REGENXBIO Inc. and AveXis, Inc. have entered into an amendment which expands upon the exclusive, worldwide license agreement they entered into in March 2014 for the development and commercialization of products to treat spinal muscular atrophy (SMA).    AveXis’ initial proprietary gene therapy candidate, AVXS-101, is in a pivotal trial for the treatment of SMA Type 1, and a Phase 1 trial for SMA Type 2. AVXS-101 uses REGENXBIO’s NAV AAV9 vector.   “An expanded relationship furthe...