What are the different types of drugs available for Nanobody?

Introduction to Nanobodies
Nanobodies are a novel class of antibody-derived drug molecules that have revolutionized the landscape of both therapeutic and diagnostic pharmaceuticals. These engineered, single-domain antibodies are derived from the heavy-chain–only antibodies naturally present in camelids such as llamas and alpacas. Owing to their minimal structure (approximately 15 kDa), high stability, and robust physicochemical properties, nanobodies have quickly become a subject of intense scientific and clinical interest. In the following sections, we will explore nanobodies in depth, beginning with a description of their basic characteristics and historical significance.

Definition and Basic Characteristics
Nanobodies are defined as the variable domains (V_HH) of heavy-chain antibodies, presenting as the smallest naturally occurring antigen-binding fragments. Despite their reduced molecular weight, they retain full antigen-binding capacity, with high specificity and affinity toward a variety of targets. Their compact size enables them to recognize hidden or cryptic epitopes that larger conventional immunoglobulins cannot access. In addition to their excellent solubility and thermal stability, nanobodies are highly adaptable—they can be expressed recombinantly in microbial systems, which translates into an economically viable and scalable production process. Their structural simplicity means they are less prone to mispairing issues common in conventional antibody fragments and can be easily engineered into bait-like modules as receptor antagonists, conjugates for drug delivery, or imaging agents.

Historical Development and Significance
The discovery of heavy-chain–only antibodies in camelids in the early 1990s marked a turning point in antibody engineering. Researchers soon realized that the variable regions of these antibodies, later termed “nanobodies” or V_HHs, possessed unique advantages over traditional antibodies. Over the past three decades, the field advanced through numerous breakthroughs in generating libraries, screening techniques (such as phage display), and site-specific conjugation methods. These developments have allowed scientists to harness nanobodies for applications ranging from intracellular protein modulation (as intrabodies), to targeted cancer therapies and non-invasive molecular imaging. Their notable capacity for chemical functionalization further enhances their potential for conjugating with toxins, radionuclides, imaging agents, and even nanoparticles to create multifunctional drug delivery systems.

Types of Nanobody-based Drugs
Over the last few years, nanobody-based drugs have emerged as a diverse category with varying applications that span both therapeutic and diagnostic fields. By leveraging the unique structural attributes of nanobodies, researchers have developed drugs that target multiple diseases, from autoimmune conditions to cancer. Here, we discuss the different types of nanobody-based drugs available, along with the specific areas in which they are applied.

Therapeutic Applications
Nanobody-based therapeutics are designed to intervene in disease pathways by specifically recognizing and modulating molecular targets. Their small size and adaptability allow them to either act directly or serve as targeting moieties in complex therapeutic constructs. Some of the primary therapeutic applications include:

1. Immune System Diseases
- Anti-Inflammatory and Autoimmune Therapy:
One of the key examples in this category is Ozoralizumab, a therapeutic nanobody approved for the treatment of rheumatoid arthritis. Ozoralizumab targets tumor necrosis factor-α (TNF-α) while also interacting with albumin to improve its half-life and biodistribution. This bispecific nanobody has demonstrated significant clinical efficacy since its approval in September 2022, offering a new avenue for immune modulation in autoimmune diseases.
- IL-4, IL-6, and IL-17 Pathways:
Other candidates include recombinant nanobodies against IL-4Rα and constructs like Sonelokimab that block IL-17A/IL-17F. These molecules, currently in the clinical trial phases (phase 2 or phase 3, respectively), are designed to modulate immune responses in conditions like inflammatory and skin diseases.
- Costimulation Blockade:
Nanobody drugs such as Brivekimig that target combined antigens (for instance, OX40L x TNF-α) illustrate strategies to modulate immune checkpoint pathways, thus potentially offering therapeutic options in both autoimmune and inflammatory contexts.

