Neither Idec Pharmaceuticals Corp.'s Zevalin ibritumomab for non-Hodgkin's lymphoma nor Matrix Pharmaceutical Inc.'s IntraDose for head and neck cancer showed statistically significant improvements in patient benefit in Phase III trials, while both had positive tumor response data. Yet the FDA's Oncologic Drugs Advisory Committee last week recommended approval of Zevalin and recommended against approval of IntraDose.

The key was the panel's belief that the tumor responses in IDPH's case ultimately would confer clinical benefit, and their skepticism about whether tumor responses in MATX's trials would do so.

ODAC voted to recommend against conventional approval of IntraDose as well as to recommend against conventional approval of Zevalin in NHL patients who have not failed Rituxan rituximab, an anti-CD20 antibody marketed for NHL by IDPH and partner Genentech Inc. (DNA, South San Francisco, Calif.).

The panel's decisions diverged on the question of recommending accelerated approval of each product. Thus in Zevalin's case, the committee did vote 15-0 to recommend approval of Zevalin to treat follicular B cell NHL that is refractory to either chemotherapy or to Rituxan - a patient group with extremely limited treatment options.

Accelerated approval may be granted when a therapeutic appears to provide benefit over available therapies on the basis of a surrogate endpoint that is reasonably likely to predict clinical benefit (see "Understanding Accelerated Approval," A9).

Accelerating Zevalin

Although ODAC voted 6-10 against recommending conventional approval of Zevalin in patients who have not failed Rituxan, the panel still was convinced that Zevalin is likely to confer a clinical benefit. Armed with the knowledge that accelerated approval would mandate a validating Phase IV clinical study, the members voted 13-2 with one abstention to recommend accelerated approval of the radiolabeled antibody against CD20 in NHL patients who have not failed Rituxan (see BioCentury Extra, Tuesday Sept. 11).