Bayer is to end its collaboration with Titan Pharmaceuticals after it was revealed that spheramine, the US firm’s investigational compound for Parkinson's disease, failed to meet primary or secondary endpoints in a Phase IIb study.

The STEPS trial, conducted by Bayer, involved 71 patients with advanced Parkinson’s disease who were randomised to receive either spheramine, a novel cell therapy consisting of retinal pigment epithelial cells that are injected into the central nervous system to produce dopamine, into both hemispheres or a sham surgical procedure which involves the drilling of a burr hole into the skull at the site of injection. No significant differences were detected between the injected spheramine and sham surgery arms of the study after 12 months of follow-up.

Titan chief executive Marc Rubin, formerly the head of global R&D for Bayer Schering Pharma, said “we are disappointed by these data as we have been diligently working to address the critical unmet medical need facing Parkinson's patients”. He added that “although we do not expect our partner…to continue development of this product, we will continue to analyse and assess these data to better understand the study findings and determine our next steps”.

Whatever that analysis comes up with, the German firm seems certain not to be participating in any future development and Bayer spokesman Jost Reinhard was quoted by Thomson Financial as saying that “we will not develop (this drug) further and we will not invest into it further”.

Dr Rubin went on to say that Titan remains “highly committed” to its two later-stage programmes, the schizophrenia drug iloperidone (partnered with Vanda Pharmaceuticals) which has a Prescription Drug User Fee Act date set for late July, and probuphine for the treatment of opioid dependence. Phase III from trials of the latter are expected in the third quarter.

However such a positive stance failed to impress investors and Titan shares collapsed 44.3% on the news to end the day at $0.73.