SPORTS scientist Stephen Dank discussed giving Essendon players a "new polymer" tested on American racehorses, text messages allegedly reveal.

And a doctor who worked with the sports scientist allegedly advised him against administering a drug the AFL believes was given to players, saying it had "more downside than upside".

The revelations come as AFL chief executive Andrew Demetriou led the football world in appealing to Mr Dank to co-operate with anti-doping investigators.

The Australian Sports Anti-Doping Authority's probe into Essendon's supplement program continues.

The Herald Sun understands there is a strong possibility doping charges could be brought against players and even officials.

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A series of text messages seen by the Herald Sun show Mr Dank allegedly asked a pharmacist for help treating players last year, and suggested testing a blended substance on "a couple of players".

The Bombers' program was described as "pharmacologically experimental" after an internal review earlier this year.

On August 5 last year, Mr Dank and the pharmacist appear to discuss mixing Thymosin, the anti-obesity drug AOD9604 and an unnamed cell-repair agent, and giving it to players.

Dank: "Have we tried it on anyone yet?"

Pharmacist: "Few dental injections for periodontal sockets but not for sporting."

Dank: "Did they go all right with efficacy?"

Pharmacist: "Yep it did the job. Amazing repair properties."

Dank: "Let us test a couple of players."

It is not clear whether the blend was ever administered to anyone at Essendon.

One of the external doctors who treated Essendon players alongside Mr Dank had urged him not to use Melanotan II, according to evidence gathered as part of the ASADA probe.

The medic allegedly told Mr Dank last April there was "more downside than upside in terms of performance".

When approached by the Herald Sun, the doctor did not deny issuing the advice to Mr Dank, but declined to comment.

The AFL had alleged Essendon players and coach James Hird had been given Melanotan II, though Hird reportedly disputes using it.

ASADA has been unable to say if Melanotan II is banned, referring the Herald Sun to the World Anti-Doping Agency, which said it was among the substances being assessed for possible prohibition under the 'S0 category'.

Mr Dank, who's denied giving anything banned or harmful to anyone at Essendon, didn't return calls.

Players signed consent forms agreeing to take AOD9604 and Thymosin, according to evidence gathered in the AFL and ASADA probe into Essendon's 2012 supplements program.

The type of Thymosin has been closely examined, over concerns it may have been a dangerous, untested type banned for athletes.

As part of its contentious plea deal with the AFL, Essendon agreed there was a risk its players had been given banned drugs but there was nothing to show the club had set out to cheat.

The AFL released a range of text messages between key figures involved in the scandal last week to publicly demonstrate its disrepute case against the club.

FULL TEXT MESSAGE EXCHANGE BETWEEN DANK AND THE PHARMACIST

August 5, 2012

Dank: I need some help with this football team.

Pharmacist: Don't worry buddy. We can start them on the cocktails next week. When is there (sic) next game?

Dank: Next Sunday against North Melbourne.

Pharmacist: How are the soft tissue injuries looking?

Dank: S--. 2 more.

Dank: I know the mechanism.

Dank: Can the AOD and the Thymosin be mixed?

Pharmacist: I can test it out. Also, is there a problem with giving them an anaesthetic in the muscle? I have discovered a new polymer which will provide a slow release system while repairing damaged cell walls. Intramuscular injection.

Dank: No problems with that all.

Dank: Is it efficacious?

Pharmacist: Very much so. It's amazing and being used in the USA for elite horse racing. I can even put the thymosin and AOD in it.

Dank: Perfect let's get going.

Dank: Have we tried it on anyone yet?

Pharmacist: Few dental injections for periodontal sockets but not for sporting.

Dank: Did they go all right with efficacy?

Pharmacist: Yep it did the job. Amazing repair properties

Dank: Let us test a couple of players.

Pharmacist: Sounds good buddy. Speak soon.