Pharmacogenetic interactions in amyotrophic lateral sclerosis: a step closer to a cure?

Genetic mutations related to amyotrophic lateral sclerosis (ALS) act through distinct pathophysiological pathways, which may lead to varying treatment responses. Here we assess the genetic interaction between C9orf72, UNC13A, and MOBP with creatine and valproic acid treatment in two clinical trials. Genotypic data was available for 309 of the 338 participants (91.4%). The UNC13A genotype affected mortality (p = 0.012), whereas C9orf72 repeat-expansion carriers exhibited a faster rate of decline in overall (p = 0.051) and bulbar functioning (p = 0.005). A dose-response pharmacogenetic interaction was identified between creatine and the A allele of the MOBP genotype (p = 0.027), suggesting a qualitative interaction in a recessive model (HR 3.96, p = 0.015). Not taking genetic information into account may mask evidence of response to treatment or be an unrecognized source of bias. Incorporating genetic data could help investigators to identify critical treatment clues in patients with ALS.

Pharmacokinetics of intravenous immunoglobulin in multifocal motor neuropathy.

BACKGROUND: Multifocal motor neuropathy (MMN) is often responsive to treatment with intravenous immunoglobulin (IVIg), but the optimal dose and intervals of IVIg maintenance treatment have not been established. Increase in IgG concentration (ΔIgG) after IVIg infusion has recently been identified as determinant of outcome in Guillain-Barré syndrome. ΔIgG may therefore represent a potentially useful biomarker to optimise IVIg dosing in patients with MMN. OBJECTIVE: The aims of this study were to determine variability of IVIg pharmacokinetics in patients with MMN in relation to treatment response, and to establish whether interindividual differences in IVIg pharmacokinetics were associated with genetic polymorphisms of the endothelial IgG receptor (FcRn) which determines IgG half-life. METHODS: Twenty-three patients with MMN receiving their first IVIg treatment at a cumulative dose of 2.0 g/kg in 5 days were included. A good treatment response was defined as an increase in muscle strength of at least one Medical Research Council point in minimally two muscle groups. IgG concentrations in serum were determined at baseline, at day 1 and day 5 of the IVIg course, and 3 weeks after treatment. FcRn copy number variation and differences in repeat length of the variable number of tandem repeats in the FcRn gene were determined by quantitative PCR and Sanger sequencing. RESULTS: Seventeen patients (74%) had a good response to treatment. Total IgG and ΔIgG levels showed large variation between patients. Mean ΔIgG was higher in IVIg responders than in non-responders, with the largest difference on day 1 (11.1 g/L vs 4.5 g/L, p=0.06), but our study lacked power to show statistically significant differences. Genetic variation in the FcRn gene was not associated with ΔIgG levels or response to treatment. CONCLUSIONS: IVIg pharmacokinetics varies in patients with MMN and may be associated with clinical response.

Immune pathogenesis and treatment of multifocal motor neuropathy.

Multifocal motor neuropathy (MMN) is a rare, probably immune-mediated chronic disorder characterized by asymmetric distal limb weakness and conduction block. The exact pathogenesis of MMN is still unclear, but IgM anti-GM1 antibodies, which can be detected in sera from approximately half of all MMN patients, are thought to play an important role. Treatment with intravenous immunoglobulin (IVIG) is effective in the vast majority of patients, but, despite IVIG maintenance treatment, many patients experience a slowly progressive decline in muscle strength. In this review we will summarize the results from studies on pathogenesis. We will discuss current treatment strategies of MMN and how insight into MMN pathogenesis may translate into novel therapies in the future.

Quantification of SMN protein in leucocytes from spinal muscular atrophy patients: effects of treatment with valproic acid.

