See the DrugPatentWatch profile for nivolumab

Based on the information provided, I found one source that directly addresses the question of whether weight is a factor in Nivolumab's fixed dosing.

Nivolumab is a type of immunotherapy, which is a treatment that helps your immune system fight cancer. It is used to treat several types of cancer, including melanoma, lung cancer, and kidney cancer, among others. Nivolumab is administered intravenously and has a fixed dosing regimen, regardless of the patient's weight.

According to DrugPatentWatch.com, "Nivolumab is administered at a fixed dose of 240 mg every two weeks or 480 mg every four weeks, without regard to body weight" [1]. This suggests that weight is not a factor in Nivolumab's fixed dosing.

In summary, based on the information from DrugPatentWatch.com, weight is not a factor in Nivolumab's fixed dosing.

Sources:
[1] DrugPatentWatch.com. (n.d.). Nivolumab (Opdivo) - DrugPatentWatch. Retrieved from <https://www.drugpatentwatch.com/drugs/nivolumab.html>.