Nanobody therapeutics
Surveying great inventors and businesses
Axial: https://linktr.ee/axialxyz
Axial partners with great founders and inventors. We invest in early-stage life sciences companies such as Appia Bio, Seranova Bio, Delix Therapeutics, Simcha Therapeutics, among others often when they are no more than an idea. We are fanatical about helping the rare inventor who is compelled to build their own enduring business. If you or someone you know has a great idea or company in life sciences, Axial would be excited to get to know you and possibly invest in your vision and company. We are excited to be in business with you — email us at info@axialvc.com
Nanobodies are the variable domains of heavy-chain antibodies found in camelids. With a molecular weight of only 12-15 kDa, they are the smallest known in vivo antigen-binding fragments. Compared to conventional antibodies (~150 kDa), nanobodies offer several key advantages including high stability, solubility, and tissue penetrability, as well as low immunogenicity and ease of production. These favorable characteristics have generated great interest in developing nanobody-based therapeutics for cancer and other diseases.
The basic structure of a nanobody consists of three complementarity determining regions (CDRs) for antigen-binding and four framework regions (FRs) providing a scaffold. Relative to conventional VH domains, nanobody CDR1 and CDR3 loops are longer, likely compensating for the lack of a VL domain to achieve high affinity and specificity for target antigens. Substitutions of hydrophobic VH residues at the former VH-VL interface also explain the high solubility and stability of isolated VH domains. Additional disulfide bonds between CDR1-CDR3 further stabilize nanobody structure. Collectively, these adaptations yield nanobodies with strong antigen recognition abilities despite their small size.
Compared to traditional antibodies, nanobodies offer enhanced tissue penetrability due to their lower molecular weight. Their high thermostability and resistance to pH/chemical denaturation are also advantageous. Moreover, nanobodies lack an Fc region, avoiding unwanted immunogenicity. Their recombinant production in microbes enables straightforward generation at lower costs compared to traditional antibodies.
Many nanobodies targeting well-known tumor-associated antigens have been generated, several of which have entered preclinical or clinical testing. For example, anti-EGFR nanobodies can antagonize receptor signaling by blocking EGF binding, thereby inhibiting cancer cell proliferation. Anti-CEA nanobodies have been explored for targeted enzyme-prodrug therapy, taking advantage of CEA overexpression in multiple cancers. Nanobodies targeting MUC1, HIF-1α, HER2, and other classic tumor antigens have also shown promise in vitro and in vivo. Additionally, nanobodies targeting the tumor neovasculature via antigens like VEGFR2 or integrin αvβ3 have been studied. Dual-targeting approaches, using bispecific nanobodies or fusion proteins against two tumor antigens, aim to improve treatment efficacy. Overall, nanobody targeting of established tumor markers has validated their potential for cancer detection and therapy.
Beyond classical tumor antigens, researchers have isolated nanobodies against novel targets like CXCR4, CTLA-4, and CD38. CXCR4 plays key roles in cancer metastasis and its nanobody inhibitors have displayed anti-tumor effects. Checkpoint inhibitor CTLA-4 represents an attractive immunotherapy target, with studies finding CTLA-4 nanobodies can stimulate anti-tumor cytotoxic T cell responses. Overexpressed in various hematologic malignancies, CD38 nanobodies have also shown promise in inhibiting tumor growth in xenograft models.
Capitalizing on their tumor-targeting abilities, nanobodies have been applied as targeting moieties for drug delivery systems and as sensitizing agents for combination therapies. Decorating nanoparticles or liposomes with anti-tumor nanobodies has enabled selective drug accumulation at tumor sites, minimizing off-target toxicity. Similarly, linking nanobodies to radionuclides or photosensitizers has improved precision in radioimmunotherapy and photodynamic therapy experiments. An area of particular interest is applying nanobodies for CAR-T cell engineering and T cell redirection. Nanobody-based CARs and T cell engagers have shown enhanced efficacy and safety profiles compared to traditional antibody-based versions. Overall, nanobodies have been successfully incorporated into diverse therapeutic modalities, often bestowing tumor-specificity to improve treatment outcomes.
While nanobodies offer immense promise as next-generation biologics, they currently face several limitations. Their rapid renal clearance can reduce circulation time and tumor accumulation. Most research has also focused on extracellular antigens, yet intracellular targets within tumor cells remain difficult to access. Moreover, clinical experience with nanobody therapeutics is still lacking compared to conventional antibodies. Future directions for the field include optimizing nanobody pharmacokinetics/biodistribution, developing strategies to reach intracellular antigens, and conducting more rigorous clinical testing. Advances in phage display, library construction, and humanization should also facilitate isolation of nanobodies against novel targets. Altogether, nanobodies are versatile and highly customizable molecules poised to make a significant impact as cancer diagnostics and therapeutics with further refinement.
Nanobodies possess numerous advantageous characteristics over traditional antibodies, including smaller size, higher tissue penetrability, greater stability, and lower production costs. They have already shown exciting preclinical efficacy against various tumor antigens via diverse therapeutic modalities. As researchers continue interrogating the cancer genome, the antigens amendable to nanobody targeting will further increase. With innovations in nanobody engineering and delivery, more efficacious and safe nanobody-based treatments are on the horizon. If key limitations can be adequately addressed, nanobodies are well-positioned to transform antibody-based cancer medicine.
