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AveXis Presents Initial Data from Pivotal U.S. Trial for SMA Type 1 and 24-Month Follow-Up Data from Phase 1 Trial of AVXS-101 in SMA Type 1 at the Annual Meeting of the American Academy of Neurology

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– A mean increase in CHOP-INTEND of 17.3 was observed at three months post gene therapy in SMA Type 1 U.S. pivotal trial –

– All patients in the therapeutic dose cohort in the Phase 1 trial were alive and event-free at 24-month follow-up –

– Patients observed in long-term follow-up from the Phase 1 trial continued to gain strength and achieve new milestones, including two additional patients who could stand with assistance –

CHICAGO, April 24, 2018 (GLOBE NEWSWIRE) -- AveXis, Inc. (NASDAQ:AVXS), a clinical-stage gene therapy company developing treatments for patients suffering from rare and life-threatening neurological genetic diseases, will present initial results from the Type 1 U.S. Pivotal trial (STR1VE) and 24-month follow-up data from the Phase 1 trial of AVXS-101 for the treatment of spinal muscular atrophy (SMA) Type 1 at the 2018 Annual Meeting of the American Academy of Neurology (AAN) Annual Meeting in Los Angeles.

"With a population closely matched to the Phase 1 trial, preliminary safety data and the early and rapid increases in CHOP-INTEND scores achieved by infants in this pivotal STR1VE trial are consistent with results of the Phase 1 trial of AVXS-101 in SMA Type 1," said John W. Day, MD, PhD, Professor, Neurology & Pediatrics, and Director of the Stanford Neuromuscular Program, Stanford University Medical Center, who will present these data at AAN. "These early signs of efficacy and safety are promising, and I look forward to seeing the trial progress."

Initial Data from Pivotal Trial of AVXS-101 in SMA Type 1 (STR1VE) as of April 11, 2018
As of April 11, 2018, 11 patients were enrolled in the trial, and six patients were symptomatic and at least one-month post gene therapy treatment. All patients had homozygous deletion of SMN1 and two copies of SMN2; no patient had the known SMN2 gene modifier mutation (c.859G>C). The patient population and baseline characteristics are closely matched to the Phase 1 trial.

Event-free Survival and Safety
All patients (6/6) were alive and event-free as of April 11, 2018. AVXS-101 appeared to have a favorable safety profile and to be generally well tolerated. At the time of gene transfer, the mean age was 3.2 months, with the oldest patient being 5.0 months of age.

In the six patients who were at least one-month post gene transfer, a cumulative total of 25 adverse events (AEs) were reported. Two patients experienced transient elevations in transaminases greater than 3x ULN that were not clinically significant and all resolved with prednisolone treatment without any clinical manifestations or sequelae. There were no serious adverse events (SAEs) reported.

Motor Function Achievement
Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) scores increased by an average of 7.8 at one month after gene transfer (in six patients) and 17.3 at three months after gene transfer (in three patients), reflecting improvement in motor function. These data correlate to CHOP-INTEND achievement by the proposed therapeutic dose cohort (Cohort 2) in the Phase 1 trial, which experienced mean increases of 9.8 points at one month and 15.4 points at three months. Early CHOP-INTEND increases have been observed to be associated with eventual milestone achievement.

The open-label, single-arm, single-dose, multi-center trial – known as STR1VE – is designed to evaluate the efficacy and safety of a one-time IV infusion of AVXS-101 of 1.1 x 1014 vector genomes/kg in patients with SMA Type 1 who are less than six months of age at the time of gene therapy, have one or two copies of the SMN2 backup gene as determined by genetic testing, and have bi-allelic SMN1 gene deletion or point mutations. The intent-to-treat population is defined as patients who are less than six months of age and symptomatic at the time of gene therapy, with two copies of the SMN2 gene as determined by genetic testing, bi-allelic SMN1 gene deletion and no c.859G>C mutation in SMN2.

The co-primary efficacy outcome measures include the achievement of the developmental milestone of independent sitting for at least 30 seconds at 18 months of age and event-free survival at 14 months of age, with an event defined as either death or at least 16 hours per day of required ventilation support for breathing for 14 consecutive days in the absence of acute reversible illness or perioperative change. Co-secondary outcome measures include the ability to thrive and the ability to remain independent of ventilatory support at 18 months of age. 

