Update on status of West Nile virus test, lot release and validation panel development

1
Update on status of West Nile virus test, lot
release and validation panel development

• Indira Hewlett, Ph.D
• CBER/FDA
• Blood Products Advisory Committee Meeting
• June 19, 2003

2
Previous FDA Actions

• March BPAC discussion of FDA proposal for
• - clinical study design
• - unit and donor management
• - FDA efforts in panel development

3
FDA Actions cont

• Study design for test sensitivity
• Repository specimens, including transfusion and
  community acquired WNV illness
• Positive cases from prospective studies
• Seroconversion panels

4
Clinical sensitivity

• Testing a common set of pedigreed specimens by
  all candidate investigational tests to determine
  whether assays have equivalent sensitivity
• Testing all reactive specimens identified during
  IND studies by all manufacturers assays

5
Analytical sensitivity

• FDAs current standard for WNV NAT assays is 100
  copies/ml for the individual donation
• Standard may be revised as assay sensitivity
  improves and additional data on viremia and
  infectivity become available in future studies

6
Unit and donor management

• FDA proposed foll scheme for donor and unit
  management
• - Reactive invest. NAT results on the
  individual donation could be confirmed by F/U
  testing with invest. NAT, alternate NAT and IgM
  
• - If F/U sample is positive by invest. NAT or
  alt. NAT, donor remains deferred for an
  additional 28 days
• - Donor may be eligible for reinstatement if
  F/U sample prior to 28 days is NAT-ve, and IgM
  ve

7
Progress on test development

• Multiple IND studies are in progress
• Two manufacturers have publicly acknowledged
  existing INDs Gen-Probe Inc. and Roche Molecular
  Systems Inc.
• IND tests are based on NAT using pooled or
  individual samples
• Intended use for whole blood, blood components,
  source plasma, bone marrow, cord blood,
  hematopoietic progenitor cells, tissue and organ
  donors

8
Progress on test development

• Expected start date for testing is early July,
  2003
• All samples will be collected under approved IRBs
  with necessary informed consent
• Analytical sensitivity of IND tests is comparable
  and between 5-15 copies/ml

9
Procleix WNV Assay

• TMA-based assay for screening blood donations for
  West Nile virus RNA
• Uses existing instrument platform as Gen-Probes
  licensed NAT blood screening assay
• Procleix Semi-automated System (eSAS) currently
  used with Procleix HIV-1/HCV Assay
• Uses existing formulations as much as possible

10
Procleix WNV Assay

• Analytical sensitivity 95 detection rate
  between 7-15 copies/ml
• Specificity in pre-clinical studies evaluated by
  testing 1180 blood donations
• No cross reactivity to other blood borne viruses
• HTLV, HIV-1/-2, HCV, HBV, HGV, Rubella, HAV, CMV,
  EBV, HCV, Parvo B19
• No cross reactivity to other flaviviruses
  Dengue (1-4), Yellow Fever Virus, and St. Louis
  Encephalitis virus

11
WNV IND

• Two Phased Clinical Protocols
• Phase I Retrospective prevalence study
• 89,000 archived American Red Cross samples from 6
  high incidence areas during the 2002 season
• Phase II Prospective donor screening
• Voluntary donations of whole blood and source
  plasma at 25 testing sites IDT or pools (site
  dependent)
• Nation-wide testing expected to begin by July 1,
  2003

12
Procleix WNV Assay Early Testing Contingency
Plan

• Upon WNV regional outbreak, samples will be
  shipped and prospective testing initiated at
  Phase I ARC site(s)
• Current testing capability limited
• Archiving samples from June 1st onward
• Testing of samples based on regional prevalence
• Contingent on IRB-approval, WNV informed consent
  in place

13
Roche WNV NAT Pre-clinical Performance Studies

• PCR-based screening assay for use with pooled
  samples
• Analytical sensitivity between 5-7 copies/ml
• No cross-reactivity seen with non-WNV
  microorganisms HTLV-I/II, HIV, HCV, HBV, CMV,
  HSV, HAV, HPV, Varicella, Adenovirus
• Clinical specificity - 400 random volunteer
  samples from WNV low- and high- prevalence areas

14
FDA Panel Development Efforts

• Lot release panel for licensure and post-market
  surveillance of NAT and IgM tests
• Qualification panel for evaluation of relative
  sensitivities of investigational NAT and IgM
  assays

15
FDA NAT Panels

• FDA NY99 and FDA-Hu2002 isolates characterized by
  genetic sequencing
• Viral infectivity determination
• PFUdetermined at both FDA and NY Dept. of Health
  Laboratories, and by cytopathic assays at FDA
• RNA concentration measurements
• Fluorescence and Optical density determination
• TaqMan
• Final panel specifications are being established
  through collaborative studies

16
PFU Results on FDA Isolates

• At FDA
• NY99 (CDC Flamingo Isolate) 108/mL
• HuWNV2002 108/mL
• At NY State Dept. of Health
• NY99 (CDC Flamingo Isolate) 5.5 x107/mL
• HuWNV2002 9.5 x106/mL

17
Viral Titer Determination Copy/mL
18
Correlation between Copy/mL and PFU/mL
19
FDA Plan for Qualification Panel

• At least 100 pedigreed clinical specimens
• RNA positive only
• IgM positive only
• Dual RNA and IgM positive
• FDA also recommends that all reactive specimens
  identified in IND clinical trials be made
  available to all manufacturers through sharing of
  samples

20
FDA IgM panel

• Panel will consist of clinical specimens
  containing varying titers of antibodies to WNV
  and some members that are also NAT positive
• Panel will be evaluated in collaborative studies
  using various candidate IgM assays
• Specifications for NAT and IgM panels will be
  established based on results of collaborative
  studies

21
Summary

• Both NY99 and FDA-Hu2002 stocks have a viral
  titer of 1010 copies/mL
• PFU titers at both NY State Dept of Health
  Laboratory and at FDA were three logs lower than
  copy numbers
• Heat treatment virus results in loss of
  infectivity and 2 to 3 log reduction in copy
  number determined by TaqMan

22
Acknowledgements

• Gen-Probe, Inc
• Roche Molecular Systems, Inc.
• Maria Rios, CBER, FDA
• Robert Lanciotti, CDC
• Laura Kramer, New York Department of Health