Sanofi is still set on taking its multiple sclerosis (MS) med tolebrutinib to the FDA, executives have told Fierce Biotech, despite the BTK inhibitor falling short in two of three phase 3 trials that read out Monday.
Tolebrutinib—which was acquired in Sanofi’s $3.7 billion takeover of Principia Biopharma in 2021—was being evaluated across two forms of the chronic neurological disorder. The HERCULES study involved patients with non-relapsing secondary progressive MS, while two identical phase 3 studies, dubbed GEMINI 1 and 2, were focused on relapsing MS.
The HERCULES study was a success, Sanofi announced Monday morning, with tolebrutinib hitting the primary endpoint of delaying progression of disability compared to placebo.
But, in the GEMINI trials, tolebrutinib failed the primary endpoint of besting Sanofi’s own approved MS drug Aubagio when it came to reducing relapses over up to 36 months. Trying to find the positives, the company said an analysis of six-month data from those trials showed there had been a “considerable delay” in the onset of disability.
The pharma has previously touted tolebrutinib as a potential blockbuster, and Sanofi’s head of R&D Houman Ashrafian, M.D., Ph.D., told Fierce in an interview that the company still plans to file the drug for FDA approval, focusing specifically on the indication of non-relapsing secondary progressive MS where it saw success in the HERCULES trial.
Unlike relapsing MS, which refers to people who experience episodes of new or worsening symptoms—called relapses—followed by periods of partial or complete recovery, non-relapsing secondary progressive MS covers individuals who have stopped experiencing relapses but still experience increasing disability such as fatigue, cognitive impairment and the ability to walk unaided.
Even before this morning’s patchy phase 3 results, Sanofi had been acclimatizing investors to a focus on reducing the progression of disability rather than preventing relapses—which has been the goal of many late-stage MS trials.
“We’re first and best in class in progressive disease, which is the largest unmet medical population,” Ashrafian said. “In fact, there is no drug for the treatment of secondary progressive [MS].”
Sanofi will engage with the FDA “as soon as possible” to discuss filing for approval in non-relapsing secondary progressive MS, he added.
When asked whether it may be harder to get approval for a drug that has just posted a pair of phase 3 failures, Ashrafian said it is a “mistake to lump MS subgroups together” as they are “genetically [and] clinically distinct.”
“The argument that we will make—and I think the patients will make and the providers will make—is that secondary progressive is a distinctive disorder with large unmet medical need,” he told Fierce. “But we will be respectful of the regulator’s perspective on relapsing remitting [MS] and others, and make sure that we make the right risk-benefit analysis, which I think really plays out in our favor in secondary [progressive MS].”
It’s not the first time tolebrutinib has faced challenges in the clinic. The FDA placed a partial hold on further enrollment on all three of today’s trials two years ago over what the company described at the time as “a limited number of cases of drug-induced liver injury that have been identified with tolebrutinib exposure.”
When asked whether this backdrop could also impact how the FDA views the upcoming approval filing, Ashrafian said it will “bring into sharp focus which patient population we should be treating.”
“We’ll continue to monitor the cases as they come through,” he continued. “But I see nothing that concerns me, and I’m a fairly conservative human being.”
On whether Sanofi has given up on ever getting tolebrutinib approved for relapsing MS, Ashrafian said the company “will certainly prioritize secondary progressive” MS.
The pharma also has another phase 3 study, dubbed PERSEUS, ongoing in primary progressive MS. A readout is expected next year.
Even if tolebrutinib had delivered the goods in the GEMINI trials, the BTK inhibitor would have faced stiff competition entering a market that already houses Bristol Myers Squibb’s Zeposia, Roche’s Ocrevus, Biogen’s Tecfidera and Sanofi’s own Aubagio.
Sanofi’s struggles in the GEMINI trials echo issues faced by Merck KGaA’s BTK inhibitor evobrutinib, which sent shock waves through the sector when it failed to beat Aubagio in a pair of phase 3 trials in relapsing MS in December. Despite having previously cited the drug’s blockbuster potential, the German pharma eventually dropped evobrutinib in March.