BACKGROUND: Spinal muscular atrophy (SMA) is caused by the homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene produces small amounts of full-length mRNA and functional SMN protein, due to a point mutation in a critical splicing site. Increasing SMN protein production by histone deacetylase inhibiting drugs such as valproic acid (VPA) is an experimental treatment strategy for SMA. OBJECTIVE: To investigate whether an SMN-specific ELISA could detect changes in SMN protein expression in peripheral blood mononuclear cells (PBMCs) after treatment with VPA. METHODS: The authors developed a sensitive SMN-specific ELISA. Six patients with SMA types 2 and 3 participated in the study. Recombinant SMN calibration curves were used to calculate SMN protein levels in PBMCs before and after 4 months of VPA treatment. RESULTS: The SMN ELISA was able to detect small differences in SMN protein concentrations, and differences in SMN protein levels in Epstein-Barr virus immortalised lymphocyte cell lines from SMA type 1 and 2 patients, carriers and healthy individuals (p<0.05). The mean SMN protein level in PBMCs from SMA patients was 22% (SD 15%) of the value in a healthy control. VPA treatment resulted in significantly increased SMN protein levels in five out of six SMA patients compared with baseline values (p<0.05), but did not restore SMN levels to normal values. CONCLUSIONS: SMN protein quantification by this SMN ELISA is a useful additional tool for evaluating the effects of experimental treatment in SMA.

Randomized sequential trial of valproic acid in amyotrophic lateral sclerosis.

OBJECTIVE: To determine whether valproic acid (VPA), a histone deacetylase inhibitor that showed antioxidative and antiapoptotic properties and reduced glutamate toxicity in preclinical studies, is safe and effective in amyotrophic lateral sclerosis (ALS) using a sequential trial design. METHODS: Between April 2005 and January 2007, 163 ALS patients received VPA 1,500mg or placebo daily. Primary end point was survival. Secondary outcome measure was decline of functional status measured by the revised ALS Functional Rating Scale. Analysis was by intention to treat and according to a sequential trial design. This trial was registered with ClinicalTrials.gov (number NCT00136110). RESULTS: VPA did not affect survival (cumulative survival probability of 0.72 in the VPA group [standard error (SE), 0.06] vs 0.88 in the placebo group [SE, 0.04] at 12 months, and 0.59 in the VPA group [SE, 0.07] vs 0.68 in the placebo group [SE, 0.08] at 16 months) or the rate of decline of functional status. VPA intake did not cause serious adverse reactions. INTERPRETATION: Our finding that VPA, at a dose used in epilepsy, does not show a beneficial effect on survival or disease progression in patients with ALS has implications for future trials with histone deacetylase inhibitors in ALS and other neurodegenerative diseases. The use of a sequential trial design allowed inclusion of only half the number of patients required for a classic trial design and prevented patients from unnecessarily continuing potentially harmful study medication.

No benefits from experimental treatment with olfactory ensheathing cells in patients with ALS.

Cell based therapies may be promising options for treating ALS. These therapies aim at neuronal replacement or they may prevent dysfunctional motor neurons from dying. Conflicting results on transplantation of olfactory ensheathing cells (OECs) in ALS mouse models indicate that this technique is not yet ready to progress to clinical trials. A Chinese group has nevertheless treated ALS patients with OECs. We carried out a prospective study of seven patients who underwent OEC treatment in China, following them from four months before departure until one year after treatment. Muscle strength, level of daily functioning and respiratory capacity were measured at regular intervals. Three patients reported subjective positive effects directly after treatment. No individual objective improvement was measured, and outcome measures gradually declined in all patients. Two patients had severe side-effects. Based on our findings in these ALS patients who underwent experimental OEC treatment, we conclude that there are no indications that this treatment is beneficial.

Clinical outcomes in multifocal motor neuropathy: A combined cross-sectional and follow-up study.

