For the remaining seven indications (29%), studies were progressing according to target timelines. Clinical benefit had not yet been confirmed for eight indications that had been initially approved at least five years prior. The most common surrogate measure in the preapproval studies was disease response, because many drugs were cancer agents. Other surrogate measures included time-to-event outcomes, such as progression-free survival and time-to-sputum culture conversion; and change in baseline biomarker levels, such as liver iron concentration. Most requirements were for randomized clinical trials (n=25); the rest (n=13) were single-group studies, including long-term extensions of preapproval studies.
Among the 22 drugs with 24 indications granted FDA accelerated approval in the studied timeframe, efficacy was often confirmed in post-approval trials a minimum of three years after approval in most studies. The confirmatory and preapproval trials had similar study elements, including using surrogate measures as outcomes. Although this type of evaluation has many limitations, the information can be useful in evaluating post-marketing safety and effectiveness for use in patients.
Michele B. Kaufman, PharmD, BCGP, is a freelance medical writer based in New York City and a pharmacist at New York Presbyterian Lower Manhattan Hospital.
Reference
- Naci H, Smalley K, Kesselheim A. Characteristics of preapproval and postapproval Studies for drugs granted accelerated approval by the U.S. Food and Drug Administration. JAMA. 2017 Aug 15;318(7):626–636. doi: 10.1001/jama.2017.9415.
