Those drugs, though, faced a potential competitive threat from Enspryng. Recently published study results showed that tocilizumab, a drug that works similarly to Enspryng, might be an effective treatment for myasthenia gravis. That, in turn, had stoked fear among investors that the Enspyring trial could establish medicines like it, IL-6 inhibitorsIL-6 inhibitors, as a “new standard-of-care” with “differentiated efficacy” and less frequent dosing than FcRn drugs, wrote Leerink Partners analyst Thomas Smith, in a note to clients Thursday. The study tested Enspyrng in a trial that randomized 185 patients to receive the drug or a placebo over 24 weeks. The main goal was to outperform a placebo on a 24-point questionnaire.
Chugai revealed Thursday that Enspyring fell short of expectations on the “degree of clinical benefit” in the trial. The company didn’t provide further details, saving them instead for a medical meeting next month. It’ll continue developing Enspryng for other rare inflammatory conditions, such as thyroid eye disease and autoimmune encephalitis. In the meantime, the effects of the findings rippled across to other developers. Argenx shared climbed 12% in Thursday morning trading, while Immunovant’s stock initially surged double digits before settling in to a smaller gain. Shares of Tourmaline Bio, which is developing an IL-6 drug for myasthenia gravis, fell nearly 40%. Smith, of Leerink, expects the results “to be viewed as confirmation of FcRn’s current role as the preferred [target]” for the disease.