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Protein Design Labs Inc. sublicensed to Genentech Inc. the development and commercialization rights for antibody-drug conjugates (ADCs) directed against the PR1 antigen, gained in PDL's $37.5 million buyout of Eos Biotechnology Inc., which was disclosed earlier this year.

"We're set up to develop naked antibodies," James Goff, senior director of investor relations for Fremont, Calif.-based PDL, told BioWorld Today. "With everything else on our plate, it was more efficient to out-license."

Genentech, of South San Francisco, is paying an up-front fee plus milestone payments and royalties on future sales, under certain conditions. Further details were not disclosed.

The PR1 antigen often is differentially expressed in prostate cancer, and researchers published preclinical work related to validation of PR1 anti-TMEFF2 monomethyl auristatin E-conjugated antibodies for prostate cancer in the August 2004 edition of Molecular Cancer Therapeutics.

Eos, also of South San Francisco, had licensed the PR1 rights from Bothell, Wash.-based Seattle Genetics Inc., which has netted ADC deals with the likes of Celltech Group plc, of Slough, UK (bought by UCB SA); CuraGen Corp., of New Haven, Conn.; Bayer Pharmaceuticals Corp. (a unit of Leverkusen, Germany-based Bayer AG); and Celera Genomics Group, of Rockville, Md.

ADC technology deploys monoclonal antibodies with drugs attached by proprietary linker systems to deliver tumor cell-killing agents in a targeted way. The linkers are stable in the bloodstream and do not release their payloads until they are inside the disease cells, thus sparing healthy tissue.

Goff said Genentech seemed an ideal candidate for PR1, "especially with the success they've had in oncology in the past year." PDL earns royalties from Genentech's blockbusters Avastin (bevacizumab) for colorectal cancer and Herceptin (trastuzumab) for breast cancer.

The takeover of Eos added two compounds to PDL's pipeline. One is Eos200-4, a chimeric antibody targeting the alpha5beta1 integrin, at the Phase I stage for solid tumors. The other is Eos200-F, the antigen-binding fragment of Eos200-4, which the firm had in preclinical development for ocular indications including age-related macular degeneration. (See BioWorld Today, Feb. 6, 2005.)

If the pipeline wasn't enough to make the complexities of developing a conjugated antibody daunting for PDL, Goff said, "now we have ESP," referring to PDL's buyout of hospital-focused ESP Pharma Inc., of Edison, N.J., for $325 million in cash and about $175 million in stock, made public earlier this year. The deal included a sales team and a basket of marketed products including the clot-buster Retavase (reteplase). (See BioWorld Today, Jan. 26, 2005.)

PDL also has a co-development deal with F. Hoffmann-La Roche Inc., of Nutley, N.J., for Zenapax (daclizumab). In September, about a year after regaining from Roche rights to the drug in all indications except transplant rejection, PDL entered a potential $205 million agreement for Roche to help develop and sell the Phase II compound for asthma and related respiratory diseases. Roche already markets the humanized antibody, which targets the interleukin-2 receptor on activated T cells, for kidney transplant rejection. (See BioWorld Today, Sept. 24, 2004.)

PDL's stock (NASDAQ:PDLI) closed Wednesday at $20.32, up 34 cents. Genentech's shares (NYSE:DNA) ended the day at $80.73, down 85 cents.

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