Gary Woodnutt

Targeting the ANGPT-TIE2 pathway in malignancy.

Angiopoietins (ANGPTs) are ligands of the endothelial cell receptor TIE2 and have crucial roles in the tumour angiogenic switch. Increased expression of ANGPT2 relative to ANGPT1 in tumours correlates with poor prognosis. The biological effects of the ANGPT–TIE system are context dependent, which brings into question what the best strategy is to target this pathway. This Review presents an encompassing picture of what we know about this important axis in tumour biology. The various options for therapeutic intervention are discussed to identify the best path forwards.

Specifically Targeting Angiopoietin-2 Inhibits Angiogenesis, Tie2-Expressing Monocyte Infiltration, and Tumor Growth

Purpose: Angiopoietin-1 (Ang1) plays a key role in maintaining stable vasculature, whereas in a tumor Ang2 antagonizes Ang1s function and promotes the initiation of the angiogenic switch. Specifically targeting Ang2 is a promising anticancer strategy. Here we describe the development and characterization of a new class of biotherapeutics referred to as CovX-Bodies, which are created by chemical fusion of a peptide and a carrier antibody scaffold. Experimental Design: Various linker tethering sites on peptides were examined for their effect on CovX-Body in vitro potency and pharmacokinetics. Ang2 CovX-Bodies with low nmol/L IC50s and significantly improved pharmacokinetics were tested in tumor xenograft studies alone or in combination with standard of care agents. Tumor samples were analyzed for target engagement, via Ang2 protein level, CD31-positive tumor vasculature, and Tie2 expressing monocyte penetration. Results: Bivalent Ang2 CovX-Bodies selectively block the Ang2–Tie2 interaction (IC50 < 1 nmol/L) with dramatically improved pharmacokinetics (T½ > 100 hours). Using a staged Colo-205 xenograft model, significant tumor growth inhibition (TGI) was observed (40%–63%, P < 0.01). Ang2 protein levels were reduced by approximately 50% inside tumors (P < 0.01), whereas tumor microvessel density (P < 0.01) and intratumor proangiogenic Tie2+CD11b+ cells (P < 0.05) were significantly reduced. When combined with sunitinib, sorafenib, bevacizumab, irinotecan, or docetaxel, Ang2 CovX-Bodies produced even greater efficacy (∼80% TGI, P < 0.01). Conclusion: CovX-Bodies provide an elegant solution to overcome the pharmacokinetic–pharmacodynamic problems of peptides. Long-acting Ang2 specific CovX-Bodies will be useful as single agents and in combination with standard-of-care agents. Clin Cancer Res; 17(5); 1001–11. ©2011 AACR.

Chemical generation of bispecific antibodies

Bispecific antibodies (BsAbs) are regarded as promising therapeutic agents due to their ability to simultaneously bind two different antigens. Several bispecific modalities have been developed, but their utility is limited due to problems with stability and manufacturing complexity. Here we report a versatile technology, based on a scaffold antibody and pharmacophore peptide heterodimers, that enables rapid generation and chemical optimization of bispecific antibodies, which are termed bispecific CovX-Bodies. Two different peptides are joined together using a branched azetidinone linker and fused to the scaffold antibody under mild conditions in a site-specific manner. Whereas the pharmacophores are responsible for functional activities, the antibody scaffold imparts long half-life and Ig-like distribution. The pharmacophores can be chemically optimized or replaced with other pharmacophores to generate optimized or unique bispecific antibodies. As a prototype, we developed a bispecific antibody that binds both vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang2) simultaneously, inhibits their function, shows efficacy in tumor xenograft studies, and greatly augments the antitumor effects of standard chemotherapy. This unique antiangiogenic bispecific antibody is in phase-1 clinical trials.

Development of a Novel Long-Acting Antidiabetic FGF21 Mimetic by Targeted Conjugation to a Scaffold Antibody

Fibroblast growth factor (FGF)21 improves insulin sensitivity, reduces body weight, and reverses hepatic steatosis in preclinical species. We generated long-acting FGF21 mimetics by site-specific conjugation of the protein to a scaffold antibody. Linking FGF21 through the C terminus decreased bioactivity, whereas bioactivity was maintained by linkage to selected internal positions. In mice, these CovX-Bodies retain efficacy while increasing half-life up to 70-fold compared with wild-type FGF21. A preferred midlinked CovX-Body, CVX-343, demonstrated enhanced in vivo stability in preclinical species, and a single injection improved glucose tolerance for 6 days in ob/ob mice. In diet-induced obese mice, weekly doses of CVX-343 reduced body weight, blood glucose, and lipids levels. In db/db mice, CVX-343 increased glucose tolerance, pancreatic β-cell mass, and proliferation. CVX-343, created by linkage of the CovX scaffold antibody to the engineered residue A129C of FGF21 protein, demonstrated superior preclinical pharmacodynamics by extending serum half-life of FGF21 while preserving full therapeutic functionality.

