Ra Pharmaceuticals Presents Data on Oral, Small Molecule Complement Inhibitors and Phase 2 RA101495 SC Program in PNH at the 23rd Congress of the European Hematology Association

Ra Pharmaceuticals, Inc. (Nasdaq:RARX) today announced the presentation
of scientific data at the 23rd Congress of the European
Hematology Association (EHA), June 14-17, 2018 in Stockholm, Sweden.

“The characterization of our first-in-class, orally bioavailable, small
molecules highlights their feasibility as effective C5 inhibitors,
illustrated by their drug-like properties and favorable pharmacokinetic
(PK) behavior,” said Alonso Ricardo, PhD, Senior Vice President and Head
of Research at Ra Pharma. “Along with the established PK/pharmacodynamic
(PD) relationship, these data provide a valuable foundation supporting
the further investigation of these molecules with potential
applicability in a broad range of complement-mediated diseases.”

“At EHA, we also highlight the results from our global, Phase 2 program
evaluating RA101495 SC in paroxysmal nocturnal hemoglobinuria (PNH), in
which RA101495 SC was shown to be safe and well-tolerated, and achieved
and maintained robust control of lactate dehydrogenase (LDH) levels in
treatment-naïve and transfusion-independent eculizumab-switch PNH
patients,” said Ramin Farzaneh-Far, MD, Chief Medical Officer of Ra
Pharma. “These data suggest that RA101495 SC, a once-daily, low-volume,
subcutaneous, self-administered therapy, has the potential to serve as a
more convenient and accessible therapeutic option for patients with PNH
and provide support for initiation of our Phase 3 program.”

Inhibition of C5 is a clinically-validated approach for the therapeutic
treatment of multiple complement-mediated disorders. Ra Pharma’s
portfolio includes RA101495, a macrocyclic peptide inhibitor of C5 being
developed for convenient, once-daily, subcutaneous self-administration
for the treatment of several debilitating disorders, including PNH,
generalized myasthenia gravis (gMG), and atypical hemolytic uremic
syndrome (aHUS). In parallel, the Company is pursuing the identification
of orally-available inhibitors of C5 with the goal of providing
additional options for patients diagnosed with these and other
complement-mediated disorders.

“These data highlight the breadth of our work in the complement
inhibition space,” said Doug Treco, PhD, President and Chief Executive
Officer of Ra Pharma. “Leveraging the validation of C5 inhibition as an
effective treatment for complement-mediated diseases, we remain
committed to addressing the limitations of currently available
therapies, which require burdensome, high-volume intravenous infusions.
These data mark significant achievements in our mission to provide
transformative complement treatments that benefit the largest population
of patients possible.”

A summary of the data presented is as follows:

Title: Characterization of Orally Bioavailable Small Molecule
Inhibitors of Complement C5Session Title: Bone marrow
failure syndromes incl. PNH – Biology & Translational ResearchPresenter:
Alonso Ricardo, Ph.D., Senior Vice President and Head of Research, Ra
PharmaDate/Time: Sunday, June 17, 8:15-8:30 CESTLocation:
Room A8Abstract Code: 3854Summary: This
presentation describes studies designed to evaluate the pharmacology in
human whole blood-based assay models, pharmacokinetics in several
pre-clinical species, and the ex vivo PK/PD relationship of
orally bioavailable, small molecule inhibitors of complement C5 after
oral administration. In pre-clinical models, the PK data demonstrate
that compounds within this series display dose-dependent oral exposure
and low clearance values. The ex vivo and in vitro assays
demonstrate selective engagement of complement C5. The PK/PD
relationship informs the level of exposure required to achieve
therapeutic efficacy in humans. Collectively, these data confirm the
feasibility of an oral, small molecule inhibitor of complement C5.

Title: RA101495, A Subcutaneously-administered Peptide Inhibitor
of Complement Component C5, For the Treatment of Paroxysmal Nocturnal
Hemoglobinuria: Phase 2 ResultsSession Title: Bone marrow
failure syndromes incl. PNH – ClinicalDate/Time: Friday,
June 15, 17:30-19:00 CESTLocation: Poster areaAbstract
Code: 1430Summary: This poster describes the results of
the Phase 2, global, multi-center, open-label, dose-finding program. RA101495,
self-administered by low volume, daily, subcutaneous injection, appears
safe and well-tolerated in patients with PNH. RA101495 SC rapidly and
robustly reduces LDH to the levels seen in patients receiving eculizumab
and which are associated with improved long-term outcomes in PNH. These
Phase 2 findings indicate that RA101495 SC may provide a more convenient
and cost-effective treatment for PNH patients.

About RA101495

Ra Pharma is developing RA101495 SC for paroxysmal
nocturnal hemoglobinuria (PNH), generalized
myasthenia gravis (gMG), atypical hemolytic uremic syndrome (aHUS),
and lupus
nephritis (LN). The product is designed for convenient, once-daily
subcutaneous self-administration. RA101495 SC is a synthetic,
macrocyclic peptide discovered using Ra Pharma’s powerful proprietary
drug discovery technology. The peptide binds complement component 5 (C5)
with sub-nanomolar affinity and allosterically inhibits its cleavage
into C5a and C5b upon activation of the classical, alternative, or
lectin pathways. By binding to a region of C5 corresponding to C5b,
RA101495 SC is designed to disrupt the interaction between C5b and C6
and prevent assembly of the membrane attack complex (MAC). This activity
may define an additional, novel mechanism for the inhibition of C5

About RA101495 SC Phase 2 PNH Clinical Program

The global, dose-finding Phase 2 program was designed to evaluate the
safety, tolerability, preliminary efficacy, PK, and PD of RA101495 SC in
patients with PNH. The study evaluated RA101495 SC in three cohorts. The
first cohort included eculizumab-naïve patients, the second cohort
included patients switching from eculizumab to RA101495 SC, and the
third cohort included patients who were currently treated with
eculizumab but had evidence of an inadequate response. Patients in all
three cohorts were eligible for entry into a long-term extension study
following the completion of the initial 12-week studies. The primary
efficacy endpoint was the change in LDH from baseline to the mean level
from week 6 to week 12.

About Ra Pharmaceuticals

Ra Pharmaceuticals is a clinical stage biopharmaceutical company
focusing on the development of next-generation therapeutics for
complement-mediated 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 Statement

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 the safety, efficacy
and regulatory and clinical progress, convenience and cost-effectiveness
of our product candidates, including RA101495 SC, statements regarding
the feasibility, efficacy and potential use of our small molecules in
pre-clinical development, and statements regarding trial design,
timeline and enrollment of our ongoing and planned clinical programs.
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 RA101495 SC, will not
successfully be developed or commercialized; the risk that topline
results as of February 7, 2018 from the Company’s global Phase 2
clinical program evaluating RA101495 SC for the treatment of PNH may not
be indicative of final study results; as well as the other important
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.

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