This yellow, oval pill imprinted with GX 623 is a Ziagen 300 MG Oral Tablet, per the NIH.
ZIAGEN is a human prescription drug. The active pharmaceutical ingredient is abacavir sulfate and is classified as, "Human Immunodeficiency Virus Nucleoside Analog Reverse Transcriptase Inhibitor [EPC], Nucleoside Analog [Chemical/Ingredient], Nucleoside Reverse Transcriptase Inhibitors [MoA]."
This pill is made by a total of 4 firms: (1) ViiV Healthcare Company, (2) State of Florida DOH Central Pharmacy, (3) GlaxoSmithKline LLC, and (4) REMEDYREPACK INC. .
There are 6 other yellow pills that with a similar imprint: "GX 623". They may be a different dosage of the same drug or a different drug entirely.