4.3.6. Pharmacophore-Based Screening

Pharmacophore-based screening was performed using two independent software. The first was SwissSimilarity (http://www.swisssimilarity.ch/, accessed on 16 April 2021) [30]. The SMILES code of the query compound was first submitted, and the FDA-approved database was selected to apply the screening. The computation method was applied according to the pharmacophore features of the input compound (i.e., spectrophores). The retrieved results were ranked according to the similarity degree (from 0 to 1).

The second used software was Ftrees (http://www.biosolveit.de/FTrees, accessed on 16 April 2021) [29]. Molecules similar to the query molecule were screened against FDA-approved drugs hosted in the Zinc database (http://zinc.docking.org/substances/subsets/fda/?page=1, accessed on 3 April 2021). This software applies a different searching approach based on a complex feature tree instead of linear fingerprint depictions [55]. Unlike fingerprint-based similarity search, the minimum FTrees similarity score between the query and the target molecules (similarity threshold) was set to a fixed value of 0.8. The FTrees visual similarities output is a particular similarity score for each query pair.