Иммунотерапевтический ландшафт амиотропического бокового склероза: библиометрический анализ тенденций в области исследований, приоритетов в области перевода и сетей сотрудничества (см.2006-2025).

Introduction

Amyotrophic lateral sclerosis (ALS) remains among the most therapeutically intractable neurodegenerative diseases. Following diagnosis, median survival ranges from 2 to 5 y, with the currently approved treatments riluzole and edaravone offering only marginal survival benefits and failing to modify the long-term disease course. 1 , 2 Although ALS was historically regarded as a motor neuron-autonomous disorder, converging evidence over the past two decades has reframed it as a disease strongly influenced by immune and inflammatory processes. 3 Microglial activation, astrocytic reactivity, peripheral immune infiltration, and adaptive immune dysfunction have been consistently documented in human tissues and experimental models. 4 , 5 This reconceptualization has catalyzed sustained interest in immunotherapy as a potential disease-modifying strategy.

Despite this expanding mechanistic understanding, therapeutic translation has lagged markedly. Since 2006, more than fifty immunomodulatory approaches have advanced to preclinical or early clinical evaluation, ranging from early strategies like microglial regulators and cytokine-targeted agents to more recent developments including regulatory T cell-based and gut-directed interventions. 6–8 However, no approach has yet demonstrated consistent and clinically meaningful disease-modifying effects, in contrast to the transformative successes of immunotherapy in oncology and classical autoimmune disorders. 9 , 10 This persistent translational gap underscores a critical need to examine why extensive mechanistic understanding of immunology has not yielded effective therapies for ALS.

A common explanation attributes this gap to biological complexity or insufficient mechanistic knowledge. However, publication trends indicate a different pattern. More than 2,000 ALS-related immunology papers have appeared since 2006, indicating sustained and diversified research activity. Rather than a lack of data, the translational impasse may reflect how knowledge in this field is organized, connected, and operationalized. Several structural features of the literature point toward this possibility. First, thematic compartmentalization is prominent. Research on microglial biology, adaptive immune responses, cytokine signaling, and microbiome-immune interactions has largely progressed in parallel, with limited cross-referencing or integrative modeling. 11 , 12 Second, uncertainty regarding the temporal dynamics of immune responses, especially the transition from potentially protective to pathogenic inflammation, has complicated therapeutic timing. 13 In the absence of clear stage-specific frameworks, several clinical trials have targeted late-stage inflammatory processes when irreversible neuronal loss may already predominate. 11 Third, preclinical-to-clinical translation remains heavily dependent on SOD1-based models, despite growing recognition that these models capture only a subset of ALS biology. 12 , 14 , 15 Systematic evaluation of which experimental findings generalize to heterogeneous human populations, and which reflect model-specific artifacts, remains limited. 16

Importantly, these challenges extend beyond the conceptual level and are embedded within the very structure of the scientific literature. The ways in which studies cite one another, research communities cluster, and collaborative networks form can either reinforce fragmentation or facilitate integration. While traditional narrative reviews are essential for synthesizing mechanistic insights, they are not designed to quantify such structural patterns or to identify where coordination breaks down across thousands of publications. Consequently, critical organizational factors that influence translational efficiency often remain implicit.

Bibliometric analysis provides a complementary approach by interrogating the architecture of knowledge production. 17 Citation networks, keyword evolution, and collaboration mapping allow quantitative assessment of how research themes emerge, converge, or remain isolated over time. In other biomedical fields, such analyses have successfully identified delays between mechanistic discovery and clinical application, as well as structural features associated with translational breakthroughs. 18 Applied to ALS immunotherapy, bibliometric methods offer an opportunity to move beyond descriptive summaries and to examine whether persistent therapeutic failure reflects strategic misalignment rather than scientific insufficiency. 19

In this study, we conducted a comprehensive bibliometric analysis of 2,256 publications on ALS immunotherapy indexed in the Web of Science and Scopus databases between 2006 and 2025, utilizing analytical tools including CiteSpace, VOSviewer, and Bibliometrix to address three interrelated questions: how the thematic focus of ALS immunotherapy research has evolved over time and whether this progression reflects meaningful conceptual integration or merely the sequential pursuit of isolated trends; the structure of collaboration networks across countries, institutions, and authors and their effectiveness in bridging mechanistic discovery and clinical translation; and which emerging research directions—such as gut-brain axis modulation, C9orf72-associated immune mechanisms, and immune-metabolic reprogramming—have developed sufficient conceptual coherence and research momentum to warrant prioritized translational investment. By mapping not only what has been studied but how the field organizes its inquiry, this work aims to clarify why extensive immunological insight has yet to yield effective ALS therapies, with the central contribution lying in reframing translational failure as a structural property of the research landscape, thereby providing an evidence-based foundation for more integrated and strategically aligned approaches to ALS immunotherapy.

Methods

Data Collection

A comprehensive literature search was conducted using two major databases: the Web of Science Core Collection (WoSCC, Thomson Reuters, New York, USA) and Scopus (Elsevier, Amsterdam, The Netherlands). The search strategy employed a combination of three term sets: TS1 = (“Amyotrophic Lateral Sclerosis” OR “ALS” OR “Lou Gehrig’s disease”), TS2 = (“immune” OR “immunotherapy” OR “immune response” OR “immunologic*”), and TS3 = (“treatment” OR “therap*”), with the final query formulated as TS = TS1 AND TS2 AND TS3. The timespan was restricted from January 1, 2006, to December 1, 2025, with language limited to English and document types filtered to include only articles and reviews.

