Seattle Genetics Hits A Key Target

An FDA advisory panel has voted unanimously to recommend Seattle Genetics’ Adcetris for accelerated approval as a treatment for two types of lymphoma in patients who haven’t responded to other therapies. If the agency eventually gives the nod, Adcetris will become Seattle Genetics’ first product and the only approved antibody-drug conjugate (ADC). Last summer, Pfizer withdrew Mylotarg, an ADC for cancer, because of efficacy and safety concerns.

ADCs have long been considered ideal cancer-fighting agents for their potential to deliver a potent cytotoxic payload by linking it to a cancer-targeting carrier. A problem, which plagued Mylotarg but that Seattle Genetics seems to have overcome, is bloodstream-stable linker chemistry. After binding to a CD30-expressing cancer cell, Adcetris, or brentuximab vedotin, is taken into the cell where proteases then cleave the linker and release the cytotoxic agent monomethyl auristatin E. This approach spares healthy cells and reduces toxic side effects.

The panel was impressed with signs from small-scale trials that Adcetris is effective, according to investment analysts who followed the proceedings. Although the advisory panel’s vote isn’t binding, FDA often follows such advice; the agency is expected to make a decision by Aug. 30.

Seattle Genetics had hoped for a full approval of the new ADC. The accelerated approval recommended by the panel requires less clinical data up front but is conditioned on postapproval efficacy and safety studies. FDA doesn’t consider the company’s ongoing Phase III trial as meeting this condition, the analysts report, and it has warned Seattle Genetics to work fast to design a new trial to avoid delays. In the company’s favor, however, is that new trials can likely also be used to expand testing against similar cancers.

“We would assume that at this point Seattle Genetics will do everything to come to agreement with the FDA to ensure approval,” Leerink Swann stock analysts wrote in a report to clients.

Sales of Adcetris are expected to exceed $100 million in its first full year on the market. Seattle Genetics is developing the drug with Millennium, part of Japan’s Takeda Pharmaceutical. In June, European regulators accepted a filing from Takeda, which has marketing rights outside the U.S. and Canada.