Meets Primary and Secondary Endpoints in Phase 3

Meets Primary and Secondary Endpoints in Phase 3

Study in Chronic Pain

Significantly Reduced Pain in Patients with Moderate to Severe

Efficacy Endpoint Achieved (p=0.0019)

Conference Call and Webcast

at 5:45 a.m. PDT/8:45 a.m. EDT

San Francisco, March

20, 2017 - Nektar Therapeutics (Nasdaq: NKTR) today announced positive results from the SUMMIT-07 Phase 3 efficacy study

of NKTR-181, a first-in-class opioid analgesic. NKTR-181 is a new chemical entity (NCE) that is the first full mu-opioid agonist

molecule designed to provide potent pain relief without the high levels of euphoria that can lead to abuse and addiction with standard

opioids.1 The U.S. Food and Drug Administration (FDA) has granted the investigational medicine NKTR-181

Fast Track designation for the treatment of moderate to severe chronic pain.

efficacy study are extremely important because they demonstrate that NKTR-181 produces strong analgesia in patients suffering from

chronic pain while NKTR-181 has also demonstrated significantly lower abuse potential than oxycodone in a human abuse potential

study," said clinical investigator Martin Hale, M.D., medical director of Gold Coast Research. "While standard

opioid analgesics, including abuse-deterrent formulations, have been the most effective way to treat chronic pain, they are associated

with serious safety concerns and many opioid-na ve patients fear taking them because of the potential for abuse and addiction.

The data for NKTR-181 suggest that it is a transformational pain medicine that could fundamentally

change how we treat patients with chronic pain conditions."

The SUMMIT-07 study compared

twice-daily dosing of NKTR-181 tablets to placebo in the treatment of over 600 patients with moderate to severe chronic

low back pain who were new to opioid therapy (opioid-na ve). The clinical trial met

the primary efficacy endpoint of the study in demonstrating significantly improved chronic back pain relief with NKTR-181 compared

to placebo (p=0.0019). Key secondary endpoints of the study were also met with high statistical significance.

Pain is one of the most

common reasons people seek medical treatment.2 Low back pain is the second most common cause of disability for

adults in the U.S. 3 Approximately 149 million work days are lost every

year because of low back pain, with total costs estimated to be $100 to 200 billion a year (of which two-thirds is due to lost

wages and lower productivity). 4 A study published in the American Pain Society's

The Journal of Pain in October 2014 estimated that 19 percent of the U.S. population, or 39 million people, suffer from

some type of persistent pain.5

The Phase 3 SUMMIT-07 study used an

enriched-enrollment randomized withdrawal (EERW) trial design in patients with moderate to severe chronic low back pain. The trial

included an open-label titration period in which patients were titrated to a tolerated, effective dose of NKTR-181 (100 mg to 400

mg twice-daily). Following this open-label titration period, patients entered a double-blind, placebo-controlled treatment period

in which they were randomized 1:1 to either continue to receive the tolerated, effective dose of NKTR-181 or to receive matching

placebo (i.e. active drug was withdrawn) for a period of 12 weeks.

During the open-label titration period

of the trial in which patients were titrated to a tolerated, effective dose of NKTR-181, average pain scores dropped by 65% (from

6.73 at screening to 2.32 at randomization, n=610).

The primary endpoint of the study was

mean change in the weekly average pain score in the double-blind randomized treatment period from baseline (end of open-label titration

period) to week 12 (end of double-blind randomized treatment period).

Primary and key sensitivity analyses:

Key secondary endpoints:

study also demonstrated that NKTR-181 had a favorable safety profile and was well tolerated. During the double-blind randomized

treatment period, the most commonly reported adverse events for patients (>5%) were nausea (10.4%) and constipation (8.7%) in

the NKTR-181 arm as compared to nausea (6.0%) and constipation (3.0%) in the placebo arm.

Patients randomized to NKTR-181 as

compared to placebo reported more favorable sleep outcomes as measured by the validated Medical Outcomes Study (MOS) Sleep Scale,

which captures debilitating aspects of sleep most strongly associated with chronic pain. Patients

reported better overall quality of sleep with less sleep problems on NKTR-181 versus placebo. There were no differences

in daytime sleepiness on NKTR-181 versus placebo.