This initial retrieval yielded 1,089 publications from WoSCC and 1,937 publications from Scopus. Considering the overlap and potential duplication between databases, we performed dataset integration and duplicate removal using the R programming language (version 4.3.1) with the Bibliometrix package. After deduplication, 770 redundant records were eliminated, resulting in a final dataset of 2,256 unique publications, comprising 932 articles (41.3%) and 1,324 reviews (58.7%), thereby ensuring high-quality data for subsequent bibliometric analyses. The complete workflow of literature search, screening, and integration is illustrated in Figure 1 . The literature search and screening process was independently conducted by two researchers to ensure reliability.

The bibliometric network analyses in this study were conducted using WoSCC and Scopus, as these databases provide the enriched metadata—including complete cited reference lists, institutional affiliations, and standardized author identifiers—required by CiteSpace, VOSviewer, and R-Bibliometrix for co-citation network construction, collaboration mapping, and citation burst detection. In addition, WoSCC and Scopus offer broader multidisciplinary coverage encompassing engineering, computational biology, and translational science journals relevant to an interdisciplinary field such as ALS immunotherapy. To complement these bibliometric analyses, we also conducted a systematic PubMed search to summarize the clinical development status of immunotherapeutic candidates. PubMed was selected for this purpose given its comprehensive indexing of clinical trial publications and its wide accessibility as the standard biomedical literature database. The PubMed-based search strategy, inclusion/exclusion criteria, and primary references for each candidate agent are detailed in the note accompanying Table 6 .

To ensure full transparency and reproducibility, the complete dataset of 2,256 publications—including titles, authors, journals, publication years, DOIs—is provided as Supplementary Table S1, enabling independent verification and reanalysis of all bibliometric findings reported herein.

Data analysis

For visual analysis and generation of knowledge maps, we utilized CiteSpace (version 6.4.R1, Drexel University, Philadelphia, USA), VOSviewer (version 1.6.20, Leiden University, Leiden, The Netherlands), and the R-Bibliometrix package (version 5.0), with Microsoft Excel 2025 employed for statistical calculations and trend visualization. CiteSpace was configured with time slicing from 2006 to 2025 (one-y intervals), node selection via g-index (k = 25), and pathfinder network pruning. Clustering employed the log-likelihood ratio (LLR) algorithm, with quality assessed using Modularity Q (>0.3 indicates significant structure) and Weighted Mean Silhouette (>0.7 indicates high confidence). This tool enabled reference co-citation analysis, keyword clustering, citation burst detection, and timeline visualization to identify emerging research fronts and thematic evolution. VOSviewer generated collaboration networks for countries, institutions, and authors, as well as keyword co-occurrence maps, where node size represents frequency, color indicates cluster membership, and link width reflects Total Link Strength (TLS). To validate cluster coherence, we manually examined 20 randomly selected publications from each cluster to confirm thematic relevance to ALS immunotherapy research. Clusters with labels derived from adjacent fields (e.g., cancer, Parkinson’s disease) were retained when publications demonstrated clear mechanistic or therapeutic connections to ALS immune mechanisms, such as shared inflammatory pathways or adapted therapeutic modalities.

The R-Bibliometrix package facilitated advanced thematic analyses through its Biblioshiny interface.

The timespan was divided into four periods of unequal duration based on publication volume distribution rather than uniform calendar intervals, a strategy recommended in bibliometric methodology to ensure comparable analytical power across periods. 34 During the early phase (2006–2016), annual output was relatively low (averaging approximately 60 publications per year), necessitating a longer aggregation window to accumulate a sufficient corpus for robust thematic mapping. In contrast, the rapid acceleration from 2022 onward (exceeding 200 publications per year) permitted shorter intervals while maintaining adequate sample sizes for reliable keyword clustering and thematic analysis. The resulting periods—2006–2016 (n ≈ 659), 2017–2021 (n ≈ 642), 2022–2023 (n ≈ 445), and 2024–2025 (n ≈ 510)—each contain a comparable number of publications, thereby enabling meaningful cross-period comparison of thematic evolution patterns.

Thematic evolution diagrams traced theme emergence and transformation across periods, while strategic diagrams positioned themes by centrality and density to identify motor themes, basic themes, emerging/declining themes, and niche themes. Multiple Correspondence Analysis (MCA) uncovered latent structures among high-frequency keywords. Additionally, dual-map overlay analysis in CiteSpace revealed interdisciplinary citation pathways between citing and cited journals. Publication trends were characterized using exponential regression, while Price’s Law and Bradford’s Law identified core authors and journals, respectively.

Results

Publication trends and global distribution

A total of 2,256 publications were identified for analysis, comprising 932 articles (41.3%) and 1,324 reviews (58.7%) ( Table 1 ). Annual output increased from 31 publications in 2006 to 260 in 2025, representing an 8.4-fold increase (y = 18.961 × 0.7041, R 2 = 0.8271). Research development progressed through three phases: an exploratory phase (2006–2013), steady expansion (2014–2019), and accelerated growth from 2020 onward ( Figure 2(A-B) ).

