A so-called miracle treatment for skin cancer has been called into question after it emerged that the NHS hospital involved with the trial conducted the study with the drug's own manufacturer.
Pembrolizumab attracted international coverage last week after a patient's tumours disappeared following treatment with the drug, which is manufactured by pharma giant Merck Sharp & Dohme (MSD).
Warwick Steele, a 64-year-old who had advanced cancer, was said to have been cured after a six-month round of treatment with the experimental drug. It was part of a wider trial on advanced melanoma.
MSD, which has its headquarters in New Jersey, is expected to apply for a European licence for the drug. If successful, applications for use in the NHS in Scotland are inevitable.
Steele's doctor, Dr David Chao, from the Royal Free London NHS Foundation Trust, said: "We cannot say for certain that he has been cured, but he is doing very well. He was aware that without an effective treatment his survival prospects were not good - maybe months.
"Pembrolizumab looks like it has potential to be a paradigm shift for cancer therapy and is firmly helping to establish immunotherapy as one of the most exciting and promising treatments in recent years.
"Some of these results are really astonishing, almost jaw-dropping. And these drugs may be applicable to many different cancer types, including ones that are hard to treat, such as lung cancer."
But the health service has been urged to closely examine the findings before making a decision.
According to a spokesman for MSD, the study came about after a "clinical trial agreement" was struck between the drugs firm and the trust, which will receive funding for the services provided.
In 2012, the trust was granted "foundation" status, meaning that it was given greater financial freedom.
Chao was not paid for his work on the clinical trial.
There is no suggestion of impropriety, but the financial ties have raised questions about the relationship between Big Pharma and the NHS. Professor David Miller, a sociology expert who campaigns for corporate transparency, said: "Headlines about so-called miracle cures are good news for pharmaceutical companies. They are rarely good science or good for the public.
"The increasingly close links between the NHS and the pharmaceutical industry raise questions about the quality of science produced. More than 20 scientific studies have shown a positive correlation between industry funding and favourable results in science."
A spokesman for MSD UK confirmed the firm would pay the trust for the trial, adding: "Collaborative working between healthcare professionals and commercial organisations has long been a positive driver for advancements in patient care and the progression of modern medicine. Healthcare professionals and commercial organisations regularly work together in a range of activities including developing innovative treatments, sharing good clinical practice and delivering patient care."
A spokesperson for the trust said: "We do not believe that funding by a trial sponsor compromises the trial findings. We believe we have a responsibility to undertake research which can potentially lead to medical advances. All clinical research studies are governed by strict clinical and ethical criteria and bound by UK and EU legislation which is all designed to ensure that internationally accepted standards are upheld."