The Californian company is developing Nexavar (sorafenib) in collaboration with Bayer Pharmaceuticals. The drug is already approved for use against kidney cancer and the two companies held high hopes for the results of the Phase III clinical trial into its effectiveness against melanoma, the most serious type of skin cancer.
Hollings Renton, chief executive of Onyx said: "We are disappointed, first and foremost, for the patients with refractory metastatic melanoma for whom treatment options are so limited."
In the clinical trial, 270 patients treated with Nexavar in conjunction with chemotherapy only experienced abated tumour growth comparable with those patients who were administered the new drug alone. The two chemotherapeutic agents used were carboplatin and paclitaxel.
Although melanoma only makes up 4 per cent of all skin cancer cases, it accounts for 77 per cent of skin cancer deaths. It is estimated to kill over 40,000 people worldwide every year.
Crucial processes in both tumour and blood vessel growth can be inhibited through a class of proteins called kinases. Once a tumour has a sufficient blood supply it is more likely to spread to other parts of the body. Therefore, preventing kinases involved in both these functions from working properly has long been a goal of drug developers.
However, it is only recently that enough was understood about these processes to allow scientists to develop a drug that can inhibit both processes simultaneously. Nexavar is one of only two such multi-kinase inhibitors that have been approved.
Although initially approved for a different cancer, a specific kinase is mutated in two-thirds of melanomas and so Onyx and Bayer initiated trials to test its efficacy in this disease. The drug is also being tested as a treatment in several other types of cancer, including lung cancer.
Renton said: "This trial does not change our commitment to, and belief in, Nexavar. We hope to demonstrate utility in a wide variety of tumours and we will continue to broaden our clinical programme, including increasing our attention to the more common malignancies in which anti-angiogenics have demonstrated activity."
"We will review the study design and our ongoing melanoma development programme."
These sentiments were echoed by Onyx chief medical officer Hank Fuchs. He said: " Because refractory melanoma is a difficult to treat disease with limited treatment options we believe that ongoing studies that could help these patients should be completed."
The other approved multi-kinase inhibitor is Pfizer's Sutent (sunitinib), which was approved for use against advanced renal cancer and gastrointestinal stromal tumour within a month of Nexavar.
Onyx has felt the loss more keenly than Bayer after their share price dropped over 30% to around $12 (?9). Onyx said they will present detailed data from the trial at a conference in April.
Several pharmaceutical companies, including AstraZeneca, GSK, Novartis, Pfizer and Bristol-Myers Squibb are developing multi-kinase inhibitors for use in cancer treatment. However, none of them are currently being tested against melanoma.