Longitudinal serum biomarker screening identifies malate dehydrogenase 2 as candidate prognostic biomarker for Duchenne muscular dystrophy

Abstract

Background Duchenne muscular dystrophy (DMD) is a fatal disease for which no cure is available. Clinical trials have shown to be largely underpowered due to inter-individual variability and noisy outcome measures. The availability of biomarkers able to anticipate clinical benefit is highly needed to improve clinical trial design and facilitate drug development.Methods In this study, we aimed to appraise the value of protein biomarkers to predict prognosis and monitor disease progression or treatment outcome in patients affected by DMD. We collected clinical data and 303 blood samples from 157 DMD patients in three clinical centres; 78 patients contributed multiple blood samples over time, with a median follow-up time of 2 years. We employed linear mixed models to identify biomarkers that are associated with disease progression, wheelchair dependency, and treatment with corticosteroids and performed survival analysis to find biomarkers whose levels are associated with time to loss of ambulation. Results Our analysis led to the identification of 21 proteins whose levels significantly decrease with age and nine proteins whose levels significantly increase. Seven of these proteins are also differentially expressed in non-ambulant patients, and three proteins are differentially expressed in patients treated with glucocorticosteroids. Treatment with corticosteroids was found to partly counteract the effect of disease progression on two biomarkers, namely, malate dehydrogenase 2 (MDH2, P = 0.0003) and ankyrin repeat domain 2 (P = 0.0005); however, patients treated with corticosteroids experienced a further reduction on collagen 1 serum levels (P = 0.0003), especially following administration of deflazacort. A time to event analysis allowed to further support the use of MDH2 as a prognostic biomarker as it was associated with an increased risk of wheelchair dependence (P = 0.0003). The obtained data support the prospective evaluation of the identified biomarkers in natural history and clinical trials as exploratory biomarkers. Conclusions We identified a number of serum biomarkers associated with disease progression, loss of ambulation, and treatment with corticosteroids. The identified biomarkers are promising candidate prognostic and surrogate biomarkers, which may support drug developers if confirmed in prospective studies. The serum levels of MDH2 are of particular interest, as they correlate with disease stage and response to treatment with corticosteroids, and are also associated with the risk of wheelchair dependency and pulmonary function.

Duchenne Muscular Dystrophy: recent advances in protein biomarkers and the clinical application

“…Over time, these biomarkers have declining abundance trajectories, as the disease progresses [107] most likely correlating with the decreasing muscle mass. The serum and/or plasma levels of CA3, MDH2, MYOM3, myosin, and troponins in DMD have been confirmed in several studies as potential disease progression monitoring biomarkers [34,36,68,70,84,92,108]. In addition, serum MDH2 has also been identified as a predictor of loss of ambulation and associated with response to steroid treatment in a longitudinal study [84] and MYOM3 as a therapy responsive biomarker in antisense oligonucleotide-mediated exon-skipping treated mdx mice [77].…”

“…The increasing availability of validated antibodies for protein profiling [83] enabled discovery of potential biomarkers using a suspension bead array platform [36,84]. This technology allows antibody-mediated capturing of protein targets to unique color coded beads and detection of the captured molecule through a covalently bound fluorescent label [36,85].…”

“…One of the muscle-specific proteins released into the blood stream of DMD patients is creatine kinase (CK). CK is elevated in DMD patients and declines as the diseases progresses [36,84,97,98]. Its increased activity has also been used as an indicator of muscle damage in clinical practice [71].…”

“…functional, cardiac status, indicating that no single biomarker can be expected to describe the disease progression. As the disease progresses the abundance of several blood biomarkers, in particular muscle-specific proteins, follow a declining trajectory that eventually plateaus in late teens, 1-2 years subsequent loss of ambulation [84,124]. This variation pattern makes such biomarkers more informative during the early stages of the disease in contrast to the late stages.…”

“…Furthermore, the biomarker's context of use defined during the discovery phase is not necessarily confirmed in the validation or qualification phase. The trajectory of muscle function associated biomarkers indicates that they are potential disease progression biomarkers that decrease as the disease progresses [84]. However, this raises the question whether such biomarkers are useful disease progression biomarkers throughout the course of the disorder, as their abundance may decrease below the limit of detection of the quantification assay.…”