A specific medication that has gotten everyone excited is the drug arbaclofen.  This drug has already been tested on small clinical trials, mostly in patients with Fragile X syndrome.  Researchers have seen some improvement in the behavior of trial participants - in particular, a decrease in the anxiety that some of these patients have.

The mechanism behind these types of drugs is that they increase the production of an amino acid call GaBAb, which inhibits neurotransmitters from being released in the synapses.  The problem that I have with these drugs for the use in the autistic spectrum is that there are drugs with similar mechanisms of action - for example, activating the GaBA receptor - that are currently in use for anxiety.  One, which you may have heard of, is called Valium.