The Peculiar Difficulties of Therapeutic Trials for Multiple Sclerosis

Meta-analysis of clinical studies of the efficacy of plasma exchange in the treatment of chronic progressive multiple sclerosis

OBJECTIVE

To examine the hypothesis that addition of therapeutic plasma exchange (TPEX) to an immunosuppressive drug regimen increases that regimen's efficacy to halt the progression of chronic progressive multiple sclerosis (CPMS).

METHODS

The literature was searched for prospective controlled clinical trials evaluating the efficacy of TPEX in CPMS. Six studies were eligible for meta-analysis. Their results were combined, using Cochran's and Peto's methods. Three outcome measures were studied: 1) the change in Kurtzke's disability status scale (DSS) scores, 2) the relative odds of neurologic decline by 1 or more DSS grades, and 3) the relative odds of neurologic improvement by 1 or more DSS grades, in the treatment versus the comparison group of patients. Reported results of neurologic evaluations at 6, 12, 24, and 36 months of follow-up were analyzed separately.

RESULTS

TPEX significantly (P < .05) reduced the proportion of patients who experienced neurologic decline (by 1 or more DSS grades) at 12 months of follow-up (relative odds of decline = 0.441, 95% confidence interval = 0.210-0.929).

CONCLUSIONS

There is a need for further clinical research into the possibility of a beneficial effect of TPEX in patients with CPMS likely to experience neurologic decline over the ensuring 12 months. Targeting treatment to a particular subgroup of CPMS patients may be necessary for TPEX to prove effective.

Multiple sclerosis and prions

The etiology of Multiple Sclerosis (MS) is unknown. Existing epidemiologic data suggests that MS can be an infectious disease. MS used to be classified as one of the 'slow infections'--many of these are caused by prions. Prions are small, proteinaceous, infectious particles--distinguished from viruses by the absence of intrinsic nucleic acids. In a contrast to the 'classic' prional diseases (Kuru, Scrapie or Creutzfeldt-Jacob Disease) that in CNS affect primarily neurons, the 'target' cell in MS is an oligodendrocyte. This may explain differences in disease presentation. This paper presents a pathophysiological model of MS based on the assumption that MS is a prional disease. Processes leading to the demyelination in Multiple Sclerosis seem also to involve lymphocytes, astrocytes and macrophages as well as the interferon system.

Preferential reductions in lymphocyte sub-populations induced by monthly pulses of chlorambucil: studies in patients with chronic progressive multiple sclerosis

Thirty-three patients with chronic progressive multiple sclerosis (MS) were assigned to intervention groups receiving monthly pulses of chlorambucil (CB) for about one year. The monthly doses ranged from 0.4 to 1.5 mg/kg. Administration of CB resulted in preferential reduction in different lymphocyte subsets which was dose- and time-dependent. The number of B-cells (CD20) decreased more rapidly than NK-cells (CD16, CD56, CD16+CD56+) or T-cell (CD3) and T-cells subsets (CD4 and CD8). At 1.2 mg/kg, CB administration resulted in a preferential drop of T-suppressor/cytotoxic cells (CD8) compared with T-helper cells (CD4), and of the less mature "virgin" CD4 cells (CD4+CD45RA+) compared with "memory" CD4 cells (CD4+CD45RA-). The expression of activation markers (transferrin receptor, CALLa, HLA-Dr and CD38[OKT10]) within CD4, CD8 or CD20 lymphocytes was not altered by CB administration. Our data, which show that CB administration results in a preferential fall in B-cell numbers, contrast with the effects of long-term administration of the related immunosuppressive drugs, azathioprine and cyclophosphamide.