Structured Discontinuation vs Continued Therapy in Suboptimal and Optimal Responders to High-dose Long-term Opioids for Chronic Pain

Inclusion Criteria:

1. Be male or non-pregnant, non-lactating female aged 18 to 75 years, inclusive.

2. Have a clinical diagnosis of non-radicular CLBP (pain that occurs in an area with
boundaries between the lowest rib and the crease of the buttocks) of Class 1 or
proximal radicular (above the knee) pain of Class 2 based on the Quebec Task Force
Classification for Spinal Disorders (subjects with previous surgery or chronic pain
syndrome, i.e., classes 9.2 or 10, will be allowed if their pain does not radiate or
radiates only proximally) for a minimum of 12 months and

1. For the Suboptimal Responder group, pain must have been present for at least
several hours a day and have an Average PI score of 6-9 on an 11-point NRS within
the past 24 hours of screening.

2. For the Optimal Responder group, subjects must have an Average PI score of 1-4 on
an 11-point NRS within the past 24 hours of screening.

3. Have been taking ER/LA opioids or immediate release opioids (at least 4 times at day)
for at least 12 months.

4. Have been taking one of the 3 index ER opioid drugs around-the-clock at a twice-a-day
frequency for at least 3 consecutive months at a total daily dose within the range
shown below.

Daily Dose Range

1. Morphine sulfate extended-release: 120-540mg

2. Oxycodone extended-release: 80-360mg

3. Oxymorphone extended-release: 40-180mg

5. Be considered, in the opinion of the Investigator, to be in generally good health
other than CLBP at screening based upon the results of a medical history, physical
examination, 12-lead ECG, and laboratory profile.

6. Speak, read, write, and understand English (to reduce heterogeneity of data),
understand the consent form, and be able to effectively communicate with the study
staff.

7. Have access to the Internet (to access the patient support program).

8. Voluntarily provide written informed consent.

9. Be willing and able to complete study procedures.

Exclusion Criteria:

1. Have any clinically significant condition that would, in the opinion of the
Investigator, preclude study participation or interfere with the assessment of pain
and other symptoms of CLBP or increase the risk of opioid-related AEs.

2. Have a primary diagnosis of fibromyalgia, complex regional pain syndrome, neurogenic
claudication due to spinal stenosis, spinal cord compression, acute nerve root
compression, severe or progressive lower extremity weakness or numbness, bowel or
bladder dysfunction as a result of cauda equina compression, diabetic amyotrophy,
meningitis, diskitis, back pain because of secondary infection or tumor, or pain
caused by a confirmed or suspected neoplasm.

3. Have undergone a surgical procedure for back pain within 6 months prior to the
Screening Visit.

4. Have had a nerve or plexus block, including epidural steroid injections or facet
blocks, within 1 month prior to the Screening Visit or botulinum toxin injection in
the lower back region within 3 months prior to screening.

5. Have a history of confirmed malignancy within past 2 years, with exception of basal
cell or squamous cell carcinoma of the skin that has been successfully treated.

6. Have uncontrolled blood pressure, i.e., subject has a sitting systolic blood pressure
>180 mm Hg or <90 mm Hg, or a sitting diastolic blood pressure >110 mmHg or <40 mm Hg
at screening.

7. Have a body mass index (BMI) >45 kg/m2. Anyone with a BMI >40 but <45 with complete a
screening tool (STOPBang Questionnaire) to rule out high risk of obstructive sleep
apnea.

8. Have clinically significant depression based on a score of ≥20 on the Patient Health
Questionnaire (PHQ-8)

9. Have suicidal ideation associated with actual intent and a method or plan in the past
year: "Yes" answers on items 4 or 5 of the Columbia-Suicide Severity Rating Scale
(C-SSRS).

10. Have a previous history of suicidal behaviors in the past 5 years: "Yes" answer (for
events that occurred in the past 5 years) to any of the suicidal behavior items of the
C-SSRS.

11. Have any lifetime history of serious or recurrent suicidal behavior. (Non-suicidal
self-injurious behavior is not a trigger for a risk assessment unless in the
Investigator's judgment it is indicated.)

12. Have clinically significant abnormality in clinical chemistry, hematology or
urinalysis, including serum glutamic-oxaloacetic transaminase/aspartate
aminotransferase or serum glutamic pyruvic transaminase/alanine aminotransferase ≥3
times the upper limit of the reference range or a serum creatinine >2 mg/dL at
screening.

13. Have severe enough psychiatric or substance abuse disorder to compromise the subject's
safety or scientific integrity of the study.

14. Have on-going litigation associated with back pain or pending applications for workers
compensation or disability issues or subjects who plan on filing litigation or claims
within the next 12 months; subjects with settled past litigations will be allowed as
will subjects who have been on workers compensation or disability claims for at least
3 months.

15. Have used a monoamine oxidase inhibitor within 14 days prior to the start of study
medication.

16. Are taking agonist-antagonists (pentazocine, butorphanol or nalbuphine),
buprenorphine, methadone, barbiturates, or more than one type of benzodiazepine within
1 month prior to screening.

17. Have a positive UDT for illicit drugs (including marijuana), non-prescribed controlled
substances (opioid or non-opioid), or alcohol at screening.

18. Have taken any investigational drug within 30 days prior to the Screening Visit or are
currently enrolled in another investigational drug study.