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1 Michael Zaiac New Product Development 25/11/05 Drug Development in HIV.

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Presentation on theme: "1 Michael Zaiac New Product Development 25/11/05 Drug Development in HIV."— Presentation transcript:

1 1 Michael Zaiac New Product Development 25/11/05 Drug Development in HIV

2 2 Contents  Background-Setting the scene  Co receptors and HIV Co-receptor tropism Co-receptors as targets  Philanthropy  Summary

3 3 No Sign of Pandemic Abating Issues  No vaccines on horizon  Resistance to ARV drugs increasing  Western World - re-invigorate public health campaigns - new ARV to address resistance & compliance  Developing World - ARV to break infection cycle - healthcare infrastructure & public education - economic stability - global political leadership

4 4 North Africa & Middle East 540,000 92,000 28,000 Sub-Saharan Africa 25.4 million 3.1 million 2.3 million Eastern Europe & Central Asia Central Asia 1.4 million 210,000 60,000 Oceania 35, North America and Western/Central Europe 1.6 million 64,000 23,000 Caribbean 440,000 53,000 36,000 Asia 8.2 million 1.2 million 540,000 New cases, 2004: 4.9 million AIDS Deaths, 2004: 3.1 million Total living cases: 39.4 million Latin America 1.7 million 240,000 95,000 UNAIDS/WHO, 2005 Estimated Number of People Living With HIV, by Region in 2004

5 5 1. Prevention of progressive immunodeficiency; potential maintenance or reconstruction of a normal immune system 2. Control of viral replication and mutation; reduce viral burden Goals of Antiretroviral Treatment Delayed progression to AIDS and prolongation of life Decreased risk of selection of resistant virus

6 6 Anti-Retroviral Therapy  Explosion in HIV research since 1980 & AZT in 1987  But…HIV challenging target - obligate parasite, so few viral targets - high mutation rate & genetic plasticity  > 20 approved agents but only 4 targets  Combination therapy (at least 3 agents) = HAART introduced in reduce propensity to resistance

7 7 Genetic Plasticity  10 9 new virions produced daily  One mutation during every replication cycle per cellular genome  Genetic plasticity enables HIV to: - evade immune system - develop resistance to ARV - produce mutants with different ‘fitness’  Multiple strains co-exist & are archived in patients’ immune cells

8 8 Total plasma HIV RNA Wild-type (WT) HIV RNA Mutant HIV RNA Havlir. Ann Int Med 1996:124:984. Time Receiving Treatment Plasma HIV RNA Emergence of HIV Resistance

9 9 Approved ARV Agents ClassDrug Nucleoside/tide Reverse Transcriptase Inhibitors Zidovudine, Zalcitabine, Didanosine/EC, Stavudine/XR, Combivir, Trizivir, Lamivudine, Abacavir, Tenofovir Non-Nucleoside Reverse Transcriptase Inhibitors Efavirenz, Delavirdine, Nevirapine Enfuvirtide Fusion Inhibitors Protease Inhibitors Saquinavir, Indinavir, Ritonavir, Nelfinavir, Amprenavir, Lopinavir/Ritonavir, Atazanavir

10 10 Problems with HAART  HAART = HIV chronic disease & saves lives  But… most agents designed for acute disease  HAART has considerable drawbacks: - toxicity & side effects - drug interactions - high pill burden & inconvenient dosing  Tox. & inconvenient dosing reduce compliance  Resistance emerges within 6 months to 5 years - up to 27% of newly diagnosed HIV is resistant

11 11 Requirements on HIV medicines Ideal features of an antiretroviral agent: - low dose - convenient regimen - better toleration - non cross resistant - new mechanisms & targets - low COG = compliance & durability

12 12 Attrition on the R&D Process 1 Medicine

13 13 Candidate attrition No. candidates Years Preclin. Phase I Phase II Phase III Registration animal toxicity, chemical stability, superior compound animal toxicity, chemical stability, superior compound Efficacy, safety, differentiation, Dose, c.o.g. Efficacy, safety, differentiation, Dose, c.o.g. human PK, tolerability, formulation human PK, tolerability, formulation long-term safety non-approval