2. Cancer Therapy
- Direct Tumor Targeting:
Nanobodies have proven capable of directly targeting tumor antigens. For example, Envafolimab, a PD-L1–targeting nanobody approved in China for certain cancer indications, impedes the PD-L1 pathway to enhance immune responses against tumors. Caplacizumab, approved for treating thrombotic thrombocytopenic purpura (TTP), although not targeting a tumor per se, demonstrates the utility of nanobody drugs in critical conditions through specific antigen binding.
- Receptor Antagonism and Signal Inhibition:
Nanobody-based drugs engineered to inhibit growth factor receptors such as EGFR or HER2 are being explored. These molecules function as receptor antagonists, blocking the interaction between the ligand and its receptor, an approach that can prevent the activation of pro-survival and proliferative pathways in tumor cells.
- Drug Conjugates (Nanobody–Drug Conjugates, ADCs):
Nanobodies have been employed to create highly selective drug conjugates. These conjugates, often consisting of a nanobody attached to potent cytotoxic agents, are designed to deliver the drug payload directly to cancer cells while sparing normal tissues. Their small size allows for deeper tumor penetration and rapid clearance from the bloodstream, thus enhancing the therapeutic index.
- Intrabodies for Intracellular Targeting:
In addition to extracellular targets, nanobodies are being developed as intrabodies for the treatment of cancers. These are engineered nanobodies that are expressed within cells to modulate intracellular processes, such as disrupting oncogenic signaling pathways. This approach has garnered attention for its potential to address targets that are inaccessible to conventional antibodies.

3. Other Therapeutic Areas
- Cardiovascular Diseases:
Nanobodies are not limited to oncology or autoimmune diseases. Recent research has extended their application to cardiovascular disorders. Novel nanobodies, for instance, have been integrated into drug delivery systems or used as imaging agents to target atherosclerotic plaques or monitor cardiac biomarkers.
- Infectious Diseases and Antiviral Therapies:
Although still at the experimental stage, nanobodies have shown promise in neutralizing viral pathogens. Their ability to efficiently bind to viral surface proteins, such as those on norovirus or SARS-CoV-2, has paved the way for therapeutic strategies that can neutralize pathogens before they launch infection.

Diagnostic Applications
The diagnostic potential of nanobodies is equally revolutionary, offering non-invasive, rapid, and precise detection of disease markers. Their high affinity and rapid clearance often translate into superior imaging contrasts in molecular imaging modalities. Key applications include:

1. Molecular Imaging Agents:
- PET and SPECT Imaging:
Nanobodies have been radiolabeled with isotopes such as gallium-68 (68Ga) for positron emission tomography (PET) imaging. These radiotracers are highly effective at delineating tumors and monitoring immune checkpoint molecules in vivo. For example, the anti-HER2 nanobody 2Rs15d has been tested in early clinical trials, demonstrating clear tumor visualization with excellent tumor-to-background ratios.
- Optical and Ultrasound Imaging:
Beyond radioisotopes, nanobodies have been conjugated with fluorescent dyes and other contrast agents to facilitate optical imaging and even guide surgical resection. Their small size allows for rapid tissue penetration and clearance, providing high-contrast images shortly after administration.

2. Biosensors and Immunoassays:
- ELISA and Lateral Flow Assays:
The high stability and ease of modification of nanobodies make them ideal candidates for diagnostic assays such as enzyme-linked immunosorbent assays (ELISAs) and lateral flow assays (LFAs). Their robust binding properties ensure consistent and sensitive detection of biomarkers, even in harsh environmental conditions. Diagnostic applications using nanobodies are particularly advantageous in resource-limited settings due to their stability at variable temperatures and reduced need for a cold chain.
- Electrochemical Immunoassays:
Advances in nanotechnology have facilitated the development of nanobody-based electrochemical biosensors that offer rapid and sensitive detection of small molecules and proteins. Such diagnostic devices are increasingly used for point-of-care testing, especially in the context of infectious diseases and cancer markers.

3. Multi-modal Diagnostic Platforms:
Nanobodies are enabling the creation of multimodal diagnostic agents. These agents combine multiple imaging techniques (for example, PET/MRI or PET/optical imaging) to provide comprehensive diagnostic data. By conjugating nanobodies to multimodal nanocarriers, it is possible to gain synergistic advantages from each imaging modality, thereby improving diagnostic accuracy and clinical decisions.

