One anomaly to the exclusivity rules is that a combination drug product containing a new chemical entity (NCE) and one or more previously approved drugs does not receive the 5-year exclusivity that a single-component NCE drug would receive. Thus, Ferring Pharmaceuticals Prepopik (sodium picosulfate, citric acid and magnesium oxide) was approved as a 505(b)(2) in July, 2012, but was awarded three years of exclusivity, despite the NCE status of sodium picosulfate.

Ferring has filed a Citizen Petition (CP) challenging this determination. The thrust of the argument is a bit narrow, in that sodium picosulfate cannot be approved as a single agent since the FDA determined that it requires the presence of magnesium citrate (stemming from magnesium oxide and citric acid) to fully function.

Similarly, Gilead filed a Citizen Petition requesting 5-year exclusivity for its HIV treatment Stribild (elvitegravir/cobicistat/emtricitabine/tenofovir). Neither elvitegravir or cobicistat have been previously approved by FDA, whether alone or in combination. Stribild was filed first, but Gilead has also filed NDA’s for the two actives. The CP shows that based on current FDA policy, Stribild and the individual active drugs will all receive 3-year exclusivity, a result, it is argued, that Congress did not intend.

The Gilead CP documents the genesis of the exclusivity provisions in 21 USC 355(c)(3)(E)(iii) and 355(j)(5)(iii), noting that FDA has always interpreted the law to mean that if a combination product contains any previously approved active moiety, then only 3-year exclusivity can apply. Gilead then goes on to request that FDA change this longstanding interpretation.