The Zebra Platform
A next-gen Approach to Exploiting Combinatorial Antibody or Peptide Libraries to Select Novel Biologic Drug Candidates
The new Zebra platform unlocks the immense and inherent diversity of existing combinatorial antibody and peptide libraries in a novel and powerful next-gen mode that :
• permits direct screening of antibody or peptide libraries in function-based assays for either agonists or antagonists of desired drug targets
• allows direct screening for antibodies or peptides that induce morphogenic or phenotypic changes in any primary cultured cell such as stem cells or progenitor cells.
• may be used to derive therapeutic candidates for new and or previously hard to drug targets.
• may be used to derive “Bio-differents ™ or pheno-copies of blockbuster agonist biologics (such as erythropoietin – EPO, or other hematopoietic growth factors). Bio-differents are fully human antibody biologic molecules being developed by Zebra that have the identical biological function of established therapeutic biologic drugs but have no structural similarity. Such molecules open up opportunities for new intellectual property, avoid all patent estates of existing biologics and offer protein engineering opportunities that can lead directly to short or long acting versions of the existing biologic as desired.
Fig. 1. Scheme for selection of agonist antibodies to receptor "X" in a function-based screening approach employing a receptor activation reporter system that result in a color change in any of the reporter cells if activated by a scFv antibody that mimics an 'agonist'.
For any know target receptor, Zebra first constructs a proprietary reporter cell-line such that activation of the target receptor (usually with the native ligand as the positive control) with any agonist will cause a color change within that cell, allowing isolation of even very rare events by FACS.
As an initial step to select potential "winners" from a large library of billions of scFv antibodies, a traditional affinity-based selection by "panning" step may be employed as a crude selection of those scFv antibodies that bind to the extracellular domain of a target receptor. In a novel patented secondary step, the initial "winner" antibody genes from the selected phage "binders" are then cloned into a lentiviral vector to allow transfection into the target receptor reporter cell-line. Using a viral construct that forces expression of any DNA pay-load (i.e. the scFv initial 'winner') as a membrane tethered protein, the reporter cell-line is transfected with the lentiviral library such that each cell receives just one scFv gene of the 100,000s of thousand selected in the initial screen. In this way each cell within the reporter cell-line assay is a discrete "autocrine" assay point. Thus in a novel function-based screen, a single petri-dish can select the very rare agonist antibodies from the many millions of scFv antibodies were selected initially as simply "binders" to the extracellular domain of the target.
Broad Applicability of the Zebra Platform Utility to Derive Novel Agonist or Antagonist Biologics
Fig 2. Extension of Zebra's core platform technology to allow:-
(a) function-based screening of known targets using a wide variety of protein/peptide libraries
(b) phenotypic screens of primary cells (e.g. bone marrow, selected progenitor cells, ES cells or IPS cell)
Developed initially to create a powerful function-based approach to selecting rare agonist antibodies from combinatorial scFv antibody libraries, Zebra has broaden the utility of the function-based approach to allow it's use to screen human peptide libraries, a Zebra developed new class of human protein-in-protein libraries and most recently large libraries of naturally occurring venom peptides. The core technology has also been successfully adapted to phenotypic/morphogenic screens in which antibodies that drive novel cell fates can be selected and the same antibody can then be used to identify the target that it activates (see "Publications" under "Our Science" for published examples)
The versatility of the Zebra technology allows it use:
• across all disease areas
• ready derivation of agonist therapeutic candidate biologics
• unbiased discovery of antibodies or peptides that can drive cellular differentiation, prevent cell death from multiple insults, induce cellular proliferation of stem or progenitor cells
• discovery of novel intracellular drug targets for small molecule targeting
• rapid development of “large molecule tools” for target validation of small molecule
Zebra’s - Two- Pronged Pipeline Strategy Zebra’s near term focus is to exploit it’s proprietary platform to derive and develop:
• A pipeline of novel biologics for and with partners under both licensing and R&D collaboration agreements.
• An internal pipeline of therapeutic candidates that Zebra will advance either to late stage pre-clinical validation for later partnering or for internal advancement into early proof-of-concept trials in man.