Accelerated approval regulations apply to drugs developed with the potential to treat life-threatening and/or and severely debilitating diseases that provide meaningful benefit to patients over existing therapies (e.g., cancer) (Fig. 7.13). The FDA can approve the product based on adequate and well-controlled studies in which a surrogate for clinical benefit is the primary end point. The surrogate must be reasonably likely to predict a clinical benefit, such as survival or reversal of morbidity. For example, the FDA may allow the use of objective response rate as a surrogate for survival for a product used to treat solid tumors. If the surrogate relationship to the clinical benefit has not already been demonstrated in other studies, after approval, the sponsor may be required to conduct additional studies to demonstrate clinical benefit. If subsequent studies fail to show clinical benefit or the sponsor does not complete the studies in a timely fashion, FDA may withdraw approval of the product.
In the cancer example, the company must continue to perform the phase 3 type study with the definitive measure of efficacy, that is, to demonstrate improved survival. If the work is not done (or the follow-up study fails to document the full clinical benefit), the FDA can withdraw the product from the market more easily than usual. In 2004, Iressa®, gefitinab, was approved as a tyrosine kinase inhibitor of tumor cell growth for non-small cell lung carcinoma (NSCLC) based on the surrogate end point of significant reduction in tumor size and progression. At the end of 2004, one of three phase 3b/4 studies was reported to show no advantage over placebo for r Accelerated approval: c For new drugs that provide meaningful therapeutic benefit over existing treatment for serious or life-threatening illnesses, using surrogate endpoint or restricted use provisions; designated by FDA
r Orphan drugs: o promoting the development of products that demonstrate promise for the diagnosis and/or treatment of rare diseases defined as prevalence in US <200,000; designated by FDA
r Rx-to-OTC switch: c OTC marketing of a product that was once available only by prescription; approved by FDA
Fig. 7.13. Regulatory "Opportunities"
the definitive survival end point in a randomized double-blind parallel design. The company, AstraZeneca, informed the FDA within 48 hours of this result, sent out a dear doctor letter, disseminated results to the health care community, and stopped promotion of the drug. Withdrawal of Iressa® from the market awaited full analyses of all study results by the company and the FDA.
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