Mechanisms of Action
Understanding the mechanisms by which nanobody-based drugs operate is critical for appreciating their advantages and potential in clinical applications. Their mode of action revolves around the specific and high-affinity interaction with biological targets, and this underpins many of their clinical benefits.

Interaction with Biological Targets
Nanobodies bind to their targets through paratope regions, which are often more variable and longer than those found in conventional antibodies. This unique structure allows them to interact with both convex and concave epitopes, including enzyme active sites, receptor-binding pockets, and other cryptic surface features. Their high binding affinity ensures that even a low concentration of the nanobody can achieve effective target occupancy. Due to their small size, these molecules can readily penetrate dense tissues and accumulate in tumors via both passive and active targeting mechanisms.

Furthermore, nanobodies can be engineered into multivalent formats—either as homo- or heterodimers—improving their avidity and allowing for simultaneous engagement with multiple epitopes on a target. This multimerization can lead to enhanced therapeutic efficacy, such as triggering receptor internalization or disrupting critical signaling pathways in cancer cells. When used as targeting modules on nanocarriers, nanobodies can also direct the delivery of encapsulated drugs, thus improving their localization and reducing systemic toxicity.

Advantages over Traditional Antibodies
Nanobodies possess several advantages over full-length monoclonal antibodies and their conventional fragments:
Size and Penetration:
At approximately 15 kDa, nanobodies are one-tenth the size of a full IgG. This small size confers enhanced tissue penetration, which is particularly beneficial in the context of solid tumors where dense tissue architecture can limit the effectiveness of larger molecules.
Stability:
Nanobodies are remarkably stable over a broad range of temperatures and pH levels. They can refold correctly after denaturation, making them ideal for applications that require prolonged storage or exposure to challenging biological environments.
Ease of Production:
Their simple structure enables high-yield recombinant expression in microbial hosts (e.g., E. coli), thus reducing production costs and facilitating rapid scalability. This ease of manufacturing has significant implications not only for therapeutic use but also for the development of diagnostic tools.
Low Immunogenicity:
Nanobodies typically exhibit low immunogenicity due to their high similarity to human VH domains once properly humanized. This can reduce the risk of adverse immune reactions in clinical applications.
Versatility in Engineering:
The genetic and chemical modularity of nanobodies allows for precise modifications. They can be conjugated to drugs, radionuclides, toxins, and imaging agents using site-specific conjugation techniques. The tailored engineering potential makes them ideal for creating bispecific or multispecific constructs and for integration into multifunctional nanomedicine platforms.

Current Market and Research
The clinical translation of nanobodies into therapeutic and diagnostic products has accelerated substantially in recent years. The current market landscape and ongoing research initiatives highlight both the successes achieved and the challenges that remain.

Approved Nanobody Drugs
Several nanobody-based drugs have moved from preclinical research into the clinic, with a few already gaining regulatory approval:
Ozoralizumab:
Approved for the treatment of rheumatoid arthritis in Japan in September 2022, Ozoralizumab represents a significant milestone. This bispecific nanobody targets TNF-α, thereby mitigating inflammatory processes, and is optimized for improved half-life due to its albumin-binding mechanism.
Envafolimab:
An immune checkpoint inhibitor that targets PD-L1, Envafolimab is approved for use in China against cancers such as colorectal cancer and microsatellite instability-high tumors. Its single-domain design provides excellent tumor penetration and rapid clearance, translating into a favorable pharmacokinetic profile.
Caplacizumab-YHDP:
Approved for thrombotic thrombocytopenic purpura (TTP) in various regions including the European Union, Caplacizumab-YHDP is a nanobody that interferes with von Willebrand factor (vWF) interactions, reducing the risk of clotting complications. Its approval underscores the versatility of nanobody drugs in critical clinical indications.

