Impact of NAT Screening of Donations on Safety Margin of Plasma Derivatives Presented By

1. Impact of NAT Screening of Donations on Safety Margin of Plasma Derivatives Presented By Albrecht Gröner, Ph.D. Aventis Behring On behalf of PPTA Pathogen Safety Steering Committee Technical meeting with FDA April 29, 2003

2. Points to Consider • Next epidemic season • Immune status of population • WNV titer in plasma of healthy (apparently healthy) individual • duration of viremic phase

3. WNV Titers • virus titer in “asymptomatic” individuals is low • 1 to 5 x 103 GE/ml or  20 pfu/ml • virus titer in symptomatic patients higher ( up to 2 x 106 GE/ml) • viremic phase lasts no longer than 2 weeks in symptomatic individuals

4. Preventive measures on donor level • Donors are • healthy • thorough questionnaire including pre-donation health status • checking vital signs including pulse/blood pressure and temperature before each donation

5. Guidance for NAT – Testing (I) • Guidance for Industry • In the Manufacture and Clinical Evaluation of In Vitro Tests to Detect Nucleic Acid Sequences of Human Immunodeficiency viruses Types 1 and 2 (December 1999) • For pool testing, minimum sensitivity level (95% detection rate) 100 copies/ml for analytical sensitivity 5,000 IU/ml in an individual donation (replacing copies to IU in March 2002) • HCV (and HIV) • transfusion relevant viruses causing chronic, life-threatening disease; public health issues due to contagion for contact persons

6. Guidance for NAT – Testing (II) • WNV- NAT Testing Proposal: 100 copies/ml in individual donation (95% detection rate) 1,000 copies/ml in individual donation (100% detection rate) Viral load in samples associated with WNV transmission from 3,000 to 5,000 copies /ml [Dr. Biswas: BPAC March 13, 2003]

7. Discrepancy in NAT Sensitivity • Healthy (apparently healthy) donors may carry high titers of HCV (and HIV) • Healthy (apparently healthy) donors may carry low titers of WNV • virtually no WNV reactive donation would be detected in standard in-process NAT testing scheme with appropriate sensitivity for plasma for fractionation (sensitivity according to HCV / HIV guideline) • testing without public health benefit even at high test sensitivity as for transfusion setting (transmission through mosquitoes)

8. Virus Inactivation is Robust • HCV load in plasma pools for fractionation • prior anti-HCV screening: 100% of pools NAT reactive • after anti-HCV screening: up to 50% of pools NAT reactive [Scheiblauer et al. 1996] • After implementation of HCV NAT testing 0.0% pools reactive • Virus load in window phase donation ~ 6 to 7 log10/ml • 1 in 10,000 to 25,000 donations window donation  plasma pool reactive for HCV RNA • NO transmission of HCV by products • with a dedicated virus inactivation step

9. Demonstrated Safety Margin for WNV • Worst case scenario: • 10,000 ml plasma used to prepare 1 therapeutic dose • 0.001 iu WNV per ml (Base Case) • 1 log10 WNV have to be inactivated • Virus inactivation of WNV ≥ 5.5 to ≥ 8.2 log10 (limit of detection) per inactivation step investigated • Robust and very effective virus inactivation by dedicated virus reduction step • Efficacy assured by batch record review of critical step results in a safe product even under worst case conditions. Further steps in the manufacturing procedure will contribute to WNV clearance

10. Conclusion • NAT testing of donations will not result in detection of WNV reactive donations (testing utilizing same approach as for chronic transfusion-transmitted virus infections in a plasma for fractionation setting) • Virus reduction capacity of manufacturing procedure for plasma derivatives has excess capacity to inactivate worst case scenario WNV load in plasma • Testing increases costs without increasing margin of safety