New drug for rare leukemia wins FDA panel vote with limited data

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Talon Therapeutics ($TLON) took one more tentative step closer to a possible FDA approval of its cancer drug Marqibo yesterday, coming out ahead in a 7-to-4 vote among a group of the agency's oncology advisers. That's hardly a winning endorsement. But as analysts scratch their heads over the drug's chances at the agency, it's a definite advantage for a biotech looking to hammer home an approval with a thin set of clinical data.

Talon took Marqibo--vincristine sulfate liposomal injection--to the FDA with data showing that 20% of the 65 acute lymphoblastic leukemia patients in a single-arm study experienced a complete or near-complete response with a median duration of 5.4 months and overall survival of 7.7 months. These patients--who suffered from a rare type of ALL--were all very sick, had failed multiple therapies and could expect only a very limited amount of time left to live. But the mid-stage study offered no control-arm comparison, which by itself could raise enough skepticism to trigger a rejection.

San Mateo, CA-based Talon, though, was able to win over a majority of the experts with the prospect of a final option for patients who had none left to them, with some advisers offering the hope that a small group of patients could be stabilized to the point that they could receive a stem cell transplant. The FDA will now have to consider whether they agree with that assessment, giving Talon a chance to wrap an ongoing study that has set out to offer confirmation of the patient benefit.

As MedPage Today notes in one of the best summaries of the vote yesterday, a majority of the patients taking the drug experienced severe side effects, though that could be linked to earlier therapies.

"We are very pleased the majority of the ODAC members agree that Marqibo offers a meaningful benefit/risk ratio for a very rare patient population that has a grave prognosis and no current standard of treatment," said Talon CEO Steven R. Deitcher, M.D. "Based on prior FDA discussions, we have received Special Protocol Assessment agreement for a large, randomized Phase III trial in front-line adult elderly ALL with sites currently open for enrollment. We look forward to working closely with the FDA in the coming weeks to address any remaining questions they may have."

- get the press release
- here's the story from MedPage Today