Efficacy and Safety of Vamorolone Over 48 Weeks in Boys With Duchenne Muscular Dystrophy: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Vamorolone is a dissociative agonist of the glucocorticoid receptor that has shown similar efficacy and reduced safety concerns in comparison with prednisone in Duchenne muscular dystrophy (DMD). This study was conducted to determine the efficacy and safety of vamorolone over 48 weeks and to study crossover participants (prednisone to vamorolone; placebo to vamorolone).

METHODS

A randomized, double-blind, placebo-controlled and prednisone-controlled clinical trial of 2 doses of vamorolone was conducted in participants with DMD, in the ages from 4 years to younger than 7 years at baseline. The interventions were 2 mg/kg/d of vamorolone and 6 mg/kg/d of vamorolone for 48 weeks (period 1: 24 weeks + period 2: 24 weeks) and 0.75 mg/kg/d of prednisone and placebo for the first 24 weeks (before crossover). Efficacy was evaluated through gross motor outcomes and safety through adverse events, growth velocity, body mass index (BMI), and bone turnover biomarkers. This analysis focused on period 2.

RESULTS

A total of 121 participants with DMD were randomized. Vamorolone at a dose of 6 mg/kg/d showed maintenance of improvement for all motor outcomes to week 48 (e.g., for primary outcome, time to stand from supine [TTSTAND] velocity, week 24 least squares mean [LSM] [SE] 0.052 [0.0130] rises/s vs week 48 LSM [SE] 0.0446 [0.0138]). After 48 weeks, vamorolone at a dose of 2 mg/kg/d showed similar improvements as 6 mg/kg/d for North Star Ambulatory Assessment (NSAA) (vamorolone 6 mg/kg/d-vamorolone 2 mg/kg/d LSM [SE] 0.49 [1.14]; 95% CI -1.80 to 2.78, p = 0.67), but less improvement for other motor outcomes. The placebo to vamorolone 6 mg/kg/d group showed rapid improvements after 20 weeks of treatment approaching benefit seen with 48-week 6 mg/kg/d of vamorolone treatment for TTSTAND, time to run/walk 10 m, and NSAA. There was significant improvement in linear growth after crossover in the prednisone to vamorolone 6 mg/kg/d group, and rapid reversal of prednisone-induced decline in bone turnover biomarkers in both crossover groups. There was an increase in BMI after 24 weeks of treatment that then stabilized for both vamorolone groups.

DISCUSSION

Improvements of motor outcomes seen with 6 mg/kg/d of vamorolone at 24 weeks of treatment were maintained to 48 weeks of treatment. Vamorolone at a dose of 6 mg/kg/d showed better maintenance of effect compared with vamorolone at a dose of 2 mg/kg/d for most (3/5) motor outcomes. Bone morbidities of prednisone (stunting of growth and declines in serum bone biomarkers) were reversed when treatment transitioned to vamorolone.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT03439670.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that for boys with DMD, the efficacy of vamorolone at a dose of 6 mg/kg/d was maintained over 48 weeks.

Agalactosyl IgG and beta-1,4-galactosyltransferase gene expression in rheumatoid arthritis patients and in the arthritis-prone MRL lpr/lpr mouse

Reduced galactosylation of immunoglobulin G (IgG) is well documented in rheumatoid arthritis (RA), but the reason for this defect is still unknown. There is some evidence supporting a defect in the biosynthetic pathway, and a reduction in the level of beta-1,4-galactosyltransferase (beta-1,4-GalTase) enzyme activity. Since glycosyltransferases are, in general, regulated at the level of transcription, we have measured the level of beta-1,4-GalTase gene expression in B cells from patients with RA and normal control individuals. We found no significant difference in mRNA levels for the transferase in these two groups (P > 0.7). MRL/Mp-lpr/lpr (MRL-lpr) mice develop a spontaneous arthritis with increased levels of agalactosyl IgG (G0). In spite of a significant reduction in the level of beta-1,4-GalTase mRNA in total spleen lymphocytes from MRL-lpr mice compared with the congenic MRL/Mp-(+/+) (MRL-(+/+) mice and with CBA/Ca mice, we found comparable levels of the beta-1,4-GalTase mRNA in purified B cells from both spleen and lymph nodes of the three strains. Amongst the lymphoid compartments examined, the spleen and peripheral blood were found to be the major contributors of G0 in MRL-lpr mice. These data indicate that in neither human RA, nor in an animal model of this disease, is reduced IgG galactosylation caused by impaired expression of the beta-1,4-GalTase gene in B lymphocytes. Furthermore, splenic B cells, which have normal levels of beta-1,4-GalTase mRNA, appear to be a major source of G0 in MRL-lpr mice.

