Enhancing Immunogenicity of Recombinant Vaccines: Chemical Conjugation

Transcription

1 Enhancing Immunogenicity of Recombinant Vaccines: Chemical Conjugation Malaria vaccine development and a role for conjugates Ashley J Birkett, PhD Director, Research & Development New Cells, New Vaccines VII: From Protein to Product Wilmington DE / March 18, 2012

2 Session 4: Overview Chair: Ashley Birkett, PATH Malaria Vaccine Initiative (MVI) 3:50 - Ashley Birkett, PhD, PATH MVI Malaria vaccine development and a role for conjugates 4:10 - Yimin Wu, PhD, NIAID/NIH Development of Pfs25-EPA: the first protein-protein conjugate TBV tested in humans 4:30 - Craig Przysiecki, PhD, Merck Research Laboratories Chemical Conjugation of Microbial Antigens to Neisseria meningitidis Outer Membrane Protein Complex Carrier for Vaccine Target Identification and Pre-Clinical Vaccine Evaluation 4:50 - David Narum, PhD, NIAID/NIH Immunogenicity of Self-Associated Aggregates and Chemically Cross-Linked Conjugates of the 42 kda Plasmodium falciparum Merozoite Surface Protein-1 22

3 To accelerate the development of malaria vaccines and catalyze their availability and accessibility in the developing world A world free from malaria 33

4 Deaths / 100,000 at risk Malaria: The burden and unmet need Malaria epidemiology ~215 million cases/year, 86% in sub-saharan Africa ~655,000 deaths/year, mostly African children under five years Tools available today Mortality rates Worldwide Insecticide-treated bed nets Indoor residual spraying Africa SE Asia Eastern Med Improved case management Rapid diagnosis & treatment Americas Western Pacific Europe Adapted from: WHO World Malaria Report

5 US$ (millions) Deaths / 100,000 / at risk Cost and sustainability Mortality rates Worldwide Africa SE Asia? 60 Eastern Med 40 Americas 20 Western Pacific Europe Adapted from: WHO World Malaria Report 2011 Unmet need for a malaria vaccine is clear 5 5

6 A problem statement Malaria caused by a parasite with a complex life cycle involving two hosts Disease caused by replication inside red blood cells Cannot rely on how most vaccines work a good memory immune response May need to do better than naturally acquired immunity 1. Infection (pre-erythrocytic stage) 2. Clinical Symptoms (asexual blood stage) 3. Mosquito Transmission (sporgonic stages) 6 6

7 Strategic goals & outcomes Goals/Impact Control & Elimination Preventing Disease & Death Outcomes Transmission Interrupted Infections Prevented Cases Averted* *Impact on asymptomatic reservoir? 7 7

8 Parasite lifecycle and vaccine opportunities Sexual/ Sporogonic/ Mosquito Preerythrocytic Asexual Blood 8 8

9 Asexual Blood Evidence of naturally acquired immunity - I Age pattern of severe, mild, and asymptomatic malaria Age Modified from Marsh, K and Kinyanjui, S. Parasite Immunology 28:51-60,

10 Asexual Blood Evidence of naturally acquired immunity - II Parasitemia following passive IgG transfer from malaria-resilient adults Modified from Cohen, S., McGregor, I. A., and Carrington, S. Nature 192: ,

11 Asexual Blood Evidence of naturally acquired immunity - III Pregnant women have a unique susceptibility to malaria infection, which diminishes as their parity increases. Malarial parasitemia is significantly more frequent in pregnant than in non-pregnant women. Parasite prevalence are highest in first pregnancy, and then fall profoundly with each subsequent pregnancy. McGregor, I. A. Am. J. Trop. Med. Hyg. 33: ,

12 Proportion infected Evidence of Noetic immunity - I Preerythrocytic Pre-erythrocytic immunity in controlled human malaria infections (CHMI) Control Test Time from challenge, days Hoffman, S.L. et al. J. Infect. Dis. 185: ,

13 GMC anti-cs ug/ml Proportion infected Evidence of Noetic immunity - II Preerythrocytic Pre-erythrocytic immunity in controlled human malaria infections (CHMI) Control RTS,S/AS02 RTS,S/AS Time from challenge, days Protected Non-protected Months Kester et al., J. Infect. Dis. 200: ,

14 RTS,S/AS01: 28+ years of effort GSK & WRAIR initiate collaboration First clinical tests in humans begin in adults in US First trials in Africa begin in the Gambia (4) GSK-MVI partnership initiated Phase 2 results in African children (2) and infants (6,11) published in Lancet and NEJM Key Phase 2 efficacy results in African children (7,10) and infants (8) published in Lancet ID Phase 3 study end Final results over 32 months of follow-up RTS,S is first created by combining the malaria CS protein and hepatitis B surface antigen Key proof-of-concept (PoC) study shows 6 of 7 volunteers in challenge trial are 100% protected (3) Key PoC study in children in Mozambique (1,9) Phase 3 study start Phase 3 study Second set of results In 6-12 week olds 12 months follow-up Key PoC study in adults in the Gambia (5) Phase 3 study First set of results In 5-17 month olds 12 months follow-up published in NEJM (12) (1) Alonso P. et al. Lancet 2004; 364: (2) Aponte J. et al. Lancet 2007; 370: (3) Stoute J. et al. NEJM 1997; 336: (4) Doherty J. et al. AJTMH 1999; 61: (5) Bojang K. et al. Lancet 2001; 358: (6) Bejon P. et al. NEJM 2008; 359: (7) Olotu A. et al. Lancet ID 2011; 11: (8) Asante KP. et al. Lancet ID 2011; 11: (9) Sacarlal J. et al. JID 2009; 200: (10) Agnandji S. et al. JID 2010; 202: (11) Abdulla S. et al. NEJM 2008; 359: (12) The RTS,S Clinical Trials Partnership. NEJM 2011; DOI: /NEJMoa

