Over the last years a rising medical need for treatment of chronic pain was identified. Based on previous findings indicating the pain modulating effects of cannabinoids in chronic pain disorders, this clinical trial investigates the long term efficacy and tolerability of the THC-focused nano endocannabinoid system modulator AP707 in patients with chronic back pain disorders. Patients receive AP707 or placebo over the course of 14 weeks as an add-on to the standard of care. Changes in pain intensity, quality of life and sleep and others measures are monitored through different scales to assess the efficacy of AP707 in patients with chronic back pain.

Inclusion Criteria:

1. Signed and dated informed consent form
2. Patients with chronic back pain since at least 3 months
3. Female and male patients (> 18 years)
4. Patients with more than 1 year life expectancy
5. Patients with optimized sCPT on study entry as defined in section 3.1.1 and section 3.1.3 of the study protocol
6. Willingness of study patients of both sexes to use reliable contraception during study participation and for three months after taking the last study medication
7. Good command of German language, in order to understand questionnaires in German
8. Current moderate to severe pain with pain intensity > 5 on Numeric Rating Scale (NRS, 0 - 10) and thus an existing need for further pain therapy
9. Completed QUISS (Quantification Inventory for Somatoform Syndromes) questionnaire with 45 or less score points
10. Completed painDETECT questionnaire with 20 or more score points

Exclusion Criteria:

1. Medical history of hypersensitivity or intolerance to the investigational product or its ingredients or to ingredients of similar chemical structure
2. Known intolerance to cannabinoids or cannabis products.
3. Participation in another clinical trial within the last four weeks prior to inclusion.
4. Pregnant or nursing women (as excluded by pregnancy testing at visit 1).
5. Other medical conditions that do not allow the trial subject to appraise the nature, scope, and potential consequences of the clinical trial
6. Indications that the trial subject is unlikely to comply with the study protocol (e.g., unwillingness to cooperate)
7. Known use of medicinal cannabis products within the last 8 weeks
8. Active malignant tumor disease, tumor pain, or other dominant severe pain other than that of the study indication
9. Known history of severe liver or kidney diseases
10. Known history of severe cardiovascular disease
11. Known history of or acute mental illness such as severe depression, psychosis, bipolar disorder, mania, anxiety, or obsessive-compulsive disorder
12. Known history of addictive disease (e.g., alcohol, medication, drug addiction)
13. Answered during Screening less than 12 times of 18 the pain intensity (NRS) inquiry
14. Laboratory liver values: Alanine aminotransferase (ALT, GPT) > 3 x ULN (Upper Limit of Normal range), Aspartate aminotransferase (AST, GOT) > 3 x ULN, Alkaline phosphatase (AP) > 2.5 x ULN, and for bilirubin > 1.5 x ULN
15. Laboratory renal value: Serum creatinine > 1.5 ULN