By Bill Berkrot
(Reuters) - An experimental leukemia treatment that Roche Holding AG hopes will improve upon its best-selling cancer drug Rituxan delayed disease progression twice as long as chemotherapy, according to preliminary trial data released on Wednesday.
Switzerland-based Roche aims to fend off cheaper competition for Rituxan, which loses patent protection in Europe later this year, threatening a product with nearly $7 billion in annual sales.
Roche's new drug in development, known as GA101 or obinutuzumab, was given in conjunction with the commonly used chemotherapy chlorambucil to previously untreated patients with chronic lymphocytic leukemia (CLL) who also had other health problems, such as heart disease. The treatment was compared against that for patients who received the chemotherapy alone in a late-stage clinical trial involving 589 people.
The combination of Roche's drug plus chemotherapy led to an 86 percent reduction in risk of disease progression, according to data from a scientific abstract released on Wednesday ahead of the American Society of Clinical Oncology's annual meeting later this month.
Patients who received GA101 went 23 months on average before their leukemia began to worsen, an interval known as progression-free survival, or PFS. That compared with 10.9 months for chemotherapy alone, according to the latest available data. Data showing the actual survival benefit will not be available for some time, the company said.
Overall and complete response rates seen in the study demonstrate the potential potency of the Roche drug.
The overall response rate was 75.5 percent compared with 30.2 percent of patients who responded to the chemotherapy alone. Twenty-two percent of those who got GA101 had a complete response, meaning the cancer was undetectable, whereas no patients receiving chemo alone had a complete response.
"We have to wait for longer follow-up to comment on duration of control of the disease," Dr Valentin Goede, the study's lead investigator, said in an interview.
"Still, these are encouraging results," said Goede, adding that he believes progression-free survival for the Roche drug was likely to improve.
HELPING THE IMMUNE SYSTEM DEFEND ITSELF
GA101 is an engineered antibody designed to better enable the immune system to attack and kill B cells, from which many blood cancers, such as CLL and lymphomas, originate. The drug, which recognizes B cells on the surface of tumors, was engineered to be more potent in attacking them than Rituxan.
Another arm of the trial, for which data will not be available until late this year or in 2014, is testing GA101 directly against Rituxan. When Rituxan plus chemotherapy was compared to chemotherapy alone, it showed progression free survival of 15.7 months and an 8.3 percent complete response rate.
If the new drug shows clear superiority over Rituxan in the head-to-head portion of the trial, Roche would be able to defend the multibillion-dollar franchise against cheaper biosimilar versions of Rituxan when they emerge. As with Rituxan, Roche will share a portion of GA101 profits with Biogen Idec after Biogen exercised its option on the drug, Roche said.
Goede, from University Hospital of Cologne in Germany, said the trial was important because it was the first large Phase III CLL study of the type of patient doctors most typically see - older with additional health problems.
It is estimated that 15,680 Americans will be diagnosed with and 4,580 will die of chronic lymphocytic leukemia in 2013, according to the National Cancer Institute.
The new medicine did have a far higher incidence of neutropenia, or reductions in white blood cell count, than either Rituxan or chemo alone. However, Goede called the safety profile acceptable because the neutropenia did not lead to infections or fever.
There were also infusion-related reactions seen with the first dose of GA101 that were not seen with chemotherapy. That was managed by splitting the first dose of the drug over two days, researchers said.
Goede noted that there had been a similar issue in early clinical trials of Rituxan. "This is a problem that can be fixed," he said.
(This version of story corrects paragraph 12 to show Biogen has stake in new drug)
(Reporting by Bill Berkrot; Editing by Michele Gershberg and Prudence Crowther)