Let's hope that they are using this method:"Monoclonal...

Let's hope that they are using this method:

"Monoclonal antibodies (mAbs) hold great promise for treating diseases ranging from cancer to infectious disease. Manufacture of mAbs is challenging, expensive, and time-consuming using mammalian systems. We describe detailed methods used by Kentucky BioProcessing (KBP), a subsidiary of British American Tobacco, for producing high quality mAbs in a Nicotiana benthamiana host. Using this process, mAbs that meet GMP standards can be produced in as little as 10 days."

https://www.sciencedirect.com/science/article/abs/pii/S0076687921001932

...but let's face it, they're probably using a time-consuming mammalian - sporadic inducing - system....