By Mary Welch

Medarex Inc. will proceed with plans for Phase III trials of MDX-210, its anti-HER-2 cancer product, as well as seek a new licensing partner now that Novartis AG has dropped out of the collaboration for the drug¿s development.

Medarex, of Annandale, N.J., reacquired the worldwide rights to MDX-210, a bispecific antibody. Those rights were part of a deal originally signed with Ciba-Geigy Ltd. (which later merged with fellow Basel, Switzerland, drug giant Sandoz Ltd. to form Novartis).

Medarex did not have to compensate Novartis for the reacquisition.

MDX-210 consists of fragments of two monoclonal antibodies linked together. It is designed to induce tumor death by simultaneously binding to the protein HER-2 on the surface of cancer cells and to a receptor on immune system killer cells, such as monocytes and other white blood cells. HER-2 is overexpressed in many cancers.

In Phase II trials of MDX-210 in hormone-refractory prostate cancer patients, 89 percent of patients experienced a reduction in the rate of increase of prostate specific antigen levels, and 65 percent experienced a reduction in PSA levels. PSA is a biochemical marker associated with disease progression and death. In some patients, PSA levels were reduced for more than 250 days, and more than a quarter of the patients reported a significant reduction in average pain levels following treatment.

¿They decided not to proceed,¿ said Donald Drakeman, president and CEO of Medarex. ¿They had other things to do.¿

The collaboration goes back to 1995, when Medarex and Ciba-Geigy entered into a deal worth potentially $39 million, including a $4 million up-front equity investment. Had Novartis opted to proceed, Medarex would have received milestones and a second equity purchase of $4 million following the Phase II trials. (See BioWorld Today, May 18, 1995, p. 1.)

Medarex is ¿pushing toward Phase III trials on our own while in discussions with potential partners,¿ Drakeman said. ¿We have promising Phase II results in prostate cancer, and several potential corporate partners have approached us.¿

Novartis and Medarex will continue their other partnership deal, signed in November, wherein Novartis will pay more than $50 million, plus royalties, to use Medarex¿s HuMAb-Mouse technology to produce high-affinity, fully human antibodies for an unlimited number of targets over a decade. (See BioWorld Today, Nov. 19, 1998, p. 1.)

Medarex¿s stock (NASDAQ:MEDX) closed Friday at $3.375, down 3 cents. n