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Pfizer Receives FDA Breakthrough Therapy Designation

April 13, 2013

Pfizer announces April 10, 2013, that the investigational compound Palbociclib (PD-0332991) receives FDA’s Breakthrough Therapy designation for potential treatment of patients with breast cancer. Palbociclib is an oral and selective inhibitor of Cyclin Dependent Kinases (CDK) 4 and 6.

Palbociclib is being evaluated as an initial treatment for the biggest subgroup of postmenopausal women whose breast cancer is locally advanced or has spread elsewhere in the body. Approximately 60% of women with this type of advanced breast cancer have tumors that are ER+ (Estrogen-Receptor Positive), but HER2-, or lacking an excess of the growth-promoting protein HER2. ER+ tumors have proteins inside and on the surface of their cells to which the estrogen hormone can attach and then fuel growth of cells. These tumors tend to grow slowly and can be fought with drugs that block estrogen’s effects. Meanwhile, about 80% of breast cancer tumor cells are HER2-, which means that they don’t produce too much of the HER2 protein. The HER2 protein results in tumors growing and spreading more aggressively than in other breast cancer types.

The Breakthrough Therapy designation is based on preliminary Phase II data which shows that women treated with the combination of Palbociclib + Letrozole achieve a statistically significant improvement in median Progression Free Survival (PFS) compared to women who receive Letrozole alone (26.1 months and 7.5 months, respectively).

Pfizer has started a randomized, multi-center, double-blind Phase III Study (Study 1008) to evaluate Palbociclib in combination with Letrozole versus Letrozole alone as a 1st-line treatment for post-menopausal women with ER+, HER2- locally advanced or metastatic breast cancer, which represents about 60% of cases. Study 1008 is open and enrolling.

Palbociclib is being developed as a treatment for other cancers.

As discussed in previous Orphan Druganaut Blog Posts, the new FDA Breakthrough Therapy Designation is for the purpose of speeding up the development and review of new drugs. In order for a drug to be designated as a Breakthrough Therapy, the sponsor must provide, per Section 902 of FDASIA :

  1. Evidence that the drug is intended , alone or in combination with 1 or more other drugs, to treat a serious or life-threatening disease or condition, and
  2. Preliminary clinical evidence indicating that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development.

Please Note #1: The Orphan Druganaut Blog has decided to include a Post on drug Palbociclib even though it isn’t an orphan drug, because the Blog has been following the new FDA Breakthrough Therapy designation since the beginning of 2013.

Please Note #2: FDA Official Logo from FDA website.

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