1 The Cancer Risk Associated with Ethylene Oxide in the Processing of Cord Blood Byron Butterworth, Ph.D. Butterworth Consulting John Chapman, Ph.D. ThermoGenesis Corp. March 30, 2007

2 Stem Cells in Cord Blood Are used to repopulate the bone marrow of chemotherapy patients – a process involving extensive cell division Are long lived, continuously dividing cells that create all hematopoietic progenitor cells for the lifetime of the patient Absolutely NO mutagenic changes are acceptable that could yield precancerous or cancerous cells

3 Ethylene Oxide (EtO) Proposed Sterilant for cord blood processing disposables FDA is proposing to allow 5 mg/disposable EtO is a potent direct-acting, DNA reactive mutagen and clastogen Produces lymphoma and/or leukemia in mice, rats and human beings Thus, these DNA cancer target sites are subject to mutagenic attack by EtO

4 Susceptibility Concerns Stem cells would be directly exposed to the DNA reactive mutagen EtO during processing –No anatomic barriers or detoxification mechanisms Proliferating cells are highly susceptible to mutation induction by DNA reactive agents L5178Y cells grown on plastic culture flasks sterilized with EtO result in mutation frequency increases of 6- to 14-fold

5 There is No “Safe” Dose of Ethylene Oxide Current FDA guidance would allow concentrations in the range of 30 to 100  g/ml of EtO in cord blood preparations No data are available that demonstrate the safety of these concentrations or any concentration of EtO for stem cell exposure FDA and EPA cancer risk models recognize no “safe” or “threshold” dose for direct acting mutagens

6 Only Gamma Irradiation or Steam should be allowed for Sterilization The cancer risk of ethylene oxide can be eliminated simply by the use of gamma irradiation or steam for the sterilization of all products for cord blood processing and storage Units of stored cord blood exposed to ethylene oxide should not be used without the transplant physician being made aware of the exposure New labeling for ethylene oxide exposed cord blood units should be considered