15 Pivotal RTS,S Phase 3 Study Context Phase 3, randomized, controlled, double-blind trial conducted in 11 centers in 7 African countries Two age categories at enrollment: Children aged 5 17 months Infants aged 6 12 weeks Co-primary endpoint: Vaccine efficacy against clinical malaria during 12 months of follow-up in each age category. Range of malaria transmission intensities (0.01 to 2.0 clinical episodes per child per year) More than half of the clinical cases from two sites* Efficacy measured in presence of other malaria control measures: 85.8% Insecticide-Treated Nets overall* (*6-12 week old age category) Nanoro, Burkina Faso Kintampo, Ghana Study sites Unstable risk Pf Malaria free Country boundary Water bodies Agogo, Ghana Lambaréné, Gabon Adapted from Hay et al, PLoS Med 2009;6:e Siaya & Kombewa, Kilifi, Kenya Kenya Korogwe, Tanzania Bagamoyo, Tanzania Lilongwe, Malawi Manhiça, Mozambique 15

16 Key findings through Month 14 RTS,S/AS01 Comparator vaccine Pooled estimate of vaccine efficacy Does not include site specific efficacy or booster data 16

17 RTS,S/AS01 Phase 3 evaluation: Key efficacy results through 12 months of follow-up Endpoint (ATP, adjusted, co-primary endpoint) (ITT, unadjusted) (ATP, adjusted) (ITT, unadjusted) (ATP) (ITT) First episode clinical malaria %Vaccine Efficacy (with 95%CI) 5-17 mo 6-12 wk 55.8% (97.5%CI: 50.6; 60.4) 50.4% (45.8; 54.6) All clinical malaria episodes 55.1% (50.5; 59.2) 53.9% (49.6; 57.8) Severe malaria 47.3% (22.4; 64.2) 45.1% (23.8; 60.5) 31.3% (97.5%CI: 23.6; 38.3) 30.1% (23.6; 36.1) 33.0% (26.4; 38.9) 32.9% (26.7; 38.5) 36.6% (4.6; 57.7) 26.0% (-7.4; 48.6) ATP: According to protocol ITT: Intent to treat NEJM 2011; 365: NEJM 2012; 367:

18 RTS,S Phase 3 data availability 18

19 Evidence of Noetic immunity - III Sexual/ Sporogonic/ Mosquito Transmission-blocking activity in standard membrane feeding assays Stained oocyst Kaslow et al., Science. 252: ,

20 Strategic goals, outcomes, and targets Goals/Impact Control & Elimination Preventing Disease & Death Outcomes Transmission Interrupted Infections Prevented Cases Averted Vaccine Targets Sexual/ Sporogonic/ Mosquito Preerythrocytic Asexual Blood 20 20

21 Global malaria vaccine pipeline Phase 1a TRANSLATIONAL PROJECTS Phase 2a Phase 1b VACCINE CANDIDATES Phase 2b Phase 3 ChAd63/MVA ME-TRAP + Matrix M Ad35.CS/ RTS,S-AS01 ChAd63/MVA MSP 1 Ad35.CS ChAd63/MVA ME-TRAP RTS,S-AS01 Polyepitope DNA EP 1300 Ad35.CS/ Ad26.CS ChAd63.AMA1/ MVA.AMA1 AMA1-C1 Alhydrogel +CPG 7909 GMZ2 PfCelTOS FMP012 ChAd63/ MVA (CS; ME-TRAP) FMP2.1-AS01B (AMA1 3D7) BSAM-2 Alhydrogel + CPG 7909 MSP3 [ ] CSVAC PfSPZ NMRC.M3V.Ad.PfCA CSP, AMA1 (PEV 301, 302) ChAd63.AMA/ MVA.AMA1 +Al/CPG7909 SR11.1 PfGAP p52- / p32- NMRC.M3V.D/ Ad.PfCA EBA 175.R2 SE36 Two dozen projects All P. falciparum Four in late development Pfs25-EPA P. falciparum vaccines: Pre-erythrocytic Blood-stage Transmission-blocking P. vivax vaccines: Pre-erythrocytic Blood-stage Transmission-blocking Data source:

22 Why are conjugates attractive? Technical Antibodies are important at all stages of lifecycle Conjugates are effective for inducing antibodies Plasmodium proteins are difficult to manufacture Safety and pharmacovigilance (PV) Carrier proteins effectively used in licensed vaccines, worldwide (CRM197, OMPC, TT) Excellent safety history Established technology platforms may reduce PV requirements, compared to novel technologies 222

23 Summary Current malaria control situation unsustainable New tools required Strong evidence to support vaccines Natural and unnatural (noetic) immunity Antibodies associated with protective mechanisms for all 3 lifecycle stages in humans Effective conjugate vaccines could overcome technical challenges and accelerate development and implementation 2323

24 Session 4: Overview Chair: Ashley Birkett, PATH Malaria Vaccine Initiative (MVI) 3:50 - Ashley Birkett, PhD, PATH MVI Malaria vaccine development and a role for conjugates 4:10 - Yimin Wu, PhD, NIAID/NIH Development of Pfs25-EPA: the first protein-protein conjugate TBV tested in humans 4:30 - Craig Przysiecki, PhD, Merck Research Laboratories Chemical Conjugation of Microbial Antigens to Neisseria meningitidis Outer Membrane Protein Complex Carrier for Vaccine Target Identification and Pre-Clinical Vaccine Evaluation 4:50 - David Narum, PhD, NIAID/NIH Immunogenicity of Self-Associated Aggregates and Chemically Cross-Linked Conjugates of the 42 kda Plasmodium falciparum Merozoite Surface Protein