That's what I was thinking, Marydoll. In the early days of the pandemic we were heaing a lot about Covid-triggered cytokine storms where the body starts to attack its own cells and tissues rather than just fighting off the virus. Maybe that is why these drugs are considered effective.
Yes I remember the consultant having to obtain permission to let me have Adalimumab (Humira) as it's so expensive. Before the exclusive patent for Humira expired it was, according to NHS England, the single medicine on which hospitals spent the most, at a cost of more than £400 million a year. I was first prescribed one of the less expensive biosimilars, Imraldi, but did not respond at all well to that and no longer take Adalimumab either.