Immunoglobulin VH-T cell receptor C alpha fusion mRNA resulting from chromosome inversion include the T cell-associated 5' exon ET

A human T cell lymphoma has been described in which an inversion of chromosome 14 results in fusion of an immunoglobulin heavy chain VH with a T cell receptor J alpha segment, potentially resulting in a chimeric protein with immunoglobulin VH region recognition plus T cell receptor effector functions. Examination of the mRNA species expressed from the IgT gene in this lymphoma shows a variety of forms but all IgT mRNA include the T cell-specific exon, ET, previously located in the distal part of the VH locus. In such mRNA species, the normal leader exon of the Ig VH segment, which encodes most of the hydrophobic signal peptide, is replaced by the short ET exon encoding mainly non-hydrophobic residues. Two forms of this mRNA exist which lack the Ig VH leader sequence and thus potentially yield non-membrane proteins in the T cell lymphoma.

Genomic structure and expression of human beta-1,4-galactosyltransferase

We have cloned 60 kilobases of overlapping human genomic DNA comprising the complete coding sequence of the biosynthetic enzyme beta-1,4-galactosyltransferase (GalTase). The human locus spans greater than 50 kb of genomic DNA and shows an exon structure similar to the mouse gene. However, contrary to the mouse and bovine systems, which yield two distinct transcripts, RNA blotting and RNase protection analysis of human mRNA derived from HeLa cells reveal only a single transcript, corresponding to the "short" form of the mouse and bovine transcripts. Furthermore, Northern analysis on a panel of human cell lines of varying tissue origin and morphology shows GalTase expression levels to be highly variable, consistent with the notion that GalTase expression and consequent cell-specific differences in galactosylation are at least partially regulated at the transcriptional level.

Alternating purine-pyrimidine tracts may promote chromosomal translocations seen in a variety of human lymphoid tumours

Chromosomal abnormalities which are prevalent in human lymphoid tumours are believed to be involved in tumour pathogenesis and their formation may be the result of erroneous activity by the V-D-J recombinase. Frequently, recombinase accessibility is provided by prior transcription of the chromosomal regions involved. However, this may not always be so and in those cases DNA structural features must be involved. Here we examine the breakpoints of three different tumour-specific translocations in the proximity of which we can detect no transcription; two of the translocations involve regions of chromosome 11, (t[11;14] [p13;q11] and t[11;14] [q13;q32]), and the third is a newly described translocation, t[7;10] [q35;q24], involving the T cell receptor beta-gene on chromosome 7. In each case, a purine--pyrimidine tract (potential Z-DNA) occurs near the translocation breakpoints. Four independent tumours with translocation t[11;14] [p13;q11] reveal a 2 kb breakpoint cluster region at 11p13 with an adjacent potential Z-DNA region of 62 bp in length; the analogous purine--pyrimidine tract at 10q24 is 32 bp long. The purine--pyrimidine tract at the 11q13 chromosome breakpoint, however, is very large as it covers approximately 800 bp. The position, surrounding sequence and potential Z-DNA tract of the human 11p13 TALLber is conserved in rodents. These results suggest that the purine--pyrimidine tracts, presumably in the Z-DNA form, can influence chromatin structure giving access for recombinase-mediated translocations. Such putative alterations of chromatin organization are supported by the observation of DNase I hypersensitive sites near to translocation breakpoints on 10q24 and 11p13.

Analysis of a T-cell tumor-specific breakpoint cluster at human chromosome 14q32

Cytogenetic abnormalities involving chromosome 14 band q32 are consistently observed in human T-cell tumors. Patients with ataxia-telangiectasia (AT) are especially prone to development of these tumors, which frequently carry either inversion inv(14)(q11;q32) or translocation t(14;14) (q11;q32) chromosomes. We have previously shown that the cytogenetic breakpoints of one t(14;14)(q11;q32) chromosome and two inv(14)(q11;q32) chromosomes in T-cell tumors from AT and non-AT patients join the T-cell receptor alpha chain locus, at chromosome band 14q11, with a region(s) at 14q32 centromeric of the immunoglobulin heavy chain variable region (VH) gene IGHV. We now show that these two inv(14) breakpoints are linked by 2.1 kb of germ-line 14q32 DNA and that the three breakpoints define, by in situ hybridization analysis, a single locus at chromosome band 14q32.1 located about 15-20 million base pairs on the centromeric side of the IGH locus. Sequence analysis of the 14q32.1 breakpoint regions indicates that abnormal recombination does not universally result from mistaken V-D-J joining (D = diversity region; J = joining region). Therefore, we invoke a tumor selection model to describe the role of the 14q32.1 locus in tumor development.

