Repurposing of Pentamidine as a Potential Inhibitor of the HMG-Box Protein in Toxoplasma gondii: An Integrated In Silico Approach

Background/Objectives: The identification of novel therapeutic targets is imperative to overcome the limitations of current anti-toxoplasmosis treatments. This study aims to investigate the potential of repurposing Pentamidine as an inhibitor against the HMG-Box domain-containing protein (TGARI_247020) in Toxoplasma gondii, a protein hypothesized to be essential for the parasite’s genomic stability. Methods: The study utilized a multi-layered in silico approach. First, the biological essentiality of the target gene was validated by analyzing CRISPR-Cas9-based phenomics data from the ToxoDB database. Second, the structural properties of the HMG-Box domain (ID: A0A139YAG1) were characterized using AlphaFold models. Finally, molecular docking simulations were conducted via the SwissDock server to evaluate the binding affinity and interaction dynamics between Pentamidine and the target protein. Results: Genomic analysis revealed a phenotype score of −1.2, confirming the indispensable role of the TGARI_247020 gene for parasite viability. Structural analysis identified a well-defined binding pocket within the HMG-Box domain. Molecular docking results demonstrated a high binding affinity for Pentamidine, yielding an optimal AC Score of −44.93, supported by a FullFitness value of −1134.13 kcal/mol. The interaction was primarily stabilized by a network of hydrogen bonds and favorable steric fits within the catalytic groove of the protein. Toxoplasmosis is widely classified as a neglected parasitic disease, posing persistent public health challenges and veterinary economic concerns globally. Traditional de novo drug discovery is often hindered by high costs and prolonged timelines, making drug repositioning (repurposing) a highly attractive and cost-effective strategy to identify novel therapeutics from established clinical agents over the past decade. Computer-Aided Drug Design (CADD), particularly Structure-Based Drug Design (SBDD), has provided a robust molecular framework to prioritize candidate drugs against essential parasitic targets. In apicomplexan parasites, high-mobility group box (HMGB) proteins, such as TgHMGB1a, serve as critical nuclear architectural factors that bind to distorted DNA structures and modulate genomic transcription, disrupting these essential DNA–protein interactions, representing a promising, yet under-explored, therapeutic target. The hypothesis for evaluating Pentamidine—an aromatic dicationic diamidine traditionally used in African trypanosomiasis—lies in its established ability to interact with nucleic acids and block critical molecular targets in other protozoa, providing a logical biochemical rationale for testing its potential as a structural inhibitor of the T. gondii HMG-box protein. Conclusions: Our findings provide preliminary in silico evidence that Pentamidine targets the HMG-Box protein, suggesting its potential for drug repurposing. However, due to established clinical limitations of Pentamidine (such as nephrotoxicity and poor blood–brain barrier permeability), further experimental in vitro and in vivo validation is strictly required to evaluate its therapeutic efficacy.