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WASHINGTON D.C. (

TheStreet

) --

Seattle Genetics

(SGEN) - Get Seagen, Inc. Report

brings its "empowered antibody" cancer drug Adcetris in front of an FDA advisory panel today. I'll be following the action and will provide updates here. (Most recent updates will be posted on top.)

5:08 pm ET:

Seattle Genetics reopened for trading a few minutes ago, down about 7-8% to $18.85.

Surprised to see the stock sell off despite two unanimous votes for Adcetris' approval? Don't be. The laws of biotech usually dictate that stocks sell off on highly expected news, and few, if anyone, believed Adcetris was in jeopardy at today's FDA advisory panel.

Potentially adding to the selling pressure is the uncertainty over confirmatory trials for Adcetris, which if not resolved quickly, could delay the drug's approval. (Although, the odds of that are small.) Still, comments from the panel's experts and FDA clearly indicate that Seattle Genetics has a lot of work ahead to reach an agreement on mandatory follow-on studies for Adcetris. The ongoing phase III study is not going to be sufficient.

3:38 pm ET:

The FDA panel voted 10-0 to recommend Adcetris for accelerated approval in ALCL. There was ample discussion and little agreement on proposed designs for a follow-on or confirmatory study.

1 pm ET:

The FDA panel is back from lunch to discuss Adcetris as a treatment for relapsed/refractory anaplastic large cell lymphoma (ALCL).

The application is based on a phase III study which showed that 86% of patients with advanced ALCL responded to treatment with Adcetris. The phase II study enrolled 58 ALCL patients, all of whom had cancer that was no longer responding to currently available therapies.

ALCL is an aggressive type of T-cell non-Hodgkin lymphoma that expresses a protein known as CD30. Between 2,000 and 3,000 patients are diagnosed with ALCL in the U.S. each year, with about half of those treated effectively with first-line chemotherapy.

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The discussion and debate in the afternoon session is likely to follow the same path as this morning. There is little doubt that Adcetris is active against ALCL but the FDA and the panel will once again discuss whether the drug deserves accelerated approval. It's worth noting Seattle Genetics has not yet announced plans for a follow-on or confirmatory study of Adcetris in ALCL.

11:28 am:

The FDA advisory panel voted 10-0 to recommend accelerated approval of Seattle Genetics' drug Adcetris for the treatment of relapsed and refractory Hodgkin's lymphoma.

Accelerated approval requires Seattle Genetics to conduct a post-approval clinical trial to confirm Adcetris' efficacy and safety. Seattle Genetics is already conducting a follow-on study of Adcetris in earlier-stage Hodgkins' lymphoma patients, although discussion at the panel suggests FDA and the panel experts may want changes made to this study or additional studies performed.

Thursday's panel vote is a recommendation but is not binding on the FDA. The agency is is expected to issue a final approval decision on Adcetris on Aug. 30.

9:45 am:

Both Seattle Genetics and FDA have finished their respective presentations for Adcetris in Hodgkin's lymphoma. Experts on the panel are now asking questions.

Nothing at the panel so far suggests that Adcetris won't be approved. In fact, FDA's cancer drug chief Richard Pazdur just said, in response to a question, that "No one doubts that it

Adcetris should be made available to the U.S. population."

The only "controversy" or unresolved issue is whether Adcetris deserves accelerated approval (FDA's view) or regular, full approval (Seattle Genetics' request.)

Either way, Adcetris will be approved and launched commercially. Investors are expecting accelerated approval, which would require Seattle Genetics to complete a

post-approval

, follow-on study to confirm Adcetris' efficacy and safety in Hodgkin's lymphoma. Seattle Genetics is already conducting that confirmatory study.

8: 15 am:

Today's FDA advisory panel is split into morning and afternoon sessions. Up first will be the discussion and review of Adcetris as a treatment for relapsed/refractory Hodgkin's lymphoma. The afternoon session tackles Adcetris in relapsed/refractory anaplastic large cell lymphoma (ALCL).

For review, Adcetris, also known as brentuximab vedotin, is designed using a technology proprietary to Seattle Genetics that delivers a lethal dose of chemotherapy directly to cancer cells while sparing healthy cells from toxic effects. Brentuximab consists of an antibody that attaches itself to a certain receptor found on tumor cells. Once inside the tumor, brentuximab releases a toxic chemotherapy payload.

The pivotal phase study for Adcetris in Hodgkin's lymphoma was designed under a Special Protocol Assessment (SPA) with the FDA. Just over 100 patients with Hodgkin lymphoma were enrolled in the study, all of whom had disease that was no longer responsive to currently approved therapies, including autologous stem cell transplants.

After treatment with Adcetris 75% of the patients demonstrated either a complete or partial response.

About 8,500 patients in the U.S. each year are diagnosed with Hodgkin lymphoma, a cancer that affects white blood cells. Most of these patients are treated successfully with a four-drug chemotherapy cocktail or stem-cell transplants. Seattle Genetics is seeking approval for Adcetris initially in the approximately 30% of patients who do not respond to current therapies or relapse.

Seattle Genetics is developing Adcetris with

Millennium Pharmaceuticals

, the U.S.-based cancer drug arm of Japanese pharmaceutical giant

Takeda

.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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