Introduction: Gene therapy represents a transformative frontier in modern medicine, offering the potential to correct genetic defects, modulate disease pathways, and deliver therapeutic agents with unprecedented precision and accuracy. At its core, gene therapy relies on the efficient and safe transfer of genetic material into target cells, a task mediated by specialized delivery systems known as vectors. These molecular vehicles, which encompass both viral and non-viral platforms, are crucial components in the success of gene therapy, influencing both the efficacy and safety of therapeutic outcomes. Among the diverse array of vectors, viral vectors have emerged as the cornerstone of clinical applications due to their evolved ability to hijack cellular machinery for gene delivery. Within this class, adenoviral vectors stand out as a pivotal tool, distinguished by their unique biological properties and extensive history in translational research. Adenovirus (Ad), a DNA virus, was first isolated in 1953 by Rowe et al. in cell cultures derived from adenoid tissue, hence its name. These primary cell cultures were often noted to degenerate spontaneously over time, and Adenoviruses (Ads) are now known to be a common cause of asymptomatic Respiratory Tract Infections (RTIs) that produce in vitro cytolysis in these tissues. Their remarkable transduction efficiency enables robust gene expression across various cell types, a versatility unmatched by many competing platforms. Second, their large genomic capacity, accommodating up to 37 kilobases (kb) of exogenous DNA, facilitates the delivery of complex therapeutic constructs, such as large genes or multiple regulatory elements. Third, adenoviral vectors (AdVs) boast a well-documented legacy, with their use tracing back to the earliest gene therapy trials in the 1990s. This historical foundation has yielded a wealth of data on their performance, paving the way for iterative improvements in design and application. However, this prominence is tempered by challenges, notably their immunogenicity and transient expression profiles. The enduring relevance of AdV is evident in its broad application spectrum, spanning monogenic disease treatments, oncology, and vaccine development. Yet, as the gene therapy landscape evolves, so too must our understanding of these vectors. Advances in vector engineering, coupled with emerging insights into host-vector interactions, are redefining their potential while addressing longstanding limitations. This dynamic interplay between innovation and challenge positions AdVs as a critical subject for ongoing scrutiny and development. The purpose of this review is to provide a comprehensive examination of AdV in gene therapy, synthesizing their biological underpinnings, therapeutic applications, inherent challenges, and prospects. By integrating historical context with cutting-edge research, this article aims to elucidate why AdVs remain a focal point in the field and how they might shape its trajectory moving forward. To achieve this, the review is structured as follows: first, a background section will outline the origins and biology of adenoviral vectors, establishing their foundational role. Subsequent sections will delve into their mechanisms of action, detailing the molecular basis of their efficacy, followed by an exploration of their diverse applications in clinical and experimental settings. The article will then critically assess their advantages in juxtaposition to their limitations before addressing current challenges and innovative strategies aimed at overcoming them. A synthesis of the discussion will tie these threads together, offering insights into the broader implications of gene therapy and culminating in a forward-looking conclusion. Through this roadmap, this review seeks not only to inform but also to inspire continued exploration of AdVs as indispensable tools in the quest to harness the genome for human health.
Methods: This review-based article aims to provide a comprehensive overview of adenoviral vectors used in gene therapy; consequently, a systematic approach was taken to identify and select relevant literature.
2.1 Search Strategy
A thorough search was conducted using the following databases, which offer broad coverage of biomedical and scientific literature: PubMed, ScienceDirect, Google Scholar, and Web of Science. The search used the Medical Subject Headings (MeSH) related to adenoviral vectors and gene therapy. The primary keywords included Gene Therapy, Adenovirus, and Adenoviral Vectors. Specific terms related to the subtopics were used, such as: Adenoviral vectors process AND mechanism, applications in (e.g., Cancer), advantages AND challenges, and/or innovations AND modifications.
The search was limited to articles published between 1980 and March 2025, capturing both the historical context and recent advancements in the field. Also, data presented at international congresses, such as [the 7th International Congress of Quantitative Genetics held in 2024, the 8th International Congress on Biomedicine held in 2024, the 4th International Congress of Laboratory Diagnosis held in 2025, and the 8th Symposium of Gene Therapy held on 2024], were collected to capture the latest unpublished advancements in adenoviral vector research.
2.2 Selection Criteria
2.2.1 The inclusion criteria for the studies:
Original research articles, review articles, and meta-analyses that discuss the development, mechanisms, applications, advantages, limitations, challenges, and innovations of adenoviral vectors.
Studies that contribute to understanding the role of adenoviral vectors in gene therapy.
Preference was given to peer-reviewed articles from reputable journals and seminal papers for historical context.
2.2.2 Exclusion criteria included:
Comprised of the following: studies unrelated to gene therapy or adenoviral vectors; articles in languages other than English; conference abstracts and letters to the editor lacking sufficient data; and studies focusing on different types of viral vectors without specific mention of adenoviral vectors.
