Amgen has reported positive top-line results from a late-stage study of its investigational ovarian cancer drug trebananib.

The biotech major says the Phase III Trinova-1 trial evaluating trebananib plus paclitaxel versus placebo plus paclitaxel in recurrent ovarian cancer met its primary endpoint of progression-free survival (PFS). A statistically significant difference was observed in PFS with a 34% reduction in the risk of disease progression or death; median PFS was 7.2 months in the trebananib arm versus 5.4 months in the control.

Amgen noted that the primary analysis of overall survival (OS) is expected to mature in 2014 but added that "an early imbalance of deaths favouring the control arm was observed". Still, there was an overall favourable OS trend for trebananib in a pre-planned interim analysis.

In the trebananib arm, the most frequently reported side effects were localised oedema, nausea and alopecia. Worryingly, the company noted that the rate of discontinuation due to adverse events was 20% for the trebananib arm versus 7% in the control.

Trinova-1 study is the first of three Phase III trials designed to evaluate trebananib, an investigational peptibody designed to inhibit the angiopoietin axis. Amgen R&D chief Sean Harper said that angiopoietin inhibition "has been a focus of research at Amgen and these results suggest that the novel biology of trebananib may offer a promising approach for patients with ovarian cancer".

In a research note, Michael Yee at RBC Capital Markets said it is uncertain whether the PFS benefit alone is sufficient to gain US Food and Drug Administration approval. Roche has not managed to get approval in ovarian cancer from the agency for its blockbuster Avastin (bevacizumab) because it has failed to demonstrate an OS benefit, although it is approved for this indication in Europe.

He added that at the recent American Society of Clinical Oncology meeting, Amgen management stated OS benefit is most compelling" and the firm might wait for "OS maturity" before filing. The analyst believes that if approved, trebananib, which is licensed from Dyax Corp, could be a $300-500 million product in recurrent ovarian cancer.

Cytokinetics pact extended

Meantime, Amgen has expanded its pact with Cytokinetics on the heart failure drug omecamtiv mecarbil to include Japan.

The move to include the latter country triggers a $25 million payment to Cytokinetics which is also eligible to receive additional payments for the development of omecamtiv mecarbil in Japan (where it will conduct a Phase I study) of up to $50 million as well as royalties. The firms originally linked up in 2006 and data from a 600-patient, Phase IIb trial are expected in mid-2013.