Regulators are to place tight restrictions on trials of the type of drug which left six men seriously ill.
Six men suffered multiple organ failure after the trial
The Medicines and Healthcare products Regulatory Agency said first-in-man trials of drugs like TGN1412 would not be authorised without expert advice.
The agency said there were no obvious errors in the trial which left six volunteers with multiple organ failure.
Its inquiry suggested the volunteers' reaction was unexpected and had not been seen in animals.
The MHRA's preliminary findings appear to back up what German manufacturers TeGenero have said.
They maintain the men's reactions were "completely unexpected" and did not reflect the results obtained from the earlier laboratory studies.
Parexel, the firm which carried out the trial at Northwick Park Hospital in London, also insists it followed all the correct procedures.
The MHRA said the drug being tested was given in correct doses and there was no sign of contamination or manufacturing errors, but added its findings were not conclusive and more tests were planned.
It added: "It would indicate that this product showed a pharmacological effect in man which was not seen in pre-clinical tests in animals at much higher doses."
As a result, the MHRA said it would now take "a precautionary approach" for all further trials involving monoclonal antibodies - the class of drug to which TGN1412 belongs.
The body makes natural antibodies in response to infection. Monoclonal antibodies are made in the lab.
Most prevent something happening in the body - they are "antagonists".
One example is Herceptin, which works by blocking the action of the Her2 protein, which can fuel the growth of breast cancers.
But TGN1412 is an "agonist" - which boosts the activity of human immune system protein called CD28 which is present on the surface of white blood cells.
First-in-man tests of these or any other novel molecules which target the immune system would not be authorised "unless additional expert opinion on whether the effects seen in the TGN1412 case may be repeated", the MHRA said.
Ministers have also agreed to set up a group of experts to learn from the Parexel clinical trials incident.
The group will look at the science surrounding monoclonal antibody treatment and how trials involving these types of drugs need to be managed in the future.
Health Minister Lord Warner said Professor Gordon Duff would chair the expert group on monoclonal antibody treatment.
"Clinical trials in general have an excellent safety record, but it is vital we learn lessons from this incident to avoid any similar situations in the future."
The group will consider what steps may be necessary before drugs tested on animals can be tested in humans for the first time.
'Committed to safety'
Martyn Day, a solicitor representing four of the men harmed in the study, said his clients would not have taken part in the trial if they had realised how revolutionary it was.
He added: "The greatest concern for my clients has been quite how cutting edge this drug was. When they were taken through the issues to do with the drug it was never spelt out to them quite how cutting edge it was."
Ann Alexander, the solicitor representing the two most seriously affected volunteers, said MHRA report was "totally inadequate".
She called for an independent Inquiry into the conduct of the trial and said that she would be making her concerns about the MHRA known to the health secretary.
Five of affected men have been released from hospital; the remaining patient is said to be making "steady progress".
The Association of the British Pharmaceutical Industry said it was vital that the appropriate lessons are drawn from the recent unprecedented events at Northwick Park hospital.
Director of the Medical Research Council's clinical sciences centre Chris Higgins said "Once in a blue moon something does not get picked up in animals which is there in man".