Shkreli openly disclosed his short position in Neoprobe as part of his citizen petition -- a gesture of full disclosure that isn't required and is therefore often lacking from other FDA citizen petitioners, adds Safir.

"We do believe the rationale behind the filing is incorrect," says Neoprobe president Mark Pykett, who adds the company isn't disputing Shkreli's right to file a citizen petition against Lymphoseek.

Neoprobe also believes FDA will approve Lymphoseek as a new lymph node detection agent based on efficacy and safety data from two phase III trials that compared Lymphoseek to vital blue dye, the only such agent currently approved by the FDA.

These two studies meet FDA's regulatory standard that will enable the agency to approve Lymphoseek with a label that indicates the agent's use for the "anatomic delineation of the lymphatic system" in patients with melanoma and breast cancer, says Pykett. This is the same FDA-approved indication for vital blue dye, which is why Neoprobe designed its registration studies using blue dye as the comparator.

Neoprobe expects to file Lymphoseek with the FDA in the third quarter.

Neoprobe critics claim FDA won't approve Lymphoseek based on these clinical studies because doctors use a combination of vital blue dye and a sulfur colloid agent to map out the lymph node system of cancer patients, even though sulfur colloids are not FDA approved for this use. In other words, Neoprobe didn't compare Lymphoseek to the current standard of care for lymph-node mapping, therefore FDA will find the clinical data lacking.

"The FDA has long held the standard of 'best current care' as a control group," writes Shkreli in his citizen petition. "This policy secures the agency's public health mandate by assuring newly approved drugs and diagnostics are attractive treatment options…License status of control group is not relevant to FDA. There are many examples where the FDA has requested control groups with off-label or non-approved agents. A 'physician's choice' control group for a sentinel lymph node biopsy study would likely result in the majority of investigators using a combination of radioactive colloid and blue dye. The FDA should not allow Lymphoseek be compared to a marginalized regimen."

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