Pharmacokinetic modelling of pentoxifylline and lisofylline after oral and intravenous administration in mice

Nanoparticulate tablet dosage form of lisofylline-linoleic acid conjugate for type 1 diabetes: in situ single-pass intestinal perfusion (SPIP) studies and pharmacokinetics in rat

Lisofylline (LSF) is an anti-inflammatory molecule with high aqueous solubility and rapid metabolic interconversion to its parent drug, pentoxifylline (PTX) resulting in very poor pharmacokinetic (PK) parameters, necessitating high dose and dosing frequency. In the present study, we resolved the physicochemical and pharmacokinetic limitations associated with LSF and designed its oral dosage form as a tablet for effective treatment in type 1 diabetes (T1D). Self-assembling polymeric micelles of LSF (lisofylline-linoleic acid polymeric micelles (LSF-LA PLM)) were optimized for scale-up (6 g batch size) and lyophilized followed by compression into tablets. Powder blend and tablets were evaluated as per USP. LSF-LA PLM tablet so formed was evaluated for in vitro release in simulated biological fluids (with enzymes) and for cell viability in MIN-6 cells. LSF-LA PLM in tablet formulation was further evaluated for intestinal permeability (in situ) along with LSF and LSF-LA self-assembled micelles (SM) as controls in a rat model using single-pass intestinal perfusion (SPIP) study. SPIP studies revealed 1.8-fold higher oral absorption of LSF-LA from LSF-LA PLM as compared to LSF-LA SM and ~5.9-fold higher than LSF (alone) solution. Pharmacokinetic studies of LSF-LA PLM tablet showed greater C_max than LSF, LSF-LA, and LSF-LA PLM. Designed facile LSF-LA PLM tablet dosage form has potential for an immediate decrease in the postprandial glucose levels in patients of T1D.

Influence of inflammatory disorders on pharmacokinetics of lisofylline in rats: implications for studies in humans

1. Despite the number of favourable properties of lisofylline (LSF), clinical trials on this compound have not yielded the expected results yet. 2. The aims of this study were to evaluate the pharmacokinetics of LSF enantiomers in rats following intravenous, oral and subcutaneous administration of (±)-LSF and to assess the influence of experimental inflammatory disorders, such as multiple organ dysfunction syndrome and severe sepsis on LSF pharmacokinetics. 3. In addition, based on the results obtained an attempt was made to elucidate the possible reasons for the failure of LSF therapy in clinical trials carried out in patients with severe inflammatory disorders. 4. A subcutaneous route of (±)-LSF administration to rats is more favourable than an oral one due to a high bioavailability and a fast absorption of both LSF enantiomers. Pharmacokinetics of LSF in rats is significantly influenced by inflammatory diseases. Too low LSF serum levels might have been one of the reasons for clinical trial failures. A long-term i.v. infusion of LSF seems to be more effective compared to short-term multiple infusions that were used in clinical trials, as it may provide concentrations above IC₅₀ for inhibition of both TNF-alpha release and cAMP degradation in serum for a longer period of time.

PK/PD studies on non-selective PDE inhibitors in rats using cAMP as a marker of pharmacological response

In recent years, phosphodiesterase (PDE) inhibitors have been frequently tested for the treatment of experimental inflammatory and immune disorders. It is suggested that anti-inflammatory properties of PDE inhibitors are related to their ability to increase cAMP levels. The aim of this study was to verify the hypothesis that cAMP may be a useful marker of pharmacological response following administration of non-selective PDE inhibitors (pentoxifylline and (±)-lisofylline) to endotoxemic rats. Male Wistar rats were administered LPS (1 mg kg⁻¹, i.v.) simultaneously with either compound given at two doses (40 and 80 mg kg⁻¹, i.v.). Levels of cAMP and both compounds in animal plasma were measured by the validated HPLC methods. Pharmacokinetic-pharmacodynamic analysis was performed using basic and modified indirect response (IDR) models II in Phoenix WinNonlin. The results of this study indicate that, in contrast to pentoxifylline, (±)-lisofylline demonstrates a non-linear pharmacokinetics in rats with endotoxemia. In vitro study using human recombinant PDE4B and PDE7A revealed the occurrence of additive interaction between studied compounds. Moreover, (±)-lisofylline is a more potent inhibitor of PDEs compared to pentoxifylline, as evidenced by lower IC₅₀ values. Following administration of both compounds, levels of cAMP in rat plasma increased in a dose-dependent manner. The modified IDR model II better described cAMP levels over time profiles. The validity of the proposed marker was confirmed by measuring plasma TNF-α levels in the studied animals. In conclusion, cAMP may be used in future preclinical and clinical studies of some PDE inhibitors to evaluate the drug concentration–effect relationship.

