Xilio Therapeutics announces initiation of Phase 2 trial for efarindodekin alfa

Xilio Therapeutics (XLO) announced the initiation of patient dosing in Phase 2 of an ongoing Phase 1/2 clinical trial evaluating efarindodekin alfa, a tumor-activated IL-12, as a monotherapy in patients with certain advanced solid tumors. In addition, Xilio announced the achievement of a $17.5M development milestone under Xilio’s license agreement with Gilead Sciences (GILD)and updated data from the ongoing Phase 1 trial for efarindodekin alfa. Efarindodekin alfa is an investigational tumor-activated IL-12 designed to potently stimulate anti-tumor immunity and reprogram the tumor microenvironment of poorly immunogenic “cold” tumors towards an inflamed or “hot” state. In March 2024, Xilio entered into an exclusive license agreement with Gilead related to Xilio’s tumor-activated IL-12 program, including efarindodekin alfa. Xilio is evaluating efarindodekin alfa as a monotherapy in an ongoing Phase 1/2 clinical trial in patients with advanced solid tumors. As of a data cutoff date of September 2, 2025, at dose levels up to the recommended Phase 2 dose efarindodekin alfa has been generally well-tolerated in Phase 1, and the majority of treatment-related adverse events were Grade 1 or 2. In Phase 1, as of the data cutoff date, efarindodekin alfa has also demonstrated encouraging anti-tumor activity, including two partial responses in patients with advanced solid tumors, as well as sustained interferon gamma ignaling without evidence of tachyphylaxis throughout treatment cycles. Based on these Phase 1 data, Xilio recently selected an initial RP2D and schedule for efarindodekin alfa and initiated patient dosing in the Phase 2 portion of the trial evaluating efarindodekin alfa as a monotherapy in patients with certain advanced solid tumors. In connection with the initiation of Phase 2, Xilio achieved a development milestone of $17.5M. Xilio recently completed enrollment in Phase 1A monotherapy dose escalation and evaluation of those patients is ongoing. In addition, Xilio continues to enroll patients in the Phase 1B monotherapy dose expansion portion of the ongoing Phase 1/2 clinical trial of efarindodekin alfa. Efarindodekin alfa has not been approved by any regulatory agency and its efficacy and safety have not been established.