Preclinical quality, safety, and efficacy of a human embryonic stem cell-derived product for the treatment of Parkinson's disease, STEM-PD.

Cell replacement therapies for Parkinson's disease (PD) based on transplantation of pluripotent stem cell-derived dopaminergic neurons are now entering clinical trials. Here, we present quality, safety, and efficacy data supporting the first-in-human STEM-PD phase I/IIa clinical trial along with the trial design. The STEM-PD product was manufactured under GMP and quality tested in vitro and in vivo to meet regulatory requirements. Importantly, no adverse effects were observed upon testing of the product in a 39-week rat GLP safety study for toxicity, tumorigenicity, and biodistribution, and a non-GLP efficacy study confirmed that the transplanted cells mediated full functional recovery in a pre-clinical rat model of PD. We further observed highly comparable efficacy results between two different GMP batches, verifying that the product can be serially manufactured. A fully in vivo-tested batch of STEM-PD is now being used in a clinical trial of 8 patients with moderate PD, initiated in 2022.

Targeting amyloid ß in Alzheimer's disease: Meta-analysis of low-dose solanezumab in Alzheimer's disease with mild dementia studies.

INTRODUCTION: Solanezumab is a monoclonal antibody that binds to the mid-domain of soluble amyloid ß peptide. This meta-analysis evaluated the effect of low-dose solanezumab on clinical progression in three phase 3 studies. METHODS: The population comprised patients aged ≥55 years with Alzheimer's disease (AD) with mild dementia, randomized to 400 mg solanezumab or placebo every 4 weeks for 80 weeks. Frequentist mixed-model repeated-measures (MMRM) and Bayesian disease progression model (DPM) longitudinal analyses were conducted. RESULTS: Pooled MMRM analyses showed a statistically significant effect of solanezumab across cognitive and functional outcome measures. DPM results were generally consistent with MMRM results, ranging from 15% to 30% slowing of clinical progression. DISCUSSION: These analyses suggest low-dose solanezumab slows clinical progression of AD with mild dementia. The ongoing A4 solanezumab study in participants with preclinical AD will ascertain the effect of a higher dose of solanezumab in an earlier disease stage. HIGHLIGHTS: Individual EXPEDITION studies were negative but suggest low-dose solanezumab had an effect in slowing the clinical progression of Alzheimer's disease (AD) with mild dementia. At 80 weeks, mixed-model repeated-measures analyses showed numeric reductions in measures of clinical decline in solanezumab-treated arms compared with placebo across almost every outcome measure, and statistical significance in multiple outcome measures in each study. Pooled analyses suggest a high probability that low-dose solanezumab has at least some effect on slowing the clinical progression of AD with mild dementia. Across cognitive and functional outcome measures, estimates from disease progression model analyses range from 15% to 30% slowing of decline with low-dose solanezumab in AD with mild dementia.

A Combined α-Synuclein/Fibril (SynFib) Model of Parkinson-Like Synucleinopathy Targeting the Nigrostriatal Dopamine System.

Injections of pre-formed α-synuclein fibrils (PFFs) or overexpression of α-synuclein using AAV vectors are commonly used as models of Parkinson-like synucleinopathy in rats and mice. In the modified method reviewed here, the "SynFib" model, the PFFs and the AAV vector are administered together unilaterally into the substantia nigra. This approach combines the key features of these two models, i.e., the generation of toxic α-synuclein aggregates and Lewy body-like inclusions, in combination with the increased vulnerability caused by increased cellular levels of α-synuclein. The combined AAV/PFF delivery offers several advantages over the standard PFF model due to the enhanced and accelerated α-synuclein pathology and microglial response induced by the PFF seeds in the presence of an elevated α-synuclein level. Injection of the AAV/PFF mixture into the substantia nigra makes it possible to target a larger proportion of the nigral dopamine neurons and obtain a level of dopamine cell loss (>60%) needed to induce significant impairments in drug-induced and spontaneous motor tests. The SynFib model shares attractive features of the standard 6-OHDA lesion model: a single unilateral stereotaxic intervention; pathology and cell loss developing over a short time span; and the possibility to monitor the degenerative changes using tests of motor behavior.

