Advantages of visualisations to evaluate and communicate adverse event information in randomised controlled trials.

BACKGROUND: Randomised controlled trials (RCTs) provide valuable information and inform the development of harm profiles of new treatments. Harms are typically assessed through the collection of adverse events (AEs). Despite AEs being routine outcomes collected in trials, analysis and reporting of AEs in journal articles are continually shown to be suboptimal. One key challenge is the large volume of AEs, which can make evaluation and communication problematic. Prominent practice is to report frequency tables of AEs by arm. Visual displays offer an effective solution to assess and communicate complex information; however, they are rarely used and there is a lack of practical guidance on what and how to visually display complex AE data. METHODS: In this article, we demonstrate the use of two plots identified to be beneficial for wide use in RCTs, since both can display multiple AEs and are suitable to display point estimates for binary, count, or time-to-event AE data: the volcano and dot plots. We compare and contrast the use of data visualisations against traditional frequency table reporting, using published AE information in two placebo-controlled trials, of remdesivir for COVID-19 and GDNF for Parkinson disease. We introduce statistical programmes for implementation in Stata. RESULTS/CASE STUDY: Visualisations of AEs in the COVID-19 trial communicated a risk profile for remdesivir which differed from the main message in the published authors' conclusion. In the Parkinson's disease trial of GDNF, the visualisation provided immediate communication of harm signals, which had otherwise been contained within lengthy descriptive text and tables. Asymmetry in the volcano plot helped flag extreme events that were less obvious from review of the frequency table and dot plot. The dot plot allowed a more comprehensive representation by means of a more detailed summary. CONCLUSIONS: Visualisations can better support investigators to assimilate large volumes of data and enable improved informal between-arm comparisons compared to tables. We endorse increased uptake for use in trial publications. Care in construction of visual displays needs to be taken as there can be potential to overemphasise treatment effects in some circumstances.

Systemic injection of AAV9-GDNF provides modest functional improvements in the SOD1G93A ALS rat but has adverse side effects.

Injecting proteins into the central nervous system that stimulate neuronal growth can lead to beneficial effects in animal models of disease. In particular, glial cell line-derived neurotrophic factor (GDNF) has shown promise in animal and cell models of Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis (ALS). Here, systemic AAV9-GDNF was delivered via tail vein injections to young rats to determine whether this could be a safe and functional strategy to treat the SOD1G93A rat model of ALS and, therefore, translated to a therapy for ALS patients. We found that GDNF administration in this manner resulted in modest functional improvement, whereby grip strength was maintained for longer and the onset of forelimb paralysis was delayed compared to non-treated rats. This did not, however, translate into an extension in survival. In addition, ALS rats receiving GDNF exhibited slower weight gain, reduced activity levels and decreased working memory. Collectively, these results confirm that caution should be applied when applying growth factors such as GDNF systemically to multiple tissues.

Glial cell line-derived neurotrophic factor-induced mice liver defatting: A novel strategy to enable transplantation of steatotic livers.

Moderate macrovesicular steatosis (>30%), which is present in almost 50% of livers considered for transplantation, increases the risk of primary graft dysfunction. Our previously published data showed that glial cell line-derived neurotrophic factor (GDNF) is protective against high-fat diet (HFD)-induced hepatic steatosis in mice. Hence, we hypothesized that perfusion of steatotic livers with GDNF may reduce liver fat content before transplantation. Livers from 8 weeks of regular diet (RD) and of HFD-fed mice were perfused ex vivo for 4 hours with either vehicle, GDNF, or a previously described defatting cocktail. The liver's residual fat was quantified colorimetrically using a triglyceride (TG) assay kit and by Oil Red O (ORO) and Nile red/Hoechst staining. Liver tissue injury was assessed by using a lactate dehydrogenase (LDH) activity assay. In vitro induction of lipolysis in HepG2 cells was assessed by measuring glycerol and free fatty acid release. ORO staining showed significantly more steatosis in livers from HFD-fed mice compared with RD-fed mice (P < 0.001). HFD livers perfused with GDNF had significantly less steatosis than those not perfused (P = 0.001) or perfused with vehicle (P < 0.05). GDNF is equally effective in steatotic liver defatting compared to the defatting cocktail; however, GDNF induces less liver damage than the defatting cocktail. These observations were consistent with data obtained from assessment of liver TG content. Assessment of liver injury revealed significant hepatocyte injury in livers perfused with the control defatting cocktail but no evidence of injury in livers perfused with either GDNF or vehicle. In vitro, GDNF reduced TG accumulation in HepG2 cells and stimulated increased TG lipolysis. In conclusion, GDNF can decrease mice liver fat content to an acceptable range and could be a potential defatting agent before liver transplantation.

