Alpine Immune Sciences, Seattle-based biotech, announced this week that it would be voluntarily stopping the enrollment in two clinical trials studying a CD28 costimulator, following a second patient death.

The drug in question is davoceticept, an investigational dual checkpoint inhibitor, and CD28 conditional costimulator. Alpine had mostly shared promising results, with phase 1 studies showing that the drug had encouraging results, especially in renal cell carcinoma. The two trials paused, NEON-1 and NEON-2, studied davoceticept in combination with Merck’s Keytruda.

According to the recent announcement, the second patient death occurred in the NEON-2 study, attributed to cariogenic shock. The participant had metastatic colorectal cancer and had been previously treated with multiple systemic chemotherapies. The first patient’s death in the trial was attributed to cariogenic shock as well.

Alpine first came onto the scene in 2015, receiving $48 million in series A financing. The biotech’s proprietary platforms consist of unique protein engineering strategies, including the directed evolution of immune proteins into multi-targeted therapeutics.

According to Alpine, the company’s primary focus will now be the development of its dual B cell cytokine antagonist, ALPN-303, against multiple autoimmune and inflammatory diseases.