Proof of Concept study of the efficacy and tolerability of a 4-week treatment with F13640 in patients in whom the adaptation of opioid therapy of cancer pain has failed. A prospective, multinational, multicentre, randomised, double-blind, placebo-controlled study.

INTERVENTION: Product Code: F13640 Pharmaceutical Form: Capsule, hard CAS Number: 208110‐64‐9 Current Sponsor code: F13640 Concentration unit: mg milligram(s) Concentration type: equal Concentration number: 0.5‐ Pharmaceutical form of the placebo: Capsule, hard Route of administration of the placebo: Oral use CONDITION: Patients who have failed adaptation of opioid therapy for cancer pain ; MedDRA version: 9.1 Level: LLT Classification code 10058019 Term: Cancer pain PRIMARY OUTCOME: Main Objective: The primary objective of the study is the enhancement of analgesia by F13640 when gradually introduced in combination with opioid treatment after 14 days to evaluated by the pourcentage (% of responders) in patients who have failed adaptation of opioid therapy for cancer pain, when administered for 2 weeks including a 7‐day titration period. Primary end point(s): Response to the trial defined by a decrease of at least 10 of the 24 hour recall pain intensity VAS score (maximum of pain at rest and mobilization on each day), between inclusion (mean value of the last 7 days before inclusion) and the end of the first 2‐week treatment period (mean value of the last 4 days before Day 14 or visit of premature withdrawal). Data will be captured on a Personal digital assistant (PDA). Secondary Objective: To evaluate if :; ‐ F13640 treatment allows decreasing cumulative opioid consumption (opioid saving) and reducing adverse effects whatever the dose administered during the treatment period.; ‐ F13640 induces a long lasting analgesic effect after the treatment period and F13640 withdrawal can cause any rebound effect in patients who have failed adaptation of opioid therapy for cancer pain, when administered for 4 weeks including a 7‐day titration period.; ‐ Other secondary objectives are to assess pain relief, impact on sleep, safety and tolerability on this population during the study period. ; INCLUSION CRITERIA: ‐ Out‐patient male or female ‐ Aged > 18 years and < or = 65 years ‐ Diagnosis of cancer confirmed ‐ Life expectancy > 3 months ‐ With cancer pain for more than one month ‐ Under fixed scheduled opioid treatment (oxycodone, morphine, hydromorphone or fentanyl only) for cancer pain for at least 7 days before inclusion ‐ In failure of opioid therapy adaptation (oxycodone, morphine hydromorphone or fentanyl only): 24‐hour recall pain intensity score > 40mm on a 0‐100mm Visual Analogue Scale (VAS rest or mobilization) at the selection visit, in spite of appropriate oral or transdermal opioid treatment at the maximum tolerated dose, where any adjunctive analgesic medication had been instituted before, such treatment shall be continued in an unchanged manner ‐ Average 24‐hour recall pain intensity score of the last 7 days before inclusion > 40 on a 0‐100 Visual Analogue Scale on a Personal Digital Assistant ‐ Record of at least 4 assessable e