Final answer:
Dupilumab is the most suitable immunomodulatory agent for Charlotte, who has severe AD and a history of an inadequate response to other treatments, including methotrexate.
Step-by-step explanation:
For Charlotte, a 17-year-old adolescent with severe symptoms of atopic dermatitis (AD), dupilumab would be the most appropriate choice among immunomodulatory agents. This is especially true after the optimization of topical therapy and a failed response to methotrexate.
Dupilumab is a monoclonal antibody that blocks interleukin-4 and interleukin-13, which are cytokines involved in the inflammatory responses of AD. Its efficacy in treating moderate-to-severe atopic dermatitis has been recognized, and it is well-suited for a patient like Charlotte who is experiencing sunlight-responsive AD and is allergic to most sunscreen products. Continuing phototherapy in conjunction with dupilumab could enhance the management of her symptoms.