He developed some shares in Pfizer.
The Gates Foundation owns stock in multiple Big pharma companies,
Pfizer included. This is not new, he's been investing into pharmaceutical industry for a while, Wall St Journal reported that his foundation bought stakes in several drug makes back in early 2000, you can look it up that was just a start.
But I'm sure some will still keep defending him, that he's a philanthropist, and that because he sold most of his stocks Microsoft he's now just a harmless well meaning pensioner or something. Per example, he "donated" $35.8 billion worth of Microsoft stock to the Gates Foundation, of course, the foundation will use that money to invest. And because it's a donation, it did not get taxed like his personal income. So he still operates that same money investing it further and did not have to pay taxes. And he's totally not a eugenic even though he wants to kill human population off but somehow Christians still defend this guy