The United States, China, Germany, Italy, and the United Kingdom ranked as the top five contributing countries ( Figure 3(A) ). International collaboration remained limited at 13.2%, with partnerships clustered regionally—a European cluster centered on Germany and Italy, and a North American cluster led by the United States ( Figure 3(B) ).

Co-citation network analysis

The co-citation network exhibited well-defined clustering (modularity Q = 0.7616, weighted mean silhouette = 0.9013), with sixteen major clusters identified along the temporal timeline ( Figure 2(C) ). Early clusters (2006–2012) focused on foundational topics: SOD1, neuroprotection, autoimmunity, and blood-brain barrier. Mid-period clusters (2010–2017) emphasized innate immunity: complement system, TREM2, and microglial biology. Recent clusters (post-2015) shifted toward translational themes: clinical trials, dysbiosis, glycolysis, and gut-brain axis.

Keyword analysis

The keyword network positioned “amyotrophic-lateral-sclerosis” centrally (occurrences = 464, total link strength [TLS] = 1,726), with strong co-occurrence with “mouse model” (TLS = 1,033), “Alzheimer’s disease” (TLS = 886), and “Parkinson’s disease” (TLS = 636). High-frequency keywords included microglia (occurrences = 54, TLS = 295), neuroinflammation, and activation (occurrences = 101, TLS = 443) ( Table 2 ; Figure 2(D) ).

Citation burst analysis

Citation burst analysis, restricted to original research articles (reviews excluded), revealed three successive waves of research emphasis ( Figure 2(E) ). Early bursts (2008–2012) were anchored in T cell – microglia interactions, with Beers DR (2008, strength = 13.38) and Chiu IM (2008, strength = 9.16) establishing that CD4 + T cells modulate microglial neuroprotection in mSOD1 mice. Mid-period bursts (2012–2018) were dominated by regulatory T cell biology: Beers DR (2011, strength = 15.08) and Henkel JS (2013, strength = 15.86)—the two strongest signals in the entire dataset – collectively demonstrated that Tregs are neuroprotective in ALS mice and that peripheral Treg levels and FoxP3 expression inversely predict disease progression in patients; Liddelow SA (2017, strength = 11.37) and Beers DR (2017, strength = 11.51) further implicated neurotoxic reactive astrocytes and Treg dysfunction as converging mechanisms. Recent bursts (2018–2024) reflect a shift toward translational and innate immune mechanisms: Yazdani S (2022, strength = 10.26) showed that T cell phenotypes at diagnosis predict ALS progression, Yu CH (2020, strength = 9.24) identified TDP-43–driven cGAS/STING activation as a neuroinflammatory pathway, and Chiot A (2020, strength = 7.82) demonstrated that peripheral macrophage modulation can suppress microglial reactivity and extend survival.

Thematic evolution

Thematic analysis across four periods (2006–2016, 2017–2021, 2022–2023, 2024–2025) demonstrated progressive refinement from general immunological concepts toward disease-specific immune mechanisms ( Figure 4(A) ). Strategic diagrams showed that inflammation and neuroinflammation migrated toward the “motor themes” quadrant, reflecting increasing centrality and internal connectivity ( Figure 4(B-C) ). Multiple correspondence analysis identified three stable configurations: a mechanism-oriented cluster (microglial activation, oxidative stress, cytokine signaling), a methodological cluster (clinical descriptors), and a disease-model cluster (mouse models, neurodegenerative comparisons) ( Figure 4(D) ).

Author and collaboration analysis

Among 8,542 contributing authors, WANG Y (33 papers), WANG J (29 papers), and APPEL S (27 papers) ranked highest in productivity ( Table 3 ). APPEL S led in local H-index (24), followed by BEERS D (15) and WANG Y (15). The author co-citation network revealed four disconnected clusters (n > 10 members each) with minimal cross-group collaboration ( Figure 3(C) ).

Institutional and journal analysis

Institutional networks showed multiple clusters anchored by established ALS research centers, with limited inter-cluster linkage ( Figure 3(D) ). The Harvard–Johns Hopkins and Chinese Academy–Tongji clusters appeared as separate hubs with only 7 joint publications among top-20 institutions.

Top journals by publication volume included International Journal of Molecular Sciences (100), Frontiers in Immunology (70), and Cells (49) ( Table 4 ; Figure 3(E) ). Dual-map overlay analysis positioned citing journals (left panel) and cited references (right panel) within a discipline-based coordinate space ( Figure 5 ). Three dominant citation trajectories (orange paths, accounting for approximately 68% of total citation flows) connected immunology and molecular biology journals on the citing side to neuroscience and pharmacology sources on the cited side. This asymmetric pattern—characterized by stronger citing-to-cited flows than reciprocal back-citations—indicates that ALS immunotherapy research predominantly imports immunological concepts into a neuroscience framework, with limited bidirectional knowledge exchange. The sparse back-citation to immunology journals suggests that ALS-specific immunological findings have had limited reciprocal impact on broader immunological theory, a structural feature that may constrain cross-disease knowledge transfer and hinder the adoption of successful immunotherapeutic paradigms developed in other fields.

