A Phase 2 Study To Assess The Efficacy, Tolerability, And Safety OF NKTR-181 In Subjects With Chronic OA Knee Pain

Inclusion Criteria:

- Willing and able to give written informed consent;

- Willing and able to understand the study procedures, and comply with all study
procedures;

- Females or males, age ≥ 18 years old;

- Body mass index 18-39, inclusive;

- In good general health;

- Clinical diagnosis of OA in one or both knees;

- Have been on a stable regimen of pain medication for the management of OA knee pain;

- Not experiencing adequate pain relief with their current dosing regimen;

- Women of childbearing potential (WCBP) must agree to use highly effective methods of
birth control. Male subjects must agree to use contraception.

Exclusion Criteria:

- Females who are pregnant or lactating;

- Known history of hypersensitivity, intolerance, or allergy to opioids;

- Diagnosed as having any chronic pain symptom that in the Investigator's opinion would
interfere with the assessment of pain and other symptoms of OA;

- Presence of any medical condition that would preclude study participation in the
opinion of the investigator;

- Clinically significant abnormalities of vital signs or clinical laboratory results;

- Clinically significant electrocardiographic abnormalities;

- Received systemic corticosteroids within 30 days prior to signing the consent form;

- Subjects who are known or suspected to be currently abusing alcohol or drugs;

- Positive urine drug screen, or alcohol breath test during Screening Period testing;

- Positive serology for the surface antigen of Hepatitis B (HBsAg) or Hepatitis C
(anti-HCV) during Screening Period testing;

- Known to be human immunodeficiency virus (HIV) positive;

- Donation of blood or plasma within 30 days prior to signing the consent form;

- Participation in another drug or biologic study within 30 days prior to signing the
consent form;

- Any other reason that, in the opinion of the Investigator or Medical Monitor, would
render the subject unsuitable for participation in the study.