Alpine Immune Sciences Announces First Subjects Dosed in Phase I Clinical Trial for Lead Autoimmune/Inflammatory Disease Program ALPN-101

First Dual ICOS/CD28 Inhibitor to Enter Clinical Trials

SEATTLE–(BUSINESS WIRE)–Alpine Immune Sciences, Inc. (NASDAQ:ALPN), a leading clinical-stage
immunotherapy company focused on developing innovative treatments for
cancer, autoimmune/inflammatory, and other diseases, today announced
successful initiation of dosing in its first-in-human Phase I study of
ALPN-101, a first-in-class dual ICOS/CD28 antagonist.

This study will evaluate the safety and tolerability of single- and
multiple-ascending intravenous and/or subcutaneous doses of ALPN-101. In
addition, pharmacokinetics, pharmacodynamics, and exploratory biomarkers
are being evaluated to help determine ALPN-101’s potential for the
treatment of autoimmune and inflammatory diseases. The company expects
data later in 2019.

This first dosing in the initial clinical trial of ALPN-101 is an
important milestone for Alpine as we have now transitioned to a
clinical-stage development company,” stated Mitchell H. Gold, MD,
Executive Chairman and Chief Executive Officer of Alpine. “We look
forward to further exploring how our first-in-class dual ICOS/CD28
antagonist will potentially improve outcomes of patients suffering from
debilitating autoimmune and inflammatory diseases such as GvHD and
psoriatic arthritis.”

AIS-A01 is a randomized, placebo-controlled, blinded study in adult
healthy volunteers to evaluate the safety, tolerability,
pharmacokinetics (PK), and pharmacodynamics of single and multiple
ascending doses of ALPN-101. The trial is being conducted in Australia.
More information is available at www.clinicaltrials.gov
(Identifier: NCT03748836).

About ALPN-101

ALPN-101 is a novel Fc fusion protein of a human inducible T cell
costimulator ligand (ICOSL) variant immunoglobulin domain (vIgD™), and a
first-in-class therapeutic simultaneously inhibiting the CD28 and ICOS
inflammation pathways. CD28 and ICOS are closely related costimulatory
molecules with partially overlapping roles in T cell activation likely
connected to multiple autoimmune and inflammatory diseases. In
preclinical models of graft versus host disease, inflammatory arthritis,
and multiple sclerosis, ALPN-101 demonstrates efficacy superior to
blockade of the CD28 or ICOS pathways alone.

ALPN-101 was engineered using Alpine’s vIgD platform, which uses
directed evolution to transform native IgSF proteins into
multifunctional protein therapeutics.

About Alpine Immune Sciences, Inc.

Alpine Immune Sciences, Inc. is committed to leading a new wave of
functional immune therapeutics. Alpine is employing directed evolution
to create potentially powerful multifunctional immunotherapies to
improve patients’ lives. Alpine has two lead programs. The first,
ALPN-101 for autoimmune/inflammatory diseases, is a dual ICOS/CD28
antagonist, engineered to reduce pathogenic immune responses. The
second, ALPN-202 for cancer, is a dual PD-L1/CTLA-4 antagonist and
PD-L1-dependent CD28 costimulator intended to combine checkpoint
inhibition with T cell costimulation – an approach currently absent from
approved checkpoint therapies. Alpine is backed by world-class research
and development capabilities, a highly-productive scientific platform,
and a proven management team. For more information, visit www.alpineimmunesciences.com.

Forward-Looking Statements

This release contains forward-looking statements within the meaning
of Section 27A of the Securities Act of 1933, Section 21E of the
Securities Exchange Act of 1934 and the Private Securities Litigation
Reform Act of 1995. These forward-looking statements are not based on
historical fact and include statements regarding our platform technology
and potential therapies, the timing of and results from clinical trials
and pre-clinical development activities, the potential efficacy, safety
profile, future development plans, addressable market, regulatory
success and commercial potential of our product candidates, the efficacy
of our clinical trial designs and our ability to successfully develop
and achieve milestones in our development programs. Forward-looking
statements generally include statements that are predictive in nature
and depend upon or refer to future events or conditions, and include
words such as “may,” “will,” “should,” “would,” “expect,” “plan,”
“intend,” and other similar expressions among others. These
forward-looking statements are based on current assumptions that involve
risks, uncertainties and other factors that may cause actual results,
events or developments to be materially different from those expressed
or implied by such forward-looking statements. These risks and
uncertainties, many of which are beyond our control, include, but are
not limited to: clinical trials may not demonstrate safety and efficacy
of any of our product candidates; our ongoing discovery and pre-clinical
efforts may not yield additional product candidates; our discovery-stage
and pre-clinical programs may not advance into the clinic or result in
approved products; any of our product candidates may fail in
development, may not receive required regulatory approvals, or may be
delayed to a point where they are not commercially viable; we may not
achieve additional milestones in our proprietary or partnered programs;
the impact of competition; adverse conditions in the general domestic
and global economic markets; as well as the other risks identified in
our filings with the Securities and Exchange Commission. These
forward-looking statements speak only as of the date hereof and we
undertake no obligation to update forward-looking statements, and
readers are cautioned not to place undue reliance on such
forward-looking statements.

“Transmembrane Immunomodulatory Protein,” “TIP,” “Variant Ig Domain,”
“vIgD” and the Alpine logo are registered trademarks or trademarks of
Alpine Immune Sciences, Inc. in various jurisdictions.

Contacts

Investor Relations:
Pure Communications
Courtney Dugan,
212-257-6723
cdugan@purecommunications.com

Media Relations:
Pure Communications
Jennifer Paganelli,
347-658-8290
jpaganelli@purecommunications.com