If you’ve ever wondered why the symbol of health is a snake spiraling a staff (the Greek god Asclepius’s staff to be specific), it’s because in Ancient Greece they used small amounts of snake venom to treat serious illnesses
"Researchers have developed", yeah. When I read such things, I always recall https://en.wikipedia.org/wiki/Epimerox - this thing promised wonders - very broad spectrum, very low toxicity - and, most importantly, it was targeting a conservative essential protein - so nearly zero resistance. And there were no updates for more than a decade.
Something developed in a lab is something we, most likely, will never see - and will never know why the thing didn't reach the 2nd stage (or the 1st).
This is because a broad spectrum antibiotic with low resistance is an essential public good that will likely rapidly be made generic by either legal action or international disregard for copyright law. So no major pharma companies will want to invest resources into the development of something like this, and governments are not under the gun enough to produce new abx to invest the billions needed to get it through the approval process. The compromise is to leave it sitting at this phase until some disaster creates enough public incentive to socialize the completion of its development.
We’ve come full circle
Something developed in a lab is something we, most likely, will never see - and will never know why the thing didn't reach the 2nd stage (or the 1st).