This series is like a trainwreck you just can't look away from - am I entertained? Yes, thoroughly. Do I enjoy it? Not really xD Just shouting and laughing at my phone at how absurd this is. None of it makes semse, the characters don't really speak properly with each other, most of them suck... Wow.
The only thing im not content with is that we know who sold the drug but we don’t know who made it.
You're probably not expecting an answer to this after a month, but I just have to add - it doesn't matter who made the drug. It was supposed to be medicine for the covid symptoms, but it had too many side effects so it got pulled from the market. In a way, this actually answers your question, it was made by a pharmaceutical company (it was also clearly explained in the series by Yi Hyuns friend)