Emerging research frontiers

Keyword clustering identified eleven thematic groups (modularity Q = 0.4685, weighted mean silhouette = 0.7648), with neurodegeneration, Parkinson’s disease, and regulatory T cells as leading clusters ( Figure 6(A) ). In the timeline visualization ( Figure 6(B) ), each horizontal band represents a distinct keyword cluster plotted against publication year, with node size proportional to citation frequency and inter-node links indicating co-citation relationships. Clusters #9 (gut microbiota) and #10 (hexanucleotide repeat) emerged comparatively later in the timeline, with their earliest substantial nodes appearing around 2015 and beyond, indicating their relatively recent entry into the ALS immunotherapy discourse. The quantitative growth trajectories of these emerging clusters are further detailed in Table 5 , which documents a 6.8-fold increase in gut microbiota publications (from 3 in 2006–2010 to 61 in 2021–2025), distinguishing these nascent research fronts from more established themes such as microglia, whose publication volume plateaued during the same period (growth rate 0.8×). Keyword burst detection identified “regulatory T cells” (2020–2025, strength = 18.6) and “gut microbiome” (2022–2025, strength = 12.3) as the strongest emerging keywords ( Figure 7(A) ). Intervention-related keywords increased from 23% (2015–2019) to 41% (2020–2025) of high-frequency terms ( Figure 7(B) ).

Sensitivity analyses

Sensitivity analyses showed that the main results were stable across database configurations and document types. Compared with the merged WoSCC+Scopus dataset, the WoSCC-only dataset contained fewer publications but exhibited higher citation density and international collaboration rates, while preserving identical core thematic clusters, temporal research phases, leading countries, and key authors. Restriction to original articles increased the relative prominence of mechanistic keywords but did not change the ranking of emerging themes, with regulatory T cells and the gut—brain axis remaining the strongest burst topics. Collaboration network structures were highly similar across all analyses.

Discussion

The following discussion integrates the quantitative bibliometric findings presented in the Results Section with external clinical evidence to provide a translational assessment of the ALS immunotherapy landscape. Rather than functioning as an independent narrative review, each subsection is anchored to specific analytical outputs—including co-citation cluster trajectories ( Figure 2(C) ), keyword burst detection ( Figures 2(E), 7(A) ), collaboration network topology ( Figure 3(C,D) ), and thematic evolution patterns ( Figure 4(A–C) )—and extends these quantitative patterns by evaluating them against recent clinical trial outcomes and mechanistic developments. This integrated approach aims to clarify the relationship between bibliometric research dynamics and translational progress, and to identify structural features of the research landscape that may either facilitate or impede therapeutic development.

Growth trends, thematic evolution, and structural barriers to translation

This comprehensive bibliometric analysis systematically evaluated global research trends in ALS immunotherapy spanning nearly two decades (2006–2025), encompassing 2,256 publications. The temporal trajectory of this field reveals distinct developmental phases. During the early period (2006–2010), annual publications remained relatively modest, averaging fewer than 45 per year, as researchers primarily focused on establishing foundational immunological concepts. A steady acceleration occurred between 2011 and 2015, with annual output surpassing 60 publications, reflecting growing recognition of neuroinflammation as a therapeutic target. The period from 2016 to 2020 witnessed substantial growth, culminating in a marked increase after 2021—annual publications more than doubled from 109 (2019) to 250 (2024). This rapid expansion likely reflects the convergence of multiple factors, including the maturation of neuroinflammation research paradigms, substantially expanded funding for neurodegeneration and immunology research, and renewed investigator interest driven by intensified clinical trial activity. 35 , 36 Geographically, the United States, China, Germany, Italy, and the United Kingdom have emerged as the primary contributors to this field. The United States maintained historical leadership with cumulative output exceeding 680 publications; however, a plateau has been observed since 2018, potentially reflecting research priority shifts or funding reallocations. In contrast, Chinese publications demonstrated substantial growth, doubling from approximately 45 (2020) to over 95 (2025) annual publications. Nevertheless, although China has become increasingly prolific in ALS immunotherapy research, its international collaboration rate remains relatively low (13.2%), indicating that research activities are predominantly domestic in nature. This pattern aligns with observations in other biomedical domains, where China’s multiple-country publication ratio typically ranges from 8–10%, reflecting structural features such as funding priorities favoring national projects and institutional norms encouraging domestic collaboration. Furthermore, analysis of institutional networks revealed that major research hubs—including Harvard—Johns Hopkins in the United States and Tongji—Chinese Academy of Sciences in China—have emerged as highly productive but largely disconnected clusters, with only seven joint publications documented among the top 20 institutions, highlighting a substantial gap in transatlantic research linkage.

The thematic evolution from general immunological concepts toward more targeted research directions represents a conceptual maturation of the field. The temporal progression of co-citation clusters reveals distinct developmental phases: the early period (2006–2012) emphasized disease pathophysiology and foundational immune mechanisms, with research clusters centered on SOD1 mutations, neuroprotection strategies, and blood-brain barrier dysfunction; the intermediate phase (2013–2018) witnessed a transition toward innate immune signaling and microglial activation, with TREM2 and complement system components emerging as prominent research foci; most recently (2019–2025), the field has shifted toward translational research and systemic mechanisms, encompassing clinical trials, dysbiosis, and gut-brain axis interactions. This evolution is quantitatively reflected in the increasing proportion of intervention-related keywords, which rose from 23% to 41% of high-frequency terms between 2015–2019 and 2020–2025. However, bibliometric prominence does not necessarily correlate with clinical efficacy or translational success, and several important caveats apply to interpretation of these trends.