14 14 New medicine development £30 million £70 million £200 million £280 million Medicine Development CostsTime/Cost of Medicine Development Phase I Phase II Phase III File Launch Years Cumulative costs £M £450 million

15 15 Co receptor Drug Development

16 16 CCR5 and CXCR4 Co-Receptors: HIV Binding and Entry CCR5 CXCR4 T-Cell Surface CD4

17 17 HIV-1 Envelope Glycoproteins CD4 CCR5 gp120 gp41 T-Cell Surface HIV-1 HIV-1EnvelopeGlycoprotein

18 18 Binding of the gp120 Subunit of the HIV-1 Envelope Glycoprotein to CD4 HIV-1 T-Cell Surface CD4 CCR5 gp120 gp41

19 19 Conformational Change Exposes the Co-Receptor Binding Site in gp120 HIV-1 T-Cell Surface CD4 CCR5 gp120 gp41

20 20 Conformational Change Allows gp120 to Bind to the Co-Receptor HIV-1 T-Cell Surface CD4 CCR5 gp120 gp41

21 21 Fusion of HIV and T-Cell Membranes HIV-1 T-Cell Surface HIV-1 Nucleocapsid HIV-1 RNA

22 22 HIV-1 Tropism Assays: MT-2 Cell Assay  Indirect measure of co-receptor use -Depends on the presence of X4 or R5/X4 isolates  Uses viral stocks from stimulated patient lymphocytes Results are reader dependent and involve the interpretation of typical cytopathic changes  Limitations HIV derived from stimulated lymphocytes may differ from that of plasma virus Qualitative nature of the assay result Detection of CXCR4 only Moore JP, et al. AIDS Res Hum Retroviruses. 2004;20: DAIDS Virology Manual for HIV Laboratories Publication NIH U.S. Department of Health and Human Services, Washington, DC.

23 23 MT2 cell assay  Prior to the discovery of the role that CCR5 and CXCR4 play in viral entry, viruses were characterized by ability to infect T-cells and cause syncytium formation MT-2 cell lines were used MT-2 cells express only CXCR4  Syncytium inducing (SI) Changed to CXCR4-using virus  Non-syncytium inducing (NSI) Changed to CCR5-using virus Schuitemaker H, et al. J Virol. 1991;65: Japour AJ. J Clin Microbiol. 1994;32: Syncytium Formation in MT-2 Cells

24 24 HIV-1 Tropism Assays: Recombinant Phenotypic Assays  Direct measure of co-receptor use Infect engineered cell lines to determine co-receptor utilization  Obtained by RT-PCR from patient plasma sample  Virus stocks pseudotyped with envelope sequences derived from patient plasma samples  Limitations >500 copies/mL May fail to detect X4 when X4 virus constitutes <10% of the viral population Sequence variation may result in assay failure Coakley E, et al. Curr Opin Infect Dis. 2005;18:9-15.

25 25 HIV entry cell assay Adapted from Petropoulos CJ et al. Antimicrob Agents Chemother 2000;44:920-8.

26 26 R5 and X4 Variants: HIV Disease Progression Kuhmann SE, et al. J Viral Entry. 2005;1:4-16. Moore JP, et al. AIDS Res Hum Retroviruses. 2004;20: Absolute Viral Load Time After HIV Transmission WeeksYears X4 Limit of Detection R5 R5 Infection

27 27 R5 and X4 Variants: HIV Disease Progression Kuhmann SE, et al. J Viral Entry. 2005;1:4-16. Moore JP, et al. AIDS Res Hum Retroviruses. 2004;20: Absolute Viral Load Time After HIV Transmission WeeksYears X4 Limit of Detection R5 R5 Infection X4 R5 Infection

28 28 R5 and X4 Variants: HIV Disease Progression Kuhmann SE, et al. J Viral Entry. 2005;1:4-16. Moore JP, et al. AIDS Res Hum Retroviruses. 2004;20: Absolute Viral Load Time After HIV Transmission WeeksYears X4 Limit of Detection R5 R5 InfectionX4 R5 + X4 Infection R5 Infection

