Marc Nasoff, Ph.D.
Director of Biotherapeutics
Antibodies are essential human proteins that are involved in the immune system’s ability to recognize and eliminate pathogens, and they can also be therapeutic treatments for a number of human diseases. The goal of the GNF antibody program is to advance biotherapeutics into the Novartis drug discovery pipeline. Currently, we are focused on the development of therapeutic antibodies, but our long-term plans include development of other types of biologics.
GNF Biotherapeutics Program Goals
Drug Discovery—(1) identify human receptor antibody agonists and antagonists as novel therapies for human diseases, (2) generate antibodies against murine receptors for in vivo target validation
Technology Development—develop an antibody platform that is capable of screening an entire immune repertoire following immunization
Basic Research—initiate studies to identify new members of signaling pathways by interfacing siRNA arrays with cell based assays. This is accomplished by using antibody agonists to stimulate specific pathways and determining the effects of reducing specific protein levels on pathway activation.
As potential therapeutic agonists and antagonists, antibodies have excellent properties: they have long half-lives in the bloodstream, they are extremely specific, they lack toxicity, and they are exceptionally potent. At GNF we recognize this potential, which is why drug discovery is a central part our antibody program.
To generate functional therapeutic antibodies against receptors, the process begins with cloning, expressing, and purifying a receptor’s extracellular domain. B cells from animals are then immunized with the appropriate receptor, fused with myeloma cells to generate hybridomas, and cell-based assays are developed for identifying functional antibody agonists or antagonists. Hybridoma supernatants are assayed for functional activity, positive clones are expanded, and the antibody is purified for further validation.
To date we have generated functional antibodies against a wide variety of receptors. We believe the strength of our program derives from the fact that our antibodies are selected based on functional activity. Because they are raised against receptor extracellular domains, each of the functional antibodies identified are specific and sensitive. Using human tumor xenograft models, murine antibodies can be tested for in vivo efficacy. Lastly, greater than 95% of the therapeutic antibodies in the clinic or currently in clinical trials have originated as monoclonal antibodies by some type of humanization strategy. Humanization is becoming a widely accepted procedure for removing potential immunogenicity.
One of the goals of our antibody program is to be able to search through the entire immune repertoire for rare functional antibodies. Current hybridoma technology is extremely inefficient in that only a very small fraction of this repertoire can be recovered following immunization. Making an array of the immune repertoire would allow one to increase the number of wells assayed from 1,000 to 1,000,000 and thus dramatically increase the chance of identifying rare functional antibodies.
To build an immunoarray from immunized transgenic animals, we plan to isolate memory B cells (surface IgG positive), dispense one cell/well into one million wells (1536-well format), develop conditions that support growth and differentiation into plasma cells, and assay supernatants in cell-based screens for rare antibody agonists/antagonists. Antibody variable region sequences from positive wells will be isolated by PCR, and variable regions will be cloned into expression vectors to create human chimeric antibodies.
Basic Discovery Research
Members of the antibody program at GNF also conduct basic scientific research, and at present, much of this work is focused on the generation of antibody agonists and antagonists against rodent targets for in vivo validation.
We are accomplishing this by immunizing old world hamsters with murine receptor extra-cellular domains, with the hope that these proteins will be immunogenic. The resulting antibodies will be used in various murine models of disease. Successful validation of targets in model species will subsequently lead to the generation of functional antibodies against the homologous human receptors.
- Rottmann S, Wang Y, Nasoff M, Deveraux QL, Quon KC. A TRAIL receptor-dependent synthetic lethal relationship between MYC activation and GSK3beta/FBW7 loss of function. Proc Natl Acad Sci U S A 2005;102(42):15195-200.
- Cohen SB, Gaskins C, Nasoff MS. Generation of a monoclonal antibody agonist to toll-like receptor 4. Hybridoma (Larchmt) 2005;24(1):27-35.