Phase II/III Sativex US cancer pain trials begin

UK-based GW Pharmaceuticals and its Japanese partner Otsuka Pharmaceutical have begun the first US phase II/III dose-ranging trials of Sativex in patients with advanced cancer who experience break-through pain.

Sativex is composed of CBD (cannabidiol) and THC (delta 9 tetrahydrocannabinol). The product will be administered as a metered dose buccal spray containing 2.7 mg of THC and 2.5 mg of CBD.

Otsuka is paying for the US trials, which involve 40 centres and contain a total of 336 patients experiencing breakthrough pain as a result of advanced, incurable cancer. The primary objective of the study is to evaluate the potential role and dose range of Sativex in these patients as an adjunct to pre-existing pain medications.

The primary endpoint of the study will be the response rate for patients at the end of five weeks of therapy, as defined by a 30 per cent or greater reduction in the 11-point, Numeric Rating Scale (NRS) for pain.

The present dose ranging study will attempt to replicate and extend data from a previous, two-week clinical trial in 177 patients conducted in Europe, where Sativex was administered to similar patients.

Regional activity
GW is already selling Sativex on the Canadian market as a treatment for MS-related pain under certain conditions. The biotech has licensing deals for the product with German drugs giant Bayer and mid-sized Spanish drugs company Almirall Prodesfarma for the EU.

There is no certainty that GW will win any regulatory approvals in the UK, and the current conditional approval in Canada might not lead to a permanent presence in that market.

For the US market, however, GW says it will receive milestone payments of up to USD 273m from Otsuka, including a signature fee of USD 18m and royalties of up to 20 per cent, according to a Reuters report.

GW hopes to file the drug with the FDA in 2010 and launch it in 2011.

Investec Securities analysts say that Sativex could achieve peak annual US sales of USD 390m.