Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Since its discovery in the 1980’s, HIV has affected the lives of millions of individuals around the
globe. Despite obvious need and an enormous amount of research a cure has remained elusive
due to the rapid onset of mutated forms of the virus. However, there has been considerable
success in reducing viral levels of infected individuals through the use of highly active
antiretroviral therapy (HAART). The first-line regimen HAART mainly targets reverse
transcriptase (RT) through the employment of two nucleoside RT inhibitors (NRTIs) and a nonnucleoside
RT inhibitor (NNRTI). NNRTIs target an allosteric pocket situated about 10 Å from
the catalytic site and cause a conformational change in the enzyme upon binding, leading to the
inhibition of viral replication. There are currently 5 FDA approved NNRTIs on the market which
successfully inhibit viral replication, but the use of these drugs is becoming limited due to the
onset of drug resistant strains of the virus.
In light of this need for the development of novel NNRTIs, we set out to explore new territory in
NNRTI drug design with a goal of maintaining efficacy in the presence of both wild-type and
mutated forms of HIV-1. To this end we designed three different NNRTI scaffolds along three
different research thrusts.
The first of these focused on the synthesis of 15 novel flexible triazole containing compounds.
With these compounds we sought to achieve π-π stacking interactions with conserved amino
acid residue Trp229 in the hope that we would be able to maintain efficacy in the presence of
mutated forms of the virus. An additional feature included hydrogen bonding interactions to the
backbone of Lys103. However, despite having thoroughly explored the triazole ring with
multiple substitution arrangements, these compounds had very poor to no activity against
whole cell HIV-1.
Secondly we focused on the synthesis of a 4-hydroxyindole scaffold as a potential NNRTI. The
focus here was to achieve interactions to Trp229 and simultaneously achieve hydrogen bonding
interactions to the backbone of Lys101 at the entrance of the pocket. This was a novel concept
in this class of compounds. We were able to successfully synthesize the indole core as a proofof-concept
using the Knoevenagel-Hemetsberger method however; this compound had no
activity against HIV-1.
Lastly, in our quest to synthesize a novel NNRTI that could maintain efficacy against HIV-1 we
decided to attempt to improve upon the stability of a lead indole-based compound synthesized
previously within our research group. The lead compound was found to be potent with an IC50 of
1 nM but was unstable in acidic media due to the presence of a methoxy functionality situated at
the 3-position on the indole. We sought to overcome this issue by introducing a substituted aryl
amine functionality at this position. We were successful in synthesizing our desired compound
but unfortunately it was significantly less active against whole cell HIV-1 than the lead
compound. However, we were not completely deterred as there are a number of unexplored
bioiososteres as possibilities to improve upon the stability of the lead compound while
maintaining its excellent activity profile. / AFRIKAANSE OPSOMMING: Sedert die ontdekking van die menslike immuniteitsvirus (MIV) in die 1980’s, het die virus al
die lewens van miljoene mense wêreldwyd geaffekteer. Ten spyte van die ooglopende behoefte
aan ‘n geneesmiddel sowel as meer navorsing, bly ‘n keermiddel sover onbekombaar as gevolg
van die verskillende mutasies wat binne die virus gebeur. Ten spyte hiervan, was daar al
heelwat sukses in terme van ‘n verlaging van die virale vlakke in besmette individue deur die
gebruik van hoogsaktiewe antiretrovirale terapie (HAART). As ‘n eerste behandeling, teiken
HAART meestal trutranskriptase (RT) deur die inspanning van twee nukleosied
trutranskriptase inhibeerders (NRTIs) en ‘n nie-nukleosied trutranskriptase inhibeerder
(NNRTI). NNRTIs teiken ‘n allosteriese leemte wat ongeveer 10 Å weg van die katalitiese posisie
is en veroorsaak dan ‘n konformasie verandering in die ensiem tydens die bindingsproses, wat
dan lei tot die inhibisie van die virus se replikasie. Daar is tans 5 FDA goedgekeurde NNRTIs op
die mark wat virale replikasie inhibeer, maar die gebruik van hierdie middels word alhoemeer
belemmer as gevolg van die onwikkeling van weerstandige stamme van die virus.
Met die oog op hierdie nood aan die ontwikkeling van nuwe NNRTIs, het ons gepoog om new
gebiede te ondersoek in terme van die ontwerp van NNRTIs, met die doel om die effektiwiteit
teen beide die wilde-tipe sowel as die gemuteerde vorme van HIV-1 te behou. Vir hierdie
doeleindes het ons drie verskillende NNRTI steiers ontwerp, wat drie navorsingsdoeleindes na
streef.
Die eerste van hierdie doeleindes was die sintese van 15 nuwe buigsame triasool-bevattende
middels. Met hierdie middels het on gepoog om π-π pakkingsinteraksies te behaal met
aminosuur residu, Trp229, en sodoende die effektiwiteit van die NNRTIs in die gemuteerde
vorm van die virus te behou. ‘n Additionele eienskap wat bygevoeg is, is ‘n waterstofbindingsinteraksie
met die ruggraat van Lys103. Ten spyte van pogings om verskeie substitusie
patrone om die triasool-ring te ondersoek, het hierdie middels baie swak tot geen aktiwiteit
teen heel sel HIV-1 getoon nie.
Tweedens, was die fokus op die sintese van ‘n 4-hidroksieindool steier as ‘n potensiele NNRTI.
Die fokus hier was om ‘n interaksie met Trp229 te kry terselfdetyd as ‘n waterstofbindingsinteraksie
met die ruggraat van Lys101, wat by die opening van die bindingssak is.
Hierdie was ‘n nuwe konsep vir hierdie klas van middele. Ons het die indool-kern van hierdie
molekules suksesvol gesintetiseer deur middel van ‘n Knoevenagel-Hemetsberger metode, maar
ongelukkig het hulle geen aktiwiteit teen HIV-1 getoon nie.
Laastens het ons gepoog om ‘n nuwe NNRTI te sintetiseer wat effiktiwiteit teen HIV-1 behou,
deur te probeer om vorderings te maak op die stabiliteit van ‘n indool-gebaseerde hoof-middel
wat al voorheen deur ons navorsingsgroep geraporteer is. Hierdie hoof-middel het ‘n IC50
waarde van 1 nM gelewer, maar was onstabiel in suur medium as gevolg van die
teenwoordigheid van ‘n metoksie-groep in die 3-posisie van die indool. Ons het gepoog om
hierdie probleem te oorkom deur ‘n gesubtitueerde arielamien in hierdie posisie te plaas. Ons
was suksesvol hierin, maar ongelukkig was die middel heelwat minder aktief teen die heel sel
HIV-1 as die metoksie-weergawe. Ten spyte hiervan, is ons optimisties dat ons hierdie probleem
kan oorkom, aangesien daar verskeie bioisostere is wat die stabilitiet van middel kan verbeter
terwyl dit moontlik die effektiwiteit kan behou.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96693 |
| Date | 04 1900 |
| Creators | Pribut, Nicole |
| Contributors | Pelly, Stephen Christopher, van Otterlo, Willem Arjen Lodewijk, Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | x, 118 pages : colour illustrations |
| Rights | Stellenbosch University |
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