The identity of the contaminant has not yet been identified, and the presence of the substance was in fact missed by earlier quality tests, and was only uncovered when magnetic resonance imaging was used as part of the investigation to get to the bottom of a health scare with the product that has been linked to as many as 800 adverse reactions and up to 19 deaths, according to the FDA.
Janet Woodcock, deputy commissioner for Scientific and Medical Programs, chief medical officer, and acting director of the FDA's Center for Drug Evaluation and Research (CEDR) revealed during a press briefing that the contaminant constituted between five per cent and 20 per cent of the API in the samples in which it was present.
"This substance . .
.
appears to act like heparin," said Woodcock, although it is unclear as yet as to whether the contaminant was added as a counterfeit API in a bid to reduce manufacturing costs, or whether there is another explanation.
"At this point, we do not know whether the introduction was accidental or whether it was deliberate," she said.
It is worth pointing out that although the FDA has identified the heparin contaminant, it is yet to prove a conclusive link between this and the events that led to the drug's recall from the market.
However, it has been confirmed that the batches of heparin that were associated with the adverse events were found to have the contaminant, while batches that did not have the contaminant were not linked to any of the cases of illness.
It has also been confirmed that although the contaminant was found in samples that were produced in both the Wisconsin plant and the China plant, all were made with APIs manufactured at the China plant.
The identity of the Chinese plant is Changzhou SPL, a factory in the city of the same name.
This facility is actually 55 per cent owned by Scientific Protein Laboratories (SPL) , the company that also supplies the heparin API from a site in Wisconsin, US.
The FDA has conducted an investigation at both of these plants, as well as a facility owned by one of Baxter's subsidiaries in New Jersey, where the finished heparin is packaged, although this facility has now all but been ruled out of the agency's investigation.
Folowing the FDA's press briefing, SPL issued a statement maintaining that "thus far, no conclusions have been reached about the root cause.
It is premature to conclude that the heparin API sourced from China and provided by SPL to Baxter is responsible for these adverse events".
"During the call with the media, FDA speculated that the source of the adverse events may be a contaminant.
It is important to note that this theory is speculation at this point, and SPL is participating actively in working with the FDA to pursue this theory as well as others so that we can understand the cause of the adverse events".
However, as a voluntary and precautionary measure, SPL said that it has agreed to voluntarily remove from the market any lots of China-sourced heparin API where tests have indicated the presence of an extra signal/peak in testing.
The firm has notified all its customers who have received certain lots of that API material.
Meanwhile, the firm said that Changzhou SPL is preparing its response to the "concerning" observations made by the FDA during the recent inspection of its facility.
"It is important to emphasise that the root cause of the heparin adverse events has not been tied to any of the agency's observations", said SPL.
Baxter was asked by Outsourcing-Pharma.com to comment but failed to do so before the time of publishing.