GDNF-induced cerebellar toxicity: A brief review.

Recombinant-methionyl human glial cell line-derived neurotrophic factor (GDNF) is known for its neurorestorative and neuroprotective effects in rodent and primate models of Parkinson's disease (PD). When administered locally into the putamen of Parkinsonian subjects, early clinical studies showed its potential promise as a disease-modifying agent. However, the development of GDNF for the treatment of PD has been significantly clouded by findings of cerebellar toxicity after continuous intraputamenal high-dose administration in a 6-month treatment/3-month recovery toxicology study in rhesus monkeys. Specifically, multifocal cerebellar Purkinje cell loss affecting 1-21% of the cerebellar cortex was observed in 4 of 15 (26.7%; 95% confidence interval [CI]: 10.5-52.4%) animals treated at the highest dose level tested (3000µg/month). No cerebellar toxicity was observed at lower doses (450 and 900µg/month) in the same study, or at similar or higher doses (up to 10,000µg/month) in subchronic or chronic toxicology studies testing intermittent intracerebroventricular administration. While seemingly associated with the use of GDNF, the pathogenesis of the cerebellar lesions has not been fully understood to date. This review integrates available information to evaluate potential pathogenic mechanisms and provide a consolidated assessment of the findings. While other explanations are considered, the existing evidence is most consistent with the hypothesis that leakage of GDNF into cerebrospinal fluid during chronic infusions into the putamen down-regulates GDNF receptors on Purkinje cells, and that subsequent acute withdrawal of GDNF generates the observed lesions. The implications of these findings for clinical studies with GDNF are discussed.

Growth factors and neuropathic pain.

A treatment for neuropathic pain is an important unmet medical need because this pain often is refractory to many medical interventions. An important element in the development of neuropathic pain is a dysfunction in the activity of peripheral nerves. Because neurotrophic factors affect nerve development and maintenance, modulating the activity of these factors can alter neuronal pathophysiology and produce a disease-modifying effect. Blocking the activity of nerve growth factor or enhancing the activity of either glial-derived neurotrophic factor or artemin has shown potential for normalizing neuronal activity and attenuating signs of neuropathic pain in animal models and clinical studies. This article discusses the role of these factors in neuropathic pain and the implications for the development of novel therapeutics.

The effects of docosahexaenoic acid on glial derived neurotrophic factor and neurturin in bilateral rat model of Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder marked by cell death in the Substantia nigra (SN). Docosahexaenoic acid (DHA) is the major polyunsaturated fatty acid (PUFA) in the phospholipid fraction of the brain and is required for normal cellular function. Glial cell line derived neurotrophic factor (GDNF) and neurturin (NTN) are very potent trophic factors for PD. The aim of the study was to evaluate the neuroprotective effects of GDNF and NTN by investigating their immunostaining levels after administration of DHA in a model of PD. For this reason we hypothesized that DHA administration of PD might alter GDNF, NTN expression in SN. MPTP neurotoxin that induces dopaminergic neurodegeneration was used to create the experimental Parkinsonism model. Rats were divided into; control, DHA-treated (DHA), MPTP-induced (MPTP), MPTP-induced+DHA-treated (MPTP+DHA) groups. Dopaminergic neuron numbers were clearly decreased in MPTP, but showed an increase in MPTP+DHA group. As a result of this, DHA administration protected dopaminergic neurons as shown by tyrosine hydroxylase immunohistochemistry. In the MPTP+DHA group, GDNF, NTN immunoreactions in dopaminergic neurons were higher than that of the MPTP group. In conclusion, the characterization of GDNF and NTN will certainly help elucidate the mechanism of DHA action, and lead to better strategies for the use of DHA to treat neurodegenerative diseases.

