Completed

A Phase 2, Enriched-Enrollment, Randomized-Withdrawal, Double-Blind, Placebo-Controlled, Multi-Center Study to Assess the Efficacy, Tolerability, and Safety of NKTR-181 in Opioid-Naïve Subjects With Moderate to Severe Chronic Pain Due to Osteoarthritis of the Knee

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What is being tested

NKTR-181

+ Placebo

Drug
Who is being recruted

Arthritis+3

+ Joint Diseases

+ Musculoskeletal Diseases

Over 18 Years
+23 Eligibility Criteria
See all eligibility criteria
How is the trial designed

Treatment Study

Placebo-ControlledPhase 2
Interventional
Study Start: June 2012
See protocol details

Summary

Principal SponsorNektar Therapeutics
Last updated: January 28, 2026
Sourced from a government-validated database.Claim as a partner

Study start date: June 1, 2012

Actual date on which the first participant was enrolled.

NKTR-181 is being developed as an analgesic compound for the treatment of moderate to severe chronic pain - active as a mu agonist, but with inherent molecular properties designed to provide a unique clinical profile, including most notably, reduced CNS side effects and an attenuated attractiveness as a target of abuse.

Official TitleA Phase 2, Enriched-Enrollment, Randomized-Withdrawal, Double-Blind, Placebo-Controlled, Multi-Center Study to Assess the Efficacy, Tolerability, and Safety of NKTR-181 in Opioid-Naïve Subjects With Moderate to Severe Chronic Pain Due to Osteoarthritis of the Knee
NCT01619839
Principal SponsorNektar Therapeutics
Last updated: January 28, 2026
Sourced from a government-validated database.Claim as a partner

Protocol

This section provides details of the study plan, including how the study is designed and what the study is measuring.
Design Details

296 patients to be enrolled

Total number of participants that the clinical trial aims to recruit.

Treatment Study

These studies test new ways to treat a disease, condition, or health issue. The goal is to see if a new drug, therapy, or approach works better or has fewer side effects than existing options.

Eligibility

Researchers look for people who fit a certain description, called eligibility criteria: person's general health condition or prior treatments.
Conditions
Criteria

Any sex

Biological sex of participants that are eligible to enroll.

Over 18 Years

Range of ages for which participants are eligible to join.

Healthy volunteers not allowed

If individuals who are healthy and do not have the condition being studied can participate.

Conditions

Pathology

ArthritisJoint DiseasesMusculoskeletal DiseasesOsteoarthritisRheumatic DiseasesOsteoarthritis, Knee

Criteria

9 inclusion criteria required to participate
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;
Show More Criteria
14 exclusion criteria prevent from participating
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;
Show More Criteria

Study Plan

Find out more about all the medication administered in this study, their detailed description and what they involve.
Treatment Groups
Study Objectives

5 intervention groups are designated in this study

20% chance of being blinded to the placebo group

Treatment Groups

Group I

Experimental
100 mg of NKTR-181 in tablet form, BID. Dosing to occur at Titration period up to 30 days and at Randomization period up to 24 days.

Group II

Experimental
200 mg of NKTR-181 in tablet form, BID. Dosing to occur at Titration period up to 30 days and at Randomization period up to 24 days.

Group III

Experimental
300 mg of NKTR-181 in tablet form, BID. Dosing to occur at Titration period up to 30 days and at Randomization period up to 24 days

Group IV

Experimental
400 mg of NKTR-181 in tablet form, BID. Dosing to occur at Titration period up to 30 days and at Randomization period up to 24 days

Group 5

Placebo
Placebo dosing will be only in the double-blind randomization arm and will be identical in form to the Experimental NKTR-181.

Study Objectives

Primary Objectives

Secondary Objectives

Study Centers

These are the hospitals, clinics, or research facilities where the trial is being conducted. You can find the location closest to you and its status.

This study has 34 locations

Suspended

Investigator Site - Mobile

Mobile, United StatesOpen Investigator Site - Mobile in Google Maps
Suspended

Investigator Site - Tuscon

Tucson, United States
Suspended

Investigator Site - Garden Grove

Garden Grove, United States
Suspended

Investigator Site - San Diego

San Diego, United States
Completed34 Study Centers