Optimization of cPTs to Improve Affinity and Potency to Target HIV-1 gp120 Trimer
In 2020, approximately 38.4 million people worldwide had ongoing HIV infections. Current therapies have significantly improved survival rates; however, there is still no cure or vaccine. Moreover, recent global reports indicate a significant increase in HAART resistant population, increasing the demand to find novel drugs with new modes of action. The gp120 trimer complex on the viral envelope on HIV is of interest as this spike attaches to host cells to allow entry of viral proteins and genetic material. The Chaiken lab group focuses on developing a peptide to bind to the CD4 Phe 43 pocket to prevent viral entry by targeting the gp120 trimer. The cyclic peptide triazole complex N2 (AAR029N2) is the lead molecule with a pharmacophore of the isoleucine, tryptophan and triazole residues. N2 will be optimized with a focus on the triazole and tryptophan moieties. The desired cPTs were synthesized through use of the CEM Liberty Blue and were then purified validated through preparative and analytical HPLC/MS. The pyrazole containing cPTs went through a second round of purification via analytical HPLC. To evaluate binding affinity and relative potencies of synthesized compounds, surface plasmon resonance and infection inhibition assays were conducted respectively. The data obtained from both infection inhibition and SPR competition assays led to the main finding that future optimization of the cPTs must diverge into two paths, one to obtain a crystal structure and the second to serve improvement of potency. The current derivatives featuring a pyrazole at the triazole-Pro residue point to this conclusion. While the SPR results show a ~2 fold increase in binding affinity (KD) of MG-II-20 compared to N2, the IC50 values do not support that MG-II-20 has the best relative potency. Additionally, the initial hypothesis regarding crystallography candidates was to tag the tryptophan residue with a bromine atom to increase chances of visibility under x-ray radiation, however with SPR data it is clear that a bromine attachment severely hinders affinity by a ~25 to 30 fold decrease. Third, the presence of sulfur is vital for membrane penetrating interactions when looking to obtain potent compounds. Future work will entail running ITC experiments to confirm current relative KD ranking among cPTs. From QSAR predictions for improving potency, a bithiophene and methyl thiophene moiety at the triazole site will be synthesized and tested next. We hope that this work can be further developed for further mechanistic insights as well as potential drug candidacy.
In 2020, approximately 38.4 million people worldwide had ongoing HIV infections. Current therapies have significantly improved survival rates; however, there is still no cure or vaccine. Moreover, recent global reports indicate a significant increase in HAART resistant population, increasing the demand to find novel drugs with new modes of action. The gp120 trimer complex on the viral envelope on HIV is of interest as this spike attaches to host cells to allow entry of viral proteins and genetic material. The Chaiken lab group focuses on developing a peptide to bind to the CD4 Phe 43 pocket to prevent viral entry by targeting the gp120 trimer. The cyclic peptide triazole complex N2 (AAR029N2) is the lead molecule with a pharmacophore of the isoleucine, tryptophan and triazole residues. N2 will be optimized with a focus on the triazole and tryptophan moieties. The desired cPTs were synthesized through use of the CEM Liberty Blue and were then purified validated through preparative and analytical HPLC/MS. The pyrazole containing cPTs went through a second round of purification via analytical HPLC. To evaluate binding affinity and relative potencies of synthesized compounds, surface plasmon resonance and infection inhibition assays were conducted respectively. The data obtained from both infection inhibition and SPR competition assays led to the main finding that future optimization of the cPTs must diverge into two paths, one to obtain a crystal structure and the second to serve improvement of potency. The current derivatives featuring a pyrazole at the triazole-Pro residue point to this conclusion. While the SPR results show a ~2 fold increase in binding affinity (KD) of MG-II-20 compared to N2, the IC50 values do not support that MG-II-20 has the best relative potency. Additionally, the initial hypothesis regarding crystallography candidates was to tag the tryptophan residue with a bromine atom to increase chances of visibility under x-ray radiation, however with SPR data it is clear that a bromine attachment severely hinders affinity by a ~25 to 30 fold decrease. Third, the presence of sulfur is vital for membrane penetrating interactions when looking to obtain potent compounds. Future work will entail running ITC experiments to confirm current relative KD ranking among cPTs. From QSAR predictions for improving potency, a bithiophene and methyl thiophene moiety at the triazole site will be synthesized and tested next. We hope that this work can be further developed for further mechanistic insights as well as potential drug candidacy.