National Editor

Unable to find a retooled deal pleasing to both sides, ImmunoGen Inc. and GlaxoSmithKline plc - which earlier said they were striving to do so - have ended their development agreement for cantuzumab mertansine (huC242-DM1).

"They've negotiated in good faith," said Carol Hausner, spokeswoman for Cambridge, Mass.-based ImmunoGen. "Our plan now is to partner it with another company."

From GSK, ImmunoGen regains all rights to the tumor-activated prodrug (TAP) compound it developed, which is composed of the humanized antibody huC242 conjugated with the cytotoxic agent DM1. The compound has completed Phase I trials and is being studied as a treatment for refractory colorectal cancer, pancreatic cancer and non-small-cell lung cancer.

More than six months ago, GlaxoSmithKline told ImmunoGen that pushing the compound into Phase II studies would be dependent on renegotiation of the product license agreement, and the companies had been working toward that end. (See BioWorld Today, June 25, 2002.)

With a new partner, "there are a number of different options" regarding the specific cancer indication in which the drug will be tested next, Hausner said.

"We'd like to have a broad-based Phase II program," she said.

No payments were made by either company in GSK's return of product rights to ImmunoGen, which has rights to the investigational new drug application for cantuzumab mertansine and Phase I data.

ImmunoGen entered the deal with London-based GSK (then SmithKline Beecham) in February 1999. The arrangement was valued at up to $45 million at the time, $41.5 million of which came in the form of up-front fees and milestone payments. (See BioWorld Today, Feb. 3, 1999.)

In June, when ImmunoGen disclosed the stock-punishing news from GSK about the demand to renegotiate - shares slid 46 percent, closing at $2.15 - the company had received $11.5 million in milestones from its partner, and GSK had made a $2.5 million equity investment in ImmunoGen. That's all ImmunoGen will take from the deal monetarily, Hausner said.

ImmunoGen's shares (NASDAQ:IMGN) slid 10 cents on the latest word, closing Friday at $2.89.

Millennium Pharmaceuticals Inc., of Cambridge, Mass., and Boehringer Ingelheim GmbH, of Ingelheim, Germany, also have ImmunoGen TAP compounds in development, both in Phase I trials for cancer, and Abgenix Inc., of Fremont, Calif., has a deal with ImmunoGen using Abgenix's XenoMouse antibodies. (See BioWorld Today, Sept. 7, 2000, and March 7, 2001.)

There's a deal with South San Francisco-based Genentech Inc., too, which said last year it would conduct more preclinical work on a separate but similar tumor-activated prodrug in order to obtain a better profile. That drug involves Genentech's breast cancer drug Herceptin (trastuzumab) with DM1, for which an IND has yet to be filed.

In November, ImmunoGen partner British Biotech plc, of Oxford, UK, said Phase I data on the TAP product huN901-DM1 (BB-10901) showed the drug can be safely administered for small-cell lung cancer at doses comparable to those that produced antitumor activity in preclinical models.

The study also came up with preliminary evidence of antitumor activity, and the companies are discussing Phase II trials with regulators. In the U.S., the drug already has moved into Phase II trials in relapsed small-cell lung cancer, Hausner said, noting that a conference call on ImmunoGen's earnings slated for Feb. 6 will provide updates on programs.

"We're built around targeted treatments for cancer," Hausner told BioWorld Today. "One element of that is our TAP technology, but we also have expertise in antibodies." In the research stage is an IGF-1 receptor antibody, and in preclinical development is HuMy9-6-DM1 for acute myeloid leukemia.

"The expression TAP is used by other [companies] for different things," she noted. GeneMax Corp., of Blaine, Wash., for example, last year gained patents for what it calls TAP-1 as an immunotherapy against cancers. The acronym stands for "transporters associated with antigen processing." Others have used the TAP acronym in their company names.

"The concept of attaching a payload to an antibody that targets cancer is not a new concept," Hausner acknowledged. "The challenge is doing it effectively."