The extension will remain open while Hemispherx submits an amended NDA, the company said.
In the request for extension, the company advised the FDA of the findings of a new potential companion diagnostic test for CFS.
The proof of principle study compared sequences from massively parallel sequenced serum DNA (Deoxyribonucleic Acid) extracted from either well vetted Hemispherx CFS sera or matching controls.
Signature DNA sequences were identified that showed statistically significant separation of CFS serum from matching control serum.
Hemispherx medical director David Strayer said they are working diligently to pursue approval for Ampligen as the first treatment for Chronic Fatigue Syndrome in the US and other countries.