A phase IV clinical trial of gastrointestinal motility in adult patients with migraine before and after initiation of a calcitonin gene-related peptide ligand (galcanezumab) or receptor (erenumab) antagonist.

OBJECTIVE: To compare effects of an initial dose of calcitonin gene-related peptide (CGRP) monoclonal antibody (mAb) antagonists on gastrointestinal (GI) motility in patients with migraine and to explore if the mechanistic difference contributes to GI adverse events (AEs). BACKGROUND: Different frequencies of constipation have been observed between CGRP mAbs that target the ligand (galcanezumab [GMB]) or receptor (erenumab [ERE]). METHODS: Patients (n = 65) with migraine without significant GI symptoms were enrolled in a multi-center, single-blind phase IV clinical trial (NCT04294147) and randomized 1:1 to receive GMB (240 mg; n = 33) or ERE (140 mg; n = 32). GI whole and regional transit times were assessed using a wireless motility capsule 1 week before and 2 weeks after mAb administration. The primary endpoint was change from baseline in colonic transit time (CTT) within each treatment group. Other measures included GI Symptom Rating Scale (GSRS), Bristol Stool Form Scale (BSFS), and spontaneous bowel movement (SBM) evaluation. AEs were monitored throughout the study. RESULTS: Baseline characteristics indicated significant GI transit time variability with minimal GI reported symptoms. While not statistically significant, a numerical mean increase in CTT was observed in ERE patients (n = 28, mean [SD] at baseline: 33.8 [29.4] h; least square [LS] mean [SE] change: 5.8 [5.7] h, 95% confidence interval [CI] -5.7 to 17.2, p = 0.320), while GMB decreased CTT (n = 31, mean [SD] at baseline: 29.3 [24.5] h; LS mean [SE] change: -5.4 [5.4] h, 95% CI -16.2 to 5.5, p = 0.328) compared to baseline. No meaningful changes were observed in other regional transit times. ERE significantly reduced BSFS (LS mean [SE] score -0.5 [0.2], p = 0.004) and SBM (LS mean [SE] -1.2 [0.5], p = 0.0120), and increased GSRS-constipation compared to baseline (LS mean [SE] score 0.3 [0.1], p = 0.016). GMB increased GSRS-constipation (LS mean [SE] score 0.4 [0.1], p = 0.002). There were no discontinuations due to or serious AEs. A higher percentage of treatment-emergent AEs were reported with ERE than GMB (ERE: nine of 32 [28.1%] versus GMB: three of 33 [9.1%]), with constipation the most frequently reported (ERE: five of 32 [15.6%] versus GMB one of 33 [3.0%]). CONCLUSION: While the primary endpoint of this study was not met, secondary and tertiary endpoints support a within- and between-treatment change in GI effects suggesting possible mechanistic differences between ligand (GMB) and receptor (ERE) antagonism.

Grafts Derived from an α-Synuclein Triplication Patient Mediate Functional Recovery but Develop Disease-Associated Pathology in the 6-OHDA Model of Parkinson's Disease.

BACKGROUND: Human induced pluripotent stem cells (hiPSCs) have been proposed as an alternative source for cell replacement therapy for Parkinson's disease (PD) and they provide the option of using the patient's own cells. A few studies have investigated transplantation of patient-derived dopaminergic (DA) neurons in preclinical models; however, little is known about the long-term integrity and function of grafts derived from patients with PD. OBJECTIVE: To assess the viability and function of DA neuron grafts derived from a patient hiPSC line with an α-synuclein gene triplication (AST18), using a clinical grade human embryonic stem cell (hESC) line (RC17) as a reference control. METHODS: Cells were differentiated into ventral mesencephalic (VM)-patterned DA progenitors using an established GMP protocol. The progenitors were then either terminally differentiated to mature DA neurons in vitro or transplanted into 6-hydroxydopamine (6-OHDA) lesioned rats and their survival, maturation, function, and propensity to develop α-synuclein related pathology, were assessed in vivo. RESULTS: Both cell lines generated functional neurons with DA properties in vitro. AST18-derived VM progenitor cells survived transplantation and matured into neuron-rich grafts similar to the RC17 cells. After 24 weeks, both cell lines produced DA-rich grafts that mediated full functional recovery; however, pathological changes were only observed in grafts derived from the α-synuclein triplication patient line. CONCLUSION: This data shows proof-of-principle for survival and functional recovery with familial PD patient-derived cells in the 6-OHDA model of PD. However, signs of slowly developing pathology warrants further investigation before use of autologous grafts in patients.

