Week 2, July 2025: Nanodiscs in Therapeutic Antibody Discovery

Nanodisc-based platforms have emerged as an approach to therapeutic antibody discovery and drug development, especially for membrane protein (MP) targets such as cell surface receptors, transporters, ion channels, and membrane-bound enzymes. Recent research highlights the full potential of therapeutic antibodies directed to target complex MPs. 

A new review by Yao & Thomson (2025) describes nanodiscs as providing a native-like lipid bilayer environment for embedding membrane proteins. They stabilize MPs by wrapping around their hydrophobic regions to keep them soluble in aqueous solutions while retaining their functional and structural properties. These self-assembling structures are typically formed using membrane scaffold proteins (MSPs) derived from apolipoprotein A-I along with synthetic or natural lipids, to fine-tune lipid-protein interactions in the target protein. However, nanodiscs can also be stabilized by other amphipathic structures like saposin-lipoprotein nanoparticles (Salipro), a lipid-binding protein-based belt system, peptides, or synthetic polymers. Advantages include:

• Display of native epitopes (for antibody generation and binding)

• Homogenous presentation of membrane proteins (for screening and antibody selection)

• Stability for large multisubunit complexes (for antibody discovery against targets previously thought too complex)

• Ability to work with native-like proteins (for drug discovery process)

Another paper highlights advanced applications of nanodisc-based platforms for antibody discovery. Nanodisc technology provides a great advantage in a synergetic combination with cell-free protein expression systems. Typically, when expressing membrane proteins in cell membranes or inclusion bodies, detergent must be used to extract or solubilize the target protein, even though detergents can disrupt the spatial structure of the protein. Varying the lipid composition of nanodiscs could provide more successful insertion and folding as better native membrane-mimicking properties. As depletion agents, nanodiscs reduce selection rounds, and have been instrumental in targeting specific conformational states of proteins such as HIV gp41. Advances such as scaffold biotinylation and direct targeting of MSPs with antibodies like biND5 further enhance nanodisc utility in antibody discovery. Similarly, SMALPs preserve MP structure in detergent-free environments, supporting techniques like SPR, FACS, and display platforms for MPs including CB1, M2, CLEC-2, and CD81.

A few examples of nanodisc application are described in another recent review. For endothelin receptor A (ETA), a class A GPCR implicated in various cancers, nanodisc-reconstituted ETA enabled the isolation of a high-affinity scFv antibody (AG8) that inhibited ETA signaling and tumor growth in vivo. Similarly, SMA nanodiscs presenting the extracellular domain (ECD) of parathyroid hormone receptor 1 (PTH1R) allowed identification of an scFvhFc antibody, aiding in the study of receptor signaling bias. For the apelin receptor (APJ), associated with chronic heart failure, nanodisc-reconstituted APJ was used to immunize camels and generate a library yielding sdAb JN241, an effective competitive antagonist. Additionally, nanodiscs presenting the tetrameric form of influenza A’s M2 protein enabled immunization of a shark species and the identification of vNAR AM2H10, which blocked M2-mediated ion influx and demonstrated antiviral activity.

Researchers from the University of Michigan demonstrated that high-density lipoprotein-mimicking nanodiscs loaded with doxorubicin (DOX) can effectively enhance immune checkpoint blockade for cancer therapy. While immune checkpoint inhibitors alone benefit only a subset of patients, combining them with nanodisc-mediated chemotherapy triggered immunogenic cell death and robust CD8⁺ T cell responses in murine tumor models. DOX-loaded nanodiscs "primed" tumors by broadening T cell recognition to include tumor-associated antigens and neoantigens, all without significant off-target toxicity. When combined with anti–PD-1 therapy, this strategy achieved complete tumor regression in 80–88% of mice with established colon carcinoma (CT26 and MC38) and provided long-term protection against recurrence. This study presents a promising and generalizable approach to synergize chemotherapy and immunotherapy via nanodisc platforms. 

On the clinical research side, an Fc-binding nanodisc restored antiviral efficacy of antibodies with reduced neutralizing effects against evolving SARS-CoV-2 variants. Researchers from Sungkyunkwan University developed an intranasally delivered Fc-binding nanodisc that binds specifically to the Fc region of IgG antibodies, enhancing both their retention in the upper respiratory tract and neutralizing activity. When complexed with this nanodisc, Sotrovimab (an FDA-approved monoclonal antibody with reduced efficacy against Omicron variants) regained strong antiviral potency. The nanodisc also significantly improved the performance of a soluble ACE2-Fc fusion protein, leading to a two-log greater reduction in lung viral load in ACE2 transgenic mice compared to sACE2-Fc alone. This approach offers a promising therapeutic platform to overcome mutational escape by extending antibody half-life and restoring function in variant-resistant SARS-CoV-2 infections. 

Despite their promise in membrane protein drug discovery and delivery, lipid nanodiscs face several limitations. Key challenges include the need for efficient, low-cost large-scale production, and a lack of understanding regarding their in vivo metabolism, degradation, and interactions with biomolecules, which are essential for ensuring safety and efficacy. Different nanodisc types also exhibit specific drawbacks: MSP nanodiscs cannot replicate natural membrane curvature or lipid asymmetry, affecting peripheral protein interactions; saposin nanodiscs are less uniform and more complex to assemble; peptidiscs are costly and less stable due to non-covalent assembly; and SMA-based nanodiscs suffer from UV absorbance, low pH and divalent ion sensitivity, reduced solubilization efficiency, and complications in affinity purification. Though polymer modifications have addressed some SMA limitations, this area remains under active development. Looking ahead, future advancements may focus on multifunctional nanodiscs with diagnostic and therapeutic capabilities, stimuli-responsive "smart" nanodiscs for controlled drug release, and personalized nanodisc-based delivery systems tailored to individual patient needs.