It looks like Biogen Inc.’s Nrf2 activator, Skyclarys (omaveloxolone), will maintain its status as the sole therapy approved for treating patients with Friedreich’s ataxia (FA), at least for now. The U.S. FDA asked for another “adequate and well-controlled study” in the complete response letter (CRL) issued to PTC Therapeutics Inc. for 15-lipoxygenase inhibitor vatiquinone. The agency said “substantial evidence of efficacy was not demonstrated.”