Bayer chalked up another approval for blockbuster-in-waiting Stivarga after Japan gave a green light for the drug's use in gastrointestinal stromal tumour (GIST).

This is the second approval for Stivarga (regorafenib) in Japan, having been cleared for the treatment of advanced or recurrent colorectal cancer in March. The product has already been approved for both indications in the US and is under review for the colorectal cancer indication in Europe.

Japan's Ministry of Health, Labour and Welfare approved the oral multikinase inhibitor for GIST patients who have previously been treated with systemic therapy such as Novartis' Glivec/Gleevec (imatinib) and Pfizer's Sutent (sunitinib).

The approval was based on the Phase III GRID study that demonstrated a statistically significant improvement in progression-free survival (PFS) for Stivarga compared to placebo (4.8 months versus 0.9 months) in patients with GIST whose disease had progressed after treatment with Glivec and Sutent.

"The approval of Stivarga in Japan is an important development as it means that patients with GIST have a new option to slow the progression of this rare but aggressive disease,” said Kemal Malik, MD, Bayer's head of global development.

Stivarga got off to a strong start in its first few months on the US market "reflecting the unmet need of a patient population who are waiting for this new treatment," said Bayer Healthcare chief executive Wolfgang Plischke recently.

The company posted sales of €87 million for Stivarga in the first six months of this year, with development partner Onyx Pharmaceuticals earning royalties on sales at a rate of 20%, bringing in a little over $10 million.

Onyx said recently it believes Stivarga can become a $1 billion product at peak, provided additional approvals in other indications are forthcoming.

Bayer is also carrying out a Phase III trial of the drug in liver cancer and is due to start a second later this year in colorectal cancer patients who have undergone surgery for liver metastases.