for use in humans.


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For schistosomiasis treatment and chemophylaxis, the World Health Organization (WHO) 39 recommends the use of the drug praziquantel (PZQ) [2], because it is an anthelmintic that is effective 40 in a single oral dose, contains low toxicity, and has a relatively low cost [3,4]. PZQ acts as an 41 antagonist of calcium ion channels (Ca 2+ ) that induce the influx of Ca 2+ , resulting in muscular spasms 42 and paralysis of worms in the adult stage [4,5]. Although this drug is effective, the appearance of 43 strains resistant to PZQ, as well as its low effectiveness against immature worms, make research and 44 new drug development extremely necessary [6][7][8]. 45 For this reason, the investigation of target molecules that act in the metabolism of Schistosoma 46 spp. and have potential to interact with compound candidates for anti-schistosomiasis therapy is 47 necessary [9,10]. This strategy focuses on energy metabolism enzymes, as they are considered 48 interesting targets for inhibitor development because they reduce energy production capacity, 49 consequently contributing to the death and elimination of the parasite [11].
3 50 Conventional research and development strategies for novel drugs are considered high-cost 51 (estimated at millions of dollars), time-consuming (between 10-17 years), and risky. The serious 52 side-effects and diminished efficacy in humans that can occur during clinical trials are common 53 factors leading to a compound not being approved for commercialization [12,13]. Moreover, 54 pharmaceutical industries are not interested in investing in the development and production of new 55 drugs for treating Neglected Tropical Diseases (NTDs), because they offer a low profit return [14]. 56 To overcome these difficulties, the repositioning of approved drugs is proposed, which offers 57 an excellent cost-benefit ratio by diminishing the time (between 3-12 years) and money spent The methodology utilized is an adaptation of the methodology used by Bispo et al. [23] and 79 Silva et al. [24]. . On the initial page, the "Targets" option was selected. Next, in the 85 "Select pathogen species of interest" field, the Schistosoma mansoni option was selected as the 86 species of interest. The filters field contained the following information: Name/Annotation, Features, 87 Structures, Expression, Antigenicity, Phylogenetic distribution, Essentiality, Validation data, 88 Druggability, Assayability, and Bibliographic references. The number of filters was limited to 89 increase the chances of getting results. For this reason, the only expanded filter was 90 "Name/Annotation," and the "Energy metabolism" option was selected in the "KEGG high-level 91 pathway" field. Finally, the "Search" option was selected. The database returned a table containing 92 the identity (ID) of each gene of interest.

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After the genes of interest list was produced, the ID of each gene was used to obtain the 94 targets' peptide sequences form the Gene DB version 2.5 database (Fig 1a) (http://www.genedb.org/) 95 [26]. On the initial Gene DB page, each gene id was inserted into the "Name/Product" field and, right 96 after, "S. mansoni" was selected in the "All organism" field, and the search was executed. The Protein 97 database (http://www.ncbi.nlm.nih.gov/protein/) was employed when the gene of interest did not 98 appear in the Gene DB search results. On the initial Protein page, the gene ids were inserted in the 99 "Gene name" field, followed by Schistosoma mansoni in the "Organism" field. The gene ids and their   In these two databases, the general strategy was based on the principle of target similarity, 117 where each S. mansoni energy metabolism target was compared with other targets that already have 118 approved drugs for treatment. All homologous drug targets with an expectation value (E-value) less 119 than 1  10 -5 obtained from the databases were input into a table as potential targets. On the initial DrugBank page, in the "Search" option, "Target Sequences" was selected. Then, 124 we inserted the protein sequence for consultation. The BLAST parameters offered by the database 125 were maintained and in the "drug types" filter, the option "approved" was marked. In the initial TTD page, the "Target Similarity" option was selected and the peptide sequence 129 was introduced into the "Input your protein sequence in FASTA format" field, and the "Search" 130 function was executed. All the results with an E-value less than 1  10 -5 were considered for analysis.  (Table 1).  Promiscuous offers different search strategies to the user: drug name, target by interest, and 147 metabolic pathway. In the present study, the search strategy chosen was to use the drug name. On the 148 initial page, the "Drugs" option was selected, and each drug name was inserted into the "Drug name" 149 field. Subsequently, the code of each drug was inserted into the PubChem field, found at 7 150 https://pubchem.ncbi.nlm.nih.go [30], and the "Only with targets" option was selected. Information 151 on the interaction between the drug and protein target and the eventual side effects were separately 152 included in a table (Table 2). 153 After obtaining results of interactions between drugs and protein targets and their side effects,   In the TDR Targets Database, 59 genes were identified that encode S. mansoni energy 182 metabolism enzymes. All the products of these genes were considered as potential therapeutic targets 183 (Table 3). The DrugBank and TTD databases returned 11 and one targets, respectively, with approved 189 drugs against them. The protein targets and their respective functions are presented in Table 1.  Involved in the glutamine metabolic process  Of the ten targets, eight had high chemotherapeutic potential because of their very low E-210 values. Five targets that interact with seven high potential anti-schistosomiasis drugs were selected.

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Detailed information on these compounds is presented in Table 2.  In this analysis, drugs identified as having therapeutic potential against schistosomiasis were 220 considered if they had a low cost, were approved for use in humans, and possessed few side effects.

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Interactions of drugs identified with other targets were investigated using the Promiscuous database 222 to meet this last criterion. Each of the drugs was subjected to analysis, and 18 of them presented 223 interactions with different molecules. In this study, only the interaction networks of drugs with high 224 anti-schistosomiasis potential were detailed (Table 2).        Table 2).

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To evaluate in vivo anti-schistosomiasis activity of thiabendazole and albendazole in mice 307 infected with S. mansoni, 100 mg/kg/day and 500 mg/kg/day doses were used, respectively. In this 308 assessment, it was found that albendazole treatment showed no effect on the number of dead adult 309 specimens and/or the elimination of eggs from this parasite. In contrast, treatment using thiabendazole hydrolysis catalyst that is also involved in calcium transport ( Fig S4)  Even though desflurane and isoflurane offer anesthetic pharmacological activity, it is possible 355 to make them usable for clinical trials against S. mansoni, using molecular remodeling.

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Alendronate is indicated for treatment of Paget's disease and osteoporosis. This drug acts as 357 an inhibitor of the ATPase type IV subunit A target, interfering in proton transport through a rotation 358 mechanism. Alendronate exhibits toxicity evidenced by esophageal mucosa damage (DrugBank 359 data). In this study, alendronate was identified as having the capacity to inhibit ATP synthase subunit 360 beta (Smp_038100), interfering with the function of proton transport connected to ATP synthesis 361 (