OBJECTIVE: To assess the clinical course of multifocal motor neuropathy (MMN) in a large cohort of patients and to identify predictive factors of a progressive disease course. METHODS: Between May 2015 and February 2016, we collected clinical data from 100 patients with MMN, of whom 60 had participated in a nationwide cross-sectional cohort study in 2007. We documented clinical characteristics using standardized questionnaires and performed a standardized neurologic examination. We used multiple linear regression analysis to identify factors that correlated with worse outcome. RESULTS: We found that age at diagnosis (45.2 vs 48.6 years, p < 0.02) was significantly increased between 2007 and 2015-2016, whereas diagnostic delay decreased by 15 months. Seven out of 10 outcome measures deteriorated over time (all p < 0.01). Patients who had a lower Medical Research Council (MRC) sumscore and absence of 1 or more reflexes at the baseline visit showed a greater functional loss at follow-up (p = 0.007 and p = 0.016). CONCLUSIONS: Our study shows that MMN is a progressive disease. Although 87% of patients received maintenance treatment, muscle strength, reflexes, vibration sense, and the Self-Evaluation Scale score significantly deteriorated over time. Lower MRC sumscore and absence of reflexes predicted a more progressive disease course. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that lower MRC sumscore and the absence of reflexes predict a more progressive disease course in patients with MMN.

Mycophenolate mofetil as adjunctive therapy for MMN patients: a randomized, controlled trial.

Multifocal motor neuropathy (MMN) is an immune-mediated disorder characterized by slowly progressive asymmetrical limb weakness. Treatment with immunoglobulins (IVIg) leads to improvement of muscle strength. Anecdotal evidence suggests that immunosuppressive drugs as adjunctive therapy may be beneficial. Mycophenolate mofetil (MMF) is a potent and safe immunosuppressant. Safety and efficacy of MMF as adjunctive therapy for MMN patients receiving IVIg maintenance treatment were evaluated in a randomized controlled trial. MMN patients responding to IVIg treatment were eligible for randomization. Muscle strength and functional status were assessed at monthly intervals for 1 year. Three months after the start of MMF or placebo treatment, IVIg doses were reduced stepwise, until a deterioration of functioning or decline in muscle strength could be observed. An IVIg dose reduction of 50% during adjunctive treatment was defined as a primary endpoint. Secondary outcome measures were improvement in muscle strength and functional status after 3 months and reduction of anti GM1-IgM titres after 12 months of MMF treatment. Twenty-eight patients were randomized. One patient allocated to MMF reached the primary endpoint of 50% IVIg dose reduction. After 12 months IVIg reduction did not differ significantly between the two treatment groups. Patients did not experience drug toxicity and none of the patients showed significant disease progression after 12 months. Muscle strength and functional scores after 3 months and anti GM1-IgM titres after 12 months did not change. Adjunctive treatment of MMN patients with MMF at a dose of 1 g twice daily is safe but does not alter disease course or allow significant reduction of IVIg doses.

Association of IgM monoclonal gammopathy with progressive muscular atrophy and multifocal motor neuropathy: a case-control study.

Monoclonal gammopathy in patients with amyotrophic lateral sclerosis (ALS) and related disorders has been reported in small studies but the validity of the reported associations remains uncertain. Presence of monoclonal gammopathy may indicate specific pathogenic pathways and may facilitate the development of novel treatment strategies. The objective of this large case-control study was to determine the prevalence of monoclonal gammopathy in motor neuron diseases (MND) and multifocal motor neuropathy (MMN). Monoclonal gammopathy was determined by immunoelectrophoresis and immunofixation in serum from 445 patients with ALS, 158 patients with progressive muscular atrophy (PMA), 60 patients with primary lateral sclerosis (PLS), 88 patients with MMN and in 430 matched healthy controls. Anti-ganglioside antibody titers were determined in sera from patients with MMN and PMA, and in ALS and PLS patients with monoclonal gammopathy. Logistic regression analysis was used to investigate associations of monoclonal gammopathy with motor neuron diseases and clinical characteristics. Neither ALS nor PLS was associated with monoclonal gammopathy. IgM monoclonal gammopathy was more frequent in patients with PMA (8 %) (OR = 4.2; p = 0.001) and MMN (7 %) (OR = 5.8; p = 0.002) than in controls (2 %). High titers of anti-GM1 IgM antibodies were present in 43 % of MMN patients and 7 % of PMA patients. Patients with PMA and IgM monoclonal gammopathy or anti-GM1 antibodies had a higher age at onset, more often weakness of upper legs and more severe outcome than patients with MMN. PMA and MMN, but not ALS and PLS, are significantly associated with IgM monoclonal gammopathy and anti-GM1 antibodies. These results may indicate that a subset of patients presenting with PMA share pathogenic mechanisms with MMN.

