Bazedoxifene: bazedoxifene acetate, TSE 424, TSE-424, WAY 140424

Bazedoxifene is a third-generation selective estrogen receptor modulator (SERM) that is being developed by Ligand Pharmaceuticals in collaboration with Wyeth. The agent has effects on bone and cardiovascular tissue, but does not affect breast or uterine tissue. Bazedoxifene is in clinical development as a monotherapy for the prevention and treatment of postmenopausal osteoperosis, and in combination with conjugated estrogens for the treatment of menopausal symptoms and prevention of postmenopausal osteoporosis. American Home Products changed its name and the names of its subsidiaries Wyeth-Ayerst and Wyeth Lederle to Wyeth in March 2002. Wyeth and Ligand entered into a discovery research collaboration for bazedoxifene in September 1994. Under the agreement, Wyeth has worldwide development rights to the compound and is solely responsible for its clinical development. In exchange, Ligand is entitled to milestone and royalty payments associated with development and commercialization achievements. Ligand entered into an agreement with Royalty Pharma in March 2002 whereby Royalty Pharma purchased the rights to a share of Ligand's entitlement to milestone and royalty payments. Under the agreement, Ligand received $US6 million from Royalty Pharma in exchange for a 0.25% stake in net sales of three SERM products (lasofoxifene, bazedoxifene and bazedoxifene/Premarin) for a period of 10 years. Subsequently, Ligand and Royalty Pharma further amended their existing royalty agreement for three SERM products in November 2004. Under the revised agreement, Royalty Pharma would purchase an additional 1.625% of the SERM products' net sales for $US32.5 million, which represents an acceleration of the previous option timetable and an increase in the royalty amount as well as aggregate purchase price. Consequently, Royalty Pharma increased its rights to a total of 3.0125% of net sales of each SERM product for 10 years following first commercial sale of each product and has no further options. Ligand retains an approximately equal portion of lasofoxifene and other SERM's net sales going forward and for periods that could exceed 10 years. The royalty rates owed to Royalty Pharma for the royalties just purchased could be reduced by one-third if product sales exceed certain thresholds. Payments from the royalty purchase are non-refundable, regardless of whether the products ever become successfully launched or not. Milestone payments owed by Ligand's partners as products achieve development and regulatory targets would be paid to Ligand as earned, and are not included in this amended agreement. The US FDA issued a second approvable for bazedoxifene in December 2007, after Wyeth submitted additional study reports from two completed clinical studies for the prevention of postmenopausal osteoporosis. The study reports provided data from two studies conducted in Asia and will form part of a complete response to safety and efficacy issues raised in an initial approvable letter issued by the FDA in April 2007. Prior to approval of the NDA, the FDA must also analyse final safety and efficacy data from a completed phase III trial, and complete an acceptable establishment evaluation on the manufacturing facilities for bazedoxifene. In January 2008, Wyeth stated that the FDA expects to convene an Advisory Committee meeting in July 2008 to review both the treatment and prevention of osteoporosis indications for bazedoxifene. While the second approvable letter issued by the FDA expressed concerns about the incidence of stroke and venous thrombotic events, Wyeth has reported that no additional studies would be needed. Initial filing of the NDA in June 2006 triggered a milestone payment from Wyeth to Ligand.A 2-year, randomized, phase III trial (study 300) has been conducted to compare bazedoxifene (10, 20 and 40 mg) and raloxifene (60 mg) in 1583 patients for the prevention of osteoporosis. Data presented in September 2007 demonstrated that bazedoxifene treatment prevented bone loss, reduced bone turnover, and was generally well tolerated in postmenopausal women with normal or low bone mineral density. Wyeth submitted an NDA to the FDA in July 2007 to gain marketing approval for bazedoxifene as a treatment for postmenopausal osteoporosis. In January 2008, Wyeth stated that the FDA expects to convene an Advisory Committee meeting in July 2008 to review both the treatment and prevention of osteoporosis indications for bazedoxifene. Wyeth has completed a phase III trial comparing bazedoxifene with raloxifene and placebo in 7492 patients with moderate-to-severe postmenopausal osteoporosis. The three-year, randomized, double-blind study commenced in October 2001, and was conducted at sites in the US. Data presented in September 2007 indicated that bazedoxifene showed significant risk reduction for new vertebral fractures, compared with placebo. In addition, Wyeth conducted a phase II trial in Japan to investigate bazedoxifene dose-response in 375 patients with postmenopausal osteoporosis. The randomized, double-blind, placebo-controlled, parallel assignment study commenced in August 2003 and is no longer recruiting patients. The patent covering bazedoxifene will expire in 2017 with the potential for extension.