Physiologically based modeling of lisofylline pharmacokinetics following intravenous administration in mice

Lisofylline (LSF), is the R-(−) enantiomer of the metabolite M1 of pentoxifylline, and is currently under development for the treatment of type 1 diabetes. The aim of the study was to develop a physiologically based pharmacokinetic (PBPK) model of LSF in mice and to perform simulations in order to predict LSF concentrations in human serum and tissues following intravenous and oral administration. The concentrations of LSF in serum, brain, liver, kidneys, lungs, muscle, and gut were determined at different time points over 60 min by a chiral HPLC method with UV detection following a single intravenous dose of LSF to male CD-1 mice. A PBPK model was developed to describe serum pharmacokinetics and tissue distribution of LSF using ADAPT II software. All pharmacokinetic profiles were fitted simultaneously to obtain model parameters. The developed model characterized well LSF disposition in mice. The estimated intrinsic hepatic clearance was 5.427 ml/min and hepatic clearance calculated using the well-stirred model was 1.22 ml/min. The renal clearance of LSF was equal to zero. On scaling the model to humans, a good agreement was found between the predicted by the model and presented in literature serum LSF concentration–time profiles following an intravenous dose of 3 mg/kg. The predicted LSF concentrations in human tissues following oral administration were considerably lower despite the twofold higher dose used and may not be sufficient to exert a pharmacological effect. In conclusion, the mouse is a good model to study LSF pharmacokinetics following intravenous administration. The developed PBPK model may be useful to design future preclinical and clinical studies of this compound.

Pretreatment with R(+)-verapamil significantly reduces mortality and cytokine expression in murine model of septic shock

It is well known that cytokines play an important role in the pathogenesis of sepsis and septic shock. There is evidence indicating that the membrane transporter, P-glycoprotein (P-gp), may be involved in the release of cytokines, such as IL-2, IL-4 or IFN-gamma. The aim of this study was to assess the influence of P-gp inhibitor, R(+)-verapamil, on cytokine expression in serum and tissues as well as survival rate of mice with LPS-induced septic shock. These effects were compared with the response to treatment with pentoxifylline, lisofylline, and prednisolone administered alone or after pretreatment with R(+)-verapamil. When given as a single agent, R(+)-verapamil significantly decreased serum levels of TNF-alpha and IFN-gamma and protected mice from endotoxin lethality. Moreover, it decreased up-regulated by LPS TNF-alpha gene expression in the liver and lungs. Given concomitantly with immunomodulatory compounds, it enhanced their beneficial impact on the survival of mice with septic shock. The highest increase in survival rate was observed in combination with pentoxifylline (7% vs. 67%). The most striking differences observed between saline and R(+)-verapamil pretreated animals on combination therapy included down-regulation of TNF-alpha, higher levels of IL-6, and decreased IFN-gamma concentrations. These results suggest that P-gp may be involved in the release of IFN-gamma, and possibly also TNF-alpha, in mice with septic shock. R(+)verapamil improves survival of mice receiving a lethal dose of LPS and significantly potentiates the protective effect of pentoxifylline and prednisolone against LPS-induced lethality, probably as a result of both P-gp inhibition and a synergistic interaction at the gene level.