Based on the information provided, it is difficult to give an exact time frame for how long Cosentyx will be effective as it can vary from person to person.

According to the Cosentyx website, it has been shown to provide relief from symptoms of psoriatic arthritis for up to 12 weeks [2]. Additionally, a study cited by Drugs.com found that Cosentyx was effective in treating psoriasis for up to 16 weeks [3].

It is also important to note that the patent for Cosentyx will expire in 2026 [1], which suggests that the drug will continue to be available and potentially effective for several more years.

In terms of long-term effectiveness, the website for Cosentyx states that it has been studied for up to 5 years and has been shown to maintain its effectiveness [2]. However, individual results may vary and it is recommended to speak with a healthcare provider for personalized information.

In summary, based on the provided information, Cosentyx has been shown to be effective for up to 12-16 weeks, and its long-term effectiveness has been studied for up to 5 years. However, individual results may vary and it is important to consult with a healthcare provider for personalized information.

Sources:
[1] <https://www.drugpatentwatch.com/p/biologics/tradename/COSENTYX>
[2] <https://www.cosentyx.com/psoriatic-arthritis/treatment-results>
[3] <https://www.drugs.com/medical-answers/long-cosentyx-work-3538718/>