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Catabasis Pharmaceuticals Phase 3 PolarisDMD Clinical Trial for Edasalonexent in Duchenne Muscular Dystrophy Progress Update and Additional Trial Sites Open for Enrollment

— Patient Enrollment Underway in U.S. with Nine Locations Open for Enrollment —
— Global Start-Up Activities Ongoing with Clinical Trial Application Approvals Received in
Canada and Multiple European Countries —

CAMBRIDGE, Mass., January 3, 2019 – Catabasis Pharmaceuticals, Inc. (NASDAQ:CATB), a clinical-stage biopharmaceutical company, today shared an update on clinical trial sites in the
United States and recent international clinical trial application approvals to perform the Phase 3 PolarisDMD trial for edasalonexent (CAT-1004) in Duchenne muscular dystrophy (DMD).
PolarisDMD clinical trial sites in the United States are actively enrolling patients. The PolarisDMD trial is evaluating the efficacy and safety of edasalonexent in patients with DMD and is intended
to support an application for commercial registration of edasalonexent. Top-line results from the Phase 3 PolarisDMD trial are expected in the second quarter of 2020.

A total of nine PolarisDMD clinical trial sites are now open for enrollment across the United States and at least ten additional sites are expected to open shortly. Additionally, Catabasis has received approval of clinical trial applications to conduct the PolarisDMD trial in Canada and multiple countries in Europe. Clinical trial sites are expected to open in Canada this month and sites in Europe as well as Australia and Israel, pending regulatory approval, are expected to open in first quarter of this year. In total, the PolarisDMD trial is expected to include approximately 40 clinical trial sites globally with enrollment expected to be completed in 2019.

“We are very excited to be screening and dosing patients in our Phase 3 PolarisDMD trial as we believe edasalonexent has tremendous potential for all those affected by Duchenne, regardless
of mutation type and from the time of diagnosis throughout their lifespan. We have received extensive inbound interest from families interested in the study and we are actively referring these
families to the enrolling clinical trial sites,” said Joanne Donovan, M.D., Ph.D., Chief Medical Officer of Catabasis. “Edasalonexent inhibits NF-kB, which plays a fundamental role in skeletal
and cardiac muscle disease in Duchenne. We are monitoring bone and heart health in the PolarisDMD trial, in addition to the assessments of skeletal muscle function, as we see these as
important potential differentiating benefits of edasalonexent.”

“There is a great need for new treatment options for Duchenne and we are very pleased that the PolarisDMD trial for edasalonexent will enroll patients at sites in Canada,” said Perry Esler,
Executive Director of Jesse’s Journey, the only charity in Canada solely focused on funding research into Duchenne. “We are very supportive of treatment options, like edasalonexent, that
have the potential to benefit all boys and men affected by Duchenne, and we know that these trials are a high priority for families.”

The global Phase 3 PolarisDMD trial is a one-year, randomized, double-blind, placebo-controlled trial. Catabasis plans to enroll approximately 125 patients ages 4 to 7 (up to 8th birthday)
regardless of mutation type who have not been on steroids for at least 6 months. Boys on a stable dose of eteplirsen may be eligible to enroll. The primary efficacy endpoint is change in the North
Star Ambulatory Assessment score after 12 months of treatment with edasalonexent compared to placebo. Key secondary endpoints include the age-appropriate timed function tests: time to
stand, 4-stair climb and 10-meter walk/run. Assessments of growth, cardiac and bone health are also included as important potential areas of differentiation. Two boys will receive 100 mg/kg/day
of edasalonexent for each boy that receives placebo, and, after 12 months, all boys are expected to receive edasalonexent in an open-label extension study. The PolarisDMD trial design was
informed by discussions with regulators as well as input from treating physicians, patient organizations and families of boys affected by Duchenne.

The Phase 3 PolarisDMD trial is designed to further validate the positive efficacy seen in the MoveDMD Phase 2 trial and open-label extension evaluating edasalonexent. In the MoveDMD
trial, edasalonexent has been shown to preserve muscle function and substantially slow DMD disease progression across all four assessments of muscle function (the North Star Ambulatory
Assessment, time to stand, 4-stair climb and 10-meter walk/run) through 72 weeks of treatment compared to an off-treatment control period. Preclinical data and clinical biomarker data from the
MoveDMD Phase 2 trial suggest that edasalonexent could have potential benefits in skeletal muscle, diaphragm and heart. Edasalonexent has been well tolerated through more than 50
patient-years of treatment with no safety signals observed.

More information about the Phase 3 PolarisDMD clinical trial is available on clinicaltrials.gov and in a recently recorded webinar with PPMD. Contact the Catabasis clinical team with any questions at DMDtrials@catabasis.com.

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