You should try reading the FDA approval for the drug; it was already approved before these publications (which aren't so much clinical trials as just medical research). The FDA approval has a whole paragraph about how the effect size was too small to demonstrate statistical significance, and the trials had n=300.
It's also indicated for use in a disease we don't understand, for people who didn't respond to all the previously approved drugs. Not a good example at all.
I'm not comparing these to the FDA approvals process, but to your claim that trials use thousands of patients. These three studies are ascertaining the pregnancy safety of a drug, irrespective of whether we understand the disease or what the response rate is.
Cimzia has been well-studied, and we understand why it works on autoimmune diseases like inflammatory arthritis. It has 6 FDA approvals for different indications, so your description of the drug itself is incorrect.