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  EACS - 12th European AIDS Conference
November 11-14, 2009
Cologne, Germany
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S/GSK1349572 Integrase Inhibitor Resistance Profile
  Reported by Jules Levin
EACS Oct 31-Nov 3 2009 Cologne, Germany
Akihiko Sato1, Masanori Kobayashi1, Tomokazu Yoshinaga1, Tamio Fujiwara1 Mark Underwood2, Brian Johns2, Scott Foster2, Richard Hazen2, Robert Ferris2, Kevin Brown2, William Spreen2, Edward Garvey2 1Shionogi & Co., Ltd., Osaka, Japan; 2GlaxoSmithKline, Research Triangle Park, NC, US
S/GSK1349572 is a potent inhibitor of HIV integrase in vitro and in cellular HIV replication assays.
S/GSK1349572 had limited cross-resistance to RAL- and ELV-resistant mutants.
In vitro passage study showed that S/GSK1349572 leads to a less diverse resistance profile with lower fold change.
S/GSK1349572 exhibited in vitro activity against most clinical isolates obtained from patients failing RAL-based therapy.
In vitro experiments support the potential for S/GSK1349572 to have a higher genetic barrier to resistance when compared to 1st generation INIs.
When combined with the unprecedented virologic responses observed during 10 day S/GSK1349572 monotherapy1,8, these data suggest potential to treat patients with RAL resistance.
These observations need to be confirmed in clinical studies, and support further development of S/GSK1349572 for patients across the treatment spectrum.





Objective: S/GSK1349572 was selected from a series of designed two-metal binding integrase inhibitor scaffolds. We demonstrate here its antiviral potency and resistance profile as a next generation integrase inhibitor (INI).
Methods: S/GSK1349572 activity was determined biochemically in a strand transfer assay with purified integrase enzyme and against different HIV strains and clinical isolates in various cell lines. HIV-1 IIIb was passaged with S/GSK1349572 under dose escalating conditions. S/GSK1349572 and raltegravir (RAL) susceptibility of clinical isolates from patients failing RAL-based therapy was determined using Monogram Biosciences Integrase PhenoSense assay.
Results: S/GSK1349572 inhibited HIV integrase in an in vitro strand transfer assay with IC50=2.7 nM. In PBMC cell assay, the antiviral IC50=0.51 and IC90=2.0 nM. In MT-4 antiviral assays, potency shift extrapolated to 100% human serum was 75-fold providing PA-IC90=152 nM in PBMCs. S/GSK1349572 had low nM potency against broad panels of HIV-1 isolates (clades A-G and group O) and against HIV-2 in PBMCs. When virus was passaged in the presence of S/GSK1349572, highly resistant mutants were not isolated; mutations which conferred low fold change (FC ≤ 4.1) were identified within the integrase active site. S/GSK1349572 demonstrated low FC in activity against RAL resistant site directed molecular clones and clinical isolates from RAL-failure patients. All longitudinal RAL virologic failure samples were more susceptible (and 19/21 were >5-fold more susceptible) to S/GSK1349572 than RAL.
Conclusions: S/GSK1349572 was a potent inhibitor of HIV integrase in biochemical assay and in cellular HIV replication assays. S/GSK1349572 had a markedly different resistance profile as evidenced by limited cross-resistance to RAL-resistant molecular clones, by its in vitro activity against clinical isolates obtained from patients failing RAL-based therapy, and in selecting different mutations with low level FC during serial passage. These data demonstrate S/GSK1349572 had a virologic profile distinct from RAL and potential to possess a higher genetic barrier.
The long-standing Shionogi-GSK Joint Venture has made considerable progress in developing next-generation integrase inhibitors.
S/GSK1349572 is the only once-daily, unboosted integrase inhibitor currently in development with unprecedented antiviral activity and a superior resistance profile.1,2,3
S/GSK1349572 has demonstrated a predictable, well-characterized exposure-response relationship and low PK variability.3
In vitro strand transfer assay: Recombinant HIV integrase was used in an in vitro strand transfer assay which measured the amount of donor DNA covalently attached to target DNA.
Cell based antiviral & cytotoxicity assays; Antiviral & cytotoxicity assays were performed using several virus strains and multiple cell lines. Testing of S/GSK1349572 against various HIV clades and HIV-1 clinical isolates was done at Southern Research Institute in PBMCs and at Monogram Biosciences using their Integrase Phenosense assay. The effects of protein binding on antiviral activity were tested using human serum albumin or human serum.
Passage study: Generation of virus resistant to inhibitor was performed by passage of IIIB virus in MT2 cells in the presence of S/GSK1349572. For comparison, the potency of INIs that have been studied in the clinic (raltegravir and elvitegravir) were also measured in the above assays. INI-resistant mutant HIV-1 viruses were produced from wild type virus NL-432 using site directed mutagenesis of the integrase coding region and were tested for susceptibility to INIs using infected HeLa-CD4 cells carrying a reporter ß-galactosidase gene driven by HIV-1 LTR.5,6
Phenotype study: Integrase resistant HIV-1 sample phenotypes were evaluated at Monogram Biosciences using the Integrase PhenoSense assay. The compounds S/GSK1349572 and RAL were tested side by side and IC50 and fold·change in IC50 vs. wild-type (FC-IC50) were generated.
The samples included 11 site directed mutant (SDM) control HIV-1 IN sequences based on NL43 and eight clinical isolates containing IN resistance mutations from Monogram Biosciences library set. In addition, 31 clinical isolate samples were evaluated from subjects experiencing virologic failure on therapy which included RAL in the UCSF SCOPE Cohort.7 Altogether, 39 clinical isolate samples were examined; 30 had IN coding region mutations and 21 of those were longitudinal samples from 9 patients.













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2. Underwood M. et al. IAS 2009, Cape Town, Poster #WEPEA098.
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7. Hatano H. et al. June 10-14, 2008. Sitges, Spain.
8. Fujiwara T. et al. EACS 2009, Cologne, Poster #PE7.2/4.