Peptide-Conjugation Induced Conformational Changes in Human IgG1 Observed by Optimized Negative-Staining and Individual-Particle Electron Tomography

Peptides show much promise as potent and selective drug candidates. Fusing peptides to a scaffold monoclonal antibody produces a conjugated antibody which has the advantages of peptide activity yet also has the pharmacokinetics determined by the scaffold antibody. However, the conjugated antibody often has poor binding affinity to antigens that may be related to unknown structural changes. The study of the conformational change is difficult by conventional techniques because structural fluctuation under equilibrium results in multiple structures co-existing. Here, we employed our two recently developed electron microscopy (EM) techniques: optimized negative-staining (OpNS) EM and individual-particle electron tomography (IPET). Two-dimensional (2D) image analyses and three-dimensional (3D) maps have shown that the domains of antibodies present an elongated peptide-conjugated conformational change, suggesting that our EM techniques may be novel tools to monitor the structural conformation changes in heterogeneous and dynamic macromolecules, such as drug delivery vehicles after pharmacological synthesis and development.

Evolution of potent and stable placental-growth-factor-1-targeting CovX-bodies from phage display peptide discovery.

Novel phage-derived peptides are the first reported molecules specifically targeting human placental growth factor 1 (PlGF-1). Phage data enabled peptide modifications that decreased IC(50) values in PlGF-1/VEGFR-1 competition ELISA from 100 to 1 μM. Peptides exhibiting enhanced potency were bioconjugated to the CovX antibody scaffold 1 (CVX-2000), generating bivalent CovX-Bodies with 2 nM K(D) against PlGF-1. In vitro and in vivo peptide cleavage mapping studies enabled the identification of proteolytic hotspots that were subsequently chemically modified. These changes decreased IC(50) to 0.4 nM and increased compound stability from 5% remaining at 6 h after injection to 35% remaining at 24 h with a β phase half-life of 75 h in mice. In cynomolgus monkey, a 78 h β half-life was observed for lead compound 2. The pharmacological properties of 2 are currently being explored.

Inhibiting complex IL-17A and IL-17RA interactions with a linear peptide.

IL-17A is a pro-inflammatory cytokine that has been implicated in autoimmune and inflammatory diseases. Monoclonal antibodies inhibiting IL-17A signaling have demonstrated remarkable efficacy, but an oral therapy is still lacking. A high affinity IL-17A peptide antagonist (HAP) of 15 residues was identified through phage-display screening followed by saturation mutagenesis optimization and amino acid substitutions. HAP binds specifically to IL-17A and inhibits the interaction of the cytokine with its receptor, IL-17RA. Tested in primary human cells, HAP blocked the production of multiple inflammatory cytokines. Crystal structure studies revealed that two HAP molecules bind to one IL-17A dimer symmetrically. The N-terminal portions of HAP form a β-strand that inserts between two IL-17A monomers while the C-terminal section forms an α helix that directly blocks IL-17RA from binding to the same region of IL-17A. This mode of inhibition suggests opportunities for developing peptide antagonists against this challenging target.

Abstract 4113: Discovery and optimization of potent SDF1α antagonist peptides.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC The SDF1α / CXCR4 axis contributes to cancer metastasis, proliferation, angiogenesis and resistance to standard of care drugs. Here we describe novel phage display derived peptide SDF1α antagonists. Phage displayed peptides were optimized through a multistep process that resulted in a 400-fold improvement in activity, from 6.4 uM IC50 inhibition of SDF1α -driven Calcium flux to 16 nM IC50. First, peptides were affinity matured via panning of focused phage libraries. Peptides exhibiting enhanced potency were bioconjugated to the CovX antibody scaffold IgG (CVX-2000), generating bivalent CovX-Bodies with 5-fold improved potency in SDF1α driven Calcium flux assays. N and C-terminal extension of the peptide and introduction of unnatural amino acids produced an additional 11-fold improvement in activity to 16 nM. Constructs with optimal pharmacokinetic stability were identified, and demonstrated single agent tumor inhibition in a Ramos B cell lymphoma xenograft model. Citation Format: Julia A. Coronella, Yanwen Fu, Kimberly Johnson, Jingping Zhong, Lioudmila Campbell, Gang Chen, Dorian Willhite, Joselyn Del Rosario, Abhijit Bhat, Gary Woodnutt, Nancy Levin. Discovery and optimization of potent SDF1α antagonist peptides. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4113. doi:10.1158/1538-7445.AM2013-4113

