GSK's move comes less than two weeks after MAGE-A3 failed in the overall trial, which tested the drug for non-small cell lung cancer.
GSK will continue to research the benefits of MAGE-A3 for melanoma in sub-populations after the drug failed in an overall study of subjects with this type of cancer.
MAGE-A3 was designed to help the immune systems of cancer patients prevent the return of the disease after surgery.
GSK's stock is -0.5%.
Shares in Agenus (AGEN), whose QS-21 Stimulon adjuvant, or booster, is used in MAGE-A3, are -9.4%. (PR)