Ruxolitinib, a Janus kinase (JAK) inhibitor, is a drug developed by Incyte Corporation and marketed as Jakafi for the treatment of myelofibrosis and polycythemia vera, two rare blood disorders. Apotex, a Canadian pharmaceutical company, sought to produce a generic version of ruxolitinib. However, the Food and Drug Administration (FDA) approval for Apotex's version has been delayed.

One of the challenges delaying Apotex's ruxolitinib FDA approval is the ongoing patent litigation between Incyte Corporation and Apotex. Incyte filed a lawsuit against Apotex in 2011, alleging that Apotex's generic ruxolitinib would infringe Incyte's patents [1]. As of 2021, the lawsuit is still ongoing, which may contribute to the delay in Apotex's FDA approval.

Another challenge is the FDA's requirement for generic drug manufacturers to demonstrate bioequivalence to the brand-name drug [2]. According to DrugPatentWatch.com, Apotex's ruxolitinib must prove bioequivalence to Incyte's Jakafi to receive FDA approval [3]. This process involves conducting clinical trials to show that Apotex's version of ruxolitinib has the same therapeutic effect as Jakafi. The FDA's rigorous testing and review process can be time-consuming, adding to the delay in Apotex's approval.

Lastly, the COVID-19 pandemic has caused significant disruptions to the FDA's operations, including reviewing generic drug applications [4]. The pandemic has led to staffing shortages, backlogs, and delays in the FDA's approval process [5]. As a result, Apotex's ruxolitinib approval may have been affected by these pandemic-related challenges.

In summary, the delay in Apotex's ruxolitinib FDA approval is due to ongoing patent litigation, the requirement to demonstrate bioequivalence, and disruptions caused by the COVID-19 pandemic.

Sources:

1. Incyte Corporation v. Apotex Inc., 1:11-cv-01201 (D. Del. 2011).
2. U.S. Food and Drug Administration. "Generic Drugs: Questions and Answers." <https://www.fda.gov/drugs/generic-drugs/generic-drugs-questions-and-answers>.
3. DrugPatentWatch.com. "Ruxolitinib (INN)." <https://www.drugpatentwatch.com/Drug/Ruxolitinib>.
4. U.S. Food and Drug Administration. "COVID-19 and the FDA: Working Together." <https://www.fda.gov/coronavirus-disease-2019/covid-19-and-fda-working-together>.
5. U.S. Government Accountability Office. "FDA Generic Drug Review: Improved Data and More Transparency Needed for Users of FDA’s Generic Drug Program." GAO-21-158, Jan 2021. <https://www.gao.gov/products/gao-21-158>.