[mac_truck]

Why would Pfizer, Merck et al, make a new drug that works just like ivermectin when one already exist?

Because Ivermectin by itself just isn't effective, and drug makers are in business to make money.

[LilFarmer]

*****Because Ivermectin by itself just isn’t effective******

No drug is 100% effective.

Again, here are 63 studies that show it is at least 86% effective as a prophylactic and 70% effective in early treatment.
https://ivmmeta.com/

If it wasn’t effective, Pfizer and Merck wouldn’t be duplicating it in their new pill.