Postmarketing safety of orphan drugs: a longitudinal analysis of the US Food and Drug Administration database between 1999 and 2018

Background

Information about the specific regulatory environment of orphan drugs is scarce and inconsistent. Uncertainties surrounding the postmarketing long-term safety of orphan drugs remain. This study aimed to evaluate the labelling changes of orphan drugs and to identify postmarketing safety-associated approval factors.

Methods

This retrospective cohort study includes all drugs with orphan drug designation approved by the Center for Drug Evaluation and Research of the US Food and Drug Administration between 1999 and 2018. Main outcomes are safety-related labelling changes up to 31 December 2019. We defined any safety-related labelling changes as postmarketing safety events (PMSE). Safety-related withdrawals, suspensions, and boxed warnings were further categorised as severe postmarketing safety events (SPSE). Outcome measurements include frequencies of PMSE, SPSE, and association between approval factors and the occurrence of safety events.

Results

Amongst the 214 drugs identified with orphan drug designation (25.7% biologics), 83.6% were approved through at least one expedited programme, and 29.4% were approved with boxed warnings. During a median follow-up of 6.74 years since approval, 69.2% and 14.5% of the analysed orphan drugs had PMSE and SPSE, respectively. Safety-related withdrawal (0%, 0/214), suspended marketing (0.46%, 1/214) and new boxed warnings are uncommon (3.7%, 8/214). The safety-related labelling changes were more frequent in the drugs approved with boxed warnings [Incidence rate ratio (IRR): 1.95 (1.02–3.73)] and approved for long-term use [IRR: 2.76 (1.52–5.00)].

Conclusions and Relevance

In this long-term postmarketing analysis, approximately 70% of FDA-approved orphan drugs had safety-related labelling changes although severe safety events were rare. While maintaining early access to orphan drugs, the drug regulatory body has taken timely regulatory action with postmarketing surveillance to ensure patient safety.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02166-9.

Characteristics on Drug Safety Measures in Japan Stratified by System Organ Classes and Therapeutic Categories in Relation to the Approval Date

Revisions of drug package inserts (PIs) may be made immediately after approval or after considerable clinical experience; however, it is unclear whether there is a relationship between the characteristics of these safety measures and the period since drug approval. Here, we analyzed 209 cases of safety measures (revisions of the PIs) taken in Japan over 5 years (FY2014 to FY2018). The median, minimum, and maximum period from approval date in Japan to PI revision date was 6.29 years (interquartile range 2.68-15.53 years), 0.16 years, and 59.69 years, respectively. The cases were classified into four groups depending on types of adverse reaction and therapeutic category in relation to the national approval date and international birth date, resulting in the grouping together of particular adverse reactions and therapeutic drugs. For example, "Hepatobiliary disorders", "Blood and lymphatic system disorders", "Respiratory, thoracic and mediastinal disorders", "Antineoplastics", "Chemotherapeutics", and "Other agents affecting metabolism" were associated with the group of safety measures taken early after approval of a drug soon after the international birth date, suggesting that careful attention at an earlier stage after approval is necessary for these adverse reactions and drugs. Understanding such features of PI revisions makes pharmacovigilance planning more appropriate, contributing to the implementation of rapid and proper safety measures after drug approval.