It is not Home Office policy to release the texts of draft treaties as to do so could jeopardise international relations between the UK and the state in question and could also prejudice the effective conduct of public affairs for any future negotiation of bilateral extradition treaties.
The treaty was negotiated in the same way that all such treaties are negotiated, following procedures laid down in the Ponsonby Rule, which has been in operation since 1924.
It is not Home Office policy to comment on the negotiation of individual treaties but I can confirm that the final text of the US-UK extradition treaty was approved by the then Home Secretary on 25 March 2003.