Direct Reprogramming of Human Fetal- and Stem Cell-Derived Glial Progenitor Cells into Midbrain Dopaminergic Neurons.

Human glial progenitor cells (hGPCs) are promising cellular substrates to explore for the in situ production of new neurons for brain repair. Proof of concept for direct neuronal reprogramming of glial progenitors has been obtained in mouse models in vivo, but conversion using human cells has not yet been demonstrated. Such studies have been difficult to perform since hGPCs are born late during human fetal development, with limited accessibility for in vitro culture. In this study, we show proof of concept of hGPC conversion using fetal cells and also establish a renewable and reproducible stem cell-based hGPC system for direct neural conversion in vitro. Using this system, we have identified optimal combinations of fate determinants for the efficient dopaminergic (DA) conversion of hGPCs, thereby yielding a therapeutically relevant cell type that selectively degenerates in Parkinson's disease. The induced DA neurons show a progressive, subtype-specific phenotypic maturation and acquire functional electrophysiological properties indicative of DA phenotype.

Author Correction: Single cell transcriptomics identifies stem cell-derived graft composition in a model of Parkinson's disease.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Impact of α-synuclein pathology on transplanted hESC-derived dopaminergic neurons in a humanized α-synuclein rat model of PD.

Preclinical assessment of the therapeutic potential of dopamine (DA) neuron replacement in Parkinson's disease (PD) has primarily been performed in the 6-hydroxydopamine toxin model. While this is a good model to assess graft function, it does not reflect the pathological features or progressive nature of the disease. In this study, we establish a humanized transplantation model of PD that better recapitulates the main disease features, obtained by coinjection of preformed human α-synuclein (α-syn) fibrils and adeno-associated virus (AAV) expressing human wild-type α-syn unilaterally into the rat substantia nigra (SN). This model gives rise to DA neuron dysfunction and progressive loss of DA neurons from the SN and terminals in the striatum, accompanied by extensive α-syn pathology and a prominent inflammatory response, making it an interesting and relevant model in which to examine long-term function and integrity of transplanted neurons in a PD-like brain. We transplanted DA neurons derived from human embryonic stem cells (hESCs) into the striatum and assessed their survival, growth, and function over 6 to 18 wk. We show that the transplanted cells, even in the presence of ongoing pathology, are capable of innervating the DA-depleted striatum. However, on closer examination of the grafts, we found evidence of α-syn pathology in the form of inclusions of phosphorylated α-syn in a small fraction of the grafted DA neurons, indicating host-to-graft transfer of α-syn pathology, a phenomenon that has previously been observed in PD patients receiving fetal tissue grafts but has not been possible to demonstrate and study in toxin-based animal models.

Single cell transcriptomics identifies stem cell-derived graft composition in a model of Parkinson's disease.

Cell replacement is a long-standing and realistic goal for the treatment of Parkinson's disease (PD). Cells for transplantation can be obtained from fetal brain tissue or from stem cells. However, after transplantation, dopamine (DA) neurons are seen to be a minor component of grafts, and it has remained difficult to determine the identity of other cell types. Here, we report analysis by single-cell RNA sequencing (scRNA-seq) combined with comprehensive histological analyses to characterize intracerebral grafts from human embryonic stem cells (hESCs) and fetal tissue after functional maturation in a pre-clinical rat PD model. We show that neurons and astrocytes are major components in both fetal and stem cell-derived grafts. Additionally, we identify a cell type closely resembling a class of recently identified perivascular-like cells in stem cell-derived grafts. Thus, this study uncovers previously unknown cellular diversity in a clinically relevant cell replacement PD model.

hESC-Derived Dopaminergic Transplants Integrate into Basal Ganglia Circuitry in a Preclinical Model of Parkinson's Disease.

