Staff Writer

Shares of OncoGenex Pharmaceuticals Inc. soared 75.6 percent on Wednesday thanks to positive survival data from a Phase II trial of lead compound OGX-011 in the first-line treatment of hormone refractory prostate cancer (HRPC).

Initial analyses showed median survival of 27.5 months for patients receiving OGX-011 combined with the chemotherapy docetaxel and the steroid prednisone, compared to 16.9 months for those receiving docetaxel and prednisone alone.

Median follow-up time for both arms of the trial is about 30 months thus far. OncoGenex President and CEO Scott Cormack said that while the control-arm data are mature, patients in the treatment arm still are being followed for survival.

Yet Bothell, Wash.-based OncoGenex was able to calculate that the final median survival for patients in the OGX-011 arm could not be lower than 22.7 months. That "worst-case scenario" would still translate into a benefit of nearly six months over the control arm, Cormack said, adding that the upside from a best-case scenario remains to be seen.

As a point of comparison, docetaxel originally was approved based on a survival advantage of just 2.4 months over the immunosuppressant mitoxantrone, the company noted.

Cormack explained that the survival calculation created a material event that prompted OncoGenex to release its preliminary data. Additional findings included a death rate that was approximately 40 percent lower for patients in the OGX-011 arm compared to the control arm.

The 82-patient Phase II study was funded and conducted by the National Cancer Institute of Canada, with additional funding from the Canadian Cancer Society. Final data are expected to be submitted for presentation at next year's American Society of Clinical Oncology meeting.

OGX-011 previously garnered positive data in Phase II trials for lung and breast cancer, as well as for the second-line treatment of HRPC.

In the Phase II, second-line HRPC study, patients receiving OGX-011 plus docetaxel had median survival of 14.7 months, and those getting OGX-011 plus mitoxantrone had median survival of 11.4 months. Both compared favorably to the 10-month median survival usually obtained with second-line chemotherapy alone, the company said.

In July, OncoGenex reached an agreement with the FDA under a special protocol assessment for a pivotal Phase III trial of OGX-011 in the second-line treatment of 765 patients with HRPC.

Patients will be randomized to receive OGX-011, docetaxel and prednisone or docetaxel and prednisone alone. The primary endpoint will be overall survival. (See BioWorld Today, July 15, 2008.)

The company also is working with the FDA on the design of a second Phase III trial in second-line HRPC, this time using durable pain palliation as a primary endpoint and survival as a secondary endpoint.

Cormack said that while the "Holy Grail" in cancer clinical trials is survival, the pain trial will require less time and money to conduct while still providing survival data from the secondary endpoint analysis.

OncoGenex hasn't made any Phase III plans in the first-line HRPC setting. But with the positive first-line HRPC data released on Wednesday, the company has a "full package" of Phase II results and is ready to begin partnering discussions, Cormack said.

OGX-011 targets clusterin, a cell-survival protein that is overproduced in several types of cancer and has been linked to faster progression and decreased survival. Clusterin levels also increase in response to certain cancer therapies - including chemotherapy and radiation - and can lead to treatment resistance.

The drug uses second-generation antisense technology licensed from Carlsbad, Calif.-based Isis Pharmaceuticals Inc. Although OncoGenex manages product development, Isis will receive royalties as well as a portion of any license fees and milestone payments that OncoGenex may get from partnering OGX-011. (See BioWorld Today, Nov. 27, 2001.)

The survival data from the Phase II first-line HRPC trial triggered the release of all remaining OncoGenex shares held in escrow following the company's merger with Sonus Pharmaceuticals Inc. (See BioWorld Today, May 29, 2008.)

Cormack said OncoGenex had seven years to complete the various milestones that would release the shares from escrow, and the company "did it in three months."

Shares of OncoGenex (NASDAQ:OGXI) rose $1.70, to close at $3.95 on Wednesday.

Published  December 4, 2008