Ann Duerr, MD, PhD, MPH

1. Ann Duerr, MD, PhD, MPH An update on HIV vaccines: Reflections on unexpected results and future possibilities October 23, 2008

2. More than a quarter of a century of the HIV epidemic • 60 million infections • 20 million deaths • A generation that has not known a world without AIDS

3. 2 decades of HIV vaccine research more than 30 products tested more than 85 trials conducted Thousands of volunteers, investigators & staff from over 25 nations participated in clinical trials more than $3 billion invested

4. So where are we now? Why do we need an HIV vaccine?

5. HIV strikes fast: CD4 memory cells massively depleted in 1st weeks (Image courtesy of Rockefeller University)

6. Other efforts fall short... Other preventive efforts • Education, counseling & behavioral interventions • STDs: early detection & treatment • Safe blood supply • Circumcision • Microbicides – not yet • Barrier methods – condoms but not diaphragm • Antiretroviral therapy • PEP and PrEP – potentially helpful but unproven and controversial • Reduction of HIV transmission: only a small fraction of 36 million infected have access to HAART Preventive HIV vaccine is critically needed!

7. Clinical Trials ofHIV Vaccines,1988-2008 1998-2003 Phase III: AIDSVAX B/B + B/E 2003-2008 Phase III: vCP 1521/gp120 2004-2008 Phase IIB: MRK Ad5 ** *includesAVEG, HIVNET, HVTN, Merck, VRC, & selected USMHRP trials ** Other includes Alphavirus and Salmonella vectors

8. Neutralization BindingAntibodies Antibodies can bind up free virions in infected secretions

9. Localized Infection in Mucosal Tissue 1-3 days Regional Spread and Latency 3-5 days Systemic Dissemination 6-9 days These immune responses act early and could block infection

10. CTL CTL Kill HIV Infected Cell Apoptotic Death Vaccines can produce T-cell memory to eliminate HIV-infected cells

11. Localized Infection in Mucosal Tissue 1-3 days Regional Spread and Latency 3-5 days Systemic Dissemination 6-9 days These immune responses act later and may not block infection

12. Vaccine Efficacy testing Early trials on antibody-based vaccine failed to protect CMI vaccines may protect against progression and transmission

13. Efficacy testing of T cell vaccine:The MRK trivalent Ad5 vaccine Test of Concept: Can a vaccine that elicits CMI protect? • Guide later development ● Smaller, cheaper, faster • May use surrogate endpoint or prototype product • Study population may be limited and focused Step: Testing ability of MRK Ad5 trivalent HIV vaccine to • Decrease HIV acquisition and/or • Reduce viral load set-point • Initiated in population thought to be most likely to benefit • Participants in clade B regions • Low prior immunity to Ad5 Phambili: planned for 3000 in South Africa (clade C region)

14. MRKAd5 trivalent clade B HIV vaccine • Vaccine: 1:1:1 admixture of 3 Ad5 vectors • Encoded transgenes: codon-optimized, near-consensus clade B HIV-1 sequences • Placebo: vaccine dilution buffer without Ad5

15. Improved course after SHIV challenge in Ad5-SIV gag immunized rhesus monkeys Shiver JW et al. Nature (2002)

16. Months Step Study Design 0 1 2 12 3 6 9 3 Adeno vectors: clade B gag clade B pol clade B nef

17. The Step Studyinclusion criteria • Between 18 and 45 years old • IDU not excluded but must have sexual risk factors. • MSM • Unprotected anal intercourse with another man • Anal intercourse with ≥2 male sexual partners • Women • Unprotected vaginal or anal intercourse with a man known to be HIV-1 infected • Unprotected vaginal or anal intercourse with a man who uses injection drugs • Exchanged sex for money, drugs, services, or gifts • Used crack cocaine at least 3 times

18. Step Study sites www.stepstudies.com

19. Step Study design:Ad5 stratification • Initial trial design: 1500 HIV-negatives with low (<200) Ad5 titers. Enrollment later opened to 1500 HIV-negatives with high (>200) Ad5 titers • Enrollment stratified by Ad5 titer • <18, • 18-200, • 201-1000, • >1000 • Follow-up ~every 6 months for HIV acquisition • Primary endpoint: protection against infection and effect on early HIV viral load (~3 months post-diagnosis) in low Ad5 group

20. Enrollment in high Ad5 stratumlagged behind low Ad5 stratum

21. Participant characteristics: well-balanced in vaccine vs. placebo

22. Immune response in most vaccineesResults similar to earlier trials *Results from a 25% random sample of study volunteers at week 8 timepoint

23. Interim analysis of HIV Acquisition No effect in men with Ad5 ≤ 200 1-tailed p-value = 0.322 (for VEINF ≠ 0) 2-tailed p-value = 0.581 (for VEINF ≠ 0) Cases accrued as of Oct 17, 2007

24. No significant difference in early HIV viral load Overall For subjects with viral load setpoint data available as of Oct 17, 2007.

25. Interim analysis indicated no benefit. Pre-set futility criteria met for beneficial effect on both primary endpoints (p>0.5) Immunizations halted, participants notified and study unblinded.

