By Randall Osborne

With its therapeutic for HIV still in Phase I/II trials, Progenics Pharmaceuticals Inc. is collaborating with Genzyme Transgenics Inc. (GTI) to produce the fusion protein known as PRO 542 in the milk of transgenic goats.

"Better to start early and have your ducks lined up — or in this case, your goats — than be sitting on your hands and have an active product but no way to make it," said Paul Maddon, CEO of Tarrytown, N.Y.-based Progenics.

Late last year, Progenics signed the deal with Framingham, Mass-based GTI, which is 43 percent owned by Genzyme Corp., of Cambridge, Mass.

"We're into the program," Maddon said. "The technology is incredible, if it lives up to its promise."

GTI has "had success with monoclonal antibodies in the milk of transgenic goats at high levels," he added. "That was a key factor for us."

With naked antibodies, as opposed to radiolabeled antibodies, a large amount of protein is needed, Maddon said.

"When you're up in that realm, you either need elaborate facilities such as Idec [Pharmaceuticals Corp., of San Diego] and Genentech [Inc., of South San Francisco] have, or you look for alternative methods," he said.

"You make a herd of the goats secreting the protein in the milk, and that's what [GTI has] done with a number of proteins," Maddon said. "I've visited the farm and petted the goats."

When the initial development phase is completed, the companies expect to enter into a commercialization agreement.

Making the deal with GTI early in Progenics' clinical studies provides a strong advantage when the time for filing a new drug application nears, Maddon said, because the FDA prefers that the company making the drug for analysis in Phase III trials also be the maker that will produce it for sale.

PRO 542 incorporates into a human antibody molecule the HIV-binding region of the human cell surface receptor. By binding to the gp120 glycoprotein on the HIV envelope, PRO 542 may prevent the virus from binding to the cell surface; by detaching the gp120 glycoprotein from the envelope, it could inactivate the virus altogether.

A Phase I/II clinical trial of PRO 542 in HIV-positive adults is under way at Mount Sinai Medical Center, in New York. Another Phase I/II study is testing the compound in HIV-positive children at three centers. Maddon said the trials are expected to conclude at the end of this year.

Progenics also is conducting Phase III clinical trials of its therapeutic melanoma vaccine, GMK. The vaccine incorporates the GM2 ganglioside, a cancer antigen present in 95 percent of all melanoma cells, conjugated with immunogenic proteins and an adjuvant to steer the immune system to destroy cancer cells.

The company raised $14 million in its initial public offering last year. (See BioWorld Today, Nov. 21, 1997, p. 1.)

GTI signed several deals in 1997. For Bristol-Myers Squibb Co., of New York, it will produce a humanized monoclonal antibody for treating psoriasis, organ transplant rejection and autoimmune disorders. (See BioWorld Today, Sept. 10, 1997, p. 1.)

For B. Braun Melsungen AG, of Melsungen, Germany, GTI will make recombinant human protein drugs. (See BioWorld Today, Oct. 1, 1997, p. 1.)

And with Advanced Cell Technologies Inc., of Worcester, Mass., GTI will work on cloning cows capable of producing human serum albumin in their milk. GTI agreed to pay Advanced Cell $10 million for its proprietary bovine cloning techniques. (See BioWorld Today, Oct. 9, 1997, p. 1.)

Along with its transgenic technology to develop and produce recombinant proteins and monoclonal antibodies, GTI is developing idiotypic vaccines with the National Cancer Institute.

Michael King, an analyst with Vector Securities International Inc., of Deerfield, Ill., rated Progenics' stock "attractive" on Thursday.

Because PRO 542 is administered by way of intravenous infusion, market assumptions are modest, King said. By the time the drug could be approved, new protease inhibitors and other anti-HIV agents are likely to be on the market, he added.

King estimated the worldwide sales for PRO 542 at $25.9 million in fiscal year 2002, and $54.6 million in fiscal year 2003.

Progenics' stock (NASDAQ:PGNX) closed Thursday at $20.50, up $2.125. GTI's shares (NASDAQ:GZTC) closed at $12.25, down $0.50. *

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