In rejecting Gilead's aztreonam lysine, the FDA requested that Gilead run another study for the compound before it would grant it marketing approval. Gilead said it would have further discussions with the FDA to see whether it could be approved without further clinical trials. That probably isn't going to happen -- no drugmaker I'm aware of has had much luck getting the FDA to change its mind about more clinical trial work. For instance, Encysive Pharmaceuticals is conducting another phase 3 trial for Thelin per the FDA's request.
Even though having to do another clinical study likely will add more than a year before aztreonam lysine can be approved, the good news is that in its press release, Gilead signaled that the FDA didn't have any problem with the drug's safety. Considering that Elan
As a consolation, Gilead still has shots with the European Union and other regulatory agencies to get aztreonam lysine approved for marketing. Encysive, for example, was able to get Thelin approved overseas while still working on approval here in the States.
It's not as if getting the drug approved would make or break Gilead. Rival compounds like Azactam and Novartis'
HIV franchise drugs and how well they compete against rival therapies from Merck