By Mary Welch

Phase III trials are under way with Sugen Inc.'s SU101, a platelet-derived growth factor receptor inhibitor, to determine if the drug blocks brain tumor growth by regulating cellular signals.

If approved by the FDA, the drug may be the first signal transduction inhibitor approved for the treatment of cancer, company officials said.

The 18-month randomized, controlled Phase III trial is expected to be complete in July 1999. It is being conducted in more than 30 sites and some 380 patients will be evaluated.

The study compares the effectiveness of SU101 against procarbazine, a chemotherapeutic agent commonly prescribed for patients with glioblastoma, a fast-growing brain cancer.

SU101 blocks the signaling of the platelet-derived growth factor receptor, the driving oncogene that causes irregular cell proliferation in brain, prostate, lung and ovarian tumors.

"What SU101 does is block the switch responsible for this abnormal signaling that results in a regulation of cell proliferation," said Susan Kinkead, manager of public affairs and investor relations.

Trial Seeks To Improve Survival 40 Percent

Of the 17,000 Americans diagnosed annually with brain tumors, two-thirds of them have glioblastoma. Symptoms include a change in mental status, such as memory loss or difficulty concentrating, seizures and overall weakness.

Among the study's endpoints are extending the survival rate by 40 percent over the control group, increasing time to disease progression and improving overall quality of life.

"This is not a typical cytotoxic drug in that it is not designed to kill the tumor cells, but rather is a cytostatic drug that arrests cell growth. We have some patients who have survived for up to two years with this highly aggressive, debilitating cancer. We have, in some cases, observed partial patient responses," Kinkead said.

In Phase II trials of 15 patients at Memorial Sloan-Kettering Cancer Center, in New York, SU101 kept tumors at bay for four months in six of 12 patients. In three of those patients, tumor size was reduced by at least 25 percent.

To date, more than 200 patients have been treated with SU101 and nearly 50 percent reported their tumors shrank or stabilized. Few side effects have been reported.

Phase II trials of SU101 for prostate cancer will be completed next month. Other patients given SU101 include those with ovarian and non-small cell lung cancers.

Sugen intends to start Phase II trials in ovarian and non-small-cell lung cancers by the end of this year and Phase III studies in prostate cancer.

Sugen's stock (NASDAQ:SUGN) closed Thursday at $18.688, up $0.063. *

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