FDA knocks back anticancer drug Marqibo

Inex Pharmaceuticals announced today that United States Food and Drug Administration (FDA) provided an action letter detailing that the anticancer drug Marqibo (vincristine sulfate liposomes injection) is "not approvable" under the FDA's accelerated approval regulations based on the phase 2 clinical trial data submitted.

INEX said the FDA "not approvable" decision was expected after the FDA's Oncologic Drugs Advisory Committee (ODAC) voted December 1, 2004 against recommending accelerated approval for Marqibo as a treatment for patients with relapsed aggressive non-Hodgkin's lymphoma (NHL) based on the phase 2 clinical trial data and comparison to available therapy.

The action letter from the FDA provided a list of deficiencies that need to be addressed prior to re-applying for approval. It also encouraged a meeting with the FDA to discuss trial designs that would be suitable for re-applying for approval. The FDA recommended such additional studies be randomized controlled studies comparing Marqibo to other chemotherapy regimens.

In addition to comments on the clinical section of the New Drug Application (NDA), the FDA also listed some deficiencies in the chemistry, manufacturing and controls section that related primarily to the packaging, labeling and product specifications. INEX believes these deficiencies are straightforward to address. There were no deficiencies mentioned for the nonclinical section of the NDA.

David Main, INEX's President and CEO, said, "The FDA action letter is consistent with our expectations after the December 1, 2004 ODAC meeting. We will work with our North American development partner Enzon Pharmaceuticals, the FDA and medical experts to evaluate a clinical program that we believe will be suitable to support approval. We are pleased that the other two sections of the NDA, the manufacturing and nonclinical sections, are essentially complete."

Marqibo is a proprietary drug comprised of the widely used off-patent anticancer drug vincristine encapsulated in INEX's sphingosomal drug delivery technology. INEX's technology is designed to provide prolonged blood circulation, tumor accumulation and extended drug release at the cancer site. These characteristics are intended to increase the effectiveness and reduce the side effects of the encapsulated drug.

In addition to relapsed aggressive NHL, Marqibo is currently being evaluated in several phase 2 clinical trials as a treatment for first-line NHL (combination therapy), relapsed Hodgkin's disease, relapsed acute lymphoblastic leukemia, relapsed NHL in combination with the approved cancer drug Rituxan (rituximab), relapsed NHL in combination with the approved cancer drug etoposide.