In an update to the FDA-approved drug label for abacavir (ZIAGEN), the wording within the Boxed Warning section has changed. It now uses stronger language to support screening for HLA-B*57:01 prior to treatment with abacavir. The following is an excerpt from the boxed warning:
"All patients should be screened for the HLA-B*5701 allele prior to initiating therapy with ZIAGEN or reinitiation of therapy with ZIAGEN, unless patients have a previously documented HLA-B*5701 allele assessment"
The previous label used the following wording:
"Prior to initiating therapy with abacavir, screening for the HLA-B*5701 allele is recommended; this approach has been found to decrease the risk of hypersensitivity reaction".
The new stronger wording on the drug label has changed its PGx level ranking on PharmGKB from "Genetic testing recommended" to "Genetic testing required". The label now has the same PGx level ranking as the European Medicines Agency (EMA) label. PharmGKB blogged in 2013 about the vague language used within FDA-approved labels that often stops short of requiring action. With this recent change, the wording on this label now has firm and direct guidance regarding testing.
Patients who carry the HLA-B*57:01 allele are at a significantly increased risk of developing a hypersensitivity reaction to abacavir as compared to those without the allele, with odds ratios well into the quadruple digits in some studies. Symptoms include fever, rash, cough, gastrointestinal symptoms, dyspnea and fatigue. A 2008 study (PREDICT-1) found that screening for this allele eliminated immunologically-confirmed hypersensitivity reactions.
See the new drug label annotation on PharmGKB
Read more about drug labels on PharmGKB
Read the PREDICT-1 study:
Mallal S, Phillips E, Carosi G, Molina JM, Workman C, Tomazic J, Jagel-Guedes E, Rugina S, Kozyrev O, Cid JF, Hay P, Nolan D, Hughes S, Hughes A, Ryan S, Fitch N, Thorborn D, Benbow A; PREDICT-1 Study Team. HLA-B*5701 screening for hypersensitivity to abacavir. N Engl J Med. 2008 Feb 7;358(6):568-79. PMID 18256392.