The French pharma heavyweight will scrap the immunostimulant Uvidem from its pipeline, which is made by loading mature dendritic cells with lysates from melanoma tumour cell lines.
The decision to end the partnership comes as part of a pipeline re-evaluation programme, initiated by IDM midway through December.
That, in turn, was sparked by expensive delays to a different cancer drug, L-MTP-PE, which is IDM's most advanced drug candidate.
IDM filed a marketing authorization application (MAA) for L-MTP-PE to European regulators but has had to ask for a one month's extension following questions raised by the Committee for Medicinal Products for Human Use (CHMP).
A decision on the approvability of the drug is now expected at the end of this month.
The firm is also suffering setbacks in its US application to the Food and Drug Administration (FDA).
It has got a 'not approvable letter' from the regulators and is now trying to collect follow up data from a Phase III trial conducted by the Children's Oncology Group (COG).
However, the firm is struggling to get hold of these data and now thinks it will be the second half of 2008 before it can prepare the amendment to the New Drug Application (NDA) for L-MTP-PE.
So with its lead candidate delayed, and Uvidem left unpartnered, IDM will now restructure its business, a move it admits will involve staff reductions as well as a review "of the assets and costs associated with products under development" .
Exactly how many jobs will be cut and what the outcome of the other reviews will be, will become clear once the plans are finalised during this first quarter of 2008, but IDM claims it will retain "a core team in key functional areas" .
"These decisions provide the company with increased flexibility in our assessment of strategic options," said Timothy P. Walbert, chief executive of IDM Pharma.
Having already been administered to 143 patients in clinical trials, IDM has already completed enrolment in three other Phase II clinical trials.
The two firms now have three months to conclude the partnership, as is prescribed in their agreement.
As of September 30, 2007, Sanofi also owned approximately 7.9 per cent of IDM's outstanding common stock.