Washington Editor

After failing to reach statistical significance in a Phase III trial in acute myeloid leukemia last spring, Protein Design Labs Inc. stopped its study of SMART M195. On Tuesday it said it would license certain rights to the antibody to Actinium Pharmaceuticals Inc.

SMART M195 is a humanized version of the murine M195 antibody that binds to the CD33 antigen present on the cancer cells of most patients with acute myeloid leukemia (AML), Fremont, Calif.-based Protein Design Labs said.

PDL developed SMART M195 as a naked antibody, whereas Actinium, of Alexandria, Va., intends to develop it as a targeted therapy using it to deliver radioisotope to a cancer cell, Jim Goff, senior director of corporate communications for PDL, told BioWorld Today.

"The point being, in previous trials this antibody has shown strong specificity and binding affinity to CD33, so it should be very appropriate as a delivery device in this particular type of strategy," Goff said.

Actinium paid PDL an up-front licensing fee and is scheduled to pay development milestones when achieved and royalties on future sales. Goff would not discuss other financial details of the agreement.

In clinical trials, PDL referred to the antibody as Zamyl. Last May, PDL said final analysis of its Phase III acute myeloid leukemia trial indicated that the overall response rate in patients who received Zamyl in combination with chemotherapy was 36 percent (n=94), and 28 percent (n=97) in patients who received chemotherapy alone (p=0.28). (See BioWorld Today, May 21, 2002.)

"We reported at that time that we did not intend to conduct additional PDL trials with this antibody, but that we would seek a partner or we would outlicense it, and that day is today," Goff said.

In a prepared statement, Maurits Geerlings, president and CEO of Actinium, said, "SMART M195 has demonstrated a clear ability to bind to cancer cells in multiple clinical trials. We believe that its binding specificity makes it a promising candidate to deliver our actinium-225 and bismuth-213 as targeted therapies in acute myeloid leukemia."

Mark McDade, PDL's CEO, said in a prepared statement that the agreement "represents the initial result of our renewed commitment to generate new revenues from our platform, in addition to humanization and patent license agreements."

Actinium is working with Memorial Sloan-Kettering Cancer Center in New York where 30 patients have been treated using SMART M195 with bismuth-213.

PDL's stock (NASDAQ:PDLI) rose 31 cents Tuesday to close at $8.15.