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The combined antiretroviral therapy (cART) can efficiently suppress HIV replication, but the cessation of cART usually results in viral rebound, mostly due to the presence of viral reservoirs. The mesenteric lymphatic system, including mesenteric lymph nodes (MLNs), is an important viral reservoir into which antiretroviral drugs poorly penetrate. In this work, we proposed a novel lipophilic ester prodrug approach, combined with oral lipid-based formulation, to efficiently deliver lopinavir (LPV) to the mesenteric lymph and MLNs. A series of prodrugs was designed using an in-silico model for prediction of affinity to chylomicrons (CMs), and then synthesized. The potential for mesenteric lymphatic targeting and bioconversion to LPV in physiologically relevant media was assessed in vitro and ex vivo. Subsequently, LPV and selected prodrug candidates were evaluated for their in vivo pharmacokinetics and biodistribution in rats. Oral co-administration of lipids alone could not facilitate the delivery of unmodified LPV to the mesenteric lymphatic system and resulted in undetectable levels of LPV in these tissues. However, a combination of the lipophilic prodrug approach with lipid-based formulation resulted in efficient targeting of LPV to HIV reservoirs in mesenteric lymph and MLNs. The maximum levels of LPV in mesenteric lymph were 1.6- and 16.9-fold higher than protein binding-adjusted IC90 (PA-IC90) of LPV for HIV-1 (140 ng/mL) following oral administration of simple alkyl ester prodrug and activated ester prodrug, respectively. Moreover, the concentrations of LPV in MLNs were 1.1- and 7.2-fold higher than PA-IC90 following administration of simple alkyl ester prodrug and activated ester prodrug, respectively. Furthermore, the bioavailability of LPV was also substantially increased following oral administration of activated ester prodrug compared to unmodified LPV. This approach, especially if can be translated to other antiretroviral drugs, has potential for reducing

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

Bexarotene is currently marketed for treatment of cutaneous T-cell lymphoma and there has been growing interest in its therapeutic effectiveness for other cancers. Neuroprotective effects of bexarotene have also been reported. In this study, a simple, sensitive and cost-efficient bioanalytical method for determination of bexarotene in rat plasma was developed and fully validated. The method utilises protein precipitation with acetonitrile and liquid-liquid extraction with n-hexane-ethyl acetate (10:1, v/v). An HPLC-UV system with a Waters Atlantis C18 column and a mobile phase of acetonitrile-ammonium acetate buffer (10 mM, pH 4.1) at a ratio of 75:25 (v/v), flow rate 0.2 mL/min was used. Chromatograms were observed by a UV detector with wavelength set to 259 nm. Intra- and inter-day validations were performed and sample stability tests were conducted at various conditions. The applicability of the method was demonstrated by a pharmacokinetic study in rats. Intravenous bolus dose of 2.5 mg/kg was administered to rats and samples were obtained at predetermined time points. As a result, pharmacokinetic parameters of AUCinf (4668 ± 452 h ng/mL), C0 (6219 ± 1068 ng/mL) and t1/2 (1.15 ± 0.02 h) were obtained. In addition, the developed method was further applied to human and mouse plasma to assess the suitability of the method for samples from other species.

In this study, Caco-2 permeability results from different laboratories were compared. Six different sets of apparent permeability coefficient (Papp) values reported in the literature were compared to experimental Papp obtained in our laboratory. The differences were assessed by determining the root mean square error (RMSE) values between the datasets, which reached levels as high as 0.581 for the training set compounds, i.e. ten compounds with known effective human permeability (Peff). The consequences of these differences in Papp for prediction of oral drug absorption were demonstrated by introducing the Papp into the absorption and pharmacokinetics simulation software application GastroPlus™ for prediction of the fraction absorbed (Fa) in humans using calibrated “user-defined permeability models”. The RMSE were calculated to assess the differences between the simulated Fa and experimental values reported in the literature. The RMSE for Fa simulated with the permeability model calibrated using experimental Papp from our laboratory was 0.128. When the calibration was performed using Papp from literature datasets, the RMSE values for Fa were higher in all cases except one. This study shows quantitative lab-to-lab variability of Caco-2 permeability results and the potential consequences this can have in the use of these results for predicting intestinal absorption of drugs.