Complement activity is associated with disease severity in multifocal motor neuropathy.

OBJECTIVE: To investigate whether high innate activity of the classical and lectin pathways of complement is associated with multifocal motor neuropathy (MMN) and whether levels of innate complement activity or the potential of anti-GM1 antibodies to activate the complement system correlate with disease severity. METHODS: We performed a case-control study including 79 patients with MMN and 79 matched healthy controls. Muscle weakness was documented with Medical Research Council scale sum score and axonal loss with nerve conduction studies. Activity of the classical and lectin pathways of complement was assessed by ELISA. We also determined serum mannose-binding lectin (MBL) concentrations and polymorphisms in the MBL gene (MBL2) and quantified complement-activating properties of anti-GM1 IgM antibodies by ELISA. RESULTS: Activity of the classical and lectin pathways, MBL2 genotypes, and serum MBL concentrations did not differ between patients and controls. Complement activation by anti-GM1 IgM antibodies was exclusively mediated through the classical pathway and correlated with antibody titers (p < 0.001). Logistic regression analysis showed that both high innate activity of the classical pathway of complement and high complement-activating capacity of anti-GM1 IgM antibodies were significantly associated with more severe muscle weakness and axonal loss. CONCLUSION: High innate activity of the classical pathway of complement and efficient complement-activating properties of anti-GM1 IgM antibodies are determinants of disease severity in patients with MMN. These findings underline the importance of anti-GM1 antibody-mediated complement activation in the pathogenesis and clinical course of MMN.

IVIg inhibits classical pathway activity and anti-GM1 IgM-mediated complement deposition in MMN.

The effects of intravenous immunoglobulins (IVIg) on anti-GM1 IgM titer and function, classical complement pathway activity, and antibody-complement interaction were investigated in 62 patients with multifocal motor neuropathy (MMN). In vitro, IVIg decreased complement deposition by anti-GM1 IgM antibodies. First IVIg treatment (2 g/kg) decreased C1q and C4 concentrations and classical pathway activity in serum. In sera from patients receiving IVIg maintenance therapy (0.4 g/kg) C4 concentrations and classical pathway activity were generally lower at higher IgG concentrations. The beneficial effects of IVIg in MMN may be explained by reduced antibody-mediated complement deposition in nerves amplified by a systemically attenuated classical pathway.

Effect of non-invasive ventilation on survival, quality of life, respiratory function and cognition: a review of the literature.

Symptoms of nocturnal hypoventilation may negatively influence the quality of life (QoL) of ALS patients long before respiratory failure ensues. Non-invasive mechanical ventilation (NIV) is considered a treatment option for nocturnal hypoventilation. The primary objective of NIV is improving quality of life (QoL). It may also prolong life by several months. A systematic review of the literature was performed to analyse what is known of the effect of NIV on survival, QoL and other outcome measures. A computerized literature search was performed to identify controlled clinical trials and observational studies of treatment of ALS-associated nocturnal hypoventilation from 1985 until May 2005. Twelve studies fulfilled the inclusion criteria. Four studies were retrospective, seven prospective and in one study randomization was used. All studies reported beneficial effects of NIV on all outcome measures. In seven studies NIV was associated with prolonged survival in patients tolerant for NIV, and five studies reported an improved QoL. In conclusion, studies on the use of NIV in ALS differ in study design and endpoint definitions. All studies suggest a beneficial effect on QoL and other outcome measures (Evidence level Class II-III). Well-designed randomized controlled trials comparing the effect on QoL and survival have not been performed.