Five months after forming a partnership with Aventis SA for its early stage cancer products, ImmunoGen Inc. plans to move two of its later-stage products into Phase II on its own.

"I'm thrilled that we're now in a position to take our lead products forward ourselves," Mitchel Sayare, chairman and CEO of Cambridge, Mass.-based ImmunoGen, said during a conference call Thursday.

The two lead products are cantuzumab mertansine, which the company regained all rights to a year ago when it terminated a deal with GlaxoSmithKline plc, and huN901-DM1, a compound that was partnered with Vernalis plc until it relinquished its rights this week.

ImmunoGen formed the deal with Winnersh, UK-based Vernalis, then called British Biotech plc, in May 2000 to develop and market huN901-DM1 to treat small-cell lung cancer. The companies brought the drug into Phase I testing, and British Biotech took over development costs. Through the deal, British Biotech gained exclusive development and marketing rights in the European Union and Japan. It also was responsible for conducting clinical trials necessary to achieve regulatory approval in the U.S., but ImmunoGen retained the rights to market the drug in the U.S. and the rest of the world. It also had rights to manufacture it worldwide. (See BioWorld Today, May 8, 2000.)

But with the deal formed last July with Aventis, of Lyon, France, for its earlier-stage products, ImmunoGen no longer needed the financial support for its later-stage products. And due to the merger of British Biotech and RiboTargets Ltd., which then merged into Vernalis last year, the agreement for huN901-DM1 was under renegotiation. Despite the return of rights to ImmunoGen, the company has no financial obligation toward Vernalis, Sayare said.

With the Aventis agreement, the companies are jointly developing antibody-based cancer products, including huMY-9-6-DM1 for acute myeloid leukemia, an IGF-1 receptor-directed naked antibody for solid tumors, and a non-Hodgkin's lymphoma product developed from the company's tumor-activated prodrug (TAP) technology. The $62 million deal did not include rights to cantuzumab mertansine, although ImmunoGen said at the time it was looking for a new partner to replace GSK. (See BioWorld Today, Aug. 1, 2003.)

Sayare said company officials met with its board, and the company changed its plan. "We are now in complete agreement that the best use of ImmunoGen's cash is to invest in our own lead products," he said.

Due to a need to manufacture clinical material, the cantuzumab trial will not begin for 12 to 18 months, while the huN901-DM1 trial could begin as early as the second half of this year.

Sayare said that it is regrettable that the company had not been manufacturing clinical material of cantuzumab mertansine all of last year, following the terminated deal with GSK. "There's no question we lost the time," he said. "We chose to use our resources internally to pursue other things at that time."

The four-year-old deal with London-based GSK was terminated in January 2003 after the companies failed to renegotiate new terms. ImmunoGen regained all rights to the TAP compound, which had completed Phase I trials and was being studied for refractory colorectal cancer, pancreatic cancer and non-small-cell lung cancer. As a condition of moving the compound into Phase II studies, GSK said the product license agreement needed to be renegotiated. (See BioWorld Today, Jan. 27, 2003.)

"We, in fact, are in possession of all of the data that Glaxo collected," Sayare said. "We do have a very solid handle on both the administration and dosages, so we think we can move quite quickly into Phase II once we have the material."

Vernalis will remain responsible for a UK Phase I study of huN901-DM1 until it is completed. It also will cover a Phase I/II study in the U.S. until June 30, when ImmunoGen will take over responsibility. Patient enrollment will continue in both of those studies. ImmunoGen specifically is interested in developing that drug for multiple myeloma and acute myeloid leukemia, Sayare said. It will know the specific cancers in which to develop cantuzumab mertansine once the clinical material is manufactured.

In order to have the infrastructure in-house to conduct the trials, ImmunoGen is hiring a senior medical affairs oncologist and a senior regulatory person, and it expects to use contract research organizations to conduct the studies.

It might consider studying its products in indications other than cancer, or partnering either of its late-stage products in Phase III trials. "Our sense is we can get the most value from these products if we do the proof studies ourselves and then out-license," Sayare said.

As of Sept. 30, the company had $107.3 million in cash and marketable securities, leaving it with enough for five to seven years of operation.

ImmunoGen's TAP technology uses a tumor-targeting antibody to deliver a cell-killing agent specifically to cancer cells. It developed cantuzumab mertansine to treat cancers that express CanAg, such as colon, pancreatic, gastric, other abdominal cancers, and many non-small-cell lung cancers. The compound is composed of ImmunoGen's huC242 antibody and DM1. Phase I studies showed it was well tolerated and had evidence of anticancer activity.

HuN901-DM1 is made of ImmunoGen's huN901 antibody, which targets CD56, and DM1.

ImmunoGen's stock (NASDAQ:IMGN), dipped 10 cents Thursday to close at $5.90.