Aimmune Therapeutics Provides Update on Ongoing AR101 Phase 3 Program for Peanut Allergy Based on FDA Feedback

— AR101 Program to Initially Address Urgent Unmet Need of
Peanut-Allergic Patients Ages 4-17, Consistent with Breakthrough Therapy
Designation —

— Potential BLA Filing to Include Safety Database of 600 Patients,
Achievable with Current Phase 3 Program —

— Conference Call Today at 5:00 p.m. Eastern Time / 2:00 p.m. Pacific
Time —

BRISBANE, Calif.–(BUSINESS WIRE)–Aimmune Therapeutics, Inc. (Nasdaq:AIMT), a biopharmaceutical company
developing treatments for life-threatening food allergies, today
announced an AR101 Phase 3 program update, based on recent feedback from
the U.S. Food and Drug Administration (FDA). AR101 is Aimmune’s
investigational biologic oral immunotherapy for desensitization of
patients with peanut allergy.

The primary efficacy analysis in the ongoing Phase 3 PALISADE trial will
now be conducted on ages 4-17 years, which aligns with the Breakthrough
Therapy Designation population, based on the company’s discussions with
the FDA. The company expects to conduct separate analyses for older
patients in PALISADE. Additionally, based on FDA feedback, the company
anticipates that the safety database for a potential Biologics License
Application (BLA) will include data from at least 600 patients treated
with AR101.

We believe that clarity on safety database size and initially focusing
on the Breakthrough Therapy Designation age group increase the
probability of regulatory success of our AR101 development program,”
said Aimmune CEO Stephen Dilly, M.B.B.S., Ph.D. “At the same time, this
initial focus allows us to target the urgent unmet need of the largest
age segment of peanut-allergic patients.”

Target Population: Prioritizing High Unmet Medical Need of Largest
Age Group

The PALISADE trial enrolled 554 patients, 90 percent of whom were
between ages 4-17. This age group, which represents a high-unmet need
for peanut allergy therapy, is the largest segment of the 6 million
peanut allergic patients in the United States and Europe. By 2018, the
number of peanut-allergic patients ages 4-17 is estimated to reach 1.6
million in the United States alone.1-4

We will move as quickly as possible to make AR101 available to 4-17
year-old patients, in whom AR101 demonstrated encouraging activity in
our Phase 2 trial,” said Dr. Dilly. “We are eager to see if our Phase 2
results are confirmed in the same patient population in our ongoing
Phase 3 program, but in much larger numbers. We remain committed to
broadening access to include older patients in the longer term based on
our overall Phase 3 data set.”

BLA Filing Expected to Include Safety Data on 600 Patients Treated
with AR101

After discussions with the FDA, the company expects that a potential BLA
for AR101 would include efficacy data from the PALISADE trial and safety
data from at least 600 patients in the PALISADE, ARC004 and RAMSES
trials. ARC004, the PALISADE roll-over trial, is currently enrolling
patients.

Aimmune plans to initiate the RAMSES trial, which will enroll
approximately 440 patients ages 4-17 in the United States, in 2Q 2017.
RAMSES is a randomized, double-blind, placebo-controlled trial that will
monitor treatment-emergent adverse events during a six-month up-dosing
period. Patients will then be followed in an open-label manner for at
least six months on the maintenance dose of 300 mg of AR101 per day.

We believe that our discussions with the FDA allow us to move forward
with a higher degree of clarity about what’s likely to be needed to get
AR101 through the regulatory process and, as beneficiaries of
Breakthrough Therapy Designation, we will continue to engage with the
agency to prepare for a potential 2018 BLA filing,” said Dr. Dilly.
With approximately $283 million in cash and investments at the start of
2017, we have sufficient funding to support the current clinical
development plan and North American and European regulatory submissions
for AR101.”

Conference Call and Webcast Information

Aimmune will host a conference call and live audio webcast Thursday,
February 16, 2017, at 5:00 p.m. ET / 2:00 p.m. PT to discuss the
announced AR101 program updates. The conference call will be accessible
via the company’s website at www.aimmune.com
on the Events page under Investor Relations. Please connect to the
company’s website at least 15 minutes prior to the start of the
conference call to ensure adequate time for any software download that
may be required to listen to the webcast. Alternatively, participants
may dial 1-877-497-1438 (domestic) or 1-262-558-6296 (international) and
refer to conference ID 74579812. An archived copy of the webcast will be
available on the company’s website for at least 30 days after the
conference call.

