Pfizer Attempts to Redefine the Troubled SERM Market at ECCEO-11

26 Apr 2011 • by Natalie Aster

At this year's ECCEO, Pfizer introduced Conbriza, the second selective estrogen receptor modulator to launch in the EU. Despite its favorable uterine and breast safety profile compared to competitor drug Evista, Datamonitor believes that a significant increase in sales of the treatment class in Europe is unlikely, due to questionable efficacy in non-vertebral fracture prevention.

Pfizer and its Spanish partner Almiral used the 2011 European Congress on Osteoporosis and Osteoarthritis (ECCEO) in Valencia, Spain, which ran between March 23 and 26, to present Conbriza (bazedoxifene), and to reinvestigate the use of selective estrogen receptor modulators (SERMs) in the treatment of osteoporosis. This class of drug is mainly used to treat osteopenia, and has not shown efficacy in preventing non-vertebral fractures. Most importantly, safety concerns, such as the increase of venous thromboembolism, have limited the use of the drug.

Pfizer held an educational lunch symposium to outline the benefits of using the newly launched Conbriza for the prevention and treatment of osteoporosis. Speakers stressed several times that not all SERMs are the same and have the same effect, in an attempt to differentiate Conbriza from other SERMs such as Evista (raloxifene; Eli Lilly), and to reduce the safety fears associated with the class.

Particular emphasis was placed on the fact that bazedoxifene was neutral on the breast and uterus and only acted on the estrogen receptors on the bone, unlike raloxifene and lasofoxifene, as well as estrogen therapy. The speakers told the audience that bazedoxifene's efficacy in reducing vertebral fracture was comparable to that of raloxifene. However, Datamonitor noted that unlike other treatments on the market, Conbriza has shown unconvincing efficacy in preventing non-vertebral fracture.

It was suggested that physicians should use SERMs in the early postmenopausal years in order to avoid exposing patients to a rise in cardiovascular events, which increase with age independently of the use of SERMs. Bisphosphonates should be used later on in treatment in order to avoid atypical fracture and other long-term issues associated with the treatment. However, despite the positive messages presented by the speakers, Datamonitor believes that it is unlikely that there will be a significant increase in sales of the SERM class.

Finally, the utility of combining bazedoxifene with conjugated estrogens was also discussed, and is thought to be a useful treatment for women who are suffering from hot flashes due to the menopause. Aprela (bazedoxifene with conjugated estrogens) has been in development for the treatment of menopausal symptoms and osteoporosis. The drug was originally developed by Wyeth and added to Pfizer's portfolio following the company's acquisition. It was considered to be very promising, but Wyeth delayed its submission for approval, probably due to the difficulties encountered with Conbriza, and with very few announcements regarding its progress in recent years, there had been doubts as to whether development had been halted.

Pfizer confirmed at the meeting that development is currently ongoing, with studies designed to determine whether this combination is safe and does not cause an increase in breast cancer risk. The panel did state that at this stage, they were confident that a combination product would remain safe, although they also stressed that this will only be confirmed at the end of the clinical trial. Should the combination product reach the market, Pfizer would possess a unique franchise that will allow patients to be treated first with the combination to address bone loss and menopausal symptoms, and then bone loss only.

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