Analysis of a compartmental model of endogenous immunoglobulin G metabolism with application to multiple myeloma

Immunoglobulin G (IgG) metabolism has received much attention in the literature for two reasons: (i) IgG homeostasis is regulated by the neonatal Fc receptor (FcRn), by a pH-dependent and saturable recycling process, which presents an interesting biological system; (ii) the IgG-FcRn interaction may be exploitable as a means for extending the plasma half-life of therapeutic monoclonal antibodies, which are primarily IgG-based. A less-studied problem is the importance of endogenous IgG metabolism in IgG multiple myeloma. In multiple myeloma, quantification of serum monoclonal immunoglobulin plays an important role in diagnosis, monitoring and response assessment. In order to investigate the dynamics of IgG in this setting, a mathematical model characterizing the metabolism of endogenous IgG in humans is required. A number of authors have proposed a two-compartment nonlinear model of IgG metabolism in which saturable recycling is described using Michaelis-Menten kinetics; however it may be difficult to estimate the model parameters from the limited experimental data that are available. The purpose of this study is to analyse the model alongside the available data from experiments in humans and estimate the model parameters. In order to achieve this aim we linearize the model and use several methods of model and parameter validation: stability analysis, structural identifiability analysis, and sensitivity analysis based on traditional sensitivity functions and generalized sensitivity functions. We find that all model parameters are identifiable, structurally and taking into account parameter correlations, when several types of model output are used for parameter estimation. Based on these analyses we estimate parameter values from the limited available data and compare them with previously published parameter values. Finally we show how the model can be applied in future studies of treatment effectiveness in IgG multiple myeloma with simulations of serum monoclonal IgG responses during treatment

Epidemiological landscape of young patients with multiple myeloma diagnosed before 40 years of age: the French experience.

Multiple myeloma (MM) is rare in young patients, especially before age 40 years at diagnosis, representing <2% of all patients with MM. Little is known about the disease characteristics and prognosis of these patients. In this study, we examined 214 patients diagnosed with MM at age ≤40 years over 15 years, in the era of modern treatments. Among them, 189 patients had symptomatic MM. Disease characteristics were similar to older patients: 35% had anemia, 17% had renal impairment, and 13% had hypercalcemia. The staging was ISS-1 in 52.4%, ISS-2 in 27.5%, and ISS-3 in 20.1%. Overall, 18% of patients had high-risk cytogenetics [del 17p and/or t(4;14)]. Ninety percent of patients received intensive chemotherapy followed by autologous stem cell transplant, and 25% of patients had allogeneic stem cell transplant predominantly at time of relapse. The median follow-up was 76 months, the estimated median overall survival was 14.5 years, and the median progression free-survival was 41 months. In multivariate analysis, bone lesions (hazard ratio [HR], 3.95; P = .01), high ISS score (HR, 2.14; P = .03), and high-risk cytogenetics (HR, 4.54; P < .0001) were significant risk factors for poor outcomes. Among predefined time-dependent covariables, onset of progression (HR, 13.2; P < .0001) significantly shortened overall survival. At 5 years, relative survival compared with same age- and sex-matched individuals was 83.5%, and estimated standardized mortality ratio was 69.9 (95% confidence interval, 52.7-91.1), confirming that MM dramatically shortens the survival of young patients despite an extended survival after diagnosis

Development and Validation of a Cytogenetic Prognostic Index Predicting Survival in Multiple Myeloma

International audienc

Heavy + light chain analysis to assign myeloma response is analogous to the IMWG response criteria

IF 2.755International audienceAutomated serum heavy + light chain (HLC) immunoassays can measure the intact immunoglobulins of each light chain type separately. We though to compare HLC assays with electrophoretic techniques in determining International Myeloma Working Group (IMWG) response criteria. 114 myeloma patients from 2 trials were included. HLC measurements were made utilizing archived sera and response assessments compared with those based on electrophoretic analysis at the time of the trials. Assessments at ∼90 days and maximal response were compared as was the power of the 2 techniques for predicting later responses, overall survival, and progression. The kappa statistic indicated good agreement between the 2 methods for determining IMWG response criteria, although HLC measurements might give better predictions of subsequent responses and frequently gave an earlier indication of change. HLC measurements could represent an alternative to electrophoretic techniques in determining IMWG response. Validation with a greater range of patient responses is needed for confirmation

Improved survival in multiple myeloma during the 2005-2009 and 2010-2014 periods

International audienc

Salvage therapy post pomalidomide-based regimen in relapsed/refractory myeloma

IF 3.083International audienceThe combination of pomalidomide and low-dose dexamethasone (Pom-Dex) has proved effective and safe in patients with end-stage relapsed/refractory multiple myeloma (RRMM), otherwise characterized by a very poor outcome. MM remains an incurable disease with unavoidable relapses, and the outcome after pomalidomide is still dismal. However, some patients demonstrate prolonged survival even beyond pomalidomide therapy.We sought to analyze the treatment of RRMM patients following Pom-Dex therapy and the response and survival after this next treatment line.We studied 134 patients treated with Pom-Dex until progression across two IFM studies. Seventy percent of these patients received further therapy after Pom-Dex. Among the treated patients, one third responded and one third maintained stable disease. The median OS for treated patients was 12 months (6.5;17), with 22 and 12.5% of patients surviving beyond 2 and 3 years, respectively. The factors associated with a better outcome were exposure to a triplet-based regimen containing a novel agent, response to therapy, absence of adverse cytogenetic, and a longer time from diagnosis to post pomalidomide therapy.This study suggests that patients relapsing after Pom-Dex therapy can still benefit from a further line of treatment. A subset of these treated patients even displayed a prolonged OS, while the prognosis remained very poor without treatment. An active approach could therefore be recommended even in this adverse situation, however guided by the patients' prognosis factors