Approval of a tuberculosis drug based on a paradoxical surrogate measure

On December 31, 2012, the US Food and Drug Administration (FDA) announced its approval of a new drug to treat multidrug-resistant tuberculosis (MDR-TB). The agency granted bedaquiline (Sirturo) “fast-track” approval, assessing its efficacy by a surrogate measure rather than an actual clinical outcome. The criterion was the capacity of the drug, compared with placebo, to convert a patient's sputum culture from positive to negative for Mycobacterium tuberculosis when added to a standard MDR-TB regimen.