Endo Pharmaceuticals Inc. late last week found itself riding an up-and-down track on the drug development roller coaster.

The Chadds Ford, Pa.-based firm, a wholly owned subsidiary of Endo Pharmaceuticals Holdings Inc., said its third MorphiDex Phase III trial did not meet its primary endpoint. Specifically, results failed to show a statistically significant difference in the primary outcome variable - to demonstrate that MorphiDex could reduce the daily morphine requirement and maintain the same degree of pain control over three months in patients with moderate to severe pain from osteoarthritis. The study also failed to meet its secondary endpoint, a reduction in analgesic tolerance for patients administered MorphiDex.

But Endo said the results reiterated its previously reported belief that the third study, regardless of outcome, would not provide sufficient data to support the filing of an amendment to the MorphiDex new drug application. And because MorphiDex will not be approved prior to March 31, the Class A transferable warrants (NASDAQ:ENDPW) and Class B non-transferable warrants will expire on that date and have no economic value.

Separately, Endo opened a new drug application for its opioid analgesic product candidate, filing with the FDA an application for both the immediate- and extended-release oxymorphone oral tablets. Endo is developing oxymorphone IR to treat moderate to severe pain where the use of an opioid is appropriate. Oxymorphone ER is designed to treat moderate to severe pain in patients requiring continuous, around-the-clock opioid therapy for an extended period of time.

The extended-release formulation was developed in collaboration with Patterson, N.Y.-based Penwest Pharmaceuticals Co., which applied its TimeRx technology to the product.

Penwest's shares (NASDAQ:PPCO) on Friday jumped 73 cents to close at $9.90. Endo's stock (NASDAQ:ENDP) closed unchanged at $7.