AstraZeneca's shares plunge 16 percent on failure of Imfinzi, tremelimumab in key lung cancer study

Shares in AstraZeneca fell as much as 16 percent Thursday after the company announced initial results from the Phase III MYSTIC study, with the combination of Imfinzi (durvalumab) and tremelimumab failing to improve progression-free survival (PFS) versus platinum-based standard-of-care chemotherapy in previously-untreated patients with metastatic first-line non-small-cell lung cancer (NSCLC).

Sean Bohen, chief medical officer at AstraZeneca, said "while the results...are disappointing, the trial was designed to assess overall survival and we look forward to evaluating the remaining primary endpoints of overall survival for both mono- and combination therapy." The drugmaker indicated that final overall survival data are expected during the first half of 2018.

The study evaluated treatment with the PD-L1 inhibitor Imfinzi alone, or a combination of the drug with the CTLA-4 inhibitor tremelimumab, versus standard-of-care chemotherapy in patients with EGFR and ALK wild-type locally-advanced or metastatic first-line NSCLC. AstraZeneca noted the primary endpoint of PFS for the combination of Imfinzi and tremelimumab was in patients whose tumours express PD-L1 on 25 percent or more of their cancer cells.

The company added that although not formally tested in the trial, Imfinzi monotherapy would not have met a pre-specified threshold of PFS benefit over chemotherapy in this disease setting.

Commenting on the results, CEO Pascal Soriot said "not everything has gone the way we'd like it to go," adding "despite the outcome of the initial readout, we must be patient as the MYSTIC trial continues as planned to evaluate overall survival." For further analysis, read ViewPoints: More uncertainty at AstraZeneca as initial MYSTIC data falls short.

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Imfinzi was recently awarded accelerated approval from the FDA in previously-treated patients with locally advanced or metastatic urothelial carcinoma. Meanwhile, in May, the drugmaker announced that the Phase III PACIFIC study of Imfinzi as sequential treatment in patients with locally-advanced, unresectable NSCLC who had not progressed following standard platinum-based chemotherapy concurrent with radiation therapy met one of its primary endpoints, significantly improving PFS versus placebo.

Separately on Thursday, AstraZeneca reported that second-quarter sales declined 10 percent year-over-year to $5.1 billion, hit by patent expiries on Crestor and Seroquel XR, while profit in the three-month period reached $477 million. The company also unveiled a deal with Merck & Co. potentially worth up to $8.5 billion to co-develop and co-commercialise the UK drugmaker's PARP inhibitor Lynparza (olaparib) for multiple cancer types, including breast, prostate and pancreatic cancers.

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