This sounds like Novartis is a biotech company that specializes in producing drugs that kill viruses and diseases. They are NOT referring to the literal meaning of "bug(insect)". The brute force method is typically referred to as trying every possible method to achieve a certain result. For example, if you are trying to use a brute force method to break a password you will do a,b,c,d,e,f,g etc until you finally get the correct password. So what are they trying to tell you? They will screen all drug candidates to kill this "bug". After they find this drug, they will run tests to make sure it is safe in humans.

chemical candidates that might be used as pesticides against a particular insect species; the substance should be a) effective in insect annihilation b) not unhealthy for the human species; This seems to be all that was there. The brute-force method is a collection of methods that are relatively easy, but very,very long as they don't have an 'inside-intelligence'; term borrowed from the algorithm science jargon.