Ra Pharmaceuticals Announces Expansion of Neuromuscular Portfolio with Clearance of IND Application for Zilucoplan for the Treatment of Immune-Mediated Necrotizing Myopathy

Multi-center Phase 2 clinical trial on track to initiate in the
second half of 2019

CAMBRIDGE, Mass.–(BUSINESS WIRE)–Ra Pharmaceuticals, Inc. (Nasdaq:RARX) today announced the U.S. Food and
Drug Administration’s (FDA) clearance of the Company’s Investigational
New Drug (IND) application for zilucoplan for the treatment of
immune-mediated necrotizing myopathy (IMNM). The Company is on track to
initiate a Phase 2 clinical trial in the second half of 2019.

“Patients with IMNM face a severe, chronic, debilitating autoimmune
disease with limited treatment options and no approved therapies,” said
Andrew Mammen, M.D., Ph.D., Muscle Disease Unit Leader, Laboratory of
Muscle Stem Cells and Gene Regulation, and Principal Investigator for
the Phase 2 study at the National Institute of Arthritis and
Musculoskeletal and Skin Diseases, National Institutes of Health,
Bethesda, MD. “Given the availability of diagnostic autoantibodies and
the central role of terminal complement activation in the
pathophysiology of the disease, zilucoplan has the potential to become a
targeted therapy for patients with IMNM. The results observed in the
recent Phase 2 clinical trial of zilucoplan in generalized myasthenia
gravis (gMG), a neuromuscular disease similarly characterized by
autoantibody-mediated complement activation and tissue injury, provide
strong rationale for the clinical evaluation of zilucoplan in this
disease.”

IMNM is an autoimmune myopathy characterized by skeletal muscle
necrosis, severe proximal limb weakness, and elevated creatine kinase
(CK) levels. IMNM is categorized into two subtypes defined by the
presence of distinct autoantibodies against
3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) or signal
recognition particle (SRP). In IMNM, these autoantibodies drive
complement-mediated necrosis of muscle fibers, resulting in severe,
progressive, and debilitating proximal muscle weakness. IMNM affects
more than 15,000 patients in the United States, European Union, and
Japan. There are currently no approved therapies for the treatment of
IMNM.

The randomized, double-blind, placebo-controlled, multi-center, Phase 2
trial will evaluate the safety, tolerability, and efficacy of zilucoplan
in patients with IMNM who are positive for anti-HMGCR or anti-SRP
autoantibodies. Patients will be randomized in a 1:1 ratio to receive
daily subcutaneous (SC) doses of 0.3 mg/kg zilucoplan or placebo.
Randomization will be stratified based on antibody status (anti-HMGCR+
versus anti-SRP+). The trial is expected to enroll approximately 24
patients with an eight-week treatment period. The primary endpoint will
be change in CK from baseline to week eight. Following completion of the
trial, patients will have the option to enter into an open-label
long-term extension study with zilucoplan.

“The IMNM program represents a meaningful expansion of our neuromuscular
pipeline for zilucoplan, as we aim to leverage the unique properties of
a small peptide in tissue-based complement-mediated disorders and build
on the success of our Phase 2 trial for zilucoplan in gMG,” said Doug
Treco, Ph.D., President and Chief Executive Officer of Ra Pharma. “We
look forward to the initiation of this Phase 2 clinical trial in the
second half of this year, an important step forward in our efforts to
bring innovative and accessible therapies to patients and build a
leading complement-focused neurology and neuromuscular portfolio.”

Analyst and Investor Event

Ra Pharma will host an analyst and investor event on Tuesday, June 18,
2019, at 8:30 a.m. E.T. The event will feature a presentation by Andrew
Mammen, M.D., Ph.D., Muscle Disease Unit Leader, Laboratory of Muscle
Stem Cells and Gene Regulation, and Principal Investigator for the Phase
2 study at the National Institute of Arthritis and Musculoskeletal and
Skin Diseases, National Institutes of Health, Bethesda, MD. The event
will be webcast live and can be accessed by visiting the investor
relations section of the Company’s website, www.rapharma.com.
A replay will be available and archived on the site for three weeks.

About Zilucoplan

Ra Pharma is developing zilucoplan and zilucoplan extended release (XR)
for generalized myasthenia gravis (gMG), immune-mediated necrotizing
myopathy (IMNM), and other tissue-based, complement-mediated disorders
with high unmet medical need. The product candidate is designed for
convenient subcutaneous (SC) self-administration. Zilucoplan is an
investigational, synthetic, macrocyclic peptide discovered using Ra
Pharma’s powerful proprietary drug discovery technology. The peptide is
designed to bind complement component 5 (C5) with sub-nanomolar affinity
and allosterically inhibit its cleavage into C5a and C5b upon activation
of the classical, alternative, or lectin pathways.

About Ra Pharmaceuticals

Ra Pharmaceuticals is a clinical-stage biopharmaceutical company focused
on leading the field of complement biology to bring innovative and
accessible therapies to patients with rare diseases. The Company
discovers and develops peptides and small molecules to target key
components of the complement cascade. For more information, please
visit: www.rapharma.com.

Forward-Looking Statements

This press release contains “forward-looking statements” within the
meaning of the Private Securities Litigation Reform Act of 1995,
including, but not limited to, statements regarding Ra Pharma’s ability
to expand patient access to important therapies, the potential, safety,
efficacy, and regulatory and clinical progress of Ra Pharma’s product
candidates, including without limitation zilucoplan and our zilucoplan
XR program, beliefs regarding clinical trial data, statements regarding
trial design, timeline, and enrollment of Ra Pharma’s ongoing and
planned clinical programs, including without limitation the Phase 2
trial of zilucoplan for the treatment of IMNM and long-term extension
study, and plans to host an analyst and investor event. All such
forward-looking statements are based on management’s current
expectations of future events and are subject to a number of risks and
uncertainties that could cause actual results to differ materially and
adversely from those set forth in or implied by such forward-looking
statements. These risks and uncertainties include the risks that Ra
Pharma’s product candidates, including zilucoplan, will not successfully
be developed or commercialized, in the timeframe we expect or at all; as
well as the other factors discussed in the “Risk Factors” section in Ra
Pharma’s most recently filed Annual Report on Form 10-K, as well as
other risks detailed in Ra Pharma’s subsequent filings with the
Securities and Exchange Commission. There can be no assurance that the
actual results or developments anticipated by Ra Pharma will be realized
or, even if substantially realized, that they will have the expected
consequences to, or effects on, Ra Pharma. All information in this press
release is as of the date of the release, and Ra Pharma undertakes no
duty to update this information unless required by law.

Contacts

Investors:
Ra Pharmaceuticals, Inc.
Natalie Wildenradt,
617-674-9874
[email protected]

Media:
Argot Partners
David Rosen, 212-600-1902
[email protected]