Thiopurines

• You may know these drugs as: Azasan®, azathiopurine, 6-Mercaptopurine
• Why they are commonly used: These anti-inflammatory, anti-cancer drugs are commonly used to treat people with autoimmune disorders or certain cancers, as well as people who have received an organ transplant.
• Side effect: Bone marrow suppression, which can lead to fatigue, infections, and be life-threatening in some cases
• What you can do: Knowing your genetic risk of side effects allows you and your doctor to choose the right drugs for you, and opt for alternatives if needed.
• Did you know? Severe side effects occur in up to 28 percent of people taking thiopurines.

Some genetic variants can make your body less effective at breaking down thiopurine drugs such as azathioprine (AZA) and 6-mercaptopurine (6-MP), which are used to treat inflammatory conditions and some cancers. That means these variants play a big part in how likely you are to experience side effects, specifically bone marrow suppression, after AZA or 6-MP therapy.

Navigenics tests for three genetic variants that allow us to determine the four most common versions of a gene associated with reduced ability to break down AZA or 6-MP. These variants are more common among African Americans and Caucasians than Asians.

One important thing to note: Doctors also sometimes prescribe one other type of thiopurine, called thioguanine or 6-TG, which is not included in this genetic result.