Nanobodies in Clinical Trials
Beyond these approved drugs, several nanobody candidates are advancing through clinical trials, reflecting the robust pipeline of nanobody-based therapeutics:
Gefurulimab:
Currently in Phase 3 clinical trials, Gefurulimab is a nanobody-based therapeutic targeting the complement component C5 in conjunction with albumin modulation. Its mechanism aims to mitigate complement-mediated damage in various disease states.
Sonelokimab:
In Phase 3 trials, Sonelokimab is a trispecific nanobody that targets IL-17A, IL-17F, and albumin simultaneously. This design intends to combine immunomodulatory effects with improved pharmacokinetics for treating inflammatory and oncological conditions.
Other Investigational Molecules:
Numerous other nanobody constructs targeting interleukins (e.g., IL-4Rα, IL-6RA), co-stimulatory molecules (e.g., OX40L), and other immune checkpoints are in various stages of clinical development. These investigational drugs reflect ongoing efforts to expand the therapeutic utility of nanobodies across different disease areas.

Nanobodies as In Vivo Imaging Agents
In parallel with therapeutic applications, nanobodies have also gained traction as non-invasive imaging probes:
Radiolabeled Nanobodies for PET/SPECT:
Nanobodies such as the anti-HER2 agent 2Rs15d have been radiolabeled for PET imaging. These agents quickly accumulate in tumors and are rapidly cleared from the bloodstream, thereby producing high-contrast images that can aid in early diagnosis and treatment monitoring.
Optical Imaging and Biosensors:
Some nanobodies are conjugated with fluorescent dyes and incorporated into biosensor platforms to detect cancer biomarkers via optical or electrochemical methods. These modalities contribute to the emerging field of personalized diagnostic devices.

Challenges and Future Prospects
Despite the promise and progress of nanobody-based drugs, their clinical adoption faces several challenges. Understanding these obstacles and the strategies to overcome them is critical for the future development of nanobody therapeutics and diagnostics.

Current Challenges
Pharmacokinetic Concerns:
Due to their small size, nanobodies may undergo rapid renal clearance. Although this rapid clearance can be advantageous for imaging (leading to low background signals), it poses challenges for sustained therapeutic action. Strategies such as bispecific constructs that include an albumin-binding domain have been developed to extend their half-life, but optimization is still an active area of research.
Manufacturing and Scale-Up:
While recombinant production in microbial systems is more straightforward compared to full-length antibodies, achieving consistent quality and batch-to-batch reproducibility remains an important factor. Scale-up processes must maintain the structural integrity and binding specificity of nanobodies, which requires stringent quality control and optimized manufacturing protocols.
Immunogenicity and Safety:
Although nanobodies generally exhibit low immunogenicity once humanized, repeated administration could still trigger immune responses. Continuous efforts are being made to refine humanization techniques further and to develop novel engineering strategies that minimize potential adverse reactions.
Regulatory Hurdles:
As a relatively new class of biological drugs, nanobodies face unique regulatory challenges. The guidelines for conventional monoclonal antibodies do not always directly apply to nanobody-based therapeutics, and regulatory agencies are still in the process of establishing standardized evaluation protocols. This can contribute to longer approval times and increased development costs.
Target Specificity in Heterogeneous Disease Environments:
Tumors and other disease tissues are often heterogeneous in their expression of target antigens. While nanobodies have an advantage due to their ability to target cryptic epitopes, ensuring consistent binding across heterogeneous cell populations can be challenging. Addressing this issue may require the development of multispecific or biparatopic nanobodies that can target multiple epitopes simultaneously.