About Aimmune Therapeutics

Aimmune Therapeutics, Inc., is a clinical-stage biopharmaceutical
company developing treatments for life-threatening food allergies. The
company’s Characterized Oral Desensitization ImmunoTherapy
(CODIT™) approach is intended to achieve meaningful levels of protection
by desensitizing patients with defined, precise amounts of key
allergens. Aimmune’s first investigational product using CODIT™, AR101
for the treatment of peanut allergy, has received the FDA’s Breakthrough
Therapy Designation for the desensitization of peanut-allergic patients
4-17 years of age and is currently being evaluated in Phase 3 clinical
trials in ages 4-55. AR101 is a characterized, regulated, oral
biological drug product containing the protein profile found in peanuts.
For more information, please see www.aimmune.com.

References

1. Sicherer, Scott H., Anne Muñoz-Furlong, and Hugh A. Sampson. 2003.
Prevalence of Peanut and Tree Nut Allergy in the United States
Determined by Means of a Random Digit Dial Telephone Survey: A 5-Year
Follow-Up Study.” The Journal of Allergy and Clinical Immunology
112 (6): 1203–7.

2. Sicherer, Scott H., Anne Muñoz-Furlong, James H. Godbold, and Hugh A.
Sampson. 2010. “US Prevalence of Self-Reported Peanut, Tree Nut, and
Sesame Allergy: 11-Year Follow-Up.” The Journal of Allergy and
Clinical Immunology
125 (6): 1322–26.

3. Gupta, Ruchi S., Elizabeth E. Springston, Manoj R. Warrier, Bridget
Smith, Rajesh Kumar, Jacqueline Pongracic, and Jane L. Holl. 2011. “The
Prevalence, Severity, and Distribution of Childhood Food Allergy in the
United States.” Pediatrics 128 (1): e9-17.

4. Nwaru, B. I., L. Hickstein, S. S. Panesar, G. Roberts, A. Muraro, A.
Sheikh, and EAACI Food Allergy and Anaphylaxis Guidelines Group. 2014.
Prevalence of Common Food Allergies in Europe: A Systematic Review and
Meta-Analysis.” Allergy 69 (8): 992–1007.

Forward-Looking Statements

Statements contained in this press release regarding matters that are
not historical facts are “forward-looking statements” within the meaning
of the Private Securities Litigation Reform Act of 1995. Because such
statements are subject to risks and uncertainties, actual results may
differ materially from those expressed or implied by such
forward-looking statements. Such statements include, but are not limited
to, statements regarding: Aimmune’s expectations for its Phase 3
PALISADE trial of AR101, including the expected timing of topline data;
Aimmune’s expectations regarding the potential benefits of AR101;
Aimmune’s expectations regarding the sufficiency of its capital
resources; Aimmune’s expectations for the RAMSES trial, including the
timing and enrollment of the trial; Aimmune’s expectations on regulatory
submissions for marketing approval of AR101 in the United States and
Europe, including the timing of these submissions; and Aimmune’s
expectations regarding potential applications of the CODIT™ approach to
treating life-threatening food allergies. Risks and uncertainties that
contribute to the uncertain nature of the forward-looking statements
include: the expectation that Aimmune will need additional funds to
finance its operations; the company’s ability to initiate and/or
complete clinical trials; the unpredictability of the regulatory
process; the possibility that Aimmune’s clinical trials will not be
successful; Aimmune’s dependence on the success of AR101; the company’s
reliance on third parties for the manufacture of the company’s product
candidates; possible regulatory developments in the United States and
foreign countries; and the company’s ability to attract and retain
senior management personnel. These and other risks and uncertainties are
described more fully in Aimmune’s most recent filings with the
Securities and Exchange Commission, including its Annual Report on Form
10-K for the year ended 2015 and Quarterly Report on Form 10-Q for the
quarter ended September 30, 2016. All forward-looking statements
contained in this press release speak only as of the date on which they
were made. Aimmune undertakes no obligation to update such statements to
reflect events that occur or circumstances that exist after the date on
which they were made.

This press release concerns a product that is under clinical
investigation and that has not yet been approved for marketing by the
U.S. Food and Drug Administration (FDA) or the European Medicines Agency
(EMA). It is currently limited to investigational use, and no
representation is made as to its safety or effectiveness for the
purposes for which it is being investigated.

Contacts

Aimmune Therapeutics, Inc.
Investors
Laura Hansen, Ph.D.,
650-396-3814
lhansen@aimmune.com
or
Media
Stephanie
Yao, 650-351-6479
syao@aimmune.com