The association of lipophilic statins with plasma lipoproteins in the presence of disturbed acid-base balance can modify the pharmacokinetics and tissue distribution of these drugs, resulting in alteration in their efficacy and toxicity profiles. The purpose of this study is to elucidate the role of hyperlipidaemia alone or in combination with acidosis/alkalosis in the development and potentiation of statin-induced myotoxicity. Statins association with plasma lipoproteins was examined under conditions of physiological and altered pH levels. The effect of this association on cellular uptake and myotoxicity of statins was also assessed at different pH levels using C2C12 cells that overexpress lipoprotein lipase. Lipophilic simvastatin displayed considerable association with the non-polar lipoprotein fractions (triglyceride-rich lipoproteins and Low-density lipoprotein). This association contributed to increased cellular uptake of simvastatin by C2C12 cells through lipoprotein lipasemediated process, resulting in enhanced muscle toxicity in hyperlipidaemic conditions. Furthermore, a combination of low pH environment (representing acidosis) and hyperlipidaemia increased the association of simvastatin with plasma lipoproteins causing potentiation of cellular uptake and myotoxicity of this drug. Comorbidities such as hyperlipidaemia, especially when coincident with acidosis, can enhance statin-associated muscle toxicity, and therefore require extra caution by prescribing clinicians. Hydrophilic rather than lipophilic statins could be a preferable choice in this patient population.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

Bexarotene is currently marketed for treatment of cutaneous T-cell lymphoma and there has been growing interest in its therapeutic effectiveness for other cancers. Neuroprotective effects of bexarotene have also been reported. In this study, a simple, sensitive and cost-efficient bioanalytical method for determination of bexarotene in rat plasma was developed and fully validated. The method utilises protein precipitation with acetonitrile and liquid-liquid extraction with n-hexane-ethyl acetate (10:1, v/v). An HPLC-UV system with a Waters Atlantis C18 column and a mobile phase of acetonitrile-ammonium acetate buffer (10 mM, pH 4.1) at a ratio of 75:25 (v/v), flow rate 0.2 mL/min was used. Chromatograms were observed by a UV detector with wavelength set to 259 nm. Intra- and inter-day validations were performed and sample stability tests were conducted at various conditions. The applicability of the method was demonstrated by a pharmacokinetic study in rats. Intravenous bolus dose of 2.5 mg/kg was administered to rats and samples were obtained at predetermined time points. As a result, pharmacokinetic parameters of AUCinf (4668 ± 452 h ng/mL), C0 (6219 ± 1068 ng/mL) and t1/2 (1.15 ± 0.02 h) were obtained. In addition, the developed method was further applied to human and mouse plasma to assess the suitability of the method for samples from other species.

In this study, Caco-2 permeability results from different laboratories were compared. Six different sets of apparent permeability coefficient (Papp) values reported in the literature were compared to experimental Papp obtained in our laboratory. The differences were assessed by determining the root mean square error (RMSE) values between the datasets, which reached levels as high as 0.581 for the training set compounds, i.e. ten compounds with known effective human permeability (Peff). The consequences of these differences in Papp for prediction of oral drug absorption were demonstrated by introducing the Papp into the absorption and pharmacokinetics simulation software application GastroPlus™ for prediction of the fraction absorbed (Fa) in humans using calibrated “user-defined permeability models”. The RMSE were calculated to assess the differences between the simulated Fa and experimental values reported in the literature. The RMSE for Fa simulated with the permeability model calibrated using experimental Papp from our laboratory was 0.128. When the calibration was performed using Papp from literature datasets, the RMSE values for Fa were higher in all cases except one. This study shows quantitative lab-to-lab variability of Caco-2 permeability results and the potential consequences this can have in the use of these results for predicting intestinal absorption of drugs.

The association of lipophilic statins with plasma lipoproteins in the presence of disturbed acid-base balance can modify the pharmacokinetics and tissue distribution of these drugs, resulting in alteration in their efficacy and toxicity profiles. The purpose of this study is to elucidate the role of hyperlipidaemia alone or in combination with acidosis/alkalosis in the development and potentiation of statin-induced myotoxicity. Statins association with plasma lipoproteins was examined under conditions of physiological and altered pH levels. The effect of this association on cellular uptake and myotoxicity of statins was also assessed at different pH levels using C2C12 cells that overexpress lipoprotein lipase. Lipophilic simvastatin displayed considerable association with the non-polar lipoprotein fractions (triglyceride-rich lipoproteins and Low-density lipoprotein). This association contributed to increased cellular uptake of simvastatin by C2C12 cells through lipoprotein lipasemediated process, resulting in enhanced muscle toxicity in hyperlipidaemic conditions. Furthermore, a combination of low pH environment (representing acidosis) and hyperlipidaemia increased the association of simvastatin with plasma lipoproteins causing potentiation of cellular uptake and myotoxicity of this drug. Comorbidities such as hyperlipidaemia, especially when coincident with acidosis, can enhance statin-associated muscle toxicity, and therefore require extra caution by prescribing clinicians. Hydrophilic rather than lipophilic statins could be a preferable choice in this patient population.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