While the mechanistic understanding of ALS immunopathology has advanced considerably over the past two decades, our collaboration network analyses reveal a fundamental structural barrier to translational progress. As quantified in Figure 3(C,D) (international co-authorship rate = 13.2%; only 7 joint publications among top-20 institutions; four disconnected author clusters with n >10 members each), the ALS immunotherapy research landscape is characterized by highly productive but relatively isolated modules at the country, institutional, and author levels. Taken together, such modularity may contribute to research duplication and inefficient resource allocation, as parallel efforts addressing similar questions proceed independently across continents. The separation between preclinical mechanistic groups and clinically oriented research networks may hinder the iterative feedback necessary for refining immunotherapeutic targets. Moreover, highly modular networks may impede recruitment for clinical trials, particularly genotype-stratified approaches requiring large, genetically characterized cohorts spanning multiple centers. Consequently, these structural features help explain why substantial immunological insight has yet to yield effective ALS therapies—translational failure reflects not only biological complexity but also strategic misalignment within the research ecosystem itself.

Lessons from clinical trial failures and negative results

Beyond the structural fragmentation identified through our collaboration network analysis ( Figure 3(C,D) , showing four disconnected author clusters and limited inter-institutional linkage) and the thematic compartmentalization revealed by keyword clustering ( Figure 6(A) , modularity Q = 0.4685), a notable gap in the bibliometric landscape is the systematic underrepresentation of negative and null results. Publication bias toward positive findings may substantially distort perceptions of therapeutic promise and contribute to unrealistic expectations regarding immunotherapeutic efficacy in ALS. Indeed, several recent high-profile failures merit careful consideration, as they provide critical lessons for future trial design and strategic prioritization. Understanding why promising preclinical candidates fail in human trials is essential for advancing the field beyond repetitive cycles of optimism and disappointment.

Of particular note, complement C5 inhibition—once considered one of the most promising immunotherapeutic approaches based on compelling mechanistic rationale and robust preclinical evidence—has now failed in multiple well-powered clinical trials. 37 The phase III CHAMPION-ALS trial of ravulizumab (Ultomiris), a long-acting anti-C5 monoclonal antibody, was stopped for futility following a pre-specified interim analysis; the published results demonstrated no significant benefit on ALSFRS-R functional decline or survival endpoints. 31 Similarly, the randomized clinical trial of zilucoplan, a subcutaneous C5 inhibitor, showed no effect on ALS disease progression at 24 weeks. 32 These negative results have markedly diminished the rationale for prioritizing complement inhibition in ALS, unless future studies can identify biomarker-defined subpopulations that may derive benefit.

Equally instructive are the earlier failures of celecoxib (a COX-2 inhibitor), 38 , 39 pioglitazone (a PPAR-γ agonist with anti-inflammatory properties), 40 , 41 and minocycline (a tetracycline antibiotic with immunomodulatory effects), 42 , 43 all of which demonstrated neuroprotective effects in SOD1 transgenic mouse models but failed to show benefit in subsequent human trials. These examples highlight the persistent challenge of translating rodent findings to human disease and underscore the importance of cautious interpretation of preclinical evidence. Importantly, however, these translational failures should not be interpreted as evidence that SOD1-based models are uniformly uninformative of human disease. A salient counterexample is tofersen, an antisense oligonucleotide targeting SOD1 mRNA, which has demonstrated meaningful clinical benefit in SOD1-ALS—including significant reductions in plasma neurofilament light chain levels and attenuation of functional decline—and has received regulatory approval as the first disease-modifying therapy for a genetic form of ALS. 28 This exception underscores that translational failure often reflects the specific therapeutic modality, mechanism, or timing of intervention rather than the inherent inadequacy of the genetic model itself; mechanistic insights derived from SOD1-based preclinical systems can indeed translate to human benefit when the therapeutic strategy is appropriately matched to the disease mechanism.

A further consideration that merits explicit discussion is whether human cellular models may be more reflective of human ALS pathology than rodent systems, and how these platforms could advance the field. Induced pluripotent stem cell (iPSC)-derived motor neurons, astrocytes, and microglia generated from ALS patients capture the genetic and epigenetic background of human disease and have revealed disease-relevant phenotypes—including TDP-43 mislocalization, impaired axonal transport, and dysregulated inflammatory signaling—that are not fully recapitulated in standard transgenic mouse models. 44 Patient-derived iPSC platforms also enable genotype-specific target validation and drug testing, and allow identification of disease modifiers that may be invisible in artificially overexpressing transgenic systems. Three-dimensional neuromuscular organoids and multi-cell-type co-culture systems incorporating immune cell populations further allow modeling of the neuroinflammatory microenvironment with greater human fidelity. 45 Systematic integration of human iPSC-derived platforms into preclinical validation pipelines could therefore serve as a critical intermediate step between basic mechanistic discovery and clinical trial initiation, potentially improving target selection, reducing animal-to-human translational failure, and ultimately enhancing the probability of success in ALS immunotherapy trials.

Collectively, the consistent failure of immunomodulatory trials points to several potential explanations for the persistent gap between mechanistic promise and clinical reality. First, timing of intervention represents a critical consideration—immune dysregulation may be most amenable to modification early in disease, before substantial motor neuron loss has occurred, yet most patients are enrolled well after symptom onset. Second, patient heterogeneity remains inadequately addressed—subpopulations defined by genetic background, inflammatory biomarker profiles, or disease phenotype may respond differentially to immunotherapy; 46 third, target engagement poses substantial technical challenges—achieving adequate CNS penetration and durable immunomodulation remains difficult for systemically administered agents; 47 and fourth, single-target limitations represent a fundamental conceptual challenge—the multifaceted nature of immune dysregulation in ALS may render single-mechanism interventions fundamentally insufficient to alter disease trajectory. As a result, future trials should systematically incorporate biomarker-based patient stratification, adaptive designs permitting early futility assessments, and pharmacodynamic endpoints confirming target engagement.

