ATX-101 (also known as Kybella), which is the study designation given to deoxycholic acid manufactured by Kythera Pharmaceuticals, is an injectable substance that kills fat cells and is being marketed as a potential magic bullet for double chins. The product recently got it FDA approval for use in the cosmetic industry, but only time will tell if it proves to be a miracle worker or just another fad that fades from the market as quickly as it surfaces.
The FDA approval means only that the product has not been shown to be dangerous in human subjects, but that does not mean that it will produce a great aesthetic result, or that it will replace gold standard approaches to treating double chins like liposuction, liposculpting, or platysma muscle repairs commonly performed with neck lift operations.
In fact, over dissolving the submental (under the chin) fat may lead to a hollowed central neck and an exaggerated appearance of vertical platysma muscle bands that appear with age. Losing too much fat in the neck can be a very difficult problem to correct, which is why most facial surgeons do not remove as much fat from the neck during facial surgery as they used to several decades ago.