Pharma BD Deal Intelligence
Sanofi acquired San Diego-based Synthorx for $68/share, ~$2.5 billion in cash, to anchor its immuno-oncology pipeline under then-new CEO Paul Hudson. The deal (announced December 9, 2019; closed January 23, 2020) was built around THOR-707 / SAR444245 (tenxilvunakin), an engineered 'not-alpha' PEGylated IL-2 designed to bias signaling toward CD8+ T and NK cells while avoiding regulatory-T-cell activation. The thesis did not pan out. In October 2022 Sanofi halted the Phase 2 platform's every-3-week dosing after efficacy came in 'lower than projected' and booked a ~EUR1.6 billion (~$1.6B) impairment, then ran a Phase 1/2 dose-intensification salvage program. In the fourth quarter of 2024 Sanofi removed SAR444245 from its R&D pipeline entirely; the lead solid-tumor study (NCT04009681) and the Pegathor Lymphoma study (NCT05179603) are both terminated per a strategic sponsor decision (not safety-driven), as verified on ClinicalTrials.gov in December 2025. The $2.5B acquisition is effectively a write-off.