Vir Biotechnology Initiates Phase 1 Trial for VIR-5525: Dual-Masked T-Cell Engager for Solid Tumors

Vir Biotechnology has begun its Phase 1 trial for VIR-5525, a dual-masked T-cell engager targeting EGFR for the treatment of solid tumors. The trial aims to evaluate the safety and efficacy of VIR-5525 as a standalone treatment and in combination with pembrolizumab. The trial's initiation triggers a $75 million milestone payment from Sanofi, reflecting the company's strategic progress in oncology.

Vir Biotechnology, Inc. (Nasdaq: VIR) has announced the first patient has been dosed in its Phase 1 clinical trial evaluating VIR-5525, an investigational dual-masked T-cell engager (TCE) targeting EGFR (epidermal growth factor receptor). The trial (NCT06960395) aims to assess the safety, pharmacokinetics, and preliminary efficacy of VIR-5525 as a monotherapy and in combination with pembrolizumab. VIR-5525 is designed to treat a variety of EGFR-expressing solid tumors, including non-small cell lung cancer (NSCLC), colorectal cancer (CRC), head and neck squamous cell carcinoma (HNSCC), and cutaneous squamous cell carcinoma (cSCC).

The Phase 1 trial is open-label and non-randomized, involving patients with EGFR-expressing solid tumors. The trial will evaluate VIR-5525 alone and in combination with pembrolizumab, a checkpoint inhibitor. The PRO-XTEN™ masking technology, licensed by Vir Biotechnology, will be employed to selectively activate the TCEs in the tumor microenvironment, mitigating damage to healthy cells and reducing toxicity.

The initiation of the trial triggered a $75 million milestone payment from Sanofi, as part of the company's 2024 exclusive worldwide license agreement for the PRO-XTEN™ platform and clinical-stage T-cell engagers. This payment will be recognized as a research and development expense in the third quarter of 2025.

Vir Biotechnology's Chief Executive Officer, Marianne De Backer, expressed excitement about the milestone, stating, "We are excited to bring our third PRO-XTEN™ dual-masked T-cell engager VIR-5525 to the clinic as we further our mission of transforming the lives of people living with hard-to-treat solid tumors." The company's Chief Medical Officer, Mark Eisner, added, "EGFR has been well characterized as a key oncogenic driver and a marker of poor prognosis in cancer. Traditional therapies have significant limitations, creating a substantial unmet need for highly efficacious and well-tolerated options."

The trial builds on Vir Biotechnology's ongoing efforts to develop innovative therapies for solid tumors. The company is advancing multiple preclinical dual-masked TCEs against clinically validated targets with potential applications across various solid tumors with high unmet need.

References:
[1] https://www.morningstar.com/news/business-wire/20250724060737/vir-biotechnology-announces-first-patient-dosed-in-phase-1-clinical-trial-of-egfr-targeting-pro-xten-dual-masked-t-cell-engager-vir-5525-for-the-treatment-of-solid-tumors