Patients were given the medicine, called PD 0332991, with Novartis (NOVN) AG's Femara. The findings reveal no tumor advancement for a median of 26.1 months, compared with 7.5 months in those who received femara independently. The drug was in its second of three mandatory stages required for U.S. approval.
PD 0332991 is the first in a new group of agents that functions by inhibiting a protein imperative to cancer cell cycle.
Dr. Mace Rothenberg, senior vice president of clinical development and medical affairs for Pfizer's Oncology Business Unit says:
"These results are especially important because of the magnitude of clinical effect observed and the fact that PD-991 represents a potential first-in-class compound. Based on these positive Phase 2 data, Pfizer is planning to open a randomized Phase 3 study of PD-991 in this patient population in 2013. We are working with regulatory authorities to advance the development of this promising compound in the most expeditious and responsible way."
The findings are significant because of the size of the advantage and comparative safety of the experimental treatment. This study consisted of 165 patients with metastatic disease, a rather small trial and should be confirmed in a larger population.
The participating women had tumors stimulated by the hormone estrogen, the most common type of breast cancer. All of the women had metastatic disease, meaning cancer that has spread to other parts of the other body and is considered incurable.
Breast cancer is the second most fatal type of cancer in women. According to the American Cancer Society, 230,000 women in the U.S. were diagnosed with year and over 39,900 will die from it.
When the investigators included women who had stable disease for 6 months or more, 70 percent of those given a combination of the drugs saw benefits, while just 44 percent of those given Femara benefited.
Pfizer will move the compound along into the final stage of testing required for approval as soon as possible, with an international trial planned to start next year.
During the study, about one in three patients needed to have their dose of the experimental drug decreased at some point. Side effects that were seen include low levels of infection-fighting white blood cells, fatigue, and anemia.
Pfizer continues to contact cancer experts to help create the most efficient studies and answer questions about when and how the drug should be prescribed, as well as what other medicines can be given to maximize the advantages.
Rothenberg said, "It's an irony of having a drug moving forward as quickly as we can. There will be gaps in our knowledge of how to give it and when. We're trying to move forward with a thoughtful, methodical approach."
Lead researcher Richard Finn concluded:
"The magnitude of this benefit I don't think should be underestimated. These are patients who have incurable breast cancer. A lot of drugs in oncology have been approved or are getting a lot of traction because of improvements that last weeks to a few months. We have gone from 7 months to 26 months. That's groundbreaking."
Written by Kelly Fitzgerald