Merck KGaA suspends Stimuvax cancer vaccine trials

FRANKFURT, Germany — German drugmaker Merck KGaA  put on hold all testing on humans of its experimental cancer vaccine Stimuvax after a Phase II trial participant contracted encephalitis.

The patient was taking part in a trial arm whose participants received Stimuvax in combination with the chemotherapeutic agent cyclophosphamide, which is not used in the other Stimuvax studies, Merck said March 23.

Germany's Merck is racing with biotech firms including Transgene, Dendreon Corp. and Antigenics to bring cancer vaccines to market.

Merck has been testing Stimuvax, based on an active ingredient known as LBLP25, in the second of three phases required for regulatory approval as a treatment against multiple myeloma.

It has also started Phase III trials of the drug, which it is co-developing with Oncothyreon Inc., as a treatment against lung cancer and breast cancer.

The U.S. Food and Drug Administration also put a clinical hold on Stimuvax.

"We understand that Merck Serono is working closely with the FDA, other regulatory agencies and the patient's physicians to evaluate the implications of this adverse reaction and to determine an appropriate course of action," Oncothyreon CEO Robert Kirkman said.

Merck, unrelated to the American drugmaker of the same name, noted that other Stimuvax studies are not used with the same intensity of cyclophosphamide.

It said the move was a "precautionary" one while it studies the "adverse event."

Though the affected patient was using the vaccine because of multiple myeloma, Merck said late-stage trials for non-small cell lung cancer and breast cancer also are affected.