Prioritization of immunotherapy subfields based on translational potential

When bibliometric signals—including citation burst strength ( Figure 2(E) ; “regulatory T cells,” strength = 18.6, active 2020–2025), keyword emergence trajectories ( Figure 7(A,B) , showing intervention-related terms rising from 23% to 41% of high-frequency keywords), and thematic cluster maturation patterns ( Figure 6(B) , Table 5 )—are interpreted alongside recent clinical trial outcomes, a clearer picture emerges regarding which immunotherapeutic directions are most likely to influence ALS progression in the near and medium term. Importantly, rather than reflecting publication volume alone, this integrated perspective weighs mechanistic relevance to ALS pathology, consistency of clinical evidence across studies, regulatory and translational maturity, and the practical feasibility of biomarker-guided patient stratification. Notably, ALS immunotherapy appears to be transitioning from a phase of mechanistic discovery toward more focused translational development.

Among the immune-based strategies currently under investigation, approaches centered on regulatory T cells (Tregs) appear to be the most advanced in terms of translational development, based on current available evidence. Mechanistically, a substantial body of work spanning over a decade has established that Tregs exert critical anti-inflammatory functions during immune activation through multiple pathways, including secretion of immunosuppressive cytokines (IL-10, TGF-β), direct cell-cell contact inhibition, and metabolic disruption of effector T cells. Remarkably, impairment of Treg suppressive capacity in ALS correlates strongly with accelerated disease progression. 48 This dysfunction is accompanied by an expansion of pro-inflammatory myeloid populations and epigenetic alterations within the Treg lineage, including increased methylation of the TSDR region. 49 Experimental studies have further shown that adoptive transfer of activated Tregs from early-stage ALS mice can suppress microglial neurotoxicity while enhancing the production of neuroprotective mediators such as GDNF and TGF-β. 50 Importantly, these mechanistic insights have translated into early clinical development: low-dose IL-2 and autologous Treg infusion have demonstrated consistent biological effects and acceptable safety in phase I studies, and the MIROCALS trial has provided the strongest clinical evidence to date for sustained Treg expansion in patients. 21 , 23 Although definitive disease-modifying effects remain to be established in larger randomized trials, additional support for the protective role of counter-regulatory IL-10-producing T cell responses comes from recent findings demonstrating that antigen-specific CD4 + T cells recognizing the C9orf72 protein are enriched in ALS patients with longer predicted survival, 51 further underscoring the therapeutic rationale for selectively amplifying regulatory immune responses. Treg-based immunotherapy currently appears to represent one of the more advanced immune-directed strategies in ALS within our translational readiness framework—though this assessment is contingent on continued positive results in ongoing and future trials.

Closely related in mechanistic importance, but considerably more heterogeneous in clinical outcomes, are interventions targeting microglial function. Microglia occupy a central position in ALS pathophysiology, serving as the primary resident immune cells of the central nervous system. Notably, these cells exhibit context-dependent roles that can either support neuronal survival through secretion of neurotrophic factors or promote neurodegeneration through release of pro-inflammatory cytokines and reactive oxygen species as disease progresses. 52 Several approaches aimed at modulating innate immune activation have entered clinical evaluation. NP001, which regulates macrophage and microglial activation states, has shown signals of clinical stabilization in patient subgroups characterized by elevated systemic inflammation. 53 In parallel, preclinical studies of CSF1R inhibition have demonstrated improvements in motor function and survival in ALS mouse models, highlighting the therapeutic relevance of microglial homeostatic pathways. 54 The TREM2–APOE axis has also emerged as a promising target, as disease progression is associated with suppression of homeostatic microglia and expansion of neurotoxic phenotypes. 55 Nevertheless, translation in this domain has been uneven. Masitinib has shown subgroup benefits in late-phase trials, but regulatory assessment has raised concerns regarding robustness and clinical relevance, while experience with TREM2-targeted therapies in Alzheimer’s disease underscores the risks of cross-disease extrapolation. 25 , 56 Together, these findings position microglial modulation as a high-impact but methodologically demanding area, in which future progress will likely depend on biomarker-driven stratification and careful patient selection.

Beyond single-target approaches, the accumulating evidence increasingly points to intrinsic limitations of monotherapy in ALS, paralleling observations in oncology where combination regimens have become the standard of care. Immune dysregulation in ALS is inherently multifaceted and evolves dynamically over the disease course, suggesting that interventions acting on a single pathway may be fundamentally insufficient to alter disease trajectory. 57 In this context, combination strategies—such as pairing Treg expansion with modulation of innate immune activation, or integrating antisense oligonucleotide therapy with immunomodulation in genetically defined patient subsets—emerge as a rational next step. 22 While such approaches remain largely conceptual at present, their mechanistic complementarity supports prioritization in future translational research, provided that issues of timing, dosing, safety, and biomarker validation are rigorously addressed.

