Take 3: Mesoblast plots path to market for twice-rejected cell therapy

Mesoblast has taken another step on the path toward its third attempt to win approval of its off-the-shelf therapy, exiting a meeting with the FDA convinced that new potency assay data and a single-arm trial can finally get the candidate to market.

The Melbourne, Australia-based biotech wants to bring the cell therapy, remestemcel-L, to market as a treatment for steroid-refractory acute graft-versus-host disease but has so far failed to persuade the FDA to sign off on an approval. Officials rejected a filing for approval in children in 2020 and asked Mesoblast to run at least one more trial. Mesoblast tried again this year, without running a new trial, and was rejected again.

Upon receiving the complete response letter last month, the biotech outlined plans to run a clinical trial and later expressed hope that it could win approval using additional potency assay results or new clinical data in adults. Now, having met with the FDA, Mesoblast has a clearer idea of what it needs to do.

The biotech exited its meeting with the agency with two key items on its to-do list. First, Mesoblast plans to generate new potency assay data to show the standardization of the identity, strength, quality, purity and dosage form of the product tested in the pediatric phase 3 trial. 

Mesoblast’s potency assays are a long-standing issue. The biotech identified a need to refine the assays after receiving its first complete response letter and, while it said the FDA acknowledged improvements in the second rejection, tests remain a barrier to approval. According to Mesoblast, the lack of a suitable potency is preventing the agency from viewing the pediatric phase 3 as an adequate study for approval.

A clinical trial in adults is the second item on Mesoblast’s to-do list. Three years after the FDA requested at least one more study, the biotech has outlined plans to run a single-arm trial in adults and children aged 12 and up. The planned study will enroll patients failed by both steroids and a second-line agent, such as ruxolitinib, and “be underpinned by a suitable potency assay,” Mesoblast said.

The biotech is yet to reach an agreement with the FDA on the study. According to Mesoblast, the agency “indicated its willingness to consider” the proposed trial design, “subject to agreement on the suitability of the potency assay.” Mesoblast calculates it can cover the cost of the trial through the cuts it made last month, which included a 30% reduction in the pay of the CEO.

Investors appeared to show some enthusiasm for the proposals, sending Mesoblast's shares up 6% to $1.39 in premarket trading. However, the stock remains well down on the more than $4 that it commanded in the run-up to the second FDA rejection.