Shares of Agenus tumbled more than 13 percent Thursday before markets opened and after the biopharmaceutical released more ineffective study results from its collaboration with GlaxoSmithKline.
The company said a potential lung cancer treatment that included Agenus' SQ-21 Stimulon vaccine adjuvant did not significantly extend the disease-free survival period when compared with patients taking a placebo or fake drug.
The Agenus product is extracted from the bark of an evergreen tree and is being studied as a component in a variety of cancer treatments. GlaxoSmithKline PLC is studying an immune therapy that targets MAGE-A3, an antigen found in cancers including melanoma, non-small cell lung cancer, head and neck cancer, and bladder cancer.
Glaxo plans to continue studying the possible treatment to determine if patients with a particular genetic signature would benefit from it. Results from that analysis are expected next year.
Glaxo had announced in September that the treatment did not lead to greater disease-free survival in melanoma patients when compared to a placebo in a mid-stage study.
Shares of Agenus Inc., based in Lexington, Mass., fell 55 cents to $3.75 more than an hour before markets opened. U.S.-traded shares of GlaxoSmithKline dropped 2 percent, or $1.12, to $53.59.