Abstract 1386: Predictive markers of efficacy for an angiopoietin-2 targeting therapeutic in xenograft models

The clinical efficacy of anti-angiogenic therapies has been difficult to predict, and in this era of personalized medicine biomarkers that can predict effect are sorely needed. CVX-060 is an angiopoietin-2 (Ang2) targeting therapeutic, consisting of two peptides that bind Ang2 with high affinity and specificity, covalently fused to a scaffold antibody. The resulting therapeutic has shown promising activity in a phase 1 clinical trial, with several phase 2 clinical programs in progress/planning. In order to optimize the use of this compound in the clinic a set of predictive biomarkers are desired. Here we describe the construction of a predictive model based on the efficacy of CVX-060 in 13 conventional xenograft models, focusing on renal and ovarian cancer. Pretreatment size tumors from each of the models were profiled for the levels of ∼25 protein markers of angiogenesis, SNP haplotype in 5 angiogenesis genes, and somatic mutation status for ∼12 genes implicated in tumor growth and/or vascularization. The markers chosen for evaluation were accumulated from angiogenesis literature and a differential gene expression analysis of CVX-060 treatment-induced changes. CVX-060 efficacy was determined as tumor growth inhibition (TGI%) at termination of each study. A predictive statistical model was constructed based on the correlation of these efficacy data with the marker profiles, and the model was subsequently tested via prospective analysis in 7 additional models The results of this work reveal a range of CVX-060 efficacy in xenograft models of diverse tissue types (0-49% TGI, median = 38%). Notably, we define a subset of 5-7 proteins, the levels of which are predictive of TGI by Ang2 blockade. The majority of these proteins are proximal to the target of CVX-060 and the direction of the associations is such that better efficacy correlates with high levels of target and low levels of compensatory/antagonizing molecules. The SNPs and somatic mutations examined here did not correlate with TGI. Our study describes a systematic approach to the problem of identifying predictive markers of anti-angiogenic affect, and demonstrates the significant ground work necessary to reveal treatment-sensitive predictive markers which can be quantitatively defined. This effort has revealed a set of predictive markers for CVX-060 efficacy that will be further evaluated in ongoing clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1386. doi:1538-7445.AM2012-1386

Abstract 2327: Anti-angiogenic activity of a CovX bi-functional antibody conjugate targeting both activin-receptor like kinase type 1 (ALK-1) and vascular endothelial growth factor (VEGF)

Angiogenesis is essential for tumor growth and metastasis, and controlling tumor-associated angiogenesis is a proven therapeutic intervention to limit tumor progression. Several pathways have been involved in tumor-associated angiogenesis and the predominant target of current interventions is the vascular endothelial growth factor (VEGF) pathway. Recently, Activin-receptor like kinase type 1 (ALK-1) has been proven to be a novel and potent target of tumor angiogenesis. Our results indicate that inhibiting VEGF and ALK1 have different effects on tumor vasculature, suggesting that targeting both pathways could have a more potent effect than targeting either pathway alone. We have created a bi-functional antibody conjugate targeting both ALK-1 and VEGF by conjugating VEGF-trap peptides to an anti-ALK1 monoclonal antibody. We demonstrate that our bi-functional molecule binds both ALK-1 and VEGF with high affinity in vitro, blocks both ALK-1 and VEGF pathways in HUVEC primary human endothelial cells and has good pharmacokinetics properties in mice. Finally, in a MDA-MB-231 xenograft model in SCID mice, the ALK-1/VEGF bi-functional antibody conjugate slowed tumor growth and prolonged survival with greater efficacy than anti-VEGF therapy alone. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2327. doi:1538-7445.AM2012-2327