a.o.pasternak@amc.uva.nl

1. “Delivering the Promise of Genetic Medicine” TM Abstract no. WEPDA0205 Autologous T-cell therapy based on a lentiviral vector expressing long antisense RNA targeted against HIV-1 env gene influences HIV replication and evolution in vivo Alexander O. Pasternak1, Nik Korokhov2, Ben Berkhout1, Vladimir V. Lukashov1, and Laurent Humeau2 1Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands, and 2VIRxSYS Corporation, Gaithersburg, MD, USA a.o.pasternak@amc.uva.nl

2. VRX496: a lentiviral vector encoding a 937-nt antisense RNA against a part of env gene (gp120) This vector retains the full LTRs of HIV, and, therefore, expression of the antisense is conditional upon wild type HIV infection of the cell Preclinical studies demonstrated complete inhibition of replication of heterologous HIV-1 strains in SupT1 cells and in primaryCD4+ T lymphocytes from healthy donors, as well as in primary CD4+ T lymphocytes from HIV-1 infected patients

3. Strategy: autologousCD4+ T lymphocytes from HIV-infected subjects are transducedex vivo with the vector, expanded, and reinfused into patients Phase I clinical trial (the first ever clinical trial with a lentiviral vector approved by FDA) demonstrated safety and tolerability of this approach (no evidence of insertional mutagenesis by deep sequencing) – Levine et al. (2006), PNAS 103(46):17372

4. Phase II trial: 43 HIV-infectedpatientswhofailed >1 cARTregimens 10-80 billion vector-modified cells were reinfused into patients Longitudinal effects of the therapy on HIV-1 env evolution were analyzed in 17 subjects sampled both pre-infusion and monthly post-infusion for 6 to 12 months Plasma-derived viral RNA from 144 samples was amplified, cloned, and the full-length gp120 coding region was sequenced in 8-10 clones for each sample

5. Transientdecrease in plasma viralload was observed in somepatients Viral Loads: Bolus 1 Dose HIV RNA per mL Days Post Infusion

6. Vector-modifiedcellswerepersistingfor up to 1 year Persistence: Bolus 1 Dose VRX496 Proviral Copies per 106 PBMCs Days Post Infusion

7. Two AS-related factors: sequence SIMilarityof the AS RNA with the targeted HIV transcripts at baseline, (b) PERsistenceof the infused vector-modified cells during the follow-up period, independently and cooperatively influenced HIV replication and evolution: Plasma viralload, changefrom baseline Degree of virus evolution from the pre-infusion to the post-infusion quasispecies (relative MRCA distances) P<0.001 P=0.003 PERlow SIMlow PERlow SIMlow PERhigh SIMlow PERhigh SIMlow PERlow SIMhigh PERlow SIMhigh PERhigh SIMhigh PERhigh SIMhigh

8. P=0.032 The degree of virus evolution from the pre-infusion to the post-infusion quasispecies negatively correlated with virus replicative fitness, assessed ex vivo by growth competition assay Low replicative fitness High replicative fitness

9. Conclusion: Same AS-related factors were associated with enhanced viral evolution and with the relative decrease in plasma viral load, suggesting that selective pressure exerted by the AS causes directional viral evolution, presumably towards escape, which is associated with the fitness loss