The US Food and Drug Administration (FDA) has released a new draft guidance document intended to bridge the gap between the status quo and the issuance of a more comprehensive guidance document on non-clinical testing on coronary and peripheral stents.
FDA explains in a Federal Register posting on 29 August 2013 that "While FDA is considering more substantial updates to the Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems guidance, we are issuing this update on select sections in order to notify the industry in a timely manner of our revise recommendations."
FDA's previous guidance was issued in 2010, but a meeting convened by FDA in March 2012 expressed a need for less burdensome and more informative corrosion testing methods.
The interim draft guidance, Select Updates for Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems, focuses on four topics:
- pitting corrosion potential
- galvanic corrosion
- surface characterization
- nickel ion release
FDA explains that with respect to corrosion testing, industry indicated that, "No single corrosion assessment can be used to assess in vivo corrosion susceptibility."
"However, nearly all respondents indicated that they performed pitting corrosion testing, and more than half of the respondents indicated that they performed galvanic corrosion testing," FDA continued. "Therefore, in the current guidance, we have updated a key aspect of sample conditioning for pitting corrosion testing that is less burdensome, and included additional information on when galvanic corrosion testing may be omitted with justification, based on information gained from the workshop."
According to regulators, their primary concern is the release of metal ions-in most cases, nickel-from the stents, which can have toxicological effects. Similar concerns have been raised in recent years about chromium ions released from deficient metal-on-metal hip implants, though their toxicological effects have not been confirmed. The guidance notes that the agency's previous recommendations on surface characterization has been modified to reflect these concerns, and may prove useful in assessing the root cause of poor device performance characteristics.
The ultimate effect of the guidance, FDA said, should be that non-clinical testing on coronary and peripheral stents should be more efficient, with fewer tests required when such tests would provide little valid scientific evidence about the safety of a device. Additional testing has been added to assess pitting and galvanic corrosion, which FDA said it believed would "aid in test protocol development."
"Taken together, the results of these tests are interrelated and provide a global perspective on the corrosion and ion leach potential of the stent," FDA concluded.
The guidance will be available for comment until 30 September 2013.
Select Updates for Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems