GlaxoSmithKline has suffered a setback after announcing more disappointing late-stage data from a non-small cell lung trial of its cancer vaccine MAGE-A3.

The UK major says that its MAGE-A3 antigen-specific cancer immunotherapeutic did not meet its first or second co-primary endpoint in a Phase III NSCLC trial. The study did not significantly extend disease-free survival when compared to placebo in the overall MAGE-A3 positive patients or patients who did not receive chemotherapy.

The MAGRIT trial enrolled 2,312 MAGE-A3-positive patients across more than 400 sites in 34 countries. Patients were given up to 13 intramuscular injections of either the immunotherapeutic or placebo over a period of 27 months.

The news follows a failure in a Phase III melanoma trial for the cancer vaccine last September but it appears that GSK is not giving up just yet. Regarding the MAGRIT study, it will continue in order to assess the third co-primary endpoint designed to identify a subset of MAGE-A3 positive patients that may benefit from the treatment.

GSK added that the independent data monitoring committee for the MAGRIT study indicated that "a review of the safety information raised no specific concern for the continuation of the trial". Results from a final analysis are expected in 2015.

However, many observers feel the end is nigh. Panmure Gordon analyst Savvas Neophytou said that after the melanoma disappointment "we had written the product off so we make no changes to forecasts at this stage. With a further read-out pending we are not pinning much hope on the product". More positively, Citi analyst Andrew Baum issued a note estimating a 10% probability that MAGE-A3 will significantly benefit the aforementioned sub-population so it could have sales of £216 million in 2022.

The news is likely to have a major effect on the share price of GSK's partner Agenus as the latter's QS-21 Stimulon adjuvant is used to boost MAGE-A3.