Title: TSE Clearance in Plasma Derivatives
1TSE Clearance in Plasma Derivatives
- TSE Advisory Committee
- February 8, 2005
- Dorothy Scott, M.D.
- DH/OBRR/CBER/FDA
2TSE Clearance Studies and Risk Assessment
- Clearance is an important factor in overall risk
estimation - Clearance by manufacturing process CAN be tested
in scaled-down studies - Viral clearance studies paradigm applied
3Paradigm Validation of Virus Removal/inactivation
Includes
- Scaling down process steps
- Spiking appropriate steps with high titer of
infectious agent (actual or model) - Determination reduction factors for each step
- Summing reduction factors from non-orthogonal
processes to give a total log10 reduction value -
4Studies of Clearance of TSE Agents
- Source of infectivity
- Brain preparations from experimentally infected
animals with human/animal TSE agents - Blood from experimentally infected animals
- Form infectious agent
- Brain homogenate
- Subcellular fractions
- Membrane-free infectious material (e.g. fibrils)
- Blood and blood fractions
- Alterations in form during manufacturing
(conditioning)
5Measures of Clearance
- Assays to measure outcomes
- In vivo infectivity laborious, expensive,
long-term experiments, but considered most
relevant and most sensitive - In vitro - measurements of PrPSc
- Bridging in vivo to in vitro results scientific
controversy exists
6TSE Clearance Evaluation Spiking Model
TSE Spike Plasma Cryoprecipitation Cryop
recipitate (FVIII) Cryopoor
Plasma Supernatant Albumin, IGIV,
A1PI, etc.
High titer caveat
7TSE Clearance Evaluation Endogenous
Infection model
Plasma from TSE-infected animal Cryoprecipitati
on Cryoprecipitate (FVIII) C
ryopoor Plasma Supernatant Albumin,
IGIV, A1PI, etc.
Low titer Relevance Limitations
8TSE Clearance Studies
- Steps studied
- EtOH precipitation
- PEG precipitation
- Salt precipitation
- Depth filtration
- Nanofiltration
- Column chromatography
- Clearance relies upon
- Partitioning (non-robust?)
- Additiveness of steps
- (demonstrated)
- Appropriate scale-down
- Relevance of model
9TSE Clearance and Individual Manufacturing
Processes
- Manufacturing processes are highly individual
- Rigorous demonstrations of TSE clearance need to
be based upon the specific manufacturing
process
10Specificity of Process Clearance PrPsc
(microsomal spike) by Depth Filtration
Influence of Starting Materials and Filter
Starting Material Depth Filter Reduction Factor
(log10) Fr V (albumin) Seitz KS80
4.9 Fr V (albumin) CUNO Delipid 1 2.3 S I
III (IGIV) Millipore AP20 (IGIV) Seitz K200 2.8 Foster et. al., Vox
Sang 78 86-95, 2000 Fr I supernatant (IGIV,
albumin) Supra P80 (albumin) Supra P80 1.1 Fr V supernatant
(albumin) Prp-sc spike Supra P80 2.4 Vey
et al, Biologicals 30187-96, 2002
11OBRR Actions to Minimize Risk of TSE Agents in
Blood Products TSE Clearance
- TSEAC (2/2003) endorsed FDA consideration of
labeling claims for TSE clearance in plasma
derivatives, based upon specific demonstration of
TSE removal during manufacturing - TSE clearance study submissions encouraged by
OBRR - Submissions received, evaluations in progress
12FDA Requests for Submission TSE Clearance Data
- Voluntary
- Best current methods
- Model selection not restricted but needs to be
justified - 3 Logs clearance for non-robust steps
considered significant - Science-in-evolution
13TSE Clearance and Risk Assessment
- TSE clearance a critical variable in risk
assessments for vCJD - Clearance can be tested on a laboratory scale,
with caveats (spike relevance, model agents,
etc.) - Data can be provided for risk assessments
specific study of product provides best
approximation of clearance - Clearance studies, and advances in these study
methods could improve precision of risk estimates
14Published TSE Clearance Studies for Plasma
Derivatives (1)
- Brown, P et al. The distribution of infectivity
in blood components and plasma derivatives in
experimental models of transmissible spongiform
encephalopathy. Transfusion 1998 38810-6 - Brown, P et al. Further studies of blood
infectivity in an experimental model of
transmissible spongiform encephalopathy, with an
explanation of why blood components do not
transmit CJD in humans. Transfusion 1999 39
1169-78 - Lee, DC et al. Monitoring plasma processing steps
with a sensitive Western blot assay for the
detection of prion protein. J. Virol. Meth. 2000
84 77-89 - Foster, PR et al. Assessment of the potential of
plasma fractionation processes to remove
causative agents of transmissible spongiform
encephalopathy. Transfusion Science 2000
2253-56 - Foster, PR et al. Assessment of the potential of
plasma fractionation processes to remove
causative agents of transmissible spongiform
encephalopathy. Vox Sanguinis 2000 7886-95 - Lee, DC et al. A direct relationship between the
partitioning of the pathogenic prion protein and
transmissible spongiform encephalopathy
infectivity during the purification of plasma
proteins. Transfusion 2001 41 449-55 -
15Published TSE Clearance Studies for Plasma
Derivatives (2)
- Cai, K et al. Solvent-dependent precipitation of
prion protein. Biochem Biophys. Acta 2002 1597
28-35 - Stenland, JS et al. Partitioning of human and
sheep forms of the pathogenic prion protein
during the purification of therapeutic proteins
from human plasma. Transfusion 2002 421497-1500 - Vey, M et al. Purity of spiking agent affects
partitioning of prions in plasma protein
purification. Biologicals 2002 30187-96 - Reichl, HE et al. Studies on the removal of a
BSE-derived agent by processes used in the
manufacture of human immunoglobulin. Vox
Sanguinis 2002 83137-45 - Van Holten, RW et al. Removal of prion challenge
from an immune globulin preparation by use of a
size-exclusion filter. Transfusion 2002
42973-4. - Van Holten RW et al. Evaluation of depth
filtration to remove prion challenge from an
immune globulin preparation. Vox Sang 2003
8520-4.
16Published TSE Clearance Studies for Plasma
Derivatives (3)
- 13. Trejo, SR, et al. Evaluation of virus and
prion reduction in a new intravenous
immunoglobulin manufacturing process. Vox Sang
2003 84176-87. - Burnouf T et al. Nanofiltration of single plasma
donations feasibility study. Vox Sang 2003
84111-119. - Gregori,et al. Partitioning of TSE infectivity
during ethanol fractionation of human plasma.
Biologicals 2004 32 1-10. - Foster, PR et al. Distribution of a bovine
spongiform encephalopathy-derived agen over
ion-exchange chromatography used in the
preparation of concentrates of fibrinogen and
factor VIII. Vox Sang 2004 8692-9.