A panel that advises the US Food and Drug Administration (FDA) on new drug approvals said the benefits of Pfizer’s bone drug Fablyn for treating postmenopausal women with osteoporosis outweighed the risks but that use should be restricted to patients at high risk of fracture or who have tried other treatments without success.

At a meeting on 8th September, the FDA’s Advisory Committee on Reproductive Health Drugs reviewed New Drug Application (NDA) 22-242 submitted by CP Pharmaceuticals International CV (with Pfizer Inc acting as US agent) to request approval for Fablyn (lasofoxifene) 0.5 mg tablets. Nine of the panel said the benefits outweighed the risks, three said they did not and one member abstained, according to a report in the Wall Street Journal.

Chairing the panel was Sandra Carson, a professor of gynecology at Brown University, who said that the overall view of the panel was that Fablyn offered another option for postmenopausal women seeking treatment for osteoporosis, a bone disease characterized by reduced bone density and other conditions that increase risk of fracture. The drug would offer most benefit to women at high risk of fracture, said Carson.

Pfizer developed Fablyn to meet a number of needs among postmenopausal women with osteporosis, namely to reduce the risk of fractures (both vertebral and nonvertebral) and also address other postmenopausal conditions including reducing risk of breast cancer and to treat vulvar and vaginal atrophy (VVA). The company has not yet submitted an approval application for Fablyn as a treatment for breast cancer.

Fablyn (lasofoxifene) is a selective estrogen receptor modulator (SERM). Unlike other estrogen receptor drugs that are either agonist or antagonist, SERMs are both, and show either agonist or antagonist ability depending on the tissue type.

The FDA does not have to follow the recommendations of its Advisory Committees, although it usually does. However, in this case, because there was no clear endorsement or rejection, experts are not sure which way the agency will go. The FDA will announce its decision sometime in October.

Last week, the FDA published a briefing document about Fablyn on its website ahead of the meeting. The document said that while Fablyn had shown positive results in treating osteoporosis in postmenopausal women at high risk of bone fracture, compared to women on placebo it also increased the risk of blood clots and invasive gynecological visits.

Forbes reported that this is the second time Pfizer has sought FDA approval for Fablyn. The first time was in 2004, and while the drug was acknowledged to be effective, the FDA had questions about risk of blood clots and stroke. So Pfizer and development partner Ligand Pharmaceuticals went back and did another study on more than 9,000 women in different countries.

The new study showed that Fablyn was not linked to increased risk of stroke or death, but there was a higher risk of blood clots compared to placebo. The results also showed that the drug decreased the risk of breast cancer.

One panel member told the press they were concerned there was no “head to head” trial of Fablyn against other FDA approved drugs, according to the Wall Street Journal.

According to a report in Bloomberg, Pfizer said in a statement that:

“We believe the data presented today demonstrates that lasofoxifene offers unique benefits for the treatment of osteoporosis in women at increased risk of fractures.”

Click here to view the Advisory Committee’s briefing document on Fablyn (PDF, on FDA website).

Source: FDA, Wall Street Journal, Forbes.

Written by: Catharine Paddock, PhD