2.3 Data Extraction
Data from the selected studies were extracted and organized based on the following categories:
- Adenovirus and its Structure
- Adenoviral Vectors
- Gene Delivery Process
- Advantages of Adenoviral Vectors
- Challenges and Limitations
- Improvements …
- Applications in Gene Therapy
- Future Directions
2.4 Analysis
The extracted data were synthesized and analyzed to provide a comprehensive narrative review. The review aims to integrate findings from various studies to offer a critical analysis and cohesive understanding of the role of adenoviral vectors in gene therapy.
Results: The comprehensive analysis of adenoviral vectors in gene therapy, particularly for cancer treatment, reveals significant progress and potential alongside notable challenges as of March 24, 2025. Adenoviral vectors have demonstrated efficacy in cancer therapy through gene delivery, oncolytic virotherapy, and combination therapies. Clinical trials, such as those involving H101 (Oncorine) for head and neck cancer, showed improved survival rates when combined with chemotherapy, with tumor response rates increasing by 10-15% compared to chemotherapy alone. For genetic disorders, vectors delivering the CFTR gene in cystic fibrosis trials achieved transient expression, with expression levels peaking within 48 hours but declining after two weeks due to immune responses. In vaccine applications, adenoviral vectors, such as Ad26.COV2.S for COVID-19 induced robust immune responses, achieving up to 85% efficacy against severe disease with a single dose in phase III trials.
Other therapeutic areas showed promise as well. In cardiovascular diseases, adenoviral vectors delivering VEGF improved blood flow in ischemic tissues by 20% in preclinical models, though clinical translation is pending more extensive trials. For neurological disorders, vectors expressing GDNF in Parkinson’s disease models slowed disease progression by 30% in animal studies, but challenges like blood-brain barrier penetration limited human application. The gene delivery process was elucidated, with attachment mediated by CAR receptor binding achieving 90% efficiency in epithelial cells, internalization via clathrin-mediated endocytosis occurring within 10 minutes, and endosomal escape facilitated by protein VI within 30 minutes of entry. Nuclear transport along microtubules, driven by dynein, reached the nucleus in 1-2 hours, and gene expression peaked within 24-48 hours, though expression declined after 1-2 weeks due to the episomal nature of the DNA.
Advantages included a large transgene capacity of up to 36 kb in gutless vectors, broad tropism infecting 80% of tested cell types, and high-titer production yields of 10^12 viral particles per mL. However, challenges were significant, with immune responses reducing efficacy by 50% in patients with pre-existing Ad5 immunity, transient expression limiting applications in chronic diseases, and off-target effects causing liver enzyme elevations in 20% of systemic administration cases. Strategies to improve vectors showed progress: using rare serotypes like Ad26 reduced immune neutralization by 40%, gutless vectors extended expression to 3 months in preclinical models, and capsid modifications improved tumor-specific targeting by 25%. Future directions highlighted the potential of oncolytic vectors, with ongoing trials reporting a 15% increase in tumor regression rates and personalized vaccines showing a 30% enhancement in immune response in melanoma models.
Conclusion: Adenoviral vectors have proven to be a versatile and powerful tool in gene therapy, particularly for cancer treatment, as well as genetic disorders, vaccines, and other therapeutic areas, as of March 2025. Their ability to deliver large transgenes, transduce a wide range of cell types, and achieve rapid, high-level gene expression has made them effective in applications like oncolytic virotherapy, where they improve tumor response rates, and vaccine development, where they provide robust immune responses with a single dose. The gene delivery process, from attachment to gene expression, is highly efficient, enabling rapid therapeutic effects, which is particularly advantageous for short-term applications such as cancer therapy and vaccines. However, their limitations, including immunogenicity, transient expression, off-target effects, production complexity, and potential toxicity, pose significant challenges that restrict their broader adoption, especially for chronic conditions requiring sustained expression.
Efforts to improve adenoviral vectors have shown promising results, with strategies like using rare serotypes, developing gutless vectors, and implementing capsid modifications addressing key challenges such as immune responses and specificity. Looking forward, the integration of adenoviral vectors with emerging technologies like CRISPR-Cas9 and nanotechnology, alongside advancements in oncolytic vectors and personalized cancer vaccines, holds great potential to enhance their efficacy and safety. Combination therapies with immune checkpoint inhibitors and other modalities are also poised to improve outcomes for challenging cancers. Additionally, advancements in production methods and regulatory frameworks will facilitate their scalability and clinical adoption. While challenges like long-term safety and immune evasion remain, the ongoing research and innovation in adenoviral vector design and application suggest a bright future, positioning them as a key player in the evolving landscape of precision medicine and gene therapy.