In our original report on Principia Biopharma, we emphasized that BTK inhibitors have failed over and over in autoimmune diseases, which we attribute to a basic problem with their mechanism of action: their main effect is to impair the production of new B-cell lineages, leaving the previously established B-cell populations that cause autoimmunity largely unscathed. Alas, Sanofi – the French pharma firm that licensed Principia’s BTK inhibitor SAR442168 for use in multiple sclerosis – doesn’t seem to have gotten the memo. During Sanofi’s recent earnings call, its global head of R&D rattled off what he views as the drug’s key virtues, all the while perpetuating several myths and misconceptions. Here we respond point to point to Sanofi’s paean to SAR442168, explaining why we remain unimpressed.

Read our full update here.