Wasn’t the whole point of the original murders to cover up the fact that the medication, which was the basis for the giant corporation, didn’t work as advertised? Wouldn’t that have become obvious after a bit of time? What am I missing?
The company would have already made a pile of money, and once a drug makes it onto the market it takes seems to require the drug cause actual harm to get it removed from the marketplace. As long as it does no harm there’s really not much blow back if it doesn’t work as well as promised.
You’re also missing that it’s spelled ‘the fugitive’ 
An arm? If so, I know a guy who’d like to talk to you.
Wasn’t the murder an accident while the one-armed man was in Kimball’s house to steal something?
Can’t recall.
Per the plot summary on Wiki (I didn’t fully remember it, either), the secret was that the drug caused significant liver damage and those cases had been concealed by the pharma company to allow them to get FDA approval. If cases popped up later they could just act surprised and insist that their drug had been fine during testing, and maybe the regular patient population was doing something different with taking the meds/abusing their livers/whatever. Meanwhile the money from sales could help them fund more research or their shareholders or whatever.
Kimball was the target for murder as he knew about the liver failure cases, and the wife just happened to be there instead.
“Ah Don’ Caare!”