Genotype-stratified immunotherapy represents another direction with substantial long-term promise. The C9orf72 hexanucleotide repeat expansion, the most common genetic cause of ALS, is associated with distinctive immune and inflammatory features, including dipeptide repeat protein accumulation and microglial activation. 58 Early clinical experience with the antisense oligonucleotide BIIB078 demonstrated target engagement and measurable biomarker effects, but failed to produce clinical benefit, highlighting the gap that can exist between molecular correction and functional outcomes. 30 A second C9orf72-targeting ASO, WVE-004 (Wave Life Sciences)—a stereopure antisense oligonucleotide evaluated in the Phase 1/2 FOCUS-C9 trial—was likewise discontinued for lack of meaningful clinical benefit despite demonstrating measurable reductions in CSF poly(GP) dipeptide repeat protein levels, confirming that target engagement alone does not guarantee functional improvement. 59 The concordant failure of two mechanistically distinct C9orf72-targeting ASOs points to several plausible explanations that should inform future trial design. First, intervention may have occurred too late in the disease course, after downstream neurodegenerative and neuroinflammatory cascades had already become self-sustaining and largely irreversible; available evidence suggests that C9orf72-related pathology begins years before symptom onset, rendering post-symptomatic ASO treatment potentially insufficient. 58 Second, reduction of toxic repeat RNA species or DPR proteins may be inadequate if concurrent haploinsufficiency of normal C9orf72 protein function—which plays important roles in autophagy, lysosomal homeostasis, and immune regulation—contributes independently to disease pathogenesis and is not restored by knockdown strategies. 60 , 61 Third, intrathecal delivery may not achieve adequate drug coverage of upper motor neurons in the motor cortex, which are critically affected in ALS. 62 Together, these results suggest that genetic stratification alone is unlikely to be sufficient, and that future success in C9orf72-ALS will likely require earlier intervention windows, improved ASO chemistry and delivery strategies targeting both cortical and spinal compartments, and combination approaches that address the full spectrum of gain-of-function toxicity and loss-of-function consequences of the repeat expansion.

Other emerging directions, such as modulation of the gut—brain axis, illustrate the important distinction between conceptual novelty and translational readiness. Although alterations in gut microbiota composition have been linked to neuroinflammation in preclinical models and observational human studies—with proposed mechanisms including microbial metabolite signaling, intestinal barrier dysfunction, and vagal nerve-mediated communication—clinical evidence remains limited to small feasibility trials with highly heterogeneous methodologies. 63 , 64 To date, interventions such as probiotic supplementation or fecal microbiota transplantation have not demonstrated reproducible disease-modifying effects, indicating that this area remains hypothesis-generating rather than clinically established. 65

In contrast, as detailed in Lessons from clinical trial failures and negative results, recent large-scale clinical failures have fundamentally reshaped the therapeutic landscape for complement-directed immunotherapy. Despite strong mechanistic rationale, inhibition of terminal complement activation has failed to improve functional decline or survival in well-powered phase III trials of ravulizumab and zilucoplan. These consistent negative results argue against continued prioritization of C5 inhibition for unselected ALS populations and underscore the importance of early futility assessments and adaptive trial designs in future immunotherapy development. However, these results do not definitively exclude a role for complement-directed therapy in biomarker-defined subgroups with documented complement pathway activation, and targeted investigations in such populations may still yield meaningful insights.

Overall, the convergence of bibliometric trends and clinical evidence suggests that immune targets related to regulatory T cell function, microglial activation pathways, and genotype-associated immune dysregulation currently offer the strongest rationale for therapeutic advancement within the present evidence base. At the molecular level, low-dose IL-2 and autologous Treg-based approaches appear to be among the more promising immunotherapeutic strategies to date, whereas complement C5 inhibition has been de-emphasized for unselected populations based on repeated late-phase failures—though targeted investigation in biomarker-defined subgroups may still be warranted. These conclusions represent our current assessment based on available evidence through early 2025 and are subject to revision as new clinical trial results emerge. The clinical development status of key candidates reflecting these trajectories is summarized in Table 6 .

Recommendations for future immunotherapy trial design

Based on the lessons from recent trial failures and the marked heterogeneity of ALS, future immunotherapy trials will likely benefit from more refined and flexible design strategies. In particular, patient stratification at enrollment using biological markers—such as serum neurofilament light chain levels, inflammatory cytokine profiles, and genetic background including C9orf72 or SOD1 status—may help reduce clinical heterogeneity and improve signal detection. 66 , 67 Equally important is the incorporation of pharmacodynamic endpoints to verify target engagement, including molecular or cellular readouts relevant to the therapeutic mechanism, rather than reliance on clinical outcomes alone. 67 Given the high attrition rate of late-phase ALS trials, adaptive or platform-based designs that allow early futility assessment and dose optimization may further mitigate the risk of large-scale failure. Combination immunotherapy approaches should be considered only after safety and biological activity have been established for individual agents, with careful attention to sequencing and interaction effects. 68 Finally, prespecified subgroup analyses based on biomarker-defined strata may provide critical insights into treatment responsiveness, even in trials that do not meet primary endpoints at the population level. 69

Limitations

Several methodological and interpretive limitations of this study warrant careful consideration. First, although we employed a dual-database approach integrating Web of Science Core Collection and Scopus to maximize coverage and reduce database-specific indexing biases, publications in non-indexed venues or those using nonstandard terminology may still be underrepresented. Second, bibliometric indicators capture patterns of research attention and citation influence rather than research quality or clinical validity; high citation counts may reflect controversy, accessibility, or timeliness rather than methodological rigor or therapeutic promise. Third, publication bias toward positive results likely inflates apparent research momentum for successful directions while obscuring failed approaches that may be equally informative for the field.

