009127-PX was the serial number for cyclodexione-4, a drug synthesized and used by the UNSC. It was a a bipolar-integration drug.
It was one of three drugs injected into the Spartan-III Gamma Company illegally. Cyclodexione-4, along with miso-olanzapine, were injected to counter the effects of the mutagen drug 009762-OO. However, this drug has to be administered regularly to prevent the mutagen from permenantly affecting higher brain functions of the Spartans.