Sanofi tries to quiet naysayers with follow-up data on MS drug at heart of $3.7B Principia buyout

A long-term follow-up study of tolebrutinib saw 98% of patients stay through the entire extension period to evaluate the drug’s safety and further outcomes. (Sanofi)

Sanofi’s $3.7 billion acquisition of Principia Biopharma has been taking barbs from all sides, so perhaps some long-term follow-up data on the multiple sclerosis candidate at the heart of the deal will quiet the criticism.

The French pharma showcased 48-week results for a phase 2b trial of tolebrutinib at the 37th Congress of the European Committee for Treatment and Research in Multiple Sclerosis on Oct. 13. The trial is examining the therapy’s use in patients with relapsing forms of MS.

Tolebrutinib reduced MS disease activity seen on MRI scans from the patients in the trial at the 48-week point, matching earlier data presented in the first half of 2020. The scans showed a reduction in brain lesions associated with the disease.

The long-term follow-up study saw 98% of patients stay through the entire extension period to evaluate the drug’s safety and further outcomes. This suggests the drug is tolerable and could become a new long-term treatment option for patients with MS, Sanofi said.

The pharma moved to advance tolebrutinib into a slew of phase 3 testing based on the earlier data.

RELATED: Sanofi posts data from contentious phase 2 multiple sclerosis trial

Sanofi’s August 2020 decision to buy Principia has been contentious among investors, and, in recent weeks, the pharma has reported nothing but bad news for the unit. In September, Sanofi closed Principia’s San Francisco laboratories and laid off about three dozen people. This came just days after one of the subsidiary's key BTK inhibitors rilzabrutinib flunked out of a phase 3 test for the skin disease pemphigus vulgaris.

The latest news for the MS candidate—even if it mostly confirmed what Sanofi had already shown—managed to convince SVB Leerink analysts that the acquisition was worthwhile. The firm anticipates that tolebrutinib could garner peak sales of 3.7 billion euros ($4.29 billion), become the “cornerstone” of Sanofi’s neuro-inflammation portfolio and be a key growth driver in 2025.

“Overall these data support the decision to advance the drug rapidly into phase 3 and justify the acquisition of Principia regardless of the results with rilzabrutinib,” SVB Leerink said of the extension study. “We currently weight the tolebrutinib opportunity in MS with a 65% probability of success.”

The long-term data suggest good news is to come from the four ongoing phase 3 trials, which are comparing tolebrutinib to Sanofi’s other MS asset Aubagio. SVB Leerink noted that while the safety data were good in the extension study, adverse events are likely to tick upward in the late-phase studies because the patients will be on the highest dose.

RELATED: Sanofi dumps Principia Biopharma's San Francisco labs with plans to immediately cut 38 jobs

Other competitors in MS include Biogen’s Tecfidera, Genentech’s Ocrevus and Bristol Myers Squibb’s Zeposia. One hallmark of MS is that patients often relapse. Tolebrutinib’s relapse rate was “at the better end” of what the competitors have shown, SVB Leerink said. About 90% of patients taking the therapy in the midstage study were relapse-free during the treatment period, which compares to a range of 60% to 83% seen in late-stage trials for the competitors at two years.

SVB Leerink predicts Sanofi may have a market contender on its hands, with a potential launch in 2025.

Whether the extension data will quiet the Principia naysayers remains to be seen.