Threshold set in companies amended agreement for toremifene was not high enough for FDA-agreed trial protocol.

GTx and its toremifene development and commercialization partner Ipsen have decided to end their collaboration on the prostate cancer drug because a second Phase III trial requested by FDA will cost more than is covered under the firms’ most recently amended partnership agreement. As a result Ipsen is passing its rights to toremifene 80 mg back to GTx, but will receive a low single-digit royalty on future net sales of the drug if U.S. approval is granted in the future.

Ipsen has been GTx’ partner on the toremifene 80 mg program since 2006. The firms were developing the oral selective estrogen receptor modulator (SERM) for use in reducing the risk of fractures in prostate cancer patients receiving androgen-deprivation therapy.

An NDA was filed in December 2008, on the back of a single Phase III study, but in October 2009 GTx received a complete response letter from FDA stating that the submitted NDA demonstrated clinical deficiencies.  More specifically, FDA wanted to see the results of a second Phase III trial demonstrating the safety and efficacy of toremifene 80 mg to reduce fractures in men with prostate cancer on androgen deprivation therapy, and in addition the results from a clinical trial demonstrating that toremifene treatment had no detrimental effect on either time-to-disease progression or overall survival.

Meetings with the agency have since led to an agreement on a protocol for a single clinical trial to address both these issues. However, GTx says the projected costs associated with the study will significantly exceed the threshold set under its 2010-amended agreement with Ipsen.

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