Safety/Efficacy Study of Retigabine vs. Placebo in Post-Herpetic Neuralgia (PHN)

Recruitment Details

Key information relevant to the recruitment process for the overall study, such as dates of the recruitment period and locations
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Pre-Assignment Details

Significant events and approaches for the overall study following participant enrollment, but prior to group assignment
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Reporting Groups

	Description
1: Retigabine	Arm Description: Participants started on a total daily dose of 150 milligrams (mg) and were titrated to their maximum tolerated dose (MTD) up to a maximum of 900 mg daily using retigabine 50 mg and/or 100 mg tablets. The dose was increased by 150 mg each week and administered 3 times daily (TID) in equally divided doses. In the Maintenance Phase, retigabine was administered in equally divided doses to maintain the participant’s MTD. Participants with moderate to severe side effects during the first week at their MTD and who had attained at least dose level 3 (450 mg) were allowed a one level dose reduction (150 mg). Participants unable to maintain the MTD discontinued the medication. In the Taper Phase, the dose was reduced by one-third during each of the first two weeks, and the study medication was stopped by the third week during the 3-week duration.
2: Placebo	Arm Description: Matching placebo tablets of dummy strengths of 50 mg and 100 mg were administered orally TID for up to 6 weeks of the Titration Phase, 4 weeks of the Maintenance Phase, and 3 weeks of the Taper Phase.

Participant Flow for 3 periods

Period 1:   Period Title 1: 6-Week Titration Phase

	1: Retigabine	2: Placebo
STARTED	125	62
COMPLETED	89	57
NOT COMPLETED	36	5
Adverse Event	18	1
Withdrawal by Subject	6	1
Lost to Follow-up	2	0
Physician Decision	1	1
Protocol Violation	1	0
Missed study drug for more than two days	3	1
Lack of Efficacy	5	0
Unknown	0	1

Period 2:   Period Title 2: 4-Week Maintenance Phase

	1: Retigabine	2: Placebo
STARTED	89	57
COMPLETED	78	55
NOT COMPLETED	11	2
Adverse Event	9	1
Missed study drug for more than two days	1	1
Lost to Follow-up	1	0

Period 3:   Period Title 3: 3-Week Taper Phase

	1: Retigabine	2: Placebo
STARTED	86 [1]	58 [1]
COMPLETED	85	58
NOT COMPLETED	1	0
Unknown	1	0

Reporting Groups

	Description
1: Retigabine	Arm Description: Participants started on a total daily dose of 150 milligrams (mg) and were titrated to their maximum tolerated dose (MTD) up to a maximum of 900 mg daily using retigabine 50 mg and/or 100 mg tablets. The dose was increased by 150 mg each week and administered 3 times daily (TID) in equally divided doses. In the Maintenance Phase, retigabine was administered in equally divided doses to maintain the participant’s MTD. Participants with moderate to severe side effects during the first week at their MTD and who had attained at least dose level 3 (450 mg) were allowed a one level dose reduction (150 mg). Participants unable to maintain the MTD discontinued the medication. In the Taper Phase, the dose was reduced by one-third during each of the first two weeks, and the study medication was stopped by the third week during the 3-week duration.
2: Placebo	Arm Description: Matching placebo tablets of dummy strengths of 50 mg and 100 mg were administered orally TID for up to 6 weeks of the Titration Phase, 4 weeks of the Maintenance Phase, and 3 weeks of the Taper Phase.
Total	Total of all reporting groups

Baseline Measures

	1: Retigabine	2: Placebo	Total
Number of Participants   [units: participants]	125	62	187
Age   [units: participants]
<=18 years	0	0	0
Between 18 and 65 years	64	34	98
>=65 years	61	28	89
Age   [units: years] Mean ± Standard Deviation	63.2  ± 11.07	61.2  ± 14.28	62.5  ± 12.23
Gender   [units: participants]
Female	64	36	100
Male	61	26	87
Region of Enrollment   [units: participants]
United States	94	47	141
South Africa	31	15	46

1.  Primary:

Primary Endpoint Will be the Change From Baseline in Average Pain Score Over the Last 7 Days of the Maintenance Phase.   [ Time Frame: Baseline and Week 4 (Maintenance Phase-MP) ]

2.  Secondary:

Change From Baseline to Weeks 2 and 4 of the Maintenance Phase in Mean In-clinic Pain Assessment   [ Time Frame: Baseline and Weeks 2 and 4 (Maintenance Phase - MP) ]

3.  Secondary:

Number of Rescue Medication Tablets Taken Per Day During the Maintenance Phase (MP)   [ Time Frame: Weeks 1, 2, 3, and 4 Maintenance Phase ]

4.  Secondary:

Change From Baseline in Pain Intensity Score at Each Week During the Maintenance Phase (MP)   [ Time Frame: Baseline and Weeks 1, 2, 3, and 4 (MP) ]

5.  Secondary:

Number of Participants Classified as Responders, With a 50% and 30% Pain Reduction From Baseline to the Last 7 Days of the Maintenance Phase   [ Time Frame: Baseline and Week 4 Maintenance Phase (MP) ]

6.  Secondary:

Change From Baseline to the End of the MP (Included All Participants Who Completed Week 4 of the MP and Who Terminated Early During the MP) in Medical Outcomes Study (MOS) Sleep Scale Scores   [ Time Frame: Baseline and End of Maintenance Phase (MP) (Week 4). ]

7.  Secondary:

Change From Baseline to the End of the MP (Included All Participants Who Completed Week 4 of the MP and Who Terminated Early During the MP) in Sleep Quantity   [ Time Frame: Baseline and End of Maintenance Phase (MP) (Week 4). ]

8.  Secondary:

Number of Participants With the Indicated Change From Baseline to the End of the Maintenance Phase in Optimal Sleep Based on the Sleep Quantity Domain of the MOS Sleep Scale   [ Time Frame: Baseline and End of Maintenance Phase (MP) (Week 4). ]

9.  Secondary:

Number of Participants With the Indicated Overall Patient Global Impression of Change (PGIC)   [ Time Frame: Baseline to the end of Maintenance Phase (MP) (Week 4) ]

10.  Secondary:

Mean Score on the Treatment Satisfaction Questionnaire for Medication (TSQM) at the End of the Maintenance Phase   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

11.  Secondary:

Scores on the Brief Pain Inventory-Short Form (BPI-SF) at the End of the MP for All Participants Who Completed Week-4 of the MP and Who Terminated Early During the MP   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

12.  Secondary:

Scores on the Medical Outcomes Short Form-36 (SF-36) at the End of the MP for All Participants Who Completed Week 4 of the MP and Who Terminated Early During the MP   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

13.  Secondary:

Scores for Reported Health Transition at the End of the MP for All Participants Who Completed Week 4 of the MP and Who Terminated Early During the MP   [ Time Frame: End of maintenance Phase (MP) (Week 4) ]

14.  Secondary:

Number of Participants With the Indicated Responses at Baseline to the Question: “How Painful Was the Affected Side Compared to the Opposite Side?” in an Assessment of Tactile Allodynia   [ Time Frame: Baseline Phase (Day -7 to Randomization Day 0) ]

15.  Secondary:

Number of Participants With the Indicated Responses at Baseline to the Questions of “Is it Cool?” and “Is it Painful?” in an Assessment of Cold Threshold and Allodynia   [ Time Frame: Timeframe: Baseline Phase (Day -7 to Randomization Day 0) ]

16.  Secondary:

Number of Participants With the Indicated Responses at Baseline to the Questions: “How Sharp Was the Affected Side Compared to the Opposite Side?” and “How Painful Was the Affected