The fact that half of clinical trials are withheld from publication by their industry sponsors is a “betrayal of our trust”, the letter said.
However, the ABPI argued that clinical trial results contain “commercially confidential information” whose publication could harm investment.
The letter is part of the growing campaign for an end to industry control of medical trial data, fuelled by the ‘Tamiflugate’ scandal.
A petition with 8,000 signatories, including the Cochrane Collaboration and the Medical Research Council, calls for the inclusion of all clinical trial data in a public register to be mandatory.
According to a 2010 study by the National Institute of Health Research, half of all clinical trials are never published, and those with results supporting the use of a drug are twice as likely to be published as those with negative findings.
The Commons Health Select Committee has backed the call for a legal obligation on pharmaceutical companies to share all trial data.
The letter from 53 clinical trial participants, some of whom are seriously ill, said that the right of companies and researchers to withhold results is “dangerous and expensive” and “holds backs good medicine”.
“It is a betrayal of our trust in clinical trial regulation and the trust of the families of those patients who volunteer for trials having had a terminal diagnosis,” the letter added.
The ABPI insisted, however, that trial protocols and results are “commercially confidential information” whose publication “could undermine investment in research and development of future medicines.”