By Deena Beasley
May 14 (Reuters) - Britain's AstraZeneca Plc, the target of a $106 billion takeover effort by Pfizer Inc, released promising data on Wednesday for a new lung cancer treatment targeting a genetic mutation that helps tumors evade current treatments.
The drug, known as AZD9291, in an early-stage trial shrank tumors in 51 percent of patients. Tumors shrank in 64 percent of patients found to have the mutation, known as T790M, which develops in about half of lung cancers that become resistant to drugs known as epidermal growth factor receptor (EGFR) inhibitors.
These drugs, such as Roche's Tarceva, or erlotinib, are used to treat various solid tumor cancers with mutated or overactive EGFR. Around 15 percent of patients with non-small cell lung cancer, the most common form of the disease, have mutations in the EGFR gene.
But most of them will eventually become resistant to available EGFR inhibitors, said Dr. Pasi Janne, professor of medicine at Dana-Farber Cancer Institute and Harvard Medical School in Boston and the study's lead investigator.
"The issue of drug resistance has been the bane of chemotherapy treatment of cancer for decades," Dr Peter Yu, president-elect of the American Society of Clinical Oncology, said during a press conference. Research that has enabled a better understanding of the molecular underpinnings of cancer is now extending to development of drugs that target new mutations, he said.
AZD9291 is one of several new drugs flagged by AstraZeneca last week in a bid to convince investors of the strength of its experimental pipeline, one of its key attractions for Pfizer. AstraZeneca has so far rebuffed the approaches from its rival.
The British company forecasts that peak annual sales of the cancer drug could reach $3 billion, which is more than the $1 billion to $2 billion currently predicted by analysts.
The Phase 1 trial, featured ahead of the annual meeting of the American Society of Clinical Oncology (ASCO) later this month, involved 199 patients with advanced non-small cell lung cancer with EGFR mutations whose disease worsened despite treatment with a current EGFR inhibitor.
The most common side effects seen in the trial included diarrhea and rash, but researchers said the level of toxicity was less severe than is seen with available EGFR inhibitors.
AstraZeneca is currently conducting a Phase 2 study of AZN9291 in patients with the T790M mutation at a daily dose of 80 milligram, which it said could enable accelerated regulatory filing in the second half of next year.
AZN9192 has been granted "breakthrough" status by the U.S. Food and Drug Administration as a second-line therapy for non-small cell lung cancer. Astra has said it will also study the drug as an initial treatment for eligible lung cancer patients.
Investors are keen to get a look at other cancer data from Astra due to be presented at the ASCO meeting.
The company's MEDI4736 has the potential to become one of the first in a new class of drugs known as anti-PDL1 treatments that fight cancer by boosting the immune system. It is initially being tested as a treatment for non-small cell lung cancer.
AstraZeneca has forecast peak sales for MEDI4736 of $6.5 billion, including combination therapies, compared with analyst estimates of $2 billion to $7 billion.
An AstraZeneca spokeswoman said updated data from trials of MEDI4736 will be presented at the conference at the end of May.
Data from another of the company's experimental cancer drugs, olaparib for ovarian cancer, will be featured at the ASCO meeting as a late-breaking abstract. AstraZeneca has forecast peak olaparib sales of $2 billion, compared with consensus analyst estimates of $1.5 billion to $3 billion. (Additional reporting by Ben Hirschler in London; Editing by Michele Gershberg and Leslie Adler)