Topic 1. Validation of Procedures to Prevent Contamination and

Cross-Contamination with TSE Agents of Human Tissue

Intended for Transplantation

TSEAC June 26, 2002

Issue

• FDA requests advice from TSEAC on– Measures for donor screening– Measures for tissue recovery and processing– Clearance of TSE agents (design of a study)

– Appropriate to prevent contamination and cross-contamination of human cells, tissues, and cellular and tissue-based products (HCT/Ps) by TSE agents

Background

• Three approaches to reduce risk of TSE transmission:– (1) careful screening of donor for TSE and

risk factors of TSE (testing if and when validated)

– (2) control of recovery and processing to prevent contamination/cross-contamination

– (3) use of steps during manufacturing to remove or inactivate (clear) TSE agents

Iatrogenic transmission through HCT/Ps

• Human dura mater transplantation– >100 cases worldwide (3 in U.S.)– Most from dura mater that had been commingled

during processing• Human corneal transplantation– 1 definite case (U.S., 1974)– 1 probable case (Japan, 1994)– 1 possible case (Germany, 1997)– Potential cases (U.K., 1999)

• Human pituitary-derived hormone administration—to be discussed

Potential Transmission of CJD/vCJD by Other HCT/Ps

• Experimental evidence in animals– Brown P et al. Annals of Neurology 1994—

300 cases of experimentally transmitted human spongiform encephalopathies

FDA’s Regulatory Approach to TSE Transmission (actual and

potential) by HCT/Ps

• Current regulations (rules)• Current recommendations (guidance)• Proposed regulations• Proposed recommendations

Current Regulations

• 21 CFR part 1270—Human Tissue Intended for Transplantation--1997– Screening and testing of potential donors for HIV,

HBV, HCV (TSE not included); written procedures; records

– Validated procedures to prevent infectious disease contamination or cross-contamination by tissue during processing-1270.31(d)

– Inspection and enforcement provisions

Current Recommendations

• (1) Guidance for Industry: Screening and Testing of Donors of Human Tissue Intended for Transplantation (’97)--defer donors with:– Diagnosis of CJD– Family history of CJD– History of receiving dura mater transplant– History of receiving human pituitary growth

hormone

Current Recommendations, cont.

• (2) Guidance for Industry: Validation of Procedures for Processing of Human Tissues Intended for Transplantation (3/’02)—clarifies 1270.31– Infectious disease contamination includes viral,

bacterial, fungal and TSE agents– Validated methods to prevent contamination by

viruses, bacteria, fungi now– Validated methods to prevent contamination by TSE

agents—if and when such methods are agreed upon by scientific experts; become available

Current Recommendations, cont.

• (3) Guidance for the Preparation of a Premarket Notification Application for Processed Human Dura Mater (10/’99)– All of above donor suitability recommendations; any

degenerative or demyelinating disease of CNS; death in a neurological/psychiatric hospital

– Gross and histological exam of full brain– Disinfection by a method validated to reduce CJD

infectivity– Prohibition of batch processing

Proposed Regulations

• (1) Suitability Determination for Donors of Human Cellular and Tissue-Based Products; Proposed Rule (9/30/99)– Screening (including medical history

interview) for risk factors and clinical evidence of HIV, HBV, HCV, TSEs; additional screening for particular HCT/Ps

– Testing for HIV, HBV, HCV, syphilis; additional testing for particular HCT/Ps

Proposed Regulations, cont.

• (2) Current Good Tissue Practice for Manufacturers of HCT/Ps; Inspection and Enforcement; Proposed Rule (1/8/01)– Controls over facilities, personnel, equipment,

environment, incoming materials, labeling, storage, process controls, process validation, record keeping, adverse reaction and product deviation reporting, tracking

– Inspection and enforcement

Proposed Regulations, cont.

• (2) GTP – Prohibition of pooling (placing in physical contact

or mixed in a single receptacle)– Exemption or alternative from any GTP

requirement—submit request with valid data• Ex.-request for an exemption from pooling prohibition:

FDA would weigh potential increased risk of contamination and cross-contamination with emerging infectious disease agents (e.g., TSE agents) against potential benefit of improved elimination of conventional infectious disease agents (virus, bacteria, fungi)

Proposed Recommendations

• Draft guidance for comment about donor screening and deferral to reduce possible risk of CJD/vCJD transmission by HCT/Ps—risk factors for CJD and vCJD--deferrals for travel/residence in BSE-affected countries—similar to guidance for blood donors (1/’02)

Additional Donor Screening Measures

• (1) Upper age limit for donors– Median age at death from CJD is 68 years – ?incubation period--?infectious during incubation

period– Proposed for blood donors, but not implemented– May seriously reduce tissue supply (e.g., 50% of U.S.

donors of ocular tissue are age 61 or older)– Not recommended by tissue bank or eye bank

standards, except semen donors <40; oocyte donors <35; donors of cardiovascular tissue <61; at the discretion of individual medical director

Additional Donor Screening Measures, cont.

• (2) Exclusion for head trauma– To avoid possible CNS contamination– Not addressed in industry standards– May reduce tissue supply (e.g., 13% of eye

donors’ cause of death is trauma)

Additional Donor Screening Measures, cont.

• (3) Negative brain autopsy– Delay in distributing time-sensitive HCT/Ps

(e.g., cornea)• (4) Negative brain biopsy– Would need to be validated to show that is it

predictive of autopsy diagnosis of TSE

Charge

• Evaluate appropriateness of the measures and controls discussed (or other) to prevent TSE transmission to recipients of HCT/Ps– Additional donor screening criteria– Specified methods of recovery and processing

specific methods of decontaminationremoval and/or inactivation of TSE agents

Charge, cont.

• Should pooling (commingling) of HCT/Ps from different donors during manufacturing ever be permitted? If so, what controls should FDA require in assessing whether a request for an exemption from the proposed pooling prohibition should be granted?

Questions for the Committee

• 1. Which of the following measures and controls is (are) appropriate to prevent TSE agent transmission to recipients of human cells and tissues?

Questions, cont.

– 1. A. Recommend additional donor eligibility/exclusion criteria• Upper age limit• Head trauma exclusion• Negative brain autopsy or biopsy

Questions, cont.– 1. B. Recommend specified methods of

HCT/P recovery and/or processing to prevent contamination and cross-contamination by TSE agents• Decontamination of instruments and surfaces• Methods for removal and/or inactivation of TSE

agents during manufacturing• Single donor aseptic processing or permit pooled

processing under certain circumstances (which ones?) with adequate controls (which ones?)

Questions, cont.

• 1. C. Other appropriate measures and controls

Questions, cont.

• 2. Please comment on the design of a satisfactory TSE agent clearance study for HCT/Ps, in terms of the following criteria:– A. Suitable TSE agent strain and animal

model– B. Accept measurement of abnormal forms

of prion protein alone, or require infectivity assays

Questions, cont.

• 2. Design of a clearance study, cont.– C. Accept substantial reduction (how

much?) or require complete elimination of detectable prion protein and/or infectivity

– D. Accept a single validated method or require that more than one validated method for eliminating TSE agents be included in the study

– E. Other