Last Updated: 2011-09-26 11:21:18 -0400 (Reuters Health)
By Kate Kelland
STOCKHOLM (Reuters) - Combining two drugs from Novartis and Pfizer to treat post-menopausal women with a certain type of advanced breast cancer more than doubled the time they lived without their disease getting worse, study data showed on Monday.
Investigators conducting a clinical trial found that women treated with a combination of Novartis' Afinitor or everolimus, and Pfizer's oestrogen-blocker Aromasin, known generically as xemestane, had progression-free survival (PFS) of as much as seven months more than women treated with the Pfizer drug alone.
"This is a highly significant improvement in the time to disease progression. It's quite remarkable," said Jose Baselga of Massachusetts General Hospital and Harvard Medical School, who led the trial and presented the data at the European Multidisciplinary Cancer Congress (EMCC) in Stockholm.
He said side effects were consistent with those previously reported in trials of Afinitor and did not lead to a worse quality of life for patients on the drug.
Baselga's analysis of the data showed that PFS for women in the Afinitor group was 6.9 months versus 2.8 months for those not taking the Novartis drug - a 57 percent improvement.
The trial was stopped early after a separate independent analysis by a central review committee showed that Afinitor extended PFS to 10.6 months compared to 4.1 months - a 64 percent improvement.
"These results are impressive and, potentially, could represent a new therapeutic option," Baselga said.
Afinitor targets mTOR, a protein that acts as an important regulator of tumor cell division, blood vessel growth and cell metabolism. Novartis says there are around 220,000 newly diagnosed cases worldwide each year of the type of advanced breast cancer that could benefit from Afinitor.
Novartis has been upbeat about the prospects for the drug, which is already approved for other types of cancer, such as kidney and a rare type of pancreatic cancer.
The Swiss firm's CEO Joe Jimenez told Reuters in a recent interview it could generate an extra $1 billion or more in annual sales from its new use in breast cancer.
Herve Hoppenot, president of Novartis's oncology division, said the magnitude of benefit seen in this trial showed that Afinitor is "a potential important new treatment approach".
The Swiss drugmaker is planning to file for regulatory approval of Afinitor in breast cancer by the end of this year.
Novartis reported Afinitor sales for cancer of $243 million in 2010 but analysts expect that number to balloon if the drug is licensed in breast cancer. Thomson Reuters Pharma data show analysts on average forecast sales of $1.53 billion by 2016.
The hormone oestrogen promotes the growth of about two thirds of breast cancers, and hormonal therapies such as Aromasin which block the effect of oestrogen or reduce its levels are used to treat these so-called hormone receptor-positive breast cancers.
But many breast cancer patients, and nearly all those with advanced forms of the disease where it has spread to other parts of the body, become resistant to hormonal therapy.
"When patients stop responding to hormonal therapy, the benefits from any secondary therapy are limited," Baselga said.
The Phase III clinical trial, known as BOLERO 2, was designed to test the efficacy of Afinitor in patients resistant to aromatase inhibitors - drugs that cut the amount of oestrogen produced and help to slow or reverse the growth of the cancer.
It was as conducted in 24 countries in 724 patients with an average age of 62. All patients had already been treated with the aromatase inhibitors anastrozole, sold by AstraZeneca as Arimidex, or the generic drug letrozole. Some had also been treated with tamoxifen, fulvestrant and chemotherapy.
Pfizer's Aromasin lost its patent in April and is now available in a cheaper generic version.
Copyright © 2011 Reuters Limited. All rights reserved.Republication or redistribution of Reuters content, including by framing orsimilar means, is expressly prohibited without the prior written consent ofReuters. Reuters shall not be liable for any errors or delays in thecontent, or for any actions taken in reliance thereon.Reuters and the Reuters sphere logo are registered trademarks andtrademarks of the Reuters group of companies around the world.