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Measles Antibody Titers in PIDD Patients

Measles Antibody Titers in PIDD Patients

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Measles Antibody Titers in PIDD Patients

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  1. Measles Antibody Titers in PIDD Patients Othmar Zenker, MD

  2. Introduction • Falling measles titers are anticipated over time in normal donors • Measles antibody titers serve as a potency test for immunoglobulin lot release with a cut-off level of 0.6 x CBER Standard Lot 176 • Reduction in plasma titers will make it difficult to achieve product specifications in the future • Increased risk of immunoglobulin shortage

  3. Protective anti measles titers • 0.12 IU/mL has been associated with protection against clinical measles disease (Chen 1990) • Measles is currently no concern for PIDD patients • Protective titer for PIDD patients is unknown • Retention samples of two clinical studies were tested in functional assay and ELISA • Obtain results on anti-measles trough levels after IGSC and IGIV treatment of PIDD patients

  4. Methods used for testing of clinical samples • ELISA • Commercial kit manufactured by Dade Behring • Calibrator: in-house plasma standard calibrated against 3rd WHO standard • Neutralization Assay • Potency testing of immunoglobulins for neutralizing antibodies against Measles virus in cell culture • The content of anti-Measles in IgG is measured in relation to the Reference Immune Globulin Lot 176 • Converted in IU/mL by using a factor of 2.54 for 1%Ig

  5. Subcutaneous study • 20 subjects with available retention sample were chosen • 20 samples were analyzed by NT • 60 samples were analyzed by ELISA • Demographic data typical for PIDD • CVID/XLA = 14 / 6 • Age: Median 26 years (9 – 62) • IgG trough level: Median 9.2 g/L (5.7 – 18.1) • Weekly IGSC dose: Median 164 mg/kg (60 - 326) • Treatment every week • Weekly dose of anti measles antibodies infused was calculated using the neutralization test results obtained at lot release

  6. All patients are well protected Mean titer is 3.17 IU/mL Good correlation between dose and titer IGSC – Dose response (NT)

  7. IGSC - anti measles and trough level (NT)

  8. Intravenous study • 53 subjects with available retention sample were chosen • 58 samples were analyzed by NT • 140 samples were analyzed by ELISA • Demographic data typical for PIDD • CVID/XLA = 42 / 11 • Age: Median 20 years (4 – 66) • IgG trough level: Median 9.7 g/L (5.5 – 17.4) • Monthly IVIG dose: Median 528 mg/kg (304 – 996) • Treatment every three or four weeks • Samples were chosen only if the same lot was given on three consecutive infusions prior to the sampling

  9. Intravenous – dose response (NT) • All patients are well protected • Mean titer is 2.98 IU/mL • Good correlation between dose titer • Higher measles titer during SC treatment

  10. Trough level simulation • Assumptions • Hypothetical lot with a potency of 0.3 x CBER Standard Lot 176 • Dose of anti measles antibodies according to this lot • Linear dose – titer correlation • No endogenous anti measles antibody titer • Methods • Calculation of the hypothetical dose of anti measles antibodies for every infusion • Calculation of the hypothetical trough anti measles titer by linear interpolation

  11. Trough level simulation

  12. Trough level simulation

  13. Summary • All samples tested are well above the protective level • IGSC results in a higher trough level than IGIV • 3 or 4 weekly IGIV treatment with product under current specification obtained trough levels far above the protective titer of 0.12 IU/mL • Even with a lot with a potency of 0.3 x CBER lot 176 patients would be protected as shown in a simulation • Based on this model even a cut off level lower than 0.48 x CBER lot 176 would be adequate

  14. Acknowledgements • Karl Fickenscher, PhD • Kathrin Minnig • Thomas Nowak, PhD • Fritz Schindel • Brigitte Siani • Roland Zehnder

  15. Back Up

  16. IGIV - Correlation ELISA and NT

  17. IGSC – Correlation ELISA and NT

  18. IGIV – Dose response (ELISA)

  19. IGSC – Dose reponse (ELISA)