Based on the provided sources, the patent for trametinib, marketed under the brand name Mekinist, is set to expire in the United States on June 27, 2027 [1]. This information is also supported by the DrugPatentWatch website, which lists the expiration date of the patent as June 27, 2027 [2].

Furthermore, the Gabi Journal provides an overview of the patent expiry of non-tyrosine kinase inhibitors approved for clinical use in the EU and USA, including trametinib. According to this source, the patent for trametinib is set to expire in Europe on July 25, 2027 [3].

It is important to note that the expiration of a patent does not automatically mean that a generic version of the drug will become available. Other factors, such as market exclusivity and regulatory approval, can affect the timing of generic availability. However, according to Drugs.com, a generic version of Mekinist (trametinib) is already available in the United States [4].

In conclusion, based on the provided sources, the patent for trametinib (Mekinist) is set to expire in the United States on June 27, 2027, and in Europe on July 25, 2027. Additionally, a generic version of trametinib is already available in the United States.

Sources:
[1] DrugPatentWatch. (n.d.). Trametinib. Retrieved from https://www.drugpatentwatch.com/p/tradename/TRAMETINIB
[2] DrugPatentWatch. (n.d.). Trametinib patents. Retrieved from https://www.drugpatentwatch.com/p/tradename/TRAMETINIB
[3] Gabi Journal. (2017). Overview of the patent expiry of non-tyrosine kinase inhibitors approved for clinical use in the EU and USA. Retrieved from http://gabi-journal.net/overview-of-the-patent-expiry-of-non-tyrosine-kinase-inhibitors-approved-for-clinical-use-in-the-eu-and-usa.html
[4] Drugs.com. (n.d.). Generic Mekinist Availability. Retrieved from https://www.drugs.com/availability/generic-mekinist.html