EXECUTIVE INTERVIEW - Salipro Biotech & Bio-Rad Laboratories: A Powerful Solution for Antibody Discovery Against Challenging Transmembrane Targets

Salipro Biotech and Bio-Rad have been working in partnership for a little over a year to provide a straightforward solution for the discovery of novel antibody therapeutics for transmembrane proteins. This collaboration has already been successful in yielding multiple novel human antibodies targeting the wildtype chemokine receptor CXCR4, with affinities exceeding those of ulocuplumab (Bristol-Myers Squibb’s monoclonal antibody designed to treat hematologic malignancies). The new CXCR4-targeting antibodies have been shown to inhibit CXCL12 mediated cell migration better than ulocuplumab, offering the potential for enhanced efficacy and novel immuno-oncology therapeutic avenues.

Drug Development & Delivery recently interviewed Dr. Jens Frauenfeld, CEO, Salipro Biotech, and Dr. Francisco Ylera, R&D Team Lead at Bio-Rad Laboratories, to understand how the collaboration is leveraging the Salipro® platform alongside Bio-Rad’s Pioneer™ Antibody Discovery Platform to target transmembrane proteins.

Q: How does the Salipro® platform enhance the drug discovery capabilities of your pharmaceutical and biotech partners?

Salipro: Our mission is to mine the vast untapped potential of membrane proteins and turn challenging drug targets into opportunities for therapeutic innovation. We have built a team with extensive expertise that, alongside our Salipro platform –which stabilizes membrane proteins in their native forms – is enabling entirely new routes to drug discovery, opening up new treatment possibilities.

By maintaining the protein’s natural environment with surrounding lipids, our Salipro platform ensures the structural and functional integrity of membrane proteins, allowing for accurate drug discovery assays and reliable structure-based drug design. The production of Salipro particles is scalable and tailored for high-throughput screening platforms, including DNA-encoded and phage display libraries, such as Bio-Rad’s Pioneer Platform. This facilitates the rapid evolution of large libraries of potential drug candidates.

The Salipro platform is applicable to a wide range of membrane proteins, including G-protein coupled receptors (GPCRs), ion channels, SLC transporters, complexes, and more. This versatility allows for a broad range of applications across various therapeutic areas with significant unmet medical needs. In addition, the technology enables a one-step reconstitution process, eliminating the need for complex and time-consuming protein engineering or the use of whole cells or virus-like particles. This facilitates the rapid evaluation of large libraries of potential drug candidates, significantly increasing the efficiency of the drug discovery process.

Q: What is Bio-Rad’s Pioneer™ Platform and how is it advancing the discovery of antibody therapeutics?

Bio-Rad: The Pioneer™ Platform is our custom therapeutic antibody service that accelerates the discovery of clinical-quality candidates in industry-leading timelines. The key advantages Pioneer offers include its large library size, ability to select antibodies with subnanomolar affinities directly from the library, and the rapid delivery of highly developable lead candidates.

Pioneer features an extensive Fab library with 225 billion unique human antibody sequences, significantly increasing the chances of identifying superior therapeutic antibodies with subnanomolar affinities. A larger library not only boosts competition for target binding but also provides broader antigen epitope coverage, resulting in more diverse, high-affinity candidates.

Additionally, the platform focuses on germlines with favorable properties often found in therapeutic antibodies, ensuring the developability of lead candidates. The library is also optimized through meticulous cloning strategies, eliminating sequences with frameshifts or stop codons. This results in an impressive 92% functional light chain (LC) and heavy chain (HC), with the library’s quality confirmed via next-generation sequencing (NGS).

The proprietary SpyDisplay selection system is at the heart of Pioneer, which uses SpyTag technology to covalently display Fabs on filamentous phage, enhancing efficiency. By utilizing a single vector for both selection and expression of clones, SpyDisplay streamlines the entire workflow. In conjunction with the TrailBlazer™ modular antibody assembly platform, Pioneer enables rapid identification and characterization of diverse lead candidates. Another advantage is its capability for bispecific generation and high-throughput screening through SpyLock Technology, setting it apart from other platforms.