Cell replacement is currently being explored as a therapeutic approach for neurodegenerative disease. Using stem cells as a source, transplantable progenitors can now be generated under conditions compliant with clinical application in patients. In this study, we elucidate factors controlling target-appropriate innervation and circuitry integration of human embryonic stem cell (hESC)-derived grafts after transplantation to the adult brain. We show that cell-intrinsic factors determine graft-derived axonal innervation, whereas synaptic inputs from host neurons primarily reflect the graft location. Furthermore, we provide evidence that hESC-derived dopaminergic grafts transplanted in a long-term preclinical rat model of Parkinson's disease (PD) receive synaptic input from subtypes of host cortical, striatal, and pallidal neurons that are known to regulate the function of endogenous nigral dopamine neurons. This refined understanding of how graft neurons integrate with host circuitry will be important for the design of clinical stem-cell-based replacement therapies for PD, as well as for other neurodegenerative diseases.

Target-specific forebrain projections and appropriate synaptic inputs of hESC-derived dopamine neurons grafted to the midbrain of parkinsonian rats.

Dopamine (DA) neurons derived from human embryonic stem cells (hESCs) are a promising unlimited source of cells for cell replacement therapy in Parkinson's disease (PD). A number of studies have demonstrated functionality of DA neurons originating from hESCs when grafted to the striatum of rodent and non-human primate models of PD. However, several questions remain in regard to their axonal outgrowth potential and capacity to integrate into host circuitry. Here, ventral midbrain (VM) patterned hESC-derived progenitors were grafted into the midbrain of 6-hydroxydopamine-lesioned rats, and analyzed at 6, 18, and 24 weeks for a time-course evaluation of specificity and extent of graft-derived fiber outgrowth as well as potential for functional recovery. To investigate synaptic integration of the transplanted cells, we used rabies-based monosynaptic tracing to reveal the origin and extent of host presynaptic inputs to grafts at 6 weeks. The results reveal the capacity of grafted neurons to extend axonal projections toward appropriate forebrain target structures progressively over 24 weeks. The timing and extent of graft-derived dopaminergic fibers innervating the dorsolateral striatum matched reduction in amphetamine-induced rotational asymmetry in the animals where recovery could be observed. Monosynaptic tracing demonstrated that grafted cells integrate with host circuitry 6 weeks after transplantation, in a manner that is comparable with endogenous midbrain connectivity. Thus, we demonstrate that VM patterned hESC-derived progenitors grafted to midbrain have the capacity to extensively innervate appropriate forebrain targets, integrate into the host circuitry and that functional recovery can be achieved when grafting fetal or hESC-derived DA neurons to the midbrain.

Fibrin-based microsphere reservoirs for delivery of neurotrophic factors to the brain.

AIM: The in vivo therapeutic potential of neurotrophic factors to modify neuronal dysfunctions is limited by their short half-life. A biomaterials-based intervention, which protects these factors and allows a controlled release, is required. MATERIALS & METHODS: Hollow fibrin microspheres were fabricated by charge manipulation using polystyrene templates and were loaded with NGF. Bioactivity of released NGF was demonstrated by neuronal outgrowth assay in PC-12 cells followed by in vivo assessment for NGF release and host response. RESULTS: Fibrin-based hollow spheres showed high loading efficiency (>80%). Neurotrophin encapsulation into the microspheres did not alter its bioactivity and controlled release of NGF was observed in the in vivo study. CONCLUSION: Fibrin hollow microspheres act as a suitable delivery platform for neurotrophic factors with tunable loading efficiency and maintaining their bioactive form after release in vivo.

The reduction in immunogenicity of neurotrophin overexpressing stem cells after intra-striatal transplantation by encapsulation in an in situ gelling collagen hydrogel.

