Amgen’s investigational skin cancer treatment talimogene laherparepvec has impressed in a late-stage trial, but further survival data will be needed if it wants to gain approval.

Results from the Phase III trial, which evaluated the efficacy and safety of talimogene laherparepvec for late-stage melanoma, met its primary endpoint of durable response rate (DRR). This is defined as the rate of complete or partial response lasting continuously for at least six months.

The drug was being compared to treatment with subcutaneous granulocyte-macrophage colony-stimulating factor (GM-CSF).

The US biotech firm said that a statistically significant difference was observed in DRR: 16% in the talimogene laherparepvec arm, versus just 2% in the GM-CSF arm.

The analysis of overall survival, a key secondary endpoint of the study, has not yet been published.

But an interim analysis has shown an OS trend in favour of talimogene laherparepvec as compared to GM-CSF, according to Amgen - the OS data is expected to be known in late 2013. If it can improve overall survival – the golden endpoint for all oncology trials – this may improve the drug’s chances of getting to market in the future.

“These are the first Phase III results of this novel approach to cancer therapy,” said Sean Harper, executive vice president of R&D at Amgen. “A high unmet need exists in melanoma and we believe the innovative mechanism of action of talimogene laherparepvec may offer a promising approach for these patients.”

Yervoy competition

Talimogene laherparepvec is an investigational cancer vaccine designed to work by causing the destruction of tumours, while also stimulating the patient’s immune system to attack the tumour, something it does not do naturally.

In this way in has a similar mode of action to Bristol-Myers Squibb’s Yervoy (ipilimumab), which also works as a cancer vaccine. This treatment received FDA approval in March 2011, and will be talimogene laherparepvec’s main competitor, should it receive marketing approval.

Yervoy was the first melanoma treatment to increase overall survival, and could be a major step forward in treating the disease – but it also carries a risk of very serious side-effects, and received a ‘black box’ warning from the FDA.

It is still, however, expected to be a blockbuster drug given that it meets an unmet medical need, and is priced highly, costing around $120,000 for a full course of treatment in the USA.

The melanoma market is expected to grow as rates of the disease increase year-on-year, and a number of pharma firms are now looking to fill the gap in this market.

Oncology specialist Roche brought its melanoma pill Zelboraf to the market in August 2011, and is expected to bring in peak annual sales of around $750 million. GlaxoSmithKline is currently awaiting approval for two of its melanoma pills from the FDA and EMA, which works by targeting certain mutations.