The association of lipophilic statins with plasma lipoproteins in the presence of disturbed acid-base balance can modify the pharmacokinetics and tissue distribution of these drugs, resulting in alteration in their efficacy and toxicity profiles. The purpose of this study is to elucidate the role of hyperlipidaemia alone or in combination with acidosis/alkalosis in the development and potentiation of statin-induced myotoxicity. Statins association with plasma lipoproteins was examined under conditions of physiological and altered pH levels. The effect of this association on cellular uptake and myotoxicity of statins was also assessed at different pH levels using C2C12 cells that overexpress lipoprotein lipase. Lipophilic simvastatin displayed considerable association with the non-polar lipoprotein fractions (triglyceride-rich lipoproteins and Low-density lipoprotein). This association contributed to increased cellular uptake of simvastatin by C2C12 cells through lipoprotein lipasemediated process, resulting in enhanced muscle toxicity in hyperlipidaemic conditions. Furthermore, a combination of low pH environment (representing acidosis) and hyperlipidaemia increased the association of simvastatin with plasma lipoproteins causing potentiation of cellular uptake and myotoxicity of this drug. Comorbidities such as hyperlipidaemia, especially when coincident with acidosis, can enhance statin-associated muscle toxicity, and therefore require extra caution by prescribing clinicians. Hydrophilic rather than lipophilic statins could be a preferable choice in this patient population.

Bexarotene is currently marketed for treatment of cutaneous T-cell lymphoma and there has been growing interest in its therapeutic effectiveness for other cancers. Neuroprotective effects of bexarotene have also been reported. In this study, a simple, sensitive and cost-efficient bioanalytical method for determination of bexarotene in rat plasma was developed and fully validated. The method utilises protein precipitation with acetonitrile and liquid-liquid extraction with n-hexane-ethyl acetate (10:1, v/v). An HPLC-UV system with a Waters Atlantis C18 column and a mobile phase of acetonitrile-ammonium acetate buffer (10 mM, pH 4.1) at a ratio of 75:25 (v/v), flow rate 0.2 mL/min was used. Chromatograms were observed by a UV detector with wavelength set to 259 nm. Intra- and inter-day validations were performed and sample stability tests were conducted at various conditions. The applicability of the method was demonstrated by a pharmacokinetic study in rats. Intravenous bolus dose of 2.5 mg/kg was administered to rats and samples were obtained at predetermined time points. As a result, pharmacokinetic parameters of AUCinf (4668 ± 452 h ng/mL), C0 (6219 ± 1068 ng/mL) and t1/2 (1.15 ± 0.02 h) were obtained. In addition, the developed method was further applied to human and mouse plasma to assess the suitability of the method for samples from other species.

In this study, Caco-2 permeability results from different laboratories were compared. Six different sets of apparent permeability coefficient (Papp) values reported in the literature were compared to experimental Papp obtained in our laboratory. The differences were assessed by determining the root mean square error (RMSE) values between the datasets, which reached levels as high as 0.581 for the training set compounds, i.e. ten compounds with known effective human permeability (Peff). The consequences of these differences in Papp for prediction of oral drug absorption were demonstrated by introducing the Papp into the absorption and pharmacokinetics simulation software application GastroPlus™ for prediction of the fraction absorbed (Fa) in humans using calibrated “user-defined permeability models”. The RMSE were calculated to assess the differences between the simulated Fa and experimental values reported in the literature. The RMSE for Fa simulated with the permeability model calibrated using experimental Papp from our laboratory was 0.128. When the calibration was performed using Papp from literature datasets, the RMSE values for Fa were higher in all cases except one. This study shows quantitative lab-to-lab variability of Caco-2 permeability results and the potential consequences this can have in the use of these results for predicting intestinal absorption of drugs.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

