Scancell, which stopped dosing clinical trial patients last month, has said the development programme for the cancer vaccine will be held up by nine to 12 months while it arranges for a fresh batch of SCIB1 to be produced at a contract manufacturer. The suspension of dosing affects eight patients in the long term extension arm of the study.
"Ongoing quality control analysis has revealed that the stored drug product is … no longer suitable for further use," said the company in a statement, noting that its current stocks of SCIB1 are more than seven years old.
The interruption in treatment should also not have any clinical impact on the patients, as it is anticipated that the anti-tumour response induced by SCIB1 "should persist and eliminate any remaining tumour cells."
SCIB1 is the lead candidate in Scancell's portfolio of ImmunoBody vaccines, which are designed to stimulate T-cell responses to malignant cells, and is currently being tested in a Phase I/II study involving melanoma patients.
The vaccine targets the tyrosinase-related protein-2 (TRP2) antigen expressed on melanoma cells and preliminary findings from the phase I/II trial revealed encouraging patient responses, including immune destruction of tumour cells.
The trial was originally expected to last just six months, but according to Scancell encouraging results resulted in the trial protocol being amended to look at higher doses of the vaccine and a long-term dosing regimen. The extension meant that the original clinical trial material (CTM) has now passed its shelf-life.
The new CTM will support not only the current trial but also a new study of SCIB1 in combination with a checkpoint inhibitor.
This is not the first time that technical issues have held up the trial, which has been ongoing since 2010 and gradually expanded over time to include its current population of 35 patients.
The original phase of the study was due to complete before the end of 2014 but was extended after the company revealed that a patient in the highest dose (8mg) cohort of the trial was no longer eligible for evaluation because of incomplete delivery of the dose from the electroporation delivery device.
Mike Mitchell, a healthcare analyst with Panmure Gordon, said the delay was a disappointment for the company but Scancell is well resourced and its therapy platforms "hold some very interesting opportunities and potential for cancer patients in otherwise very difficult to treat indications."