Mu and delta opioid receptors on nociceptors attenuate mechanical hyperalgesia in rat.

Sensitization to mechanical stimuli is important in most pain syndromes. We evaluated the populations of nociceptors mediating mechanical hyperalgesia and those mediating mu-opioid receptor (MOR) and delta-opioid receptor (DOR) agonist-induced inhibition of hyperalgesia, in the rat. We found that: (1) intradermal injection of both the endogenous ligand for the Ret receptor, glia-derived growth factor (GDNF), and the ligand for the tropomyosin receptor kinase A (TrkA) receptor, nerve growth factor (NGF)-which are present on distinct populations of nociceptors-both produce mechanical hyperalgesia; (2) DOR agonist 4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide (SNC) but not MOR agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) inhibit GDNF-induced hyperalgesia; (3) both DAMGO and SNC inhibit NGF hyperalgesia, even in rats pretreated with isolectin B4 (IB4)-saporin, a toxin that destroys IB4-binding neurons; (4) co-administration of low doses of DAMGO and SNC produce enhanced analgesia, and; (5) repeated administration of DAMGO produces cross-tolerance to the analgesic effect of SNC. These findings demonstrate that, most nociceptors have a role in mechanical hyperalgesia, only the DOR agonist inhibits GDNF hyperalgesia, and MOR and DOR are co-localized on a functionally important population of TrkA-positive nociceptors.

Pharmacokinetics and safety in rhesus monkeys of a monoclonal antibody-GDNF fusion protein for targeted blood-brain barrier delivery.

PURPOSE: Glial-derived neurotrophic factor (GDNF) is a potential therapy for stroke, Parkinson's disease, or drug addiction. However, GDNF does not cross the blood-brain barrier (BBB). GDNF is re-engineered as a fusion protein with a chimeric monoclonal antibody (MAb) to the human insulin receptor (HIR), which acts as a molecular Trojan horse to deliver the GDNF across the BBB. The pharmacokinetics (PK), toxicology, and safety pharmacology of the HIRMAb-GDNF fusion protein were investigated in Rhesus monkeys. METHODS: The fusion protein was administered as an intravenous injection at doses up to 50 mg/kg over a 60 h period to 56 Rhesus monkeys. The plasma concentration of the HIRMAb-GDNF fusion protein was measured with a 2-site sandwich ELISA. RESULTS: No adverse events were observed in a 2-week terminal toxicology study, and no neuropathologic changes were observed. The PK analysis showed a linear relationship between plasma AUC and dose, a large systemic volume of distribution, as well as high clearance rates of 8-10 mL/kg/min. CONCLUSIONS: A no-observable-adverse-effect level is established in the Rhesus monkey for the acute administration of the HIRMAb-GDNF fusion protein. The fusion protein targeting the insulin receptor has a PK profile similar to a classical small molecule.

Effective GDNF brain delivery using microspheres--a promising strategy for Parkinson's disease.

Glial cell line-derived neurotrophic factor (GDNF) has shown promise in the treatment of neurodegenerative disorders of basal ganglia origin such us Parkinson's disease (PD). In this study, we investigated the neurorestorative effect of controlled GDNF delivery using biodegradable microspheres in an animal model with partial dopaminergic lesion. Microspheres were loaded with N-glycosylated recombinant GDNF and prepared using the Total Recirculation One-Machine System (TROMS). GDNF-loaded microparticles were unilaterally injected into the rat striatum by stereotaxic surgery two weeks after a unilateral partial 6-OHDA nigrostriatal lesion. Animals were tested for amphetamine-induced rotational asymmetry at different times and were sacrificed two months after microsphere implantation for immunohistochemical analysis. The putative presence of serum IgG antibodies against rat glycosylated GDNF was analyzed for addressing safety issues. The results demonstrated that GDNF-loaded microspheres, improved the rotational behavior induced by amphetamine of the GDNF-treated animals together with an increase in the density of TH positive fibers at the striatal level. The developed GDNF-loaded microparticles proved to be suitable to release biologically active GDNF over up to 5 weeks in vivo. Furthermore, none of the animals developed antibodies against GDNF demonstrating the safety of glycosylated GDNF use.

