Antaak was a Klingon doctor in the Klingon Imperial Fleet who specialized in metagenic research in the 22nd century. Born into the warrior caste, his father disowned him from the House of Antaak when he became a healer.
In 2149, he disguised himself as a Mazarite and attended an Interspecies Medical Exchange conference on Tiburon. At the conference, Doctor Phlox presented a document on the subject of viral propagation.
In 2154, Antaak met Phlox when the Denobulan doctor was captured and forced to assist in finding a cure for a mutagenic virus that was spreading through the Klingon Empire. This was caused by the Klingons attempting to create Klingon Augments. The problem was that General K'Vagh also wanted an Augment developed. K'Vagh gave Antaak and Phlox five days to find a cure. Antaak tried to convince Phlox to help him create an Augment to appease the General and Klingon High Council, so that they could give them more time to find a cure. Phlox refused. Later after K'Vagh had Phlox beaten, Antaak nursed his injuries. He also discovered that Phlox might have found a cure for the Klingon augment virus. They could stop the genetic effects of the virus in the early stages, removing the deadly effects of the virus. There would be changes in the affected Klingons' appearances, but there would be no special power developments, such as enhanced strength and speed. Antaak would assist Phlox in curing the virus, but let K'Vagh believe that they were also developing an augment. Antaak allowed himself to be infected with the virus in order to discover which strain of the virus held the cure. An anti-virus was developed and the plague was stopped. However, the Empire - including Antaak – was forever changed when he and Phlox were unable to stop the virus' removal of Klingon cranial ridges.