dc.contributor.advisor | Engh, Richard | |
dc.contributor.author | Thakkar, Balmukund | |
dc.date.accessioned | 2017-06-15T12:41:14Z | |
dc.date.available | 2017-06-15T12:41:14Z | |
dc.date.issued | 2017-04-28 | |
dc.description.abstract | With pharma R & D witnessing rising cost, high attrition rates and an overall decline in productivity in recent times, newer approaches are needed for more efficient early phase drug discovery. This thesis describes a new approach, “biofocussed chemoprospecting”. The essence of the approach is to use diverse, yet “bio-like” compounds for efficient hit-finding, along with property filtering and optimization of qualities such as diversity of physicochemical properties, drug likeness, ease of synthesis and low cost for efficient selection of compounds.Three libraries based on biomolecules such as linear and cyclic dipeptides, and tartaric acid were designed. Virtual libraries were generated, and their physicochemical properties and drug likeness were analysed. The libraries of compounds with optimum diversity were synthesized, and multiple compounds with significant bioactivities were found. The substitution effects for cyclization reaction were rationalized using QM methods to enable synthetic efficiency as a parameter of library design. The overall success of the approach can be attributed essentially to the efficient library design as an outcome of focus on bio-likeness and optimized diversity – the core ideas of the biofocussed chemoprospecting approach. | en_US |
dc.description.doctoraltype | ph.d. | en_US |
dc.description.popularabstract | New drug discovery and development is typically a long process involving enormous resources in terms of time, money, labour and intellect. The strategies for drug discovery range from broad random screening to focussed target-based approaches. Structure and substrate information greatly enable target-based design, but this is currently limited to relatively few targets. Cell-based screening, on the other hand, can identify new targets, but often suffers from low hit rates and difficult hit optimization. Therefore, newer approaches that can improve the overall efficiency of the combination of screening and hit optimization in early phase drug discovery are needed.
This thesis details our efforts to develop "biofocussed chemoprospecting" as a hybrid approach. The essence of the approach is to use diverse, yet “bio-like” compounds for efficient hit-finding, along with property filtering and optimization of qualities such as diversity of physicochemical properties, drug likeness, ease of synthesis and low cost for efficient selection of compounds. While biofocussing enhances hit-rates; upfront chemical synthesis enables the choice of efficient protocols and diversification potential, and the screening approaches enable discovery of novel therapeutic targets and mechanisms.
Three diverse libraries based on biomolecules--linear and cyclic dipeptides, along with tartaric acid--were designed. Virtual libraries were generated, and their physicochemical properties and drug likeness were analysed. Libraries of compounds chosen to provide good diversity of scaffolds, substitutions and physicochemical properties were synthesized and tested for various biological activities. Many of the synthesized compounds showed significant bioactivities on both target and cell based assays. The N-substituted dipeptide esters showed the most significant bioactivities, including loss of viability on cancer cell lines, as well as activities on opioid and neurokinin receptors and other enzymes such as COX-1,2 and prolyl oligopeptidase. The piperazine-2,5-diones provided interesting hits for anti-cancer activity and BRSK1 enzyme inhibition. With smaller libraries and screening, the tartaric acid bisamides and related compounds can be tested on broader screening platforms to discover novel bioactivities.
In sharp contrast to conventional approaches that use libraries comprising hundreds of thousands of compounds, often synthesized at very high costs, the libraries synthesized following the biofocussed chemprospecting approach provided hits from small libraries at low cost with hit-rates comparable to target-based approaches, with additional potential to identify novel drug targets and mechanisms.
In addition, theoretical QM studies on cis/trans isomerization and cyclization of secondary amides using density functional theory highlighted key features of the reactions used in library synthesis, including energy barriers, the pyramidalization and inversion of nitrogen in cis/trans isomerization, observed substituent effects in cyclization reaction. Such studies can be integrated into future efforts to include synthetic efficiency as a parameter of library design.
The success of the approach can be attributed essentially to the efficient library design as an outcome of focus on bio-likeness and optimized diversity – the core ideas of the biofocussed chemoprospecting approach. | en_US |
dc.description.sponsorship | University of Tromsø, MABIT | en_US |
dc.description | The paper 3 of this thesis is not available in Munin. <br>
Paper 3: Thakkar, B. S., Svendsen, J. S., Engh, R. A.: «Density functional studies on cis/trans isomerization in secondary amides: reaction paths, nitrogen inversion and relevance to peptidic systems”. (Manuscript). Published version with title "Cis/Trans Isomerization in Secondary Amides: Reaction Paths, Nitrogen Inversion and Relevance to Peptidic Systems" available in <a href=http://dx.doi.org/10.1021/acs.jpca.7b05584> J. Phys. Chem. A 2017. </a> | en_US |
dc.identifier.isbn | 978-82-8236-256-6 (trykt) og 978-82-8236-257-3 (pdf) | |
dc.identifier.uri | https://hdl.handle.net/10037/11155 | |
dc.language.iso | eng | en_US |
dc.publisher | UiT Norges arktiske universitet | en_US |
dc.publisher | UiT The Arctic University of Norway | en_US |
dc.rights.accessRights | openAccess | en_US |
dc.rights.holder | Copyright 2017 The Author(s) | |
dc.rights.uri | https://creativecommons.org/licenses/by-nc-sa/3.0 | en_US |
dc.rights | Attribution-NonCommercial-ShareAlike 3.0 Unported (CC BY-NC-SA 3.0) | en_US |
dc.subject | VDP::Mathematics and natural science: 400::Chemistry: 440::Organic chemistry: 441 | en_US |
dc.subject | Synthesis, Peptide coupling, Cyclization, Tartaric acid bisamides, Piperazine-2,5-diones, Dipeptide esters, Tartrimides, Diversity oriented synthesis | en_US |
dc.subject | VDP::Mathematics and natural science: 400::Chemistry: 440::Theoretical chemistry, quantum chemistry: 444 | en_US |
dc.subject | Density functional theory, Geometry optimization, Transition state search, Intrinsic reaction coordinates, Conformational search, B3LYP, DFT | en_US |
dc.subject | VDP::Mathematics and natural science: 400::Chemistry: 440::Pharmaceutical chemistry: 448 | en_US |
dc.subject | Drug discovery, Hit-generation, Lead optimization, Bioprospecting, Chemoprospecting, Biofocussed chemoprospecting, Peptidomimetics, Cheminformatics, Computer aided drug design (CADD), Docking, Homology modelling | en_US |
dc.subject | VDP::Matematikk og Naturvitenskap: 400::Kjemi: 440::Organisk kjemi: 441 | en_US |
dc.subject | VDP::Matematikk og Naturvitenskap: 400::Kjemi: 440::Teoretisk kjemi, kvantekjemi: 444 | en_US |
dc.subject | VDP::Matematikk og Naturvitenskap: 400::Kjemi: 440::Legemiddelkjemi: 448 | en_US |
dc.title | A Biofocussed Chemoprospecting Approach to Drug Discovery: Design, Synthesis and Bioactivity Screening of Diverse Biofocussed Chemical Libraries | en_US |
dc.type | Doctoral thesis | en_US |
dc.type | Doktorgradsavhandling | en_US |