Q: What are the synergies between the two platforms, and how do they integrate?

Salipro: The combined approach uses purified proteins rather than just target overexpressing cells to optimize the antibody generation and characterization process. This approach allows for rapid initial in vitro antibody characterization, for example measuring antibody affinity or demonstrating target specificity, speeding up the overall workflow compared to running corresponding cell assays.

The synergies between these two technologies extend beyond antibody discovery however. The Salipro-stabilized membrane proteins also serve as tools for characterizing newly discovered antibodies. Techniques such as surface plasmon resonance (SPR) and bio-layer interferometry (BLI) are often hindered by the instability of membrane proteins, making it difficult to accurately assess antibody binding kinetics and affinities. Salipro’s technology overcomes this, providing a stable platform for detailed antibody characterization.

Bio-Rad: Salipro and Bio-Rad have developed a powerful solution which simultaneously tackles two critical bottlenecks in the antibody discovery process. By stabilizing membrane proteins and facilitating efficient antibody screening and characterization, the combined workflow will work to accelerate antibody drug discovery and development.

Q: What are the most significant challenges associated with the study of membrane proteins?

Salipro: Membrane proteins play a critical role in fundamental cellular processes, representing about 30% of the human proteome. They are therefore attractive targets for therapeutic intervention across a wide range of diseases, including cancer, cardiovascular disease, and neurological disorders, and are the targets of more than 60% of drugs on the market.

Despite their significance, the majority of membrane proteins currently remain undruggable, mainly because they are notoriously challenging to work with due to their inherent instability outside of their natural lipid bilayer environment.

Current standard methods for studying membrane proteins suffer from limitations that significantly impair drug discovery efforts. These include difficulties in preserving the correct folding and functionality of the proteins, as well as time consuming protein engineering efforts that often result in non-native membrane proteins. As a result, these standard methods often fail to support efficient screenings for new drug candidates or fail to provide reliable structural data for rational drug design.

The Salipro platform technology addresses these critical bottlenecks by stabilizing membrane proteins in their native forms, via the direct reconstitution of membrane proteins with their native lipids from crude cell membranes into Salipro particles, enabling the development of next-generation therapeutics targeting previously inaccessible membrane proteins.

Q: What are the outcomes of the collaboration, and how will these results accelerate the development of antibody therapeutics?

Bio-Rad: The collaboration has achieved very exciting results in a short timeframe, demonstrating the potential of the combination of the Salipro and Pioneer platforms to accelerate the development of antibody therapeutics.

Following Salipro’s first hit generation campaign, a number of CXCR4-specific antibody clones demonstrated superior affinity and improved performance in a functional cell assay in comparison to the benchmark CXCR4 therapeutic antibody, potentially offering a promising alternative.

 Salipro: We see three main outcomes from this collaboration:

1) The identified antibody clones, which have stronger binding to CXCR4, and improved functionality compared to ulocuplumab, could therefore lead to better therapeutic outcomes. They may be more effective in stopping cancer growth and spread, and could potentially be effective at lower doses, resulting in fewer side effects.

2) We also observe that several of the antibodies may bind to a different epitope as compared to ulocuplumab or may have a different way of binding to CXCR4. This could become a key differentiator to develop novel approaches in cancer therapy. Depending on further characterization, these binders have the potential to provide a new mechanism of action, which can enhance the therapeutic efficacy of the antibodies.

3) The Salipro technology works efficiently with all classes of membrane proteins, suggesting that it could rapidly enable the development of novel antibodies against a wide range of prominent drug targets previously considered undruggable.

Q: What are the next steps for this collaboration?

Salipro: We have received several requests from pharma companies expressing interest in the new anti-CXCR4 binders, based on their exciting characteristics. This is work in progress and may lead to additional collaboration opportunities to fully develop the antibodies as novel therapies.

Bio-Rad: We are very excited by the results of the pilot project and look forward to supporting our customers in combining the Pioneer Antibody Platform with Salipro’s technology to provide a powerful solution for their challenging transmembrane targets.