Conclusion

This comprehensive bibliometric analysis of ALS immunotherapy research spanning nearly two decades (2006–2025) demonstrates that the field has expanded rapidly—particularly since 2020, when annual publications more than doubled—accompanied by a significant shift from broad immunological concepts toward more targeted therapeutic strategies, including regulatory T cell—based approaches, microglial modulation, gut—brain axis interventions, and genotype-stratified therapies. However, despite this intellectual maturation, the research landscape remains highly fragmented, with modular collaboration networks that may impede effective translation from mechanistic discovery to clinical application. Importantly, recent high-profile trial failures, most notably the consistent negative results of complement C5 inhibition with ravulizumab and zilucoplan, highlight a persistent disconnect between biological rationale and clinical efficacy and reinforce the urgent need for more rigorous translational frameworks. Taken together, integrating bibliometric trends with clinical evidence suggests that near-term efforts should focus on immunotherapeutic strategies with the greatest translational readiness, particularly Treg-based and microglia-targeted approaches, while deprioritizing complement inhibition in unselected populations. Progress will further depend on strengthening international collaboration, systematically embedding biomarker-guided patient stratification and pharmacodynamic validation into trial design, and rigorously capturing negative results to inform collective learning. In conclusion, with coordinated efforts across disciplines and institutions, and with realistic recognition of recent failures, the evolving immunotherapeutic landscape retains cautious but meaningful potential for disease modification in ALS.

Supplementary Material

Table S1.xlsx

Biographies

Jialin C. Zheng is a doctoral supervisor and dean of Tongji University School of Medicine. He is elected as an academician of the European Academy of Sciences (Life Sciences) and the European Academy of Sciences and Arts (Medicine), and is recognized as a national overseas high-level talent. He currently directs the Brain Aging-Related Medicine Basic Innovation Center of the Ministry of Education and serves as the Shanghai director of the Municipal Catalytic Medicine Frontier Research Base. His research focuses on the pathogenesis of neurodegenerative diseases, novel diagnostic and therapeutic strategies, and stem cell-based treatments. Prof. Zheng has published over 250 papers in leading international journals and has led several major national research initiatives, including projects under the National Natural Science Foundation of China, the National Key Research and Development Program, and the 973 Program.

Qihui Wu is a Distinguished Research Fellow under the “Young Hundred Talents” Program at Tongji University School of Medicine, with a joint appointment at Shanghai Fourth People’s Hospital, and serves as a doctoral supervisor. He received his Ph.D. from Peking University and completed postdoctoral training (2017–2021) in the laboratory of Prof. Virginia Lee (2020 Breakthrough Prize laureate) at the University of Pennsylvania. His research focuses on the pathological and physiological functions of disease-associated proteins in neurodegenerative disorders using electrophysiology, live-cell imaging, and in vivo techniques. Dr. Wu has been recognized as a Shanghai Overseas High-Level Talent and Shanghai Pujiang Talent. He has published as first or corresponding author in leading journals including Neuron , Acta Neuropathologica , and Science Signaling (cover article), and has led projects funded by the National Natural Science Foundation of China and Shanghai Municipal Science and Technology Commission.

Ge Gao is an associate professor and graduate supervisor at Tongji University School of Medicine. Her research primarily investigates the role and mechanisms of immune inflammation in central neurodegenerative diseases. In the past five years, she has published 15 SCI papers as the first, co-first, or corresponding author in prestigious journals including Advanced Science, Cancer Research, Signal Transduction and Targeted Therapy , and Clinical and Translational Medicine . She has led multiple research projects funded by the National Natural Science Foundation of China (Youth and General Programs) and the Shanghai Municipal Science and Technology Commission. Dr. Gao has authored and edited several academic works, serving as the chief editor of Surgical Treatment of Cerebral Palsy: Fundamentals and Clinical Practice and Abnormal Posture Assessment and Correction , and contributing to textbooks such as Functional Assessment and Anatomical Analysis of Spinal Nerves and Modern Surgical Treatment and Rehabilitation of Cerebral Palsy .

Funding Statement

This work was partially supported by grants from the National Natural Science Foundation of China [82471448 to G.G., 82101486 and 82371426 to Q.W., 82530039 to J.C.Z.], Science and Technology Commission of Shanghai Municipality (STCSM) grant [24ZR1468500 to G.G. and 23ZR1467900 to Q.W.], Ningxia Hui Autonomous Region Key Research and Development Project [2022BFH02012 to Q.W.], Shanghai Fourth People’s Hospital affiliated to Tongji University School of Medicine [sykyqd02301 and sykyqd02302 to Q.W.], the Fundamental Research Funds for the Central Universities [22120240333 to G.G.], Tongji University Medicine-X Interdisciplinary Research Initiative [No. 2025-0650-ZD-06 to Q.W.], Shanghai Pujiang Program [21PJ1412100 to Q.W.].

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data presented in this study are available on request from the corresponding author.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21645515.2026.2664985

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Associated Data

Supplementary Materials

Table S1.xlsx

Data Availability Statement

The data presented in this study are available on request from the corresponding author.