 It is an immunomodulatory double stranded RNA drug synthesized in the 1970s and manufactured by Hemispherx Biopharma.Although Ampligen was cleared for use in Canada in 1997, and obtained orphan drug status for treatment of CFS in the European Union in 2000, it is so far without FDA approval, and therefore classed as experimental in the United States.In 2007, Hemispherx filed a New Drug Application (NDA) with the U.S. Food and Drug Administration (FDA) to market and sell rintatolimod for the treatment of CFS, but this was rejected in December 2009, because the FDA concluded that the two RCTs "did not provide credible evidence of efficacy" and "because of clinical, statistical, clinical pharmacology, nonclinical, product quality, and facilities inspection deficiencies."