29 29 R5 and X4 Viruses Target Different Subsets of CD4 + T-Cells Douek DC, et al. Ann Rev Immunol. 2003;21: Kuhmann SE, et al. J Viral Entry. 2005;1:4-16. R5 Infection (common, early) R5 viruses target memory T-cells (eg, GALT) Naïve T-cells become targets once activated to the memory phenotype Relative CD4 Cell Counts Time (y) Memory T-Cells Naïve T-Cells

30 30 R5 and X4 Viruses Target Different Subsets of CD4 + T-Cells Douek DC, et al. Ann Rev Immunol. 2003;21: Kuhmann SE, et al. J Viral Entry. 2005;1:4-16. R5 Infection (common, early) R5 viruses target memory T-cells (eg, GALT) Naïve T-cells become targets once activated to the memory phenotype Relative CD4 Cell Counts Time (y) Memory T-Cells Naïve T-Cells X4 Infection (very rare) X4 viruses target naive T-cells (eg, thymus) CXCR4 expression on some memory cells makes them targets Relative CD4 Cell Counts Time (y) Naïve T-Cells T-Cells Memory

31 31 Will a CCR5 Antagonist Drive the Emergence of X4 Viruses In Vivo? Scenario 1 R5 viruses remain suppressed X4 viruses do not expand Absolute Viral Load Time (days) CCR5Antagonist X4 Threshold of Detection R5 X4

32 32 Will a CCR5 Antagonist Drive the Emergence of X4 Viruses In Vivo? Scenario 1 R5 viruses remain suppressed X4 viruses do not expand Absolute Viral Load Time (days) CCR5Antagonist X4 Threshold of Detection R5 X4 Scenario 2 R5 viruses remain suppressed Sustained, possible reciprocal expansion of X4 virus pool Viral Load Time (days) CCR5Antagonist X4 Threshold of Detection R5 X4

33 33 Scenario 3: Partial Expansion of the X4 Virus Pool R5 viruses remain suppressed Sustained, partial expansion of X4 virus pool Absolute Viral Load Time (days) CCR5Antagonist X4 Threshold of Detection R5 X4 Scenario 3

34 34 Prevalence of HIV Co-Receptor Usage Prevalence of Usage (%) R5X4R5 + X4 Fätkenheuer (n=116) Brumme (n=979) 2 82<118 Moyle (n=563) 3 85<115 Demarest (n=299) Whitcomb (n=612) Fätkenheuer G, et al. Nat Med. 2005;11: Brumme ZL, et al. J Infect Dis. 2005;192: Moyle GJ, et al. J Infect Dis. 2005;191: Demarest J, et al. 44 th ICAAC. Washington, DC, Abstract H Whitcomb JM, et al. 10 th CROI. Boston, Abstract 557.

35 35 CCR5 Use by Baseline CD4 and HIV RNA to >50,000 to >100,000 50, ,000 HIV RNA (copies/mL) <100 CD4 cell count (cells/mm 3 ) >300 Moyle GJ et al. 15 th IAC Abstract WePeB5725 CCR5 use (%)

36 36 CCR5- a drugable target?

37 37 Δ32 inhibition of coreceptor-mediated entry Δ32 CCR5 WT CCR5 < 20%~ 80%< 1.5% Delayed progressionNormal progression (Essentially) no progression Huang Y, et al. Nature Med 1996; 2:1240–1243. Michael NL, et al. Nature Med 1997; 3:1160–1162. Eugen-Olsen J, et al. AIDS 1997; 11:305–310. Lui R, et al. Cell 1996; 86:367–377. Samson M, et al. Nature 1996; 382:722–725. Dean M, et al. Science 1996; 273:1856– % AIDS free Years since seroconversion n = 39 n = 110 Genotype +/+ Genotype +/∆32

38 38 Drug development crystallography SAR Designer Drugs High-throughput in vitro testing HIV inhibition Normal function CCR5CXCR4

39 39 Unknown effects of entry inhibitors Normal Function natural ligand allosteric inhibition by drug Internalisation of receptor ? Normal function ? Internalisation of receptor Viral mutations overcome