Future Research Directions and Innovations
Despite these challenges, the future of nanobody-based drugs is bright, and numerous innovative approaches are being actively pursued:
Engineering Multispecific and Bispecific Formats:
Advances in protein engineering are enabling the creation of nanobody constructs that can simultaneously target multiple antigens or combine therapeutic and diagnostic functions. Such multispecific formats could significantly improve efficacy by engaging multiple pathways and enhancing tumor penetration.
Improved Nanocarrier Conjugation:
Nanobodies are increasingly being used as targeting ligands on various nanocarriers, including liposomes, polymeric nanoparticles, and dendrimers. Future research is focused on optimizing the conjugation of nanobodies to these carriers to improve drug payload delivery, minimize off-target effects, and control drug release kinetics.
Enhanced Imaging Techniques and Multimodal Platforms:
The integration of nanobodies with advanced imaging modalities such as combined PET/MRI or PET/optical imaging represents a promising frontier. Such multimodal probes could provide clinicians with comprehensive diagnostic information, from anatomical details to functional aspects, thereby facilitating personalized treatment strategies.
Development of Intrabodies for Intracellular Targets:
With the growing list of intracellular targets in cancer and other diseases, the development of intrabodies—nanobodies expressed within cells—represents an exciting research direction. These molecules have the potential to modulate intracellular signaling pathways that are otherwise inaccessible to conventional antibodies, opening new therapeutic avenues.
Nanobody-based Immunodiagnostics and Biosensors:
Future innovations are expected in the field of point-of-care diagnostics. Given their stability, ease of production, and high specificity, nanobodies are ideal candidates for the development of robust, rapid, and affordable diagnostic assays, including electrochemical immunoassays and lateral flow devices. This is particularly relevant for monitoring infectious diseases and detecting cancer biomarkers in resource-limited settings.
Regulatory and Quality-Control Innovations:
As the regulatory landscape evolves, research efforts are also being directed toward developing standardized quality control parameters for nanobody-based drugs. This includes in-depth characterization of pharmacokinetic profiles, immunogenicity assessments, and the identification of reliable biomarkers for efficacy and safety monitoring. Collaborative efforts between industry, academia, and regulatory authorities will be crucial to streamline the clinical translation of these novel drugs.

Conclusion
In summary, the range of drugs available for nanobody-based applications is exceptionally diverse and continues to expand rapidly. On the therapeutic side, key approvals such as Ozoralizumab, Envafolimab, and Caplacizumab have paved the way for the adoption of nanobody-based treatments in immune system diseases and oncology. These drugs leverage the unique properties of nanobodies—small size, stability, ease of engineering, and high target specificity—to modulate critical disease pathways. In addition to direct therapeutic applications, nanobodies have shown immense promise as diagnostic agents. Radiolabeled nanobodies and conjugates used in biosensors offer precise, non-invasive imaging capabilities that are indispensable for early disease detection and treatment monitoring.

Mechanistically, the efficacy of nanobody-based drugs is rooted in their ability to effectively interact with biological targets, blocking pathogenic pathways while offering several advantages over traditional antibodies. Their rapid tissue penetration and clearance translate to high safety margins and improved therapeutic indices, although the challenge of rapid renal clearance necessitates further innovation. The current market presents a promising picture with several approved drugs and many candidates in clinical trials, yet challenges remain regarding scale-up, regulatory approval, and the fine-tuning of pharmacokinetics.

Looking forward, future research directions point toward multispecific constructs, innovative nanocarrier conjugation techniques, and multimodal diagnostic platforms. With continuous advances in protein engineering and nanotechnology, nanobody-based drugs are poised to address unmet medical needs in oncology, autoimmune diseases, cardiovascular conditions, and infectious diseases. The integration of emerging quality-control and regulatory frameworks will further solidify the role of nanobodies in modern medicine.

Overall, nanobody-based drugs represent a transformative shift in both therapeutic and diagnostic paradigms. By offering general improvements—from improved specificity and greater tissue penetration to reduced immunogenicity and the ability to target intracellular antigens—nanobodies have opened new avenues for personalized and precision medicine. As the field continues to evolve, it is likely that nanobody-based pharmaceuticals will play an increasingly prominent role in clinical care, ultimately leading to better patient outcomes across a range of challenging diseases.

In conclusion, the different types of drugs available for nanobodies cover a broad spectrum—from direct therapeutic agents that modulate immune responses and target tumor cells to diagnostic agents that enable high-contrast imaging and sensitive detection in diverse clinical settings. Their versatile mechanisms of action, along with intrinsic advantages over conventional antibody formats, make them highly attractive for overcoming current limitations in drug delivery and disease management. The continued expansion of the nanobody pipeline, accelerated by robust clinical research and innovative engineering, heralds a new era in personalized medicine, where tailored interventions and precise diagnostics are within reach.