Sanofi Halts Phase 2 Trials of IL-2 Cancer Drug SAR444245 After Disappointing Efficacy
Key Insights
Sanofi is halting Phase 2 trials for its IL-2 cancer (search) drug candidate, SAR444245, due to lower-than-projected efficacy in mid-stage clinical data.
The company will restart the program with Phase 1/2 trials, adjusting the dosing schedule to improve the drug's target profile.
This decision results in a nearly €1.6 billion impairment charge, attributed to delays in launch timelines for key indications.
Sanofi is resetting its development program for SAR444245, an interleukin-2 (IL-2) based cancer (search) immunotherapy, after initial data from Phase 2 trials revealed efficacy below expectations. The decision, announced alongside the company's third-quarter financial results, will lead to a €1.6 billion impairment charge. The drug, acquired through Sanofi's $2.5 billion purchase of Synthorx (search) in 2019, was being evaluated across several advanced cancers.
IL-2 Therapy and SAR444245
SAR444245 represents Sanofi's entry into the competitive field of IL-2 cancer (search) immunotherapies. IL-2 is a cytokine known for stimulating a potent immune response against cancer cells. However, existing IL-2 therapies, such as the only FDA-approved IL-2 treatment, are limited by significant toxicity. Sanofi aimed to overcome these limitations with SAR444245, a "non-alpha" IL-2 variant engineered for greater precision and longer duration of action.
The Phase 2 program for SAR444245 included trials in advanced skin cancers (search), head and neck cancers (search), non-small cell lung cancer (search)/mesothelioma (search), and lymphoma (search). The trials were evaluating a dosing schedule of once every three weeks. However, this regimen did not yield the desired efficacy, prompting the company to reassess its approach.
New Phase 1/2 Program
Sanofi plans to initiate a new Phase 1/2 program to refine the dosing schedule of SAR444245. The goal is to establish a "best-in-class target profile" for the drug. The company emphasized that the decision to halt the Phase 2 trials was not driven by safety concerns. The financial writedown reflects "updated cash flow projections due to delays in launch timelines in key indications."
Competition in IL-2 Therapies
Sanofi faces competition from other companies developing novel IL-2 therapies. Bristol Myers Squibb (search) and Nektar Therapeutics previously discontinued development of bempegaldesleukin, an IL-2 drug, due to lack of efficacy in melanoma (search), bladder, and kidney cancers (search). Companies like Werewolf Therapeutics, Xilio Therapeutics, Asher Bio, and Avenge Bio are pursuing alternative strategies to improve the safety and efficacy of IL-2-based cancer (search) immunotherapies.