A phase 2 trial of Zynerba Pharmaceuticals’ Fragile X syndrome drug met its primary endpoint. The beleaguered biotech’s stock doubled on news of the route to redemption, despite the study’s lack of a control arm leaving reason to question how big an effect the drug had on the patients.

Investigators enrolled 20 patients with Fragile X and gave the ZYN002 cannabidiol gel on top of the drugs they were already receiving. By week 12, participants had experienced a 46% improvement in symptoms on the Anxiety, Depression, and Mood Scale (ADAMS) over baseline. That drop was enough for the trial to hits its primary endpoint with a p value of less than 0.0001.

Investors responded to the news by driving up the value of Zynerba’s stock by close to 100% before the market opened. That huge jump reflected the fact that Zynerba was in the last-chance saloon going into the readout. Zynerba found itself in that diminished position after ZYN002 fell short in a phase 2 epilepsy trial last month, a setback that left it with a market cap of about $82 million.

The question now is whether the phase 2 result is a portent of future success or a mirage that will lead to futile expenditure on a drug that doesn’t work. Zynerba’s supporters are clear about which side of the fence they are on. 

"The data from the FAB-C trial are very exciting and demonstrate that ZYN002 may have a profound effect on improving many of the most disabling symptoms of Fragile X, such as anxiety and difficult behaviors," Keck School of Medicine of USC’s Steven Siegel, M.D., Ph.D., said in a statement. "This study suggests that ZYN002 is ready for the next phase of development, and I believe that this drug holds great promise as a potential treatment for these very difficult-to-treat symptoms."

The case against this rosy assessment of the data centers on the design of the trial. Without a control arm, it is hard to know what effect ZYN002 had, particularly as the ADAMS scores of Fragile X patients in other studies have responded to placebo.  

Such doubts were overwhelmed by the suggestion that Zynerba may be able to dig itself out of a hole, though. The next step is to meet with the FDA with a view to moving into a pivotal phase 2/3 trial next year.