Full data from the SUMMIT-07 study will be presented at a medical meeting in the second half of 2017.

"As a new molecule, NKTR-181 has a highly differentiated

profile with the potential to be one of the most important advancements in pain medicine," said Howard W. Robin, President

and CEO of Nektar Therapeutics. "Given the seriousness of the current opioid epidemic in the U.S. and the significant number

of people battling chronic pain, we are committed to bringing this new molecule to patients and physicians as quickly as possible."

In March 2017, results from a separate human abuse potential

trial of NKTR-181 were published in the American Academy of Pain Medicine's journal of Pain Medicine.

The human abuse potential study assessed the relative abuse potential of a range of therapeutic doses of NKTR-181 (100 mg to 400

mg), the same dose range evaluated in the Phase 3 SUMMIT-07 efficacy trial. All doses of

NKTR-181 tested for abuse potential were rated similarly to placebo in "drug liking" and "feeling high"

scores and had highly statistically significant lower "drug liking" scores and reduced "feeling high" scores

as compared to 40 mg oxycodone (p < 0.0001). In addition, all doses of NKTR-181 also scored lower on sleepiness

when compared to 40 mg oxycodone (p < 0.0001).

there is a pressing societal need for better and safer analgesics," said Dr. Jack Henningfield, Ph.D., Adjunct

Professor of Behavioral Biology in the Department of Psychiatry and Behavioral Sciences at the Johns Hopkins University School

of Medicine and Head of Health Policy and Abuse Liability at Pinney & Associates

in Bethesda, MD. "In the human abuse potential study, even the highest analgesic dose of NKTR-181 was barely distinguishable

from placebo with respect to both drug-liking and feeling high and these effects were modest compared to those produced by oxycodone.

Drug-liking and feeling high are two of the most important metrics that help us understand the abuse potential of a medicine.

Importantly, as NKTR-181 is a new chemical entity, the properties of NKTR-181 are inherent to its molecular structure and independent

of any abuse-deterrent formulation. Today's reported efficacy and safety results, along with the human abuse potential

data published this past week in Pain Medicine, suggest NKTR-181 may be a major advance towards safer opioid therapy for the treatment

of moderate to severe chronic pain."

Conference Call and Webcast Information

Nektar will host a conference call and webcast presentation

today, March 20, 2017, at 8:45 a.m. Eastern Daylight Time to discuss the study results. The call can be accessed by dialing (877)

881-2183 (U.S.) or (970) 315-0453 (international), and entering passcode 89288091. To access the live webcast, or the subsequent

archived recording, visit the Investors section of the Nektar website at www.nektar.com. The webcast will be available

for replay on Nektar's website for two weeks following the call.

NKTR-181 is the first

long-acting, selective mu-opioid agonist designed to provide potent pain relief without the inherent high levels of euphoria which

lead to abuse and addiction with standard opioids. The novel molecular structure of NKTR-181 is designed to have low permeability

across the blood-brain barrier in order to slow its rate of entry into the brain and attenuate the dopamine release that underlies

euphoria. NKTR-181 is the first opioid molecule to exhibit reduction in specific CNS-mediated

side effects, like euphoria, through the strategic alteration of brain-entry kinetics. NKTR-181 is an investigational

medicine and has not been approved by the FDA or any other regulatory agencies.

Current strategies of

abuse deterrence to address the addictive qualities of standard opioids rely on formulations alone. All abuse-deterrent formulations

are limited in that once the opioid within the formulation is liberated through tampering, it can rapidly enter the brain and is

highly euphorigenic. Preclinical data show that the inherent properties of NKTR-181 reduce its rate of entry into the brain compared

to standard mu opioids, regardless of route of administration.12

About the SUMMIT-07 Study Design

SUMMIT-07 used an enriched-enrollment, randomized withdrawal

(EERW) design and enrolled opioid-na ve patients ages 18 to 75 years who had moderate to severe non-neuropathic chronic low

back pain for at least six months. The study included an open-label, dose-titration period followed by a randomized, double-blind,

placebo-controlled 12-week treatment period.

During the open-label titration phase, study participants with