Preclinical comprehensive physicochemical and pharmacokinetic profiling of novel nitroimidazole derivative IIIM-019 - A potential oral treatment for tuberculosis

Third Generation Solid Dispersion-Based Formulation of Novel Anti-Tubercular Agent Exhibited Improvement in Solubility, Dissolution and Biological Activity

The long treatment period and development of drug resistance in tuberculosis (TB) necessitates the discovery of new anti-tubercular agents. The drug discovery program of the institute leads to the development of an anti-tubercular lead (IIIM-019), which is an analogue of nitrodihydroimidazooxazole and exhibited promising anti-tubercular action. However, IIIM-019 displays poor aqueous solubility (1.2 µg/mL), which demands suitable dosage form for its efficient oral administration. In the present study, third generation solid dispersion-based formulation was developed to increase the solubility and dissolution of IIIM-019. The solubility profile of IIIM-019 using various polymeric carriers was determined and subsequently, PVP K-30 and P-407 were selected for preparation of binary and ternary solid dispersion. The third-generation ternary solid dispersion comprising PVP K-30 and P-407 revealed a remarkable enhancement in the aqueous solubility of IIIM-019. Physicochemical characterization of the developed formulations was done by employing FTIR spectroscopy, scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and dynamic light scattering analysis. The dissolution study indicated an impressive release profile with the optimized formulation. The optimized formulation was further examined for cytotoxicity, cellular uptake, and hemolytic activity. The results indicated that the formulation had no apparent cytotoxicity on Caco-2 cells and was non-hemolytic in nature. Moreover, the optimized formulation showed significantly improved anti-tubercular activity compared to the native molecule. These findings showed that the developed third generation ternary solid dispersion could be a promising option for the oral delivery of investigated anti-tubercular molecule.

Drug re-engineering and repurposing: A significant and rapid approach to tuberculosis drug discovery

The prevalence of tuberculosis (TB) remains the leading cause of death from a single infectious agent, ranking it above all other contagious diseases. The problem to tackle this disease seems to become even worse due to the outbreak of SARS-CoV-2. Further, the complications related to drug-resistant TB, prolonged treatment regimens, and synergy between TB and HIV are significant drawbacks. There are several drugs to treat TB, but there is still no rapid and accurate treatment available. Intensive research is, therefore, necessary to discover newer molecular analogs that can probably eliminate this disease within a short span. An increase in efficacy can be achieved through re-engineering old TB-drug families and repurposing known drugs. These two approaches have led to the production of newer classes of compounds with novel mechanisms to treat multidrug-resistant strains. With respect to this context, we discuss structural aspects of developing new anti-TB drugs as well as examine advances in TB drug discovery. It was found that the fluoroquinolone, oxazolidinone, and nitroimidazole classes of compounds have greater potential to be further explored for TB drug development. Most of the TB drug candidates in the clinical phase are modified versions of these classes of compounds. Therefore, here we anticipate that modification or repurposing of these classes of compounds has a higher probability to reach the clinical phase of drug development. The information provided will pave the way for researchers to design and identify newer molecular analogs for TB drug development and also broaden the scope of exploring future-generation potent, yet safer anti-TB drugs.

Comparison of Pinoresinol and its Diglucoside on their ADME Properties and Vasorelaxant Effects on Phenylephrine-Induced Model

Pinoresinol (PINL) and pinoresinol diglucoside (PDG), two natural lignans found in Eucommia ulmoides Oliv. (Duzhong), have several pharmacological activities. However, there is no report available on their absorption, distribution, metabolism, and elimination (ADME) properties. Given the possible wide spectrum of their application in therapeutic areas, this area should be investigated. This work studied the in vitro ADME properties of PDG and PINL, including their kinetic solubility, permeability across monolayer cells (PAMPA), protein binding, and metabolic stabilities in liver microsomes. The in vivo pharmacokinetic study and in vitro vasorelaxant effects on isolated phenylephrine-induced aortic rings of PINL and PDG were also investigated. It was found that both of their kinetic solubility in PBS (pH 7.4) was greater than 100 μM, indicating that they are both soluble compounds. The permeability investigations (P_eff) by PAMPA indicated that PINL had higher permeability than PDG (p < 0.05). Both components represented moderate plasma protein binding activities (average binding rate in human plasma: PINL 89.03%, PDG 45.21%) and low metabolic rate (t_1/2 in human liver microsome: PINL 1509.5 min, PDG 1004.8 min). Furthermore, the results of pharmacokinetic studies indicated that PINL might be eliminated less quickly than PDG from the rat plasma, and its cumulative urinary excretion was much lower than that of PDG. The phenylephrine-induced aortic rings demonstrated concentration-dependent vasorelaxation in PDG, PINL, or their combination group. The vasorelaxant effects of PINL were more obvious than those of PDG, whereas the vasorelaxant effect of the combinations was significantly better than that of the single component (p < 0.05). The similarity or difference between PINL and its diglucoside in these pharmaceutical aspects may offer valuable insights into the further exploration of lignans and might contribute to relevant studies involving natural products with similar molecular structure and their glucosides.