Many of today's drugs are derived from natural sources, an example would be the worlds best selling drug, Lipitor, which is a derivative of a chemical found in a fungi, it has made the pharmaceutical company Pfiza $81billion. This statin is used to lower cholesterol which, in turn, greatly reduces the risk of cardiovascular disease (CVD). Many people believe that the reasons organisms have these chemicals within them is to act as a toxin, to deter any potential predators. Either way, many useful chemicals are found occurring naturally and can be modified to tweak their effects.
So what does this have to do with genetic modification? Well maybe organisms can be developed so that the required modification of the active chemical is done within the organism, potentially saving time and money.
Below is a picture of Akira Endo, who's work is often forgotten. He discovered the first statin, which unfortunately caused tumours to form in animals during tests. However, other statins were developed as a result of his research, one of which just had the absence of a methyl group (shows how just tiny tweaks can change whether a drug is highly toxic or relatively safe for consumption). So despite being the "father of statins" and helping save millions of lives, he didn't make any money.