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Investing in our common stock involves a high degree of risk. You should consider carefully the risk factors described
below together with all of the risks, uncertainties and assumptions discussed in our most recent Annual Report on Form 10-K and our most recent Quarterly Report on Form 10-Q, which are
incorporated herein by reference, together with the information in this prospectus supplement, the accompanying prospectus, the documents incorporated herein by reference and in any free writing
prospectus that we have authorized for use in connection with this offering, before deciding whether to invest in shares of our common stock.
Risks related to our recent business developments
We must establish, to the FDA's satisfaction, that our proposed potency assay for AVXS-101 sufficiently
characterizes the key product characteristics of our clinical and commercial product supply.
We recently held a Type B Chemistry, Manufacturing and Controls, or CMC, meeting with the United States Food and Drug Administration, or
the FDA, to seek alignment with the FDA regarding our proposed Good Manufacturing Practice, or GMP, commercial manufacturing process for AVXS-101, which we are primarily conducting using our own
manufacturing facility. Our proposed GMP manufacturing process incorporates a novel adherent cell culture approach, which differs from the Hyperstack approach utilized by Nationwide Children's
Hospital, or NCH, to manufacture the product used in the Phase 1 clinical trial of AVXS-101 for spinal muscular atrophy, or SMA, Type 1. In order to reliably and accurately characterize
the dose of the product for our planned clinical trials and, if approved, commercial demand, we will need to be able to reliably and consistently assess the key characteristics of the product we
manufacture. During the CMC meeting, we presented our AVXS-101 potency assay and qualification plans to the FDA. In response, the FDA has requested, among other things, that we complete the
implementation of our potency assay qualification plans, including presenting the FDA with data from the appropriate production runs of AVXS-101, to enable the agency to assess the feasibility of our
plans. We have already begun the work to address this request, and we expect to submit these data to the FDA in the August 2017 timeframe.
outcome of our potency assay and qualification development, including the results of the analyses that we are conducting in response to the FDA's request, are not yet known. As a
result, we cannot guarantee that the comprehensive data package that we generate from these production runs will be sufficient for the FDA to determine that our proposed potency assay or the product
tested with this assay is acceptable. If, upon review of this data, the FDA does not determine that our proposed potency assay is acceptable, we may be required to conduct additional work to develop
and validate an acceptable potency assay for AVXS-101 and/or manufacture additional qualification lots of AVXS-101, which would likely delay our planned clinical studies, including the U.S. pivotal
clinical trial of AVXS-101 in SMA Type 1 and our planned Phase 1/2a clinical trial of AVXS-101 in SMA Type 2. Any such delays could have a material adverse effect on our business
Our transition from the NCH manufacturing process to our own manufacturing process, conducted at our own
facility and at facilities of third party manufacturing partners, requires us to conduct a comprehensive comparability study, which may result in delays to the approval process for AVXS-101.
Our Phase 1 clinical trial was conducted with AVXS-101 manufactured by NCH that was produced using a traditional Hyperstack process
utilizing ampicillin-resistant genetic markers for plasmid selection. We are in the process of transitioning the primary manufacturing of AVXS-101 to our own manufacturing facility, which uses a
process based on a novel adherent cell culture