After new cancer drugs receive regulatory approval, researchers often pursue trials testing the drug in indications or combinations that would extend the use of the drug beyond the indication for which it was initially approved. Sometimes, such efforts are aimed at obtaining a revision to an Food and Drug Administration (FDA) label, other times they aim at discovering an off-label use that can be recommended in clinical practice guidelines. Such ‘label-extending’ trials are facilitated by the fact that newly approved cancer drugs are less likely to elicit unexpected safety issues, regulatory approval standards are weaker for post-approval trials, and the ease of testing an already approved and manufactured drug are likely to be much less as compared with a drug that has not yet received approval.

In numerous cases, label-extending trials have uncovered new uses for approved drugs—especially in the setting of rare malignancies. For example, imatinib was approved for hyper-eosinophilic syndrome, chronic eosinophilic leukemia and dermatofibrosarcoma, indications that were not launched into clinical trials until after the initial approval of imatinib in chronic myeloid leukemia. However, where much is known about the volume and clinical impact of pre-license clinical trials in cancer, there is much less systematic evidence about label-extending research activities. A previous study suggested that label-extending t rials can sometimes be very extensive and failure-prone. A 2016 report found that 550 trials of the approved checkpoint inhibitor drugs pembrolizumab and nivolumab were open. Such label-extending clinical trial activities, if they do not lead to regulatory approvals or major advances, can deprive other potentially productive lines of cancer drug development of eligible patients and resources. It can also lead to excess patient burden.

We previously reported that combination anticancer therapy drug development efforts launched after a new drug approval are associated with high levels of patient burden but limited clinical impact. Such findings can potentially encourage more stringent review when considering proposed post approval trials for funding or ethical approval. Here we extend those findings to mono-therapy anticancer drugs. In what follows, we estimate the patient burden, magnitude of investment and success associated with label-extending mono-therapy research efforts for drugs that were newly approved in the years 2005–2007, inclusive.