AIM-listed biotech firm EpiStem has maintained its full-year guidance for the period just gone but admitted that talks over a key supply and distribution agreement for its TB test have fallen through.The company was in discussions with medical technology company Becton Dickinson (BD) to expand the existing agreement regarding its Genedrive diagnostic device which would have led to additional revenues of £1-1.2m being for the year to June 30th. However discussions with BD "have not been successfully concluded", meaning that the original supply and distribution agreement entered into in August 2012 has been called off, EpiStem said. The company is to repay BD $1m under the terms of the original deal."Whilst this represents an initial disappointment, it will enable us to undertake the necessary work to validate our TB assay without the challenging timelines set out in the BD agreement," said Chairman David Evans."We see significant value in the TB opportunity and we will look to exploit this in different ways with other channel partners."The firm will soon complete its Indian clinical trials and hopes to launch its TB test on the market once the latest test modifications have been fully validated.EpiStem still expects revenues for the year to the end of June of £5.4m, down from £5.6m the year before, and a loss after tax widening to £1.2m, from just £0.2m previously. Results are due on October 22nd.The stock fell 5.45% to 520p in early trading on Monday.BC