Shares in AstraZeneca have slipped this morning on the news that the firm has withdrawn regulatory submissions for its investigational cancer drug Zactima.

Specifically, the Anglo-Swedish drugmaker has pulled filings with the US Food and Drug Administration and the European Medicines Agency for the use of Zactima (vandetanib) 100mg in combination with chemotherapy in patients with advanced non-small cell lung cancer. The applications were made in June 2009.

The company said that decision to withdraw these submissions was based on an updated analysis that demonstrated no overall survival advantage when vandetanib was added to chemotherapy. AstraZeneca added that it had also received “preliminary feedback from regulatory agencies that the current package with progression-free survival as the primary endpoint may not be sufficient for approval”.

The news is a blow for AstraZeneca, and some analysts believe the drug could be a blockbuster, but the firm insists that Phase III results have demonstrated that Zactima is clinically active when used in combination with chemotherapy. The company will complete an ongoing late-stage clinical programme “which will give a more complete view of vandetanib efficacy in different clinical settings”.

Two studies looking at Zactima as a monotherapy (the first in patients with advanced NSCLC who have previously received an epidermal growth factor receptor inhibitor and the second in advanced medullary thyroid cancer) are expected in late 2009 or early 2010.

Investors are concerned, however, and at 1pm (UK time), AstraZeneca’s shares were down 1.2% to £27.96.