Xilio Therapeutics has reported preliminary data from its Phase I clinical trial of XTX101 for the treatment of advanced solid tumours.

XTX101 is an investigational tumour-activated, Fc-enhanced anti-CTLA-4 which depletes regulatory T cells upon activation in the tumour microenvironment.

The study has enrolled 25 patients with various advanced and treatment-refractory solid tumours including non-small cell lung cancer (NSCLC), colorectal cancer and pancreatic cancer.

Additionally, 76% of patients previously received treatment with at least three prior lines of anti-cancer therapy and 44% with at least one immuno-oncology agent.

Out of the total patients, 25 received XTX101 7mg to 180mg once every three weeks (Q3W) and 150mg once every six weeks (Q6W).

Of these subjects, 20 were dosed in Part IA of monotherapy dose-escalation and five patients in Part IB of monotherapy dose-expansion.

The study showed favourable preliminary safety, pharmacokinetic and pharmacodynamic data for XTX101.

Based on the data, a recommended Phase II dose (RP2D) of 150mg Q6W was determined. No dose-limiting toxicities and immune-related endocrine or skin adverse events were observed.

Xilio Therapeutics president and research and development head Martin Huber said: “Following treatment with XTX101 monotherapy at the recommended Phase II dose of 150mg 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-tumour activity occurred in the absence of meaningful observed activation of the immune system in the periphery, suggesting tumour-selective activation of XTX101.

“Based on this Phase I data, we plan to explore opportunities to evaluate XTX101 in combination with an anti-PD-(L)1 in historically immunotherapy-resistant tumour types.”