Xilio Therapeutics Announces Preliminary Clinical Data from Phase 1 Trial of XTX101, a Tumor-Activated, Fc-Enhanced Anti-CTLA-4, in Patients with Advanced Solid Tumors

Xilio Therapeutics, Inc. (Nasdaq: XLO), a clinical-stage biotechnology company discovering and developing tumor-activated immuno-oncology therapies for people living with cancer, today announced preliminary data from its Phase 1 clinical trial evaluating XTX101, an investigational tumor-activated, Fc-enhanced anti-CTLA-4, in patients with advanced solid tumors.

“We are encouraged by the preliminary data from the Phase 1 trial for XTX101 showing evidence of tumor-selective activation,” said Martin Huber, M.D., president and head of research and development at Xilio. “Following treatment with XTX101 monotherapy at the recommended Phase 2 dose of 150 mg once every six weeks, we observed a partial response in a patient with PD-L1 negative advanced non-small cell lung cancer. Importantly, this anti-tumor activity occurred in the absence of meaningful observed activation of the immune system in the periphery, suggesting tumor-selective activation of XTX101. Based on these Phase 1 data, we plan to explore opportunities to evaluate XTX101 in combination with an anti-PD-(L)1 in historically immunotherapy-resistant tumor types.”

Data from the Ongoing Phase 1 Clinical Trial for XTX101

As of a data cutoff date of May 2, 2023, 25 patients had been treated with XTX101, including dose levels ranging from 7 mg to 180 mg administered once every three weeks (Q3W) and one dose level at 150 mg administered once every six weeks (Q6W). Of these patients, 20 patients were dosed in monotherapy dose-escalation (Part 1A) and five patients were dosed in monotherapy dose-expansion (Part 1B).

Patients had a wide range of advanced and treatment-refractory solid tumors, including colorectal cancer (CRC), non-small cell lung cancer (NSCLC) and pancreatic cancer. In addition, 76% of patients had been previously treated with at least three prior lines of anti-cancer therapy, and 44% had been previously treated with at least one immuno-oncology (I-O) agent. As of the data cutoff date, three patients were continuing on treatment with XTX101, and 22 patients had discontinued treatment with XTX101.

Preliminary Safety Data

A recommended Phase 2 dose (RP2D) and schedule of 150 mg Q6W was determined based on the favorable preliminary safety, pharmacokinetic (PK) and pharmacodynamic (PD) data for XTX101. At the…