Amgen Inc's Kyprolis drug failed to extend survival compared to standard care in a trial involving patients with advanced multiple myeloma, a type of blood cancer that develops in the bone marrow.
Shares of Amgen were down 2.1 percent at $124.65 in after-hours trading on Wednesday.
"The negative results commercialization of this drug in earlier lines of myeloma, as well as other indications raise questions about the future development and ," Sanford Bernstein analyst Geoffrey Porges said in a research note.
He also said the findings "place Kyprolis at a significant regulatory and competitive disadvantage" to Pomalyst, a multiple myeloma drug sold by Celgene Corp.
Amgen said the 315-patient, phase III trial also showed an increase in bad kidney events for patients given Kyprolis when compared to the control group and to the risks described on the drug's current label.
The trial, known as FOCUS, included patients whose multiple myeloma had relapsed and worsened despite at least three prior therapies.
RBC Capital Markets analyst Michael Yee said failure of the trial "was widely expected," given that patients in the control arm could eventually be treated with Kyprolis if their disease got worse.
He also said the incidence of kidney-related side effects is "not a big concern" since the trial enrolled only very sick patients.
Kyprolis, acquired by Amgen in its $10 billion takeover of Onyx Pharmaceuticals, was approved in the United States for treating advanced multiple myeloma based on data showing that patients responded to the drug.
FOCUS was intended to show that the drug helped patients live longer, something that European regulators generally require before approving a drug.
Amgen said in a statement that it believes positive results announced earlier this month from a separate study of Kyprolis in patients with earlier-stage disease "will be sufficient to support regulatory submissions around the world."
Separately, the Thousand Oaks, California, company said it would recall nine lots of syringes pre-filled with anemia drug Aranesp in several countries outside of the United States after finding particulate matter in a small number of syringes during a routine quality examination.
(Reporting by Deena Beasley; Editing by Paul Simao, Bernard Orr)