Neurotrophic factors as a therapeutic target for Parkinson's disease.

BACKGROUND: The search for therapeutic agents that might alter the disease course in Parkinson's disease (PD) is ongoing. One area of particular interest involves neurotrophic factors (NTFs), with those of the glial cell line-derived neurotrophic factor (GDNF) family showing greatest promise. The safety and efficacy of these therapies has recently come into question. Furthermore, many of the key questions pertaining to such therapies, such as the optimal method of delivery, timing of treatment and selection of patients most likely to benefit, remain unanswered. OBJECTIVE: In this review we sought to evaluate the therapeutic potential of NTFs in the treatment of PD. We appraised the evidence provided by both in vitro and in vivo work before proceeding to a critical assessment of the relevant clinical trial data. METHODS: Relevant literature was identified using a PubMed search of articles published up to October 2007. Search terms included: 'Parkinson's disease', 'Neurotrophic factors', 'BDNF' (Brain-derived neurotrophic factor), 'GDNF' and 'Neurturin'. Original articles were reviewed, and relevant citations from these articles were also appraised. CONCLUSION: NTF therapy has potential in the treatment of nigrostriatal dysfunction in PD but numerous methodological and safety issues will need to be addressed before this approach can be widely adopted. Furthermore PD is now recognized as being more than a pure motor disorder, and one in which neuronal loss is not just confined to the dopaminergic nigrostriatal system. Non-motor symptomatology in PD is unlikely to benefit from therapies that target only the nigrostriatal system, and this must inform our thinking as to the maximal achievable benefit that NTFs are ever likely to provide.

Unilateral intraputaminal glial cell line-derived neurotrophic factor in patients with Parkinson disease: response to 1 year each of treatment and withdrawal.

OBJECT: Glial cell line-derived neurotrophic factor (GDNF) infused unilaterally into the putamen for 6 months was previously shown to improve motor functions and quality of life measures significantly in 10 patients with Parkinson disease (PD) in a Phase I trial. In this study the authors report the safety and efficacy of continuous treatment for 1 year or more. After the trial was halted by the sponsor, the patients were monitored for an additional year to evaluate the effects of drug withdrawal. METHODS: During the extended study, patients received unilateral intraputaminal infusion of 30 mg/day GDNF at a basal infusion rate supplemented with pulsed boluses every 6 hours at a convection-enhanced delivery rate to increase tissue penetration of the protein. When the study was stopped, the delivery system was reprogrammed to deliver sterile saline at the basal infusion rate of 2 ml/hour. The Unified PD Rating Scale (UPDRS) total scores after 1 year of therapy were improved by 42 and 38%, respectively, in the "off" and "on" states. Motor UPDRS scores were also improved: 45 and 39% in the off and on conditions, respectively. Benefits from treatment were lost by 9 to 12 months after GDNF infusion was halted. At that time, the patients had returned to their baseline UPDRS scores and required higher levels of conventional antiparkinsonian drugs to treat symptoms. After 11 months of treatment, the delivery system had to be removed in one patient because of the risk of infection. In seven patients antibodies to GDNF developed, with no evidence of clinical sequelae. There was also no evidence of GDNF-induced cerebellar toxicity, as evaluated using magnetic resonance imaging analysis and clinical testing. CONCLUSIONS: Unilateral administration of GDNF results in significant, sustained bilateral benefits. These improvements are lost within 9 months after drug withdrawal. Safety concerns with GDNF therapy can be closely monitored and managed.