Canadian drugmaker Aeterna Zentaris could only watch on in horror yesterday as its shares nosedived as much as 70% as investors shrank back on news that a late-stage trial of cetrorelix for enlarged prostate failed to hit targets.

In the 667-patient, multi-centre, double-blind, Phase III trial (Study Z-033) patients with benign prostatic hyperplasia were randomised to receive either cetrorelix, a placebo, or a mix of both, but after 52 weeks the group said there were “no clear differences in overall efficacy” within the three treatment arms.

All three groups showed about the same improvement in prostate symptom scores throughout the trial, findings which were "unexpected in light of the previous Phase II experience," commented lead investigator Herbert Lepor.

On the plus side, it seems that cetrorelix was generally well tolerated by patients, with adverse events - the most frequent being hot flushes, nasopharyngitis, injections site pain and headache - classed as “mostly mild and transient in intensity”, the company said.

Although Aeterna stressed that it remains committed to the development of cetrorelix in this indication, a programme partnered with sanofi-aventis in the US, analysts are saying the trial’s failure could delay a potential regulatory approval by up to three years, according to media reports, giving investors the jitters.