24-Month Follow-Up Data from Phase 1 Trial of AVXS-101 in SMA Type 1
The following 24-month follow-up data from the Phase 1 trial will be presented during platform presentations by Samiah Al-Zaidy, MD, Co-Investigator for the trial; Linda Lowes, PhD, Director of Clinical Therapies Research and a member of the Center for Gene Therapy at the Research Institute of Nationwide Children's Hospital; and Richard Shell, MD, member of the Section of Pulmonary Medicine at Nationwide Children's Hospital.

The Phase 1, open-label, dose-escalation trial was designed to evaluate the safety and tolerability of AVXS-101 in patients with SMA Type 1. The key measures of efficacy were the time from birth to an event and video confirmed achievement of ability to sit unassisted. Additionally, several exploratory objective measures were assessed, including a standard motor milestone development survey and CHOP INTEND. After the 24-month follow-up, to date, 11 patients have enrolled in the Long-Term Follow-Up (LTFU) trial for ongoing evaluation.

Event-free Survival and Safety

Twenty-four months following gene transfer, 15 of 15 (100%) patients were alive and without need for permanent ventilation. The median age at last follow-up was 27.8 months and 30.7 months for patients in the Cohort 2 and low-dose cohort (Cohort 1), respectively. Natural history indicates only eight percent of untreated patients with SMA Type 1 survive event-free at 20 months of age.

AVXS-101 appeared to have a favorable safety profile and to be generally well tolerated, with no new treatment-related safety or tolerability concerns identified at the 24-month follow-up.

  • A cumulative total of 319 AEs (five treatment-related AEs and 314 non-treatment related AEs) were reported following monitoring and source verification. Of these, 60 were determined to be SAEs and 259 were non-serious AEs.
  • As reported in 2016, one patient in Cohort 1 had a pulmonary event that required increased use of bi-level positive airway pressure (BiPAP) in advance of surgery related to hypersalivation, a condition experienced by some SMA patients; the event was determined by independent review to represent progression of disease and not to be related to the use of AVXS-101. Following surgery, the respiratory support needs decreased below event definition threshold.
  • As has been previously reported, a total of five AEs in four patients were deemed treatment-related. Of these, two were SAEs experienced by two patients, and three were non-serious AEs experienced by two patients. All consisted of clinically asymptomatic liver enzyme elevations and were resolved with prednisolone treatment. There were no clinically significant elevations of gamma-glutamyl transferase, alkaline phosphatase or bilirubin and, as such, Hy's Law was not met. Other non-treatment-related AEs were expected and were associated with SMA.

Treatment Durability and Motor Milestone Achievement from Long-Term Follow-Up Study

Patients in Cohort 2 continued to achieve new milestones during the LTFU trial. Detailed Cohort 2 motor milestone data is included in the chart below.

  • Two additional patients achieved the ability to sit unassisted for 30 seconds or more. Eleven of 12 (92%) patients could sit unassisted.
  • Two additional patients achieved the ability to stand with assistance. Four of 12 (33%) could stand with assistance.
  • Three of four patients achieving these new milestones were on AVXS-101 alone (one sitting and two standing with assistance).
  • The oldest child from Cohort 2 at the time of last visit in the LTFU study was 46.2 months and 40.6 months post gene therapy.
         
Cohort 2 Age at Gene Transfer (mos) Event-Free Survivala Event-free Survival and Motor and Other Milestones Among the 12 Patients in Cohort 2 as of December 15, 2017*  
Brings Hand to Mouth Controls Head Rolls Overb Sits with Assistance Sits Unassistedc Other Achievements  
 
≥5 seconds ≥10 seconds ≥30 seconds Speaks Swallows No NIV Use No Nutritional Supportd  
E.04 5.6 31.1   + + + + + O O + +      
E.05 4.2 28.5   + + + + + + + + + + +  
E.06 1.9 26.1   + + + + + + + + + + +  
E.07 3.6 28.1   + + + + + + O + + +    
E.08 7.9 32.4   +                      
E.09 4.9 28.9   + + + + + + + + + + +  
E.10 0.9 25.3   + + + + + + + + + + +  
E.11 2.3 27.7   + + + + + + + + +      
E.12 2.6 26.8   + + + + + + + + + + +  
E.13 0.9 25.4   + +   + + + + + +      
E.14 4.1 27.9   + +
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