Interactions of prednisolone and other immunosuppressants used in dual treatment of systemic lupus erythematosus in lymphocyte proliferation assays

Physiologically Based Pharmacokinetics of Lysosomotropic Chloroquine in Rat and Human

A semimechanistic physiologically based pharmacokinetic (PBPK) model for chloroquine (CQ), a highly lysosomotropic weak base, was applied to digitized rat and human concentration versus time data. The PBPK model in rat featured plasma and red blood cell (RBC) concentrations, extensive and apparent nonlinear tissue distribution, fitted hepatic and renal intrinsic clearances, and a plasma half-life of about 1 day. Tissue-to-plasma CQ ratios at 50 hours after dosing were highest in lung, kidney, liver, and spleen (182-318) and lower in heart, muscle, brain, eye, and skin (11-66). The RBC-to-plasma ratio of 11.6 was assumed to reflect cell lipid partitioning. A lysosome-based extended model was used to calculate subcellular CQ concentrations based on tissue mass balances, fitted plasma, interstitial and free cytosol concentrations, and literature-based pH and pKa values. The CQ tissue component concentrations ranked as follows: lysosome > > acidic phospholipid > plasma = interstitial = cytosol ≥ neutral lipids. The extensive lysosome sequestration appeared to change over time and was attributed to lowering pH values caused by proton pump influx of hydrogen ions. The human-to-rat volume of distribution (Vss) ratio of 7 used to scale rat tissue partitioning to human along with estimation of hepatic clearance allowed excellent fitting of oral-dose PK (150-600 mg) of CQ with a 50-day half-life in humans. The prolonged PK of chloroquine was well characterized for rat and human with this PBPK model. The calculated intratissue concentrations and lysosomal effects have therapeutic relevance for CQ and other cationic drugs. SIGNIFICANCE STATEMENT: Sequestration in lysosomes is a major factor controlling the pharmacokinetics and pharmacology of chloroquine and other cationic drugs. This report provides comprehensive physiologic modeling of chloroquine distribution in tissues and overall disposition in rat and human that reveals expected complexities and inferences related to its subcellular association with various tissue components.

Naturally Occurring Fc-Dependent Antibody From HIV-Seronegative Individuals Promotes HIV-Induced IFN-α Production

A majority of adults without HIV infection and with a low risk of HIV-exposure have plasma IgG antibodies that enhance the rate and magnitude of HIV-induced interferon alpha (IFN-α) production. Fc-dependent IgG-HIV complexes induce IFN-α rapidly and in high titers in response to HIV concentrations that are too low to otherwise stimulate an effective IFN-α response. IFN-α promoting antibody (IPA) counters HIV-specific inhibition of IFN-α production, and compensates for the inherent delay in IFN-α production common to HIV infection and other viruses. Naturally occurring IPA has the potential to initiate a potent IFN-α response early in the course of HIV mucosal invasion in time to terminate infection prior to the creation of a pool of persistently infected cells. The current study adds IPA as a mediator of an Fc-dependent antiviral state capable of preventing HIV infection.

Therapy and pharmacological properties of hydroxychloroquine and chloroquine in treatment of systemic lupus erythematosus, rheumatoid arthritis and related diseases

OBJECTIVES

This review examines the pharmacokinetics, modes of action and therapeutic properties of the anti-malarial drugs, hydroxychloroquine (HCQ) and chloroquine (CQ), in the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and related conditions, as well as osteoarthritis (OA).

KEY FINDINGS

Both HCQ and CQ have historically been employed successfully for the treatment of SLE and RA for over 70 years. HCQ has been used extensively for SLE where it has a good reputation for controlling the dermatological complications in SLE. It has also been reported to effectively control the symptoms of Sjøgren's syndrome, as well as preventing thrombosis in phospholipid antibody (aPL) syndrome. In RA and SLE, HCQ is preferred because of the lower incidence of gastrointestinal adverse reactions compared with CQ and it might have a lower risk of ocular adverse reactions. There is increasing evidence that HCQ may reduce atherosclerosis and risks of cardiovascular disease in rheumatic patients. Both HCQ and CQ have been shown to improve glycaemia and reduce the risks of type II diabetes mellitus. Although both HCQ and CQ are effective in low-moderate RA, HCQ is now preferred as part of combination therapy for more severe disease. The advantages of combination therapy are that the doses of the individual drugs may be lowered so reducing adverse reactions. Both HCQ and CQ are diastereoisomers, have basic properties and are given as the sulphate and phosphate salts. While being relatively well absorbed orally and with good bioavailability, they have long and variable plasma terminal elimination half-lives (approximately 40-60 days). This reflects their high volume of distribution, V D (HCQ 44,000L; CQ 65,000L) which extends into aqueous compartments, long mean residence time (HCQ 1300 h; CQ 900 h) and with about half the drugs (metabolites) undergoing renal clearance. The strong binding to melanin reflects the ocular injury and dermatological properties of these drugs. The consensus is that the occurrence of ocular adverse reactions can be minimised by close attention to the dose (which should be set on a body weight basis) with regular (e.g. quarterly) retinal examination. Although HCQ and CQ can pass through the placenta, the use of these drugs during pregnancy does not appear to risk harm to the baby and might be beneficial to the mother with SLE and her child by controlling the SLE disease activity, which is known to be an important factor affecting pregnancy outcome. The modes of action of HCQ and CQ in these arthritides represent somewhat of an enigma. Undoubtedly, these drugs have multiple actions related, in part, their ability to accumulate in lysosomes and autophagosomes of phagocytic cells as well as affecting MHC Class II expression and antigen presentation; actions of the production of pro-inflammatory cytokines [e.g. interleukin-1 (IL-1) tumour necrosis factor-α (TNFα)]; control of toll-like receptor-9 activation; and leucocyte generation of reactive oxygen species (ROS); i.e. antioxidant activity. The actions of these drugs on T and B cells are less clear but may depend on these leucocyte-mediated actions. Anti-malarials also protect against cytokine-mediated cartilage resorption. This and other actions may underlie the potential benefits in treating OA. The exact relationships of these various actions, mostly determined in vitro, have not been specifically defined in vivo or ex vivo in relation to clinical efficacy.

OUTCOMES

HCQ and CQ have a good reputation for being effective and relatively safe treatments in SLE, mild-moderate RA and Sjøgren's syndrome. There is need for (a) more information on their mode of action in relation to the control of these diseases, (b) scope for developing formulations that have improved pharmacokinetic and therapeutic properties and safety, and (c) further exploring their use in drug combinations not only with other disease modifying agents but also with biologics.

Interactions of everolimus and sorafenib in whole blood lymphocyte proliferation

PURPOSE

Everolimus is an immunosuppressant that blocks growth factor-mediated proliferation of hematopoietic cells by targeting the mammalian target of rapamycin (mTOR). Sorafenib is a multikinase inhibitor that inhibits cell proliferation by arresting cells in the G0-G1 phase of the cell cycle. These agents are under investigation as combination therapy for various cancers. Because the two drugs individually inhibit lymphocyte proliferation, this study examined the effects of everolimus and sorafenib on lymphocyte proliferation in order to anticipate possible immunosuppression.

METHODS

Inhibition of lymphocyte proliferation was evaluated ex vivo over a range of concentrations of these drugs, alone and in combination. Data analysis, using a population approach to characterize interactions, employed the Ariens noncompetitive interaction model, which was modified to accommodate interactions of the two drugs.

RESULTS

Everolimus alone caused partial inhibition of lymphocyte proliferation, with a mean IC(50) of 4.5 nM for females and 10.5 nM in males. Sorafenib alone caused complete inhibition, with a mean IC(50) of 11.4 μM and no difference between genders.

CONCLUSION

The population estimate for the interaction term was greater than 1, suggesting that the two drugs exert slight antagonism in terms of inhibition of lymphocyte proliferation.

Pharmacokinetics of prednisolone at steady state in young patients with systemic lupus erythematosus on prednisone therapy: an open-label, single-dose study

BACKGROUND

Current prednisone dosing in the treatment of young patients with childhood-onset systemic lupus erythematosus (cSLE) is largely based on achieving balance between therapeutic efficacy and toxicity, with weight-based dosing a common clinical practice. Despite the widespread use of prednisone, few attempts have been made to improve its clinical dosing regimen, and response to prednisone therapy remains variable.

OBJECTIVE

The purpose of this study was to characterize the pharmacokinetic (PK) properties of prednisolone, the metabolite of the prodrug prednisone, in cSLE patients and explore the relationship between PK properties and cSLE disease activity.

METHODS

Blood samples were taken 1 hour before the morning prednisone dose and at 20, 40, 60, and 90 minutes, and 2, 3, 4, 6, and 9 hours from 8 patients (ages 12-28 years) after an 8-hour fast. The mean weight-adjusted daily prednisone dose, stable for at least 30 days pre-study, was 0.29 mg/kg/d. PK analysis of prednisolone was performed using noncompartmental analysis with WinNonlin. cSLE disease activity was measured using the British Isles Lupus Assessment Group index and Systemic Lupus Erythematosus Disease Activity Index.

RESULTS

Mean total prednisolone AUC(0-9), prednisone CL/F at steady state, and half-life were 1094 (range, 467-2404) ng/h/mL, 11 (range, 6.7-13.7) L/hr, and 2.6 (range, 1.3-3.9) hours. Mean total prednisolone AUC(0-9) normalized to prednisone dose by weight was 4361 (range, 1136-9580) ng/h/mL/mg/kg. Mean total prednisolone C(max) normalized to prednisone dose by weight was 1097 (range, 301-2211) ng/mL/mg/kg at 1.84 (range, 0.48-4) hours (T(max)). Patients on prednisone had interindividual variability in prednisolone AUC(0-9) (61% CV) and dose-adjusted AUC(0-9) (58% CV).

CONCLUSIONS

Interindividual variability in systemic exposure to prednisolone in cSLE patients was observed.