Patient recruitment can restart in two trials of AstraZeneca's PD-L1 inhibitor durvalumab placed under temporary suspension by the FDA, says the company.
The US regulator placed a partial clinical hold on the trials - in patients with head and neck squamous cell carcinoma - last month after bleeding side effects were reported in patients taking durvalumab either alone or in combination with AZ's CTLA4 inhibitor tremelimumab.
"The phase III KESTREL trial has already re-opened for new patient enrolment at some clinical study sites and the EAGLE trial is expected to resume recruitment shortly," said AZ in a statement, adding that no amendment has been required to the protocol of either study.
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.
The company said it will "progressively resume enrolment for all HNSCC trials across the participating sites in the US and globally, subject to national health authority and ethics committee approval where required".
Haemorrhaging is not uncommon in patients with head and neck cancers, in part because of the proximity of these tumours to major blood vessels, and it now appears that durvalumab is not thought to have played a direct role in the bleeds.
The relaxation of the clinical hold is a massive relief for AZ, as durvalumab is considered one of the company's key pipeline projects, with analysts at Credit Suisse predicting sales could reach $1.8bn by 2019 with around $400m of that total coming from HNSCC and a sizeable proportion expected to come from combination use with tremelimumab.
Those figures are healthy but well shy of the expectations for two PD-1 inhibitors - Bristol-Myers Squibb's Opdivo (nivolumab) and Merck & Co's Keytruda (pembrolizumab) - and Roche's PD-L1 inhibitor Tecentriq (atezolizumab) which are already on the market.