The agreement also gives Vir access to Sanofi’s Pro-XTEN protease-cleavable masking platform along with the three TCEs, SAR446309, SAR446329, and SAR446368, yielded by Sanofi’s masking platform.

Under the terms of the agreement, Sanofi will receive an upfront payment of $100 million, and an additional $75 million will be escrowed for the milestone of SAR446368 achieving “first in human dosing” by December 2026.

“The licensed assets and platform have great synergy with Vir’s existing capabilities and platform technology. We also believe this agreement brings complementary expertise to Vir through welcoming 50 key employees,” a spokesperson for Vir told BioProcess Insider.

“The key Sanofi employees we are bringing in offer extensive expertise in oncology clinical development, in-depth knowledge of the proprietary masking platform and valuable expertise in manufacturing dual-masked molecules.”

SAR446309 (AMX-818), SAR446329 (AMX-500), and SAR446368 (AMX-525) are all dual-masked, bispecific T-cell engagers that use proprietary protease-activated masking technology. The dual masking technology is designed to minimize off-target toxicity by preventing the T-cell engagers from activating T-cells in healthy tissues.

According to the firm, this approach aims to widen the therapeutic window and improve the safety profile of treatments when compared with unmasked TCEs. Each asset targets a different tumor-associated antigen: HER2 for SAR446309 (breast cancer), PSMA for SAR446329 (prostate cancer), and eGFR for SAR446368 (renal disease).

In 2021, Sanofi bought the Pro-XTEN platform for $1 billion through its acquisition of immuno-oncology firm Amunix Pharmaceuticals. At the time of the acquisition, a Sanofi spokesperson told us, “The technology is very well suited to complement Sanofi’s existing biologics modalities.”

“Our monoclonal antibody (mAb) platform enables the rapid generation of novel antibodies for identified tumor targets. By combining our antibody discovery capabilities with the Pro-XTEN masking technology, we can rapidly create a new generation of masked T-cell engagers that can address a broad range of tumor antigens, expanding the potential impact of this modality,” the spokesperson added.