CROI 2017 Abstract e-Book

Abstract eBook

Poster and Themed Discussion Abstracts

506 EVOLUTION OF GAG AND GP41 IN PATIENTS RECEIVING FIRST-LINE PI AND NNRTI REGIMENS Justen Manasa 1 , Vici Varghese 1 , Soo-Yon Rhee 1 , Jeffry Fessel 2 , Karen S. Jang 1 , Elizabeth White 1 , David Katzenstein 1 , Robert Shafer 1 1 Stanford Univ, Stanford, CA, USA, 2 Kaiser Permanent Med Cntr, San Francisco, CA, USA Background: Several groups have proposed that genotypic determinants in HIV-1 gag matrix (MA) and the gp41 cytoplasmic domain (gp41-CD) cause PI resistance. However, MA and gp41-CD mutations selected by PI therapy have not been identified. Methods: We sequenced PR, RT, complete gag and/or gp41 (codons 35-345) before and after therapy in 60 pts with VF on an initial PI (n=40) or NNRTI (n=20) regimen including 34 pts from ACTG A5202 and 26 California clinic pts. To detect selective evolutionary pressure on gag and gp41, we calculated the dn/ds ratios in these genes for each sequence pair. Additionally, each gag and gp41 amino acid was characterized by its prevalence in subtype B sequences from PI-naïve pts in the LANL HIV Sequence Database. We then identified mutations in our dataset at which conserved or relatively common amino acids changed to an amino acid that was >10-fold less prevalent and defined these as having a high selection index. Results: Of 40 pts with VF on an initial PI regimen, we sequenced gag + gp41 in 12 pts, gag alone in 12 pts, and gp41 alone in 16 pts. The median duration of PI therapy was 24.5 months. 36 received ATV/r and 4 received LPV/r. 37 pts attained plasma VL <100 copies/ml at some time during therapy. 3 developed PI DRMs and 10 developed NRTI DRMs. Of 20 pts with VF on an initial NNRTI regimen, we sequenced gag + gp41 in 13 pts, gag alone in 3 pts, and gp41 alone in 4 pts. There were no significant differences between the PI and NNRTI pts in the median number of gag (6 vs 6), gag-MA (4 vs 4), gp41 (4 vs 3), or gp41-CD (1 vs 3) mutations or in the gag dn/ds (0.14 vs 0.22), gag-MA dn/ds (0.20 vs. 0.39), gp41 dn/ds (0.27 vs 0.27), or gp41-CD dn/ds (0.36 vs. 0.30) ratios. In PI pts, there were 27 gag changes (12 in MA) with a high selection index including two in 2 pts: A115T and the P2/NC cleavage site mutation M378I. There were also 38 gp41 changes (27 in CD) with a high selection index including two in 2 pts: A268V and S293N. However, there was no significant difference in the number of highly selected gag, gag-MA, gp41, or gp41-CD changes between the PI and NNRTI pts. Conclusion: There was no evidence for an overall difference in selective pressure in gag-MA or gp41-CD between patients receiving an initial PI or NNRTI regimen. The accumulation of additional sequences obtained before and after PI therapy will make it possible to determine whether individual gag-MA or gp41-CD mutations are selected by PIs. 507 RESISTANCE TO POTENT AND BROADLY ACTIVE HIV-1 MATURATION INHIBITORS Background: Maturation Inhibitors (MI), a new class of anti-HIV-1 compounds, act by blocking the maturation of virions into infectious particles. Bevirimat (BVM), a first-in-class betulinic acid-based compound, acts by blocking a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate into mature CA. BVM was shown to be safe and effective in reducing viral loads in patients. However, polymorphisms in the SP1 region of Gag reduced HIV-1 susceptibility to BVM in patients, effectively halting BVM’s clinical development. Methods: We carried out extensive screening to identify BVM derivatives with both increased potency against multiple HIV-1 clades and activity against primary isolates containing polymorphisms in SP1. Compound activity was tested in biochemical and biological assays measuring CA-SP1 processing and virus replication kinetics. Selection experiments with both clade B and clade C isolates were performed to identify mutations that confer resistance. Virological, structural, and molecular approaches were applied to elucidate the mechanism of resistance for each mutant. Further, combination assays with MIs alongside protease or integrase inhibitors were performed to determine inhibitor synergy or antagonism. Results: We identified a set of BVM derivatives that are markedly more potent than BVM against clade B HIV-1 and show robust activity against SP1 polymorphic strains, clinical isolates, and some BVM-resistant mutants. Selection experiments with a clade B isolate identified an SP1-A1V mutation, and a CA-P157A mutation located in the major homology region (MHR) of CA. Selections with a clade C isolate identified several mutations in SP1. The P157A mutant was resistant to not only BVM and the second-generation BVM analogs but also to the structurally distinct maturation inhibitor PF-46396. Analysis of the HIV-1 database reveals that Ala1 of SP1 and Pro157 of CA are conserved in ~99.95% of available sequences. To date, combination assays with potent MI candidates have shown no antagonismwith protease or integrase inhibitors. Conclusion: This study identifies a panel of BVM derivatives that display improvements upon BVM in antiviral potency and breadth of activity. The characterization of resistant mutants provides insights into the structure of the maturation inhibitor binding site and the role of SP1 and the CA MHR in virus assembly and maturation. This study supports ongoing clinical development of this class of inhibitors. 508 CLINICAL VALIDATION OF A NOVEL DIAGNOSTIC HIV-2 TOTAL NUCLEIC ACID QUALITATIVE ASSAY Ming Chang 1 , Audrey J. Wong 1 , Dana Raugi 1 , Robert Smith 1 , Jose Ortega 1 , Selly Ba 2 , Moussa Seydi 2 , Geoffrey Gottlieb 1 , Robert Coombs 1 , for the University ofWashington-Dakar HIV-2 Study Group 1 Univ of Washington, Seattle, WA, USA, 2 CHU de Fann, Dakar, Senegal Background: The current 4th-generation HIV diagnostic screening algorithm utilizes HIV-1/2 antigen/antibody combination immunoassays. Reactive samples are then tested by orthogonal immunoassays to confirm and discriminate between HIV-1 and HIV-2 antibodies. Additional HIV nucleic acid testing (NAT) is often required to resolve indeterminate or undifferentiated HIV seroreactivity. Undetectable HIV-2 plasma RNA (<10 copies/mL) is reported in one-third of treatment-naïve HIV-2-infected patients; as such, a second-line NAT that detects HIV-2 DNA/RNA in peripheral blood mononuclear cells (PBMC) is essential to confirm HIV-2 infection in this circumstance. Justin A. Kaplan 1 , Emiko Urano 1 , Sherimay Ablan 1 , Nishani Kuruppu 1 , David Martin 2 , T.J. Nitz 2 , Ritu Gaur 3 , Carl Wild 2 , Eric Freed 1 1 NCI, Frederick, MD, USA, 2 DFH Pharma, Inc, Gaithersburg, MD, USA, 3 South Asian Univ, Akbar Bhawan, Chanakyapuri, New Delhi, India

Poster and Themed Discussion Abstracts

CROI 2017 211