What would happen next?
Well, I'll tell you what would happen next:
Nothing short of an astonishing, mind-blowing, paradigm-shifting exponentially surging growth in new and stunningly advanced technology in a wide range of engineering, scientific, computing, aerospace fields that have absolutely NOTHING to do with the pharmaceutical sector!
A spectacular burst of scintillating wealth generation would be going off all over the world (and possibly our entire solar system!) if the pharmaceutical companies somehow developed advances in technology that could achieve what this hypothetical question is asking.
How so?
Well... this is simply because... a so called universal cure to all/most cancers, along with the ability to seek out, target, and completely isolate and clean a patient's blood and tissues from nano-scale viruses (that are incredibly smaller than bacteria) would mean only 1 thing:
That the pharmaceutical companies have achieved astonishingly advanced nano-technology!
A singularity moment in human history would have arrived.
Think about it: I once heard a scientist describe how a virus is so much smaller than a bacteria cell, that if the Empire State Building were a single bacteria cell, then the virus would be about the size of a human walking into the front door of the building.
That is how INCREDIBLY small viruses are, in comparison to much LARGER bacteria, and that is why we have so many cures to bacterial diseases (often just a course of 2 weeks of antibiotics!) but virtually no cures for viruses.
Viruses are just simply so small... that it is becoming painfully obvious it will take a nano-technology revolution, to truly/fully CURE people of many virus related diseases.
Same with cancer... cancer has complex operations occurring at the nano-scale.
But we will get there... just not yet.
So instead of focusing on the usual "conspiracy theory" and "legal issues/retribution" responses to this type of conspiracy hypothetical question...
Far more interesting to consider are the scientific, engineering, and economic revolutionary changes that would rapidly occur, if pharmaceutical companies finally developed nano-technology to allow them to achieve this.
If the pharmaceutical companies really have achieved this, then they stand to make TRILLIONS of dollars by licensing their nano-technologies to other fields, aside from the pharmaceutical sector.
They would have NO REASON to hide this... their investors and CEO's and boards of directors would be falling all over themselves to begin licensing this out.
They'd quickly lose interest in their baseline "pharmaceutical business" and would be sipping cool-ones on the beach, checking their billion dollar account balances.
So again, there is NO REASON for them to hide such technology in a ludicrous conspiracy that would keep them from making trillions from such technology/advances.