Vertex Presses Pause on CF Study, Reports Major Write-Down

Vertex Pharmaceuticals has announced a temporary pause in part of a clinical trial evaluating its cystic fibrosis (CF) candidate, VX-522, due to a tolerability concern. The update was included in the company’s release and comes alongside a separate $379 million impairment charge tied to a discontinued diabetes program.
The trial pause affects the multiple ascending dose segment of the phase 1/2 study of VX-522, an experimental mRNA therapy developed in partnership with Moderna. Vertex did not disclose specific details regarding the tolerability issue but stated more information would be provided as it becomes available. The company emphasized the temporary nature of the pause.

VX-522 is a nebulized mRNA-lipid nanoparticle (LNP) therapy designed to address the root cause of CF by enabling lung cells to produce functional CF transmembrane conductance regulator proteins. The candidate received fast-track designation from the U.S. Food and Drug Administration. The collaboration between Vertex and Moderna began in 2020, with Vertex providing $75 million to support a three-year research effort that resulted in the development of VX-522.
Analysts from William Blair described the trial pause as “unfortunate” but noted that the decision to temporarily halt, rather than terminate, the study suggests Vertex remains encouraged by data collected so far. The trial is being conducted as an open-label study, which may provide continued insights despite the pause.
The CF program update comes as competitors in the inhaled mRNA-LNP space, including Arcturus Therapeutics and ReCode Therapeutics, are expected to share clinical data in the near term. The competitive landscape could shift depending on how these therapies progress through development.
In addition to the trial pause, Vertex reported a $379 million intangible asset impairment charge. The charge is linked to the discontinuation of VX-264, an islet cell therapy for diabetes that was combined with a delivery device. The decision to cease work on VX-264 followed results from a phase 1/2 trial that indicated the treatment was unlikely to produce adequate insulin levels. The write-down impacted the company’s GAAP operating income for the first quarter of the year.

This is the latest in a series of pipeline adjustments by Vertex, which recently concluded its work with adeno-associated virus (AAV) vectors used in gene therapy delivery. The shift was disclosed at the end of the prior week.
Despite the changes, William Blair analysts have maintained an “outperform” rating on Vertex’s stock, citing what they described as ongoing clinical progress and disciplined business development. Vertex continues to advance a diversified pipeline, including zimislecel, a beta-cell therapy for Type 1 diabetes that requires immunosuppression and may be submitted for regulatory review in the coming year.