Sanofi’s Darzalex rival hits primary endpoint in phase 3

A phase 3 trial of Sanofi’s Darzalex rival isatuximab in multiple myeloma has hit its primary endpoint. The anti-CD38 antibody prolonged progression-free survival over standard of care, providing a boost for Sanofi’s shift toward in-house programs. 

Isatuximab, like Johnson & Johnson’s Darzalex, is designed to capitalize on the uniform expression of CD38 by multiple myeloma cells to treat the disease via multiple mechanisms, including direct killing and immunomodulatory effects. Darzalex has shown these mechanisms can yield impressive efficacy and blockbuster sales. But its headstart and strong performance have also raised the bar for rivals.

Celgene dropped out of the fight in 2015 but Sanofi has stuck it out with isatuximab, formerly known as SAR650984. Sanofi’s efforts have culminated in the release of top-line results from a phase 3 trial of isatuximab in relapsed or refractory multiple myeloma.

The release disclosing the results lacks the key details that will determine whether isatuximab is a legitimate rival to Darzalex. But the information shared to date suggests the program is on the right track. Most notably, adding isatuximab to pomalidomide and low-dose dexamethasone in patients who had received two or more prior lines of treatment improved PFS over standard of care alone.

Sanofi plans to use the data to support regulatory submissions later this year. Isatuximab is also being evaluated in three other phase 3 studies that are enrolling slightly different patient populations or testing it in combination with different standard of care regimens.

Early on in development there was little evidence to suggest isatuximab would have a significant edge over Darzalex in terms of efficacy, safety or convenience. If Sanofi emerges from the pivotal trial program without such evidence, it may have to compete on price to win market share from J&J’s well-established multiple myeloma drug.

Whatever the financial impact of isatuximab, the drug will have symbolic importance to Sanofi if it comes to market. Through a period in which partnerships have been critical to Sanofi, isatuximab was one of the in-house assets management pointed to as evidence that internal R&D was firing again. Sanofi’s researchers developed isatuximab with ImmunoGen but were heavily involved as far back as preclinical. With Sanofi looking internally for innovation, it needs isatuximab to be an R&D lodestar.