40 40 some Co-receptor antagonists have fallen by the wayside SCH-CQT AMD-3100cardiac abnormalities but stem cell mobilization ALX 404 Cno oral formulation TAK 779toxicity at injection sites Aplavirochepatic side effects

41 41 Tropism shift Using CCR 5 antagonists

42 42 Impact of Current Antiretroviral Agents on R5 and X4 Virus Dynamics  In 3 cohorts, patients on HAART who were X4 or X4/R5 tropic showed a: 1-4 Preferential suppression of X4 Shift from X4 to R5 Loss of X4 from T-cell reservoirs in some cases Treatment experience associated with greater risk of X4 in some cohorts 5  Acquisition of X4 virus in 8 persons homozygous for  32 6 Rapid initial CD4 decline Established wide variation in viral load “set point” Rapid progression not invariable Suggested behavior of X4 virus less pathogenic than in late stage Is X4 cause or effect of progression? 1 Skrabel K, et al. AIDS. 2003;107: Philpott S, et al. J Clin Invest. 2001;107: Equils O, et al. J Infect Dis. 2000;182: Van Rij RP, et al. J Virol. 2000;76: Demarest J, et al. 44 th ICAAC. Washington, DC, Abstract H Sheppard HW, et al. AIDS. 2002;29:

43 43 Data summary

44 44 CCR5 Antagonists: Potential Advantages  Inhibit entry of HIV-1 into host cells  Activity against viral strains resistant to current agents  Human protein target versus viral gene target  Extracellular mechanism of action

45 45 Challenges in CCR5 Antagonist Use  Utility may be related to disease stage, rather than treatment experience Higher prevalence of X4 virus in patients with advanced disease Trends toward later initiation of therapy may limit utility of CCR5 antagonists  Clinical trials underway to address: Long-term safety of CCR5 inhibition Frequency/risk/implications of X4 emergence/unmasking Risk/benefit in patients with mixed infection  Possible need for laboratory monitoring of viral tropism?

46 46 Possible scenarios  Noninferiority proven  New class Unknown risks  Laboratory issues  ‘Superiority’ proven  Salvage – as part of last viable regimen  NRTI sparing  Substitution studies

47 47 Pfizer philanthropy

48 48 Diflucan Partnership Program  Donation of Diflucan (fluconazole) and training of health care providers  22 countries (915+facilities) in Africa, Asia and Caribbean participating  67,000 patients treated for HIV-related fungal opportunistic infections  More than 18,000 health care professionals trained The Diflucan Partnership is “the first of, we hope, many other successful public/ private partnerships initiated by parties who have demonstrated that they care enough to act.” —Dr. Manto Tshabalala-Msimang, Minister of Health, South Africa The Diflucan Partnership is “the first of, we hope, many other successful public/ private partnerships initiated by parties who have demonstrated that they care enough to act.” —Dr. Manto Tshabalala-Msimang, Minister of Health, South Africa

49 49

50 50 International Trachoma Initiative  Public-private partnership focused on eliminating blinding trachoma The world’s leading cause of preventable blindness  ITI now in place in 9 countries in Africa and Asia 90% reduction in prevalence in Morocco 50% in Tanzania 75% in Vietnam  Donated $225 million worth of Zithromax  10 million antibiotic treatments to date

51 51 Infectious Diseases Institute  $11 million commitment to fund regional Center of Excellence for HIV/AIDS treatment and training at Makerere University in Kampala  Extensive, one-month HIV training program for 150 physicians each year in Uganda and the region  Care and treatment for more than 50,000 patients annually  Construction of facility completed March 2004

52 52 Pfizer Global Health Fellows  “Peace Corps” for Pfizer employees  Up to 6-month overseas assignments for employees to work with NGOs fighting HIV/AIDS in developing countries  Many NGO partners  18 Global Health Fellows selected to serve in 2003

53 53 A Leading Corporate Giver Source: Chronicle of Philanthropy, 7/24/2003 $0 $100 $200 $300 $400 $500 $600 $700 ($ Millions) MerckPfizerBMSJ&JMicrosoftWal- Mart IBMAltriaFord Motor Intel Product Giving Cash Giving


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