There has been an escalating interest in the medicinal use of Cannabis sativa in recent years. Cannabidiol (CBD) and ∆9-tetrahydrocannabinol (THC), the main constituents of Cannabis sativa, have well documented immunomodulatory effects in vitro and following administration of high doses to animals. However, these effects have not been clearly evident in humans following oral administration of cannabinoids, probably due to low systemic bioavailability. To note, cannabis and cannabis-containing medicines are currently used for symptomatic relief in autoimmune diseases, such as multiple sclerosis (MS), and in cases of immunodeficiency, such as in cancer patients on chemotherapy regimens. In this thesis, we aimed to elucidate the impact of enhancing the transport of orally administered cannabinoids to the intestinal lymphatic system, the major host of immune cells, on the immunomodulatory effects of cannabinoids. Oral administration of lipophilic cannabinoids with long-chain triglycerides (LCT) was investigated as a simple approach to enhance the intestinal lymphatic transport. The effect of LCT on the intraluminal processing of orally administered cannabinoids was assessed by means of in vitro lipolysis model. The results of in vitro lipolysis demonstrated that at least one-third of CBD dose would be solubilised and readily available for absorption to the enterocytes when orally administered in LCT-formulation. The association of CBD with chylomicrons (CM) in the enterocytes and subsequent intestinal lymphatic transport was estimated using an in silico model, in vitro association by artificial CM-like lipid particles, and ex vivo uptake by plasma-derived CM from rats and humans. The results of CM association studies revealed high intestinal lymphatic transport potential for CBD in rats and humans. Similar high lymphatic transport potential was also reported for THC in our laboratory. Oral co-administration of CBD and THC with LCT to rats increased the systemic exposure

Bexarotene is currently marketed for treatment of cutaneous T-cell lymphoma and there has been growing interest in its therapeutic effectiveness for other cancers. Neuroprotective effects of bexarotene have also been reported. In this study, a simple, sensitive and cost-efficient bioanalytical method for determination of bexarotene in rat plasma was developed and fully validated. The method utilises protein precipitation with acetonitrile and liquid-liquid extraction with n-hexane-ethyl acetate (10:1, v/v). An HPLC-UV system with a Waters Atlantis C18 column and a mobile phase of acetonitrile-ammonium acetate buffer (10 mM, pH 4.1) at a ratio of 75:25 (v/v), flow rate 0.2 mL/min was used. Chromatograms were observed by a UV detector with wavelength set to 259 nm. Intra- and inter-day validations were performed and sample stability tests were conducted at various conditions. The applicability of the method was demonstrated by a pharmacokinetic study in rats. Intravenous bolus dose of 2.5 mg/kg was administered to rats and samples were obtained at predetermined time points. As a result, pharmacokinetic parameters of AUCinf (4668 ± 452 h ng/mL), C0 (6219 ± 1068 ng/mL) and t1/2 (1.15 ± 0.02 h) were obtained. In addition, the developed method was further applied to human and mouse plasma to assess the suitability of the method for samples from other species.

The association of lipophilic statins with plasma lipoproteins in the presence of disturbed acid-base balance can modify the pharmacokinetics and tissue distribution of these drugs, resulting in alteration in their efficacy and toxicity profiles. The purpose of this study is to elucidate the role of hyperlipidaemia alone or in combination with acidosis/alkalosis in the development and potentiation of statin-induced myotoxicity. Statins association with plasma lipoproteins was examined under conditions of physiological and altered pH levels. The effect of this association on cellular uptake and myotoxicity of statins was also assessed at different pH levels using C2C12 cells that overexpress lipoprotein lipase. Lipophilic simvastatin displayed considerable association with the non-polar lipoprotein fractions (triglyceride-rich lipoproteins and Low-density lipoprotein). This association contributed to increased cellular uptake of simvastatin by C2C12 cells through lipoprotein lipasemediated process, resulting in enhanced muscle toxicity in hyperlipidaemic conditions. Furthermore, a combination of low pH environment (representing acidosis) and hyperlipidaemia increased the association of simvastatin with plasma lipoproteins causing potentiation of cellular uptake and myotoxicity of this drug. Comorbidities such as hyperlipidaemia, especially when coincident with acidosis, can enhance statin-associated muscle toxicity, and therefore require extra caution by prescribing clinicians. Hydrophilic rather than lipophilic statins could be a preferable choice in this patient population.

In this study, Caco-2 permeability results from different laboratories were compared. Six different sets of apparent permeability coefficient (Papp) values reported in the literature were compared to experimental Papp obtained in our laboratory. The differences were assessed by determining the root mean square error (RMSE) values between the datasets, which reached levels as high as 0.581 for the training set compounds, i.e. ten compounds with known effective human permeability (Peff). The consequences of these differences in Papp for prediction of oral drug absorption were demonstrated by introducing the Papp into the absorption and pharmacokinetics simulation software application GastroPlus™ for prediction of the fraction absorbed (Fa) in humans using calibrated “user-defined permeability models”. The RMSE were calculated to assess the differences between the simulated Fa and experimental values reported in the literature. The RMSE for Fa simulated with the permeability model calibrated using experimental Papp from our laboratory was 0.128. When the calibration was performed using Papp from literature datasets, the RMSE values for Fa were higher in all cases except one. This study shows quantitative lab-to-lab variability of Caco-2 permeability results and the potential consequences this can have in the use of these results for predicting intestinal absorption of drugs.