The firm stopped administering the DNA cancer vaccine to the eight melanoma patients involved in the study arm last Friday.
It said: “In discussion with the MHRA Clinical Trials Unit, and with patient safety of primary importance, the Company has concluded that it is no longer suitable for further use, although no new side effects have emerged.”
The study – known as SCIB1-001 – was initiated in 2010 by Scancell's CRO PharmaNet (which was acquired by inVentiv in 2011). The programme recruited 35 skin cancer patients at sites in the UK and was originally intended to last six months.
However, it was extended several times in response to “continuing encouraging results and an excellent side effect profile” according to Scancell, which pointed out that “as a result, some of the trial materials have now been stored for over 7 years.”
Scancell said it plans to make more SCIB1 which be provided to patients in the long term study arm and predicted that production would be complete in the next nine to 12 months.
The supplies will also be used in a new study examining the vaccine in combination with a checkpoint inhibitor.
The UK biotech said it has hired a contract manufacturing organisation (CMO) to produce SCIB1 on its behalf.
SCIB1 is a plasmid DNA that encodes a human antibody that express two cytotoxic T cell epitopes derived from the melanoma antigens: Tyrosinase-Related Protein 2 (TRP2) and gp100 plus two helper T cell epitopes.
After the vaccine is administered the antibody is expressed and then taken up by dendritic cells, resulting in the development of immune responses against tumour cells expressing the TRP2 and gp100 antigens.