AveXis Announces Plan to Initiate Phase 1 Trial in SMA Type 2 Utilizing Intrathecal Delivery of AVXS-101

Chicago, Ill. (December 13, 2017) – AveXis, Inc. (NASDAQ: AVXS), a clinical-stage gene therapy company developing treatments for patients suffering from rare and life-threatening neurological genetic diseases, today announced the U.S. Food and Drug Administration (FDA) has notified the company that, based on review of data submitted, the company may initiate its planned Phase 1 clinical trial of AVXS-101 for patients with spinal muscular atrophy (SMA) Type 2 via the intrathecal (IT) route of administration, using material produced by the company’s Good Manufacturing Practice (GMP) commercial manufacturing process at the AveXis manufacturing facility. The company plans to initiate this trial immediately.

“We are quite pleased to initiate our first trial of AVXS-101 in patients with SMA Type 2,” said Sean Nolan, President and Chief Executive Officer of AveXis. “Our goal has been to expand the study of gene therapy beyond Type 1 infants to address the urgent medical needs of children with SMA Type 2, and we look forward to understanding the potential clinical impact of AVXS-101 in these patients who, left untreated, will never walk on their own and most will never stand without assistance.”

U.S. Phase 1 Trial in SMA Type 2 (STRONG)
The open-label, dose-comparison, multi-center Phase 1 trial – known as STRONG – is designed to evaluate the safety, optimal dosing, and proof of concept for efficacy of AVXS-101 in two distinct age groups of patients with SMA Type 2, utilizing a one-time IT route of administration. The trial will enroll 27 infants and children with a genetic diagnosis consistent with SMA, including the bi-allelic deletion of SMN1 and three copies of SMN2 without the SMN2 genetic modifier, who are able to sit but have no historical or current ability to stand or walk.

Two dosage strengths will be evaluated and patients will be stratified into two age groups: patients less than 24 months, and patients at least 24 months but less than 60 months. There will be at least a four-week interval between the dosing of the first three patients for each dose being studied and, based on the available safety data, a decision will be made whether to proceed.

• Cohort 1 (Dose A) will receive a dose of 6.0 x 1013 vg of AVXS-101 and enroll three patients less than 24 months of age.
o If safety is established according to the Data Safety Monitoring Board (DSMB), the study will proceed to Cohort 2.
• Cohort 2 (Dose B) will receive a dose of 1.2 X 1014 vg of AVXS-101 and enroll three patients less than 60 months of age.
o If safety is established according to the DSMB, an additional 21 patients will be enrolled until there are a total of 12 patients less than 24 months, and 12 patients at least 24 months but less than 60 months of age, who have received Dose B.

According to the well-characterized natural history of the disease by the Pediatric Neuromuscular Clinical Research Network, 100 percent of children with SMA Type 2 will never walk without support, 95 percent of children will never stand without assistance and more than 30 percent will die by 25 years of age. Additionally, children with SMA Type 2 experienced a mean decrease of – 0.33 points on the Hammersmith Function Motor Scale Expanded over a 12-month period.

Outcome Measures for Patients Less than 24 Months of Age
• The primary outcome measure for patients less than 24 months of age at the time of dosing is the achievement of the ability to stand without support for at least three seconds.
• The secondary outcome measure is the proportion of patients who achieve the ability to walk without assistance, defined as taking at least five steps independently while displaying coordination and balance.
• Developmental abilities, including motor function, will be evaluated as exploratory objectives.

Outcome Measures for Patients Between 24 and 60 Months of Age
• The primary outcome measure for patients between 24 months and 60 months of age at the time of dosing is the achievement of change in Hammersmith Functional Motor Scale Expanded from baseline.
• The secondary outcome measure is the proportion of patients who achieve the ability to walk without assistance, defined as taking at least five steps independently displaying coordination and balance.
• Developmental abilities, including motor function, will be evaluated as exploratory objectives

The trial is projected to be conducted at 11 sites in the United States, including: Ann and Robert H. Lurie Children’s Hospital of Chicago, Boston Children’s Hospital, Children’s Hospital of Philadelphia, David Geffen School of Medicine at UCLA, Johns Hopkins Pediatric Neurology, Nationwide Children’s Hospital, Stanford University Medical Center, University of Central Florida College of Medicine, University of Texas Southwestern Medical Center, University of Utah and Washington University School of Medicine.

For more information about these clinical trials, please visit clinicaltrials.gov.

“This Phase 1 trial in children with SMA Type 2 will allow us to evaluate safety, optimal dosing and proof-of-concept for efficacy of AVXS-101 compared to the well-characterized natural history using the one-time intrathecal route of administration,” said Dr. Sukumar Nagendran, Chief Medical Officer of AveXis. “Because AVXS-101 targets the root cause of SMA, we are optimistic that we will observe a similar preclinical to clinical translation in this Type 2 trial as was seen in the SMA Type 1 study using intravenous administration.”

SMA Type 1 Update
On December 5, 2017, the company had an end-of-Phase 1 meeting with FDA with respect to AVXS-101 for SMA Type 1. The company anticipates providing an update on feedback from FDA following the receipt of the final meeting minutes in early January.

Today’s Conference Call Information
AveXis will host a conference call and webcast at 4:30 p.m. EST today, December 13, 2017. Analysts and investors can participate in the conference call by dialing (844) 889-6863 for domestic callers and (661) 378-9762 for international callers, using the conference ID 2945908. The webcast can be accessed live on the Events and Presentations page in the Investors and Media section of the AveXis website, www.AveXis.com. The webcast will be archived on the company’s website for 90 days and will be available for telephonic replay for 14 days following the call by dialing (855) 859-2056 (Domestic) or (404) 537-3406 (International), conference ID 2945908.