Based on the information available, it is not explicitly stated whether Apotex has already filed a generic version of Ruxolitinib in the US. However, according to DrugPatentWatch.com, the patent for Ruxolitinib (trade name Jakafi) expired on November 14, 2020 [1]. This means that Apotex or any other pharmaceutical company can now file an Abbreviated New Drug Application (ANDA) with the Food and Drug Administration (FDA) to produce a generic version of Ruxolitinib [2].

It's important to note that the filing of an ANDA does not guarantee approval from the FDA. The FDA reviews the application to ensure that the generic drug is equivalent to the already approved drug in terms of safety, effectiveness, strength, stability, and quality [3].

Therefore, while Apotex or any other company could have filed an ANDA for Ruxolitinib, it is not publicly known if they have done so.

Sources:
[1] https://www.drugpatentwatch.com/drugs/ruxolitinib
[2] https://www.fda.gov/drugs/development-approval-process-drugs/abbreviated-new-drug-application-anda
[3] https://www.fda.gov/patients/learn-about-expired-and-generic-drugs/generic-competition-and-drug-prices-questions-and-answers