The founders of AngioDesign are world leaders in enzyme structure determination and rational drug design. The company has built unique expertise in solving the crystal structures of complex enzymes, such as ACE, and using that information to guide the rational design of next-generation therapeutics. Our rational drug design capabilities are complemented by deep and extensive expertise in medicinal chemistry, computational hit and lead selection, and preclinical pharmacokinetic (PK) and pharmacodynamics (PD) development of leading drug candidates.
ACE protein crystallisation and structure determination:
For many years the ACE crystal structure was a holy grail in both industry and academia because of the enormous importance of ACE as a therapeutic target. Efforts to crystallize ACE and determine its structure had been going on since the late 1980's in numerous laboratories and had all failed. The key problems included obtaining ACE in a form and in quantities sufficient to facilitate crystallization trials, and in establishing crystallization conditions that would yield crystals suitable for x-ray diffraction. These problems were solved by two of the company's founders, Ravi Acharya and Ed Sturrock, and led to determination of the crystal structure at an extremely high resolution (Natesh R., Schwager S.L., Sturrock E.D., Acharya K.R. Nature 421, 551-4, 2003).
The ACE founders developed innovative solutions that finally cracked the ACE structure problem. Large proteins like ACE are difficult to crystallize. The common somatic form of ACE contains more than 1,400 amino acids, as well as numerous complicated sugar residues, which hinder crystallization. To overcome these problems, the company's founding scientists focused on the isolated C- and N-Domains of ACE (which were known to be independently active). Numerous minimally glycosylated protein forms were engineered and expressed for crystallisation trials, eventually producing diffraction-quality crystals.
The ACE crystals were exposed to high-energy x-rays in a synchrotron source, generating high-resolution diffraction patterns. Importantly, ACE was also co-crystallized with various types of ACE inhibitors, which would lead to crucial insights into how the active site functions and how to design improved inhibitors. The diffraction data were processed by sophisticated computer programs, which eventually produced a precise three-dimensional picture of the protein. This structure revealed the exact shape of ACE, how it is regulated, and how the active site, the business end of the enzyme, acts on the peptides that are its target. The way the active site functions is the key to future rational drug design.
Using these techniques, the structures of both the C and N domains were solved by the Company's founders. The two domains are highly similar but also reveal subtle yet significant differences. Detailed knowledge of these differences is essential for the design and synthesis of novel domain-selective inhibitors.
With access to the proprietary crystal structures of the C and the N-Domains, as well as the proprietary right to use the information to design and synthesize N- and C-domain-selective ACE inhibitors, AngioDesign has a unique competitive advantage. Moreover, AngioDesign's scientists and senior advisors possess unique know-how crucial for the rapid co-crystallization of ACE with novel domain-selective inhibitors as they are synthesized, which is essential for fine-tuning and lead optimization. Collectively, this puts AngioDesign in an unassailable position to develop novel, domain-selective ACE inhibitors.
AngioDesign works closely with H3-D Drug Discovery (http://h3d.co.za/) to access state-of-the-art medicinal chemistry tools that efficiently advance drug discovery projects from hit identification through lead optimisation, to drug candidates. Together with H3-D, our medicinal chemists have extensive experience in synthetic chemistry and drug development, and work closely with a team of computational chemists and structural biologists to provide comprehensive drug discovery strategies.
Protein expression and engineering
Fundamental to all of our work is deep expertise in protein expression and engineering, which is an integrated platform that advances projects from an engineered DNA construct to purified proteins that are ready for high-throughput enzyme activity assays and high-resolution crystal structure determination. Multiple expression systems, such as bacterial, baculovirus, and eukaryotic systems, are used to ensure the correct posttranslational modifications and folding of the proteins. Further, a broad choice of purification systems, such as affinity, size exclusion, and ion exchange chromatography, are employed to robustly produce recombinant proteins of high purity and quality.
High-throughput enzyme assays
AngioDesign is able to develop and validate enzyme and ligand-binding assays in a wide range of spectrophotometric, calorimetric, and fluorescence-based formats. AngioDesign's founder Ed Sturrock has developed a rapid and sensitive high-throughput fluorimetric enzyme assay that can be used for routine screening of ACE inhibitors or more detailed kinetic analyses (Schwager SLU, Carmona AK, Sturrock, ED. Nature Protocols 1(4): 1961-1964, 2006).
Pharmacometrics is an emerging science that quantifies drug and disease information to aid efficient drug development and/or regulatory decisions. Drug models describe the relationship (both desired and undesired effects) between drug exposure (defined by pharmacokinetics), response (pharmacodynamics), and individual patient characteristics. Using such tools, we recently evaluated the pharmacokinetics of a novel C-domain ACE inhibitor LisW-S, which showed promising Cmax and terminal elimination half-life values (Denti P, et al. Eur J Pharm Sci 56, 113-119, 2014). AngioDesign carries out most of its pharmacometric analyses in the accredited Division of Clinical Pharmacology at the University of Cape Town.