UPDATED: In a setback, AstraZeneca's immunotherapy tremelimumab flunks mesothelioma test

AstraZeneca's Robert Iannone

Just weeks after AstraZeneca ($AZN) reported a success for a combination study of durvalumab and tremelimumab, the pharma giant has been forced to concede that the CTLA-4 drug tremelimumab flunked a solo challenge for mesothelioma.

AstraZeneca's big MedImmune subsidiary recruited 571 patients for its Phase IIb registrational challenge on mesothelioma. But the drug failed to hit its primary endpoint on overall survival. The statement cited only top-line data, with no specifics on just how badly the drug did in the study.

The pharma giant announced plans to beef up its mid-stage program for tremelimumab into a registration study--aiming for marketing approval--during the 2014 ASCO meeting in Chicago. AstraZeneca's shares were down 2% in early trading Monday. 

Tremelimumab has been one of AstraZeneca's top drug prospects and is a leading example of the kind of cancer programs the pharma giant hopes to use to generate billions of dollars in new sales. A setback here will raise fresh questions for AstraZeneca as it attempts to play catch-up to the market leaders in checkpoint inhibitors. Durvalumab is now a distant fourth in the market, likely to follow Roche's ($RHHBY) atezolizumab and well behind Merck ($MRK) and Bristol-Myers Squibb ($BMY), the market leader.

The focus at AstraZeneca will now likely shift back to combo studies including this drug. In early February, investigators reported that a combo using tremelimumab and durvalumab registered a 23% tumor response rate in a small proof-of-concept study. AstraZeneca is now pursuing combo studies for non-small cell lung cancer (NSCLC), squamous cell carcinoma of the head and neck, bladder, pancreatic, gastric and liver cancers.

"We are disappointed that tremelimumab monotherapy did not demonstrate a survival benefit in this patient population with no approved medicines beyond first-line treatment," said Robert Iannone, AstraZeneca's head of immuno-oncology. "However, we remain confident in tremelimumab's clinical activity in combination, as shown in our recently published Study 006 trial of tremelimumab and durvalumab in non-small cell lung cancer."

- here's the statement

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