Human T-cell tumours containing chromosome 14 inversion or translocation with breakpoints proximal to immunoglobulin joining regions at 14q32

T-cell tumours are frequently found to carry an inversion of chromosome 14 (inv(14)) (q11;q32) or more rarely a chromosome 14 translocation t(14;14) with the same cytogenetic breakpoints (q11;q32). We have examined the molecular junctions of an inv(14) and a translocation t(14;14) using T-cell receptor (TCR) alpha joining (J) region probes. Both of these chromosomal abnormalities have breakpoints within the TCR J alpha locus at 14q11 and both have breakpoints which are proximal (i.e. on the centromeric side) to the immunoglobulin heavy chain JH region at 14q32. The cloned segments corresponding to the junctions at 14q32 are not associated with obvious immunoglobulin-like sequences. This contrasts to the previously described inv(14) in the cell line SUP-T1 and places a potential cluster of chromosome 14 breakpoints downstream of the Ig JH locus. The possible role of the varying breakpoints in the development of these tumours is discussed.

A human chromosome 8 region with abnormalities in B cell, HTLV-I+ T cell and c-myc amplified tumours

We describe a region of human chromosome 8q24 involved in variant Burkitt's lymphoma translocations, and where an interstitial deletion occurs in an HTLV-I+ ATL and three c-myc amplicons terminate. The deletion in the ATL DNA begins within 1.3 kb of the cloned Burkitt's lymphoma translocation breakpoint and ends within 700 bases of the cloned human equivalent of the rat retroviral insertion site, mis-1. In addition, three c-myc amplicons terminate in this region and the end of one of these (the colon carcinoma COL0320) maps within 12 kb of the distal end of the ATL deletion. This region is probably approximately 300 kb downstream of c-myc and the consistent occurrence of abnormalities in this region implies involvement in tumour aetiology in several different cell types.

E alpha u and E beta u chain association: where lies the anomaly?

H-2u haplotype mice are unique among all E alpha+ strains because they do not provide in heterozygotes an E alpha chain that interacts with E betak,s,etc. sufficiently well to allow certain E-restricted immune responses. As a first step in understanding this peculiarity, we have sequenced E alpha u and E beta u cDNA and compared the derived amino acid sequences with those of previously analyzed alleles. Although no glaring structural abnormalities were found, we have identified some u-specific residues and suggest which are the most likely to provoke a pairing anomaly.

E alpha u and E beta u chain association: where lies the anomaly?

H-2u haplotype mice are unique among all E alpha+ strains because they do not provide in heterozygotes an E alpha chain that interacts with E betak,s,etc. sufficiently well to allow certain E-restricted immune responses. As a first step in understanding this peculiarity, we have sequenced E alpha u and E beta u cDNA and compared the derived amino acid sequences with those of previously analyzed alleles. Although no glaring structural abnormalities were found, we have identified some u-specific residues and suggest which are the most likely to provoke a pairing anomaly.

Gene conversion between murine class II major histocompatibility complex loci. Functional and molecular evidence from the bm 12 mutant

The experiments presented in this study define the molecular basis of the bm 12 mutation. Initial characterization of an alloreactive T cell clone, 4.1.4, showed this clone to recognize an allodeterminant present on the E beta b and A beta bm12 chains, but not on the bm 12 parent A beta b chain. To define the extent of sequence shared between the I-E beta product and the mutant I-A beta product, we isolated a cDNA clone of the E beta b gene and determined its nucleotide sequence. Comparison of the nucleotide sequences of E beta b, A beta b, and A beta bm12 shows the the A beta bm12 gene to be identical to the E beta b gene in the region where it differs from its A beta b parent. We predict that the bm 12 mutation arose by gene conversion of this region, which spans 14 nucleotides between amino acid residues 67-71 of the mature A beta chain, from the E beta b locus to the corresponding position at the A beta b locus. Recognition of this region, which spans one of the previously defined E beta allelic "hypervariable" regions, by an alloreactive T cell clone provides the first direct evidence of the functional importance of these hypervariable regions in T cell stimulation. The identification of a gene conversion event involving one of these allelic variable regions implicates conversion as a mechanism that acts on class II beta genes to create sequence diversity in regions of Ia molecules that interact with foreign antigen or a T cell receptor, regions where protein sequence polymorphism would presumably be selected for by the expanded ability it affords the organism to mount effective immune responses against a wider variety of foreign antigens.

Isolation and characterization of a cDNA clone for the murine I-E beta polypeptide chain

The Ia antigens, encoded within the I region of the major histocompatibility complex, are a group of cell surface glycoproteins that are involved in the control of immune responsiveness. We isolated and determined the sequence of a 1,045-base-pair cDNA clone for one of the murine immune response genes, Ek beta. Comparison of the predicted amino acid sequence of the product of Ek beta with that of Ed beta shows that most of the amino acid differences are clustered in short stretches of peptide sequence in the first external protein domain. This clustering of allelic variation suggests that observed haplotype-specific immune responsiveness to certain antigens may be controlled, at least in part, by differences in configuration defined by these regions of allelic variability in the NH2-terminal domain of the E beta chain.