Delivery of neurotrophic factors to the brain via genetically modified bone marrow-derived mesenchymal stem cells (MSCs) offers a promising neuroprotective strategy for neurodegenerative diseases. However, MSCs delivered to the CNS typically show poor survival post-transplantation, which is accompanied by microglial activation and astrocyte recruitment at the graft site. Recent studies have shown the potential of biomaterials to provide a supportive matrix for transplanted cells which may assist in the grafting process. In this study, an in situ gelling type I collagen hydrogel was evaluated as an intracerebral transplantation matrix for delivery of glial cell line-derived neurotrophic factor (GDNF)-overexpressing MSCs to the rat brain (GDNF-MSCs). In vitro analyses demonstrated that this collagen hydrogel did not affect the viability of the GDNF-MSCs nor did it prevent GDNF secretion into the surrounding medium. In vivo analyses also confirmed that the collagen hydrogel did not negatively impact on the survival of the cells and permitted GDNF secretion into the striatal parenchyma. Importantly, this study also revealed that transplanting GDNF-MSCs in a collagen hydrogel significantly diminished the host brain's response to the cells by reducing the recruitment of both microglia and astrocytes at the site of delivery. In conclusion, this hydrogel, which is composed of the natural extracellular matrix, collagen, was shown to be a well-tolerated cell delivery platform technology which could be functionalised to further aid cell support and graft integration.

Further characterisation of the LPS model of Parkinson's disease: a comparison of intra-nigral and intra-striatal lipopolysaccharide administration on motor function, microgliosis and nigrostriatal neurodegeneration in the rat.

Chronic neuroinflammation has been established as one of the many processes involved in the pathogenesis of Parkinson's disease (PD). Because of this, researchers have attempted to replicate this pathogenic feature in animal models using the potent inflammagen, lipopolysaccharide (LPS), in order to gain better understanding of immune-mediated events in PD. However, although the effect of intra-cerebral LPS on neuroinflammation and neurodegeneration has been relatively well characterised, its impact on motor function has been less well studied. Therefore, the aim of this study was to further characterise the neuropathological and behavioural impact of intra-nigral and intra-striatal administration of LPS. To do, LPS (10 µg) or vehicle (sterile saline) were stereotaxically injected into the adult rat substantia nigra or striatum on one side only. The effect of LPS administration on lateralised motor function was assessed using the Corridor, Stepping and Whisker tests for two weeks post-injection, after which, amphetamine-induced rotational asymmetry was completed. Post-mortem, the impact of LPS on nigrostriatal degeneration and microgliosis was assessed using quantitative tyrosine hydroxylase and OX-42 immunohistochemistry respectively. We found that intra-nigral administration of LPS led to localised microgliosis in the substantia nigra and this was accompanied by nigrostriatal neurodegeneration and stable spontaneous motor deficits. In contrast, intra-striatal administration of LPS led to localised microgliosis in the striatum but this did not lead to any nigrostriatal neurodegeneration and only induced transient motor dysfunction. In conclusion, this study reveals the impact of intra-cerebral LPS administration on PD-related neuropathology and motor function, and it indicates that the intra-nigral model may be a highly relevant model as it is associated with stable motor decline underpinned by nigral microgliosis and nigrostriatal neurodegeneration.

Kinetics of thermally induced heat shock protein 27 and 70 expression by bone marrow-derived mesenchymal stem cells.

Although bone marrow-derived mesenchymal stem cells (MSCs) are an attractive cell therapy candidate, their potential is limited by poor survival following transplantation. Over-expression of anti-apoptotic heat shock proteins using viral vectors can improve the survival of these cells under stressful conditions in vitro and in vivo. It is also possible to induce heat shock protein expression in many cell types by simply exposing them to a transient, nonlethal elevation in temperature. The response profile of MSCs to such a thermal stress has not yet been reported. Therefore, this study sought to determine the kinetics of thermally induced heat shock protein expression by MSCs in vitro. To determine if heat shock protein expression was a function of thermal stress exposure time, MSCs were exposed to 42°C for 15, 30, 45, and 60 min and were harvested 24 h later. To establish the time-course of heat shock protein expression, MSCs were heat shocked for 60 min and harvested 2, 24, 48, 72, 96, and 120 h later. The cells were then analyzed for Hsp27 and Hsp70 expression by Western blot. Densitometric analysis revealed that exposure to a thermal stress induced expression of both Hsp27 and Hsp70 and that the level of expression was dependant on stress exposure time. Following 60 min of heat stress, both Hsp27 and Hsp70 accumulated maximal expression after 48 h with both proteins returning to constitutive expression levels by 120 h. This study demonstrates that heat shock protein expression can be induced in MSCs by a simple thermal stress.