Xilio Therapeutics dosed the first patient in the Phase 1/2 trial of XTX501 for metastatic NSCLC

CAR-T Digest - August 2020

26 October 2026: Xilio Therapeutics dosed the first patient in the Phase 1/2 trial of XTX501 for metastatic NSCLC

Xilio Therapeutics has dosed the first patient in a phase 1/2 clinical trial of XTX501, an investigational PD-1/masked IL-2 bispecific antibody fusion protein, in patients with metastatic non-small cell lung cancer previously treated with anti-PD-(L)1 therapy. The trial also includes selected patients with other advanced solid tumors

The first-in-human trial will initially assess safety and tolerability of XTX501 as monotherapy in a multicenter, open-label study. Xilio expects to report initial phase 1 data in metastatic NSCLC in Q4 2027
The program targets an important unmet need in patients whose cancers have progressed after checkpoint inhibitor treatment, where restoring or enhancing antitumor immune activity remains a key therapeutic challenge
XTX501 combines PD-1 pathway inhibition with a masked, high-potency, alpha-optimized IL-2 variant. Its PD-1-binding component is designed to direct IL-2 activity toward PD-1-positive, antigen-experienced T cells, while Xilio’s proprietary masking technology aims to limit peripheral immune activation and improve tolerability compared with non-masked IL-2 therapies
Strategically, XTX501 expands Xilio’s masked immuno-oncology pipeline with a dual-mechanism approach intended to combine checkpoint blockade and T-cell stimulation in one molecule. If successful, the platform could offer a differentiated strategy for patients with resistance to prior immunotherapy and potential for future combination regimens