26. More HIV infections among vaccinees in some subgroups (MITT men) Overall Ad5 > 200 1-tailed p-value = 0.044 (for VEINF ≠ 0) 2-tailed p-value = 0.077 (for VEINF ≠ 0) 1-tailed p-value = 0.020 (for VEINF ≠ 0) 2-tailed p-value = 0.029 (for VEINF ≠ 0) Cases accrued as of Oct 17, 2007

27. Vaccine effect varies in men with or without pre-existing Ad5 immunity Ad5 ≤ 18 18 < Ad5 ≤ 200 200 < Ad5 ≤ 1000 Ad5 > 1000

28. Higher HIV incidence in vaccinees who are Ad5+ (>18) or uncircumcised *Demographics and risk behavior in 6 months before trial Univariate hazards ratios; p values for interaction test comparing treatment effect in subgroups

29. Highest HIV incidence in Ad5+ uncircumcizedModel-Based Hazard Ratios (95% CIs) [V:P](HR > 1 favors Placebo) “p” = 2-tailed p-value for overall treatment effect; males with unknown circumcision status (N=49, 2.7%) were excluded from the analysis. All univariate and multivariate analyses are based on the Cox proportional hazards regression model for time-to-event data.

30. Why was there no protection against HIV and why were certain subgroups more likely to become infected if vaccinated?

31. Failure to protect against HIV acquisition not explained by poor immune response % Resp.: 74 86 86 65 75 75 61 58 58 67 68 53 51 33 34 n: 23 143 23 143 23 143 15 173 15 173 15 173 100 Ad5 < 200 Ad5 > 200 80 Cases Non-Cases 60 % Responders 40 20 0 > 1 > 2 All 3 > 1 > 2 All 3 Number of Antigens with Positive ELISPOT Response

32. CD4+ and CD8+ T cell responses not different in cases vs. non-cases

33. Difference in behavioral risk does not explain increased HIV risk in vaccinees

34. Higher HIV acquisition in uncircumcised and Ad5-seropositive vaccinees • The interaction between HIV risk, vaccination and circumcision status remains a very perplexing issue • Uncircumcised men: higher risk for men reporting unprotected insertive anal sex with HIV+ or unknown status partners (HR vaccine vs placebo = 6.1 vs 2.5). Increased risk not seen among circumcised men (HR~1). • Increased risk among uncircumcised vaccinees remains after correcting for other risk behaviors • Activated cells are more susceptible to HIV • Could vaccine-induced activation at mucosal sites (foreskin, rectum) have lead to increased susceptibility?

35. HIV acquisition does not appear to “cluster” around vaccination times Crude estimation method using 26 week intervals Time interval of estimated HIV infection in weeks relative to randomization;Summaries exclude 1 female infection (placebo group with Ad5 ≤ 18). MITT population includes all HIV cases diagnosed after baseline.

36. Are differences due to decreased HIV acquisition in placebos in Ad 5 >18 strata ? V = vaccine, P = placebo; f/up = follow-up for HIV acquisition; N = number of subjects randomized & vaccinated. 18 is the LOQ for the Ad5 titer assay. Results are based on all HIV cases that accrued after baseline (MITT population)

37. Why Didn’t We See an Effect on Set Point Viremia?

38. Vaccine effects of post-acquisition clinical course Set point viremia only part of the story VL trajectory Rate of CD4 decline Preservation of memory cell populations No vaccine effect seen to date on HIV viral load or CD4 trajectory. HVTN will follow entire cohort for 2 more years and HIV positive persons for 6.5 years with the primary endpoint to evaluate time to initiation of ART. Investigating relation of vaccine-induced response and clinical course

39. Possible reasons for lack of vaccine efficacy currently under study • Insufficient breadth of response • Insufficient duration of response • Quality of T-cell response doesn’t afford protection • Vaccine response doesn’t target protective epitopes • Limited vaccine response at mucosal surfaces • Rapid immune escape after infection

40. Step Study Results • Two major issues with likely different mechanisms • No protection against HIV infection was seen. In fact increased acquisition was seen in subgroups of vaccinees (Ad 5-seropositive, uncircumcised) • The vaccine, despite eliciting excellent CD8 effector T cell responses in PBMC, demonstrated no overall efficacy on viral load

41. Post Step Reverberations • Traumatic result for the field • Widespread use of lay terms such as “scientific failure” not just by lay journalists, but by scientists • Reality: • STEP trial was a flawlessly conducted trial. • The failure of the MRK vaccine is a product failure and a set back for the rapid availability of an effective HIV vaccine • The trial itself a major success in defining questions and issues that must be answered for developing an effective HIV vaccine

42. Step study results: bottom line Well designed trial, timely assessment of lack of efficacy.Explanation unclear, multivariate & immunologic assessments ongoing.Results underscore the need for more predictive animal model and new classes of vaccine candidates

43. Can attenuated vectors give better control of viremia (single-cycle SIV)? Evans et al. JV, 2005

44. Strategies for eliciting neutralizing antibodies to prevent HIV infection

45. Vaccine development:Harder than you think

46. http://www.hvtn.org/

47. The Study Volunteers, sites and protocol team For their dedication and commitment in the search for an HIV vaccine Acknowledgments

48. Susan Buchbinder Michael Robertson Dan Fitzgerald Ann Duerr Dale Lawrence Audrey Mosley Missy Shaughnessy Colleen Linehan Gabriela O’Neill Joy Ginanni Chandra Misra Carlette Heath Rachael McClennan Ellen MacLachlan Andrew McKelvey Steve Self Devan Mehrotra David Li Sarah Alexander Steve Wakefield Jen Sarche Paula Frew Dewayne Mullis The STEP Study Protocol Team www.stepstudies.com

49. An AIDS Vaccine Our Best Minds. Our Best Science. Our Best Hope.

50. Next session: November 6, 2008 Listserv: itechdistlearning@u.washington.edu Email: DLinfo@u.washington.edu