A BANNED horseracing peptide has become the focus of the anti-doping case against the Essendon Football Club.

In a development that could embroil the entire playing list, the Bombers will be formally asked to answer allegations they took the banned peptide, thymosin beta-4.

ASADA will issue show cause notices — potentially to dozens of players — asking them to explain why they should not be served with infraction notices.

Infraction notices for multiple players could trigger bans from the sport, throwing the Bombers’ 2014 season into ­disarray.

BOMBERS MAY PLAY ON EVEN IF CHARGED

The AFL is believed to be unaware of the impending action.

TB-4, which is commonly used on race horses, is banned under anti-doping rules.

ASADA has spent the past 14 months investigating whether that drug and a raft of others had been used by the club under sports scientist Stephen Dank in 2012.

A number of those drugs are not banned.

One of them, AOD9604, is now known to be banned but early confusion over its status means the case against the Bombers will not involve that drug.

Last May, the Herald Sun revealed consent forms signed by Essendon players showed recommendations for weekly injections of AOD-9604.

WATSON: PUT PLAYERS OUT OF MISERY

Injection schedules for thymosin were also documented.

Consent forms stated: “The recommendation for the following intervention for you: Thymosin injection once a week for six weeks and then 1 injection per month.”

Some types of thymosin are banned and at the time, Essendon hadn’t said which strain its players were recommended by then club sports scientist Dank.

ASADA had retired judge Garry Downes review its case before deciding to proceed against the players.

It is believed Downes’ review, which finished in April, backed the view of those in ASADA who believe the evidence warrants charges against players for allegedly using TB-4.

The original investigation, and the review, required inquiries to be made with individuals as far away as China.

There is no suggestion players knew they were receiving a banned substance and Essendon believes the type of thymosin given to its players was a permitted type.

The Herald Sun revealed the significance of TB-4 last May when anti-ageing clinician Shane Charter exposed text messages allegedly showing Dank had ordered TB-4 from him.

The AFL included a circumstantial case that Dank administered TB-4 while at Essendon in an annexure to its charges against the club over governance breaches last year.

The 34-point document refers to a series of text and email exchanged between Charter and Dank, as well as emailed instructions from Charter to Dank and Nima Alavi, a compound pharmacist who prepared substances for Dank during his time at Essendon, on how to prepare and use the peptide.

Dank, who has refused to co-operate with anti-doping investigators, this March denied receiving drugs from Charter.

The Anti Doping Rule Violation Panel is deciding whether Dank should be dealt an infraction notice.

Essendon’s list stretched to 46 players, including rookies, in 2012.