The drug has not been approved for human use anywhere and, as such, is banned by the World Anti-Doping Agency. Edited extracts from Metabolic Pharmaceuticals' patent application, December 2012. The claims in a December 2012 patent application by Melbourne company Metabolic Pharmaceuticals, made without the knowledge of the footballers, came just months after the Essendon supplements program collapsed and its instigator, Stephen Dank, was sacked by the club. The application, which was based on in-vitro research on animal cells and tests on rabbits, does not specify which club the footballers are from. But Fairfax Media has confirmed that the Australian Sports Anti-Doping Authority believes it to be Essendon. Acting Essendon chief executive Ray Gunston said on Friday night the club was ''extremely concerned about this allegation''.

''We will be sending this documentation on to both the AFL and ASADA and will be seeking their advice,'' he said. ''It would be very concerning to the club if any of our players, or information about our players, were used in this way.'' The supplements program, described by Essendon's investigator, Ziggy Switkowski, as a ''pharmacologically experimental environment'', had an unspecified number of players given AOD-9604 at a volume and frequency far exceeding that of its clinical trials. ASADA has questioned Metabolic chief executive David Kenley over the use of AOD-9604 in Essendon players and whether he had financial ties to any club officials. ASADA investigators are also believed to have examined detailed player performance records showing that some have been unable to match their 2012 training performances since the supplements program lapsed. Essendon players found to have been effectively used as virtual human guinea pigs may have the option of lodging criminal complaints of assault and be able to launch civil action over future health concerns, several well-placed sources have suggested.

Players signed forms consenting to the use of the drug but they are understood to have been unaware that its effect was being measured and allegedly passed to external parties with a financial interest. The patent application claims AOD-9604's performance-enhancing effects include ''an increase in muscle mass'' and ''to promote muscle recovery from injury or trauma or damage or overuse through training''. The Metabolic documents refer to a 24-year-old professional footballer with a calf tear, a 22-year-old professional footballer with a hamstring tear, a 23-year-old with a shoulder tendon injury and a 24-year-old with a corked quad muscle. Each study describes AOD-9604 being applied to injured tissue and concludes that footballers recovered faster than expected, with pain associated with the injury found to ''diminish quite rapidly''. In the case of the player with the calf injury, the study found: ''The athlete's injury was resolved in two weeks. This was considerably a reduction in time frame given the original nature of the injury.''

Since the drugs-in-sport scandal broke in February, Metabolic and Essendon have sought to play down the supposed performance-enhancing effects of AOD-9604. In a statement to the Australian Stock Exchange in April, Metabolic's parent company, Calzada Limited, said: ''There is no evidence that AOD-9604 dosing increases the number of muscle or cartilage cells.'' Mr Dank has repeatedly denied providing anything harmful to players and last month told Fairfax Media he was unaware of information about Essendon's supplements program being passed to external parties. Loading Mr Kenley previously has said his company provided no financial incentive to Mr Dank.

Further comment was being sought from him about his company's patent application and its reference to tests on players.