The FDA is seeking more information on Spectrum Pharmaceuticals' cancer drug Zevalin. And that news cut into the company's share price, which dropped 15 percent. Spectrum swiftly countered by announcing that it will respond to the FDA's complete response letter by Wednesday, but added that the agency's request will delay any approval by two months. Zevalin was originally approved in 2001" but never lived up to expectations. Spectrum is now seeking approval to use the therapy as a first-line treatment for patients with non-Hodgkin's lymphoma. "This is clearly not the result we were looking for, but we're still very confident about [Zevalin's] approval," Spectrum spokesman Paul Arndt told TheStreet Sunday night. Report