Dr. Michael Sabel of the University of Michigan critiqued the Lymphoseek clinical trials during a session at the American Society of Clinical Oncology (ASCO) annual meeting last week. He called Lymphoseek a "good first step" but raised questions about the use of vital blue dye as the comparator in the two phase III studies, noting that the standard of care in lymph node mapping is vital blue dye plus a sulfur colloid agent.
Neoprobe's Pykett says Shkreli and other critics are making a fundamental mistake because the company is not seeking Lymphoseek approval (at least initially) for sentinel lymph node biopsy -- a procedure in which doctors map the lymphatic system to find the first lymph node closest to the primary tumor. Finding the sentinel node is important because it's the point at which cancer spreads, or metastasizes, throughout the body.
"Sentinel lymph node biopsy has a specific meaning and requires a higher burden of proof," says Pykett. Neoprobe is conducting a third phase III study in head and neck cancer patients which compares Lymphoseek to regional nodal dissection, a current standard of care in that type of cancer. If the study is positive, Neoprobe will seek expanded approval for Lymphoseek for the detection of sentinel lymph nodes.
Pykett says the decision to move ahead with Lymphoseek's initial approval filing based on studies comparing Lymphoseek to vital blue dye alone came after "at length" discussions with FDA in which the agency made a clear distinction between a lymph node mapping indication similar to vital blue dye and sentinel lymph node detection."I think the FDA will appreciate that the two are the same," responds Shkreli. "Neoprobe is trying to make the distinction that anatomic delineation of the lymphatic system doesn't imply that they're selecting the sentinel node. However, the only reason blue dye is used is to identify the sentinel node. So in essence, they're trying to piggyback on something that needs to be clinically validated, which the regulators won't like." --Written by Adam Feuerstein in Boston.
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