AstraZeneca's immuno-oncology ambitions have hit a hurdle after its tremelimumab candidate failed to show activity in a trial involving patients with a rare form of cancer.
The CTLA-4 inhibitor failed to show activity against mesothelioma - a form of cancer affecting the lungs or abdomen linked to exposure to hazardous materials such as asbestos - in a phase IIb trial involving 571 patients.
The disappointment comes just weeks after AZ reported that tremelimumab given alongside PD-L1 inhibitor durvalumab achieved impressive results in a non-small cell lung cancer (NSCLC) trial, and the company was quick to stress that the drug "remains a key component of immuno-oncology combination strategy".
Nevertheless, the disappointing results in a trial that had been predicted to support registration of the drug is a setback for AZ as it tries to close the gap behind the leaders in the immuno-oncology category, Bristol-Myers Squibb (BMS) and Merck & Co.
Durvalumab also hit a couple of hurdles last year, including a failed study as a monotherapy in NSCLC and the suspension of two trials in combination with AZ's recently approved Tagrisso (osimertinib) on safety concerns.
Tremelimumab was being tested as a 10mg/kg monotherapy in the DETERMINE study, which involved mesothelioma patients who had already been treated with other drugs and were not candidates for surgery.
The company did not provide any data from the trial, just noting that its drug did not have a significant impact on overall survival, the primary outcome measure. The FDA had previously awarded breakthrough status to tremelimumab as a mesothelioma therapy, recognising that there are few effective treatment options for this aggressive form of cancer.
Tremelimumab works in a similar way to BMS' already-approved Yervoy (ipilimumab) drug, which is used alongside the company's PD-1 inhibitor Opdivo (nivolumab) as a treatment for melanoma. Yervoy brought in $1.13bn in sales last year while Opdivo added $942m to BMS' top-line.
"We are disappointed that tremelimumab monotherapy did not demonstrate a survival benefit in this patient population with no approved medicines beyond first-line treatment", AZ's head of immuno-oncology Robert Iannone.
"However, we remain confident in tremelimumab's clinical activity in combination", he added.