AstraZeneca (AZ) shares started to slip yesterday after the company confirmed the US FDA has placed a partial clinical hold on a trial of its lead immuno-oncology candidate durvalumab.
The partial hold - which means the trials are closed to new recruitment but will continue with the existing patients - applies to trials of the drug both alone and in combination with AZ's tremelimumab in head and neck squamous cell carcinoma (HNSCC).
It has been prompted by bleeding side effects "that were observed as part of routine safety monitoring of the phase III KESTREL and EAGLE trials," said AZ in a statement, adding that it submitted an analysis of the events to the FDA and will try to resume patient recruitment "as soon as possible".
The drugmaker says that bleeding complications are known to be features of head and neck cancers "due to the nature of the underlying disease, the proximity of tumours to major blood vessels and use of prior cancer therapies, which may involve surgery and radiation".
KESTREL is comparing durvalumab and tremelimumab in combination or durvalumab monotherapy to Eli Lilly's Erbitux (cetuximab) plus chemotherapy, while EAGLE is comparing the same two AZ regimens with the standard of care selected by the physician.
AZ's shares fell almost 4% as news of the enrolment suspension broke late in the day yesterday and continued on the downward path this morning as investors tried to work out the significance of the announcement.
The decline reflects the importance attached to durvalumab, a PD-L1 inhibitor that AZ is hoping will join two PD-1 inhibitors - Bristol-Myers Squibb's Opdivo (nivolumab) and Merck & Co's Keytruda (pembrolizumab) - and Roche's PD-L1 inhibitor Tecentriq (atezolizumab) that are already on the market.
Along with CTLA4 inhibitor tremelimumab, durvalumab is a key component of AZ's aspirations in immuno-oncology, an emerging cancer treatment category expected to be worth tens of billions of dollars a year in the future.