Diminished production of type-I interferons and interleukin-2 in patients with multiple sclerosis

Several lines of evidence have supported the role of immunological mechanisms in the pathogenesis of multiple sclerosis (MS) and new immunomodulatory strategies for its treatment, e.g. subcutaneous application of interferon (IFN)-beta, have emerged. We investigated the ability of peripheral blood mononuclear cells (PBMC) in 21 consecutive patients with clinically definite MS to produce interferons and lymphokines in response to viral or mitogenic stimulation. Ten patients showed clinical signs of disease activity (acute relapse) and 11 patients were in a stable condition. Additionally, white blood count, leukocyte differentiation and lymphocyte subtyping were performed. A group of age-related healthy blood donors served as control (n=20). There was no difference between patients and controls in the production of IFN-gamma, tumor necrosis factor (TNF)-alpha and soluble interleukin (IL)-2 receptor. IFN-alpha and IFN-beta responsiveness, however, was significantly lower in patients with stable disease than in patients with active disease and controls (p<0.001). Furthermore, secretion of IL-2 after stimulation was significantly diminished in both patient groups as compared to the control group (p<0.01). Analysis of T-cell subsets revealed a significantly lower amount of CD8+ T-cells in patients with stable disease, leading to a significantly higher CD4/CD8 ratio in this group as compared to patients with active disease. Our study depicted an IL-2 deficiency in MS patients which is shared with other autoimmune diseases. In addition, our findings suggest that the ability to produce type-I IFNs, IFN-alpha and IFN-beta, is primarily impaired in MS patients and changes in correlation to the course of disease activity.

Current developments in pharmacogenomics of multiple sclerosis

Pharmacogenomics has a significant potential to impact how we treat diseases. It involves targeting genetically identifiable populations with therapeutic interventions that promises to yield immediate positive health outcomes with lower or no side effects. The 'trial and error' method of treatment will no longer be necessary with the successful implementation of personalized medicine. The following is an overview of some new developments in pharmacogenomics of multiple sclerosis, and how it has the potential to improve future treatment.

Impact of dose selection on parameter estimation using a rapid binding approximation model of target-mediated drug disposition

The purpose of this study was to examine the role of dose selection on population pharmacokinetic (PK) parameter estimation using a rapid binding approximation of a target-mediated drug disposition (TMDD) model previously developed for interferon-β (IFN-β). A total of 50 replicate datasets each containing 100 subjects were created using NONMEM. The study design included IV injection of IFN-β followed by the SC route in a crossover manner, with each dose and route of administration separated by a 1,000 h washout period. Serial plasma PK samples were simulated up to 48 h for all subjects following each dose. Population mean PK parameters were re-estimated in NONMEM for each simulated dataset using the same TMDD model after including the following doses (MIU/kg): (A) 1, 3 and 10 (original study); (B) 1, 3 and 7; (C) 1, 3 and 5; (D) 1, 3 and 4; (E) 1 and 3; (F) 3 and 10; or (G) 10 MIU/kg only. Bias in the model fit was assessed by calculating the percent prediction error (PE%) for each of the population mean PK parameters relative to the estimates obtained from the fit to the 1, 3, and 10 MIU/kg doses (Case A). Relatively unbiased population mean PK parameter estimates (median PE% <8%) were obtained only when the study design included 1, 3 and a minimum higher dose of 7 MIU/kg. Bias increased for various parameters when the highest dose was less than 7 MIU/kg along with 1 and 3 MIU/kg being the low and intermediate dose levels. An increase in the bias for binding capacity, R(tot), and the equilibrium dissociation constant, K (D), was observed as the highest dose included in the dataset was reduced from 5 to 3 MIU/kg (median PE% ranged from -4.71 to -23.9% and -4.76 to -34.6%). Similar increases in the range of median PE% were also observed for other model parameters as the highest dose was reduced from 5 to 3 MIU/kg. Severely biased results were obtained from the study design that included only the 10 MIU/kg dose (Case G) suggesting that it is not sufficient to study just a high dose group. This bias was greatly reduced (median PE% <14%) for all parameters except K (D) when the 3 and 10 MIU/kg doses were co-modeled (Case F). Plots of the PE% for R(tot) and K (D) versus the molar ratio of maximum dose to R(tot) suggest that study designs should evaluate at least one IFN-β dose 3.5- to 4-fold higher than R(tot) along with the 1 and 3 MIU/kg dose levels to obtain unbiased population PK parameter estimates. In summary, for the IFN-β model and study design, dose selection influences the ability to generate relatively unbiased population mean TMDD parameter estimates, which is based on maximum dose levels relative to R(tot). This simulation study highlights the role of dose selection in optimal study design strategies for drugs such as IFN-β that exhibit TMDD properties.