Sliding doors in mRNA

In the race to turn mRNA into an actual drug, Translate Bio notched a minor victory when it beat the wealthier Moderna Therapeutics to start a clinical trial. But a pair of diverging updates from the FDA — a bad one for Translate and a good one for Moderna — illustrate just how fickle novel technologies can be.

On Tuesday, Translate disclosed that the FDA has put one of the company’s early-stage therapies on hold because the agency has “additional clinical and nonclinical questions.” That’s bad news, and it delays indefinitely the start of a trial. The hold doesn’t affect Translate’s lead program, which is in the midst of a study in cystic fibrosis, but it still took more than 10 percent off the company's stock price.

Meanwhile, over at Moderna, the FDA gave the company permission to start its first rare-disease trial, which will test an mRNA therapy against methylmalonic acidemia. Such permission is usually a dog-bites-man milestone in biotech, but Moderna’s efforts in rare disease have been rocky and heavily scrutinized, so the FDA’s decision, however incremental, is a check in the credibility column for a much-debated company.