I read some speculation that it is the tomb of, Olympias, the mother of Alexander. The dates - as cited here - would make sense. Although she was executed - stoned to death - by political rivals, she may have been given a royal tomb. She would have been a royal and prestigious figure, simply because of being the mother of Alexander.
It was probably some mover-and-shaker of the time, who died at the top of his or her fame, and fell into obscurity almost immediately. That’s the case with most of the burials in Egypt as well. Alexander the Great’s sarcophagus is described in at least one surviving ancient source, and probably slid into the Mediterranean during that quake that also destroyed the Pharos lighthouse. But that’s the one burial everyone would just love to find on dry land. :’)
Julius Caesar’s cremation spot:
http://www.google.com/search?q=julius+caesar’s+cremation+spot&sa=X&oi=image_result_group&tbm=isch
By contrast, I’ve never heard that any of the graves of the scumbags who murdered him are known today.