A "life-extending" skin cancer drug should not be given to patients as a first-line treatment, NHS officials have said.
In draft guidance, the National Institute for Health and Care Excellence (Nice) said that i pilimumab should only be used in newly diagnosed advanced malignant melanoma patients who are taking part in clinical trials.
The prognosis for advanced melanoma is very poor, and those who are diagnosed often have just months to live.
But manufacturer Bristol-Myers Squibb said that the therapy - which stimulates the patient's own immune system to fight cancer - has the potential to offer "long term survival" in some patients.
Guidance issued by Nice in December 2012, gave the go-ahead for use of the drug, which is also known as yervoy, on the NHS for advanced malignant melanoma patients who have already undergone chemotherapy.
At the time, Nice called the drug a " breakthrough treatment" saying that it could " potentially significantly improve the prognosis for some people with malignant melanoma".
Last year, European health officials extended the licence of the drug so it could also be used to treat previously untreated patients - not just ones who had undergone chemotherapy .
But Nice has now said that the manufacturer has not provided enough evidence to show that the drug as a first-line treatment can extend the lives of patients compared to current treatment options available.
According to the body's preliminary draft guidance, newly diagnosed NHS patients in England and Wales should only be offered the drug if they are willing to be part of a clinical trial.
"In preliminary draft guidance, Nice recommends that the drug ipilimumab is used only in the context of research as a first-line treatment for patients with advanced malignant melanoma which is either unresectable (when the full tumour cannot be removed) or metastatic (the cancer has spread to other parts of the body)," the organisation said.
Consultant oncologist Professor John Wagstaff said the news was " disappointing ".
"Clinically, there is little difference between pre-treated and untreated advanced melanoma patients and ipilimumab is licensed to treat both types," he said.
" Today's decision will be disappointing news for many patients with advanced melanoma who have not received prior treatment, leaving them without immediate access to this innovative therapy.
"Ipilimumab has demonstrated its ability to increase overall survival in this cancer, in some cases having a long-term effect on the survival of previously-treated patients. Making it available as a first treatment option should therefore be seen as an important step in helping to maximise survival in this disease."
Nice's chief executive Sir Andrew Dillon said: "There are limited first-line treatment options available for patients with this type of advanced skin cancer. Which is why it is disappointing that the evidence put forward by the company did not conclusively demonstrate the degree to which the regulator-approved dose of ipilimumab can extend life when compared with current standard care in the NHS.
"We understand that clinical trials are ongoing that could provide an answer to this important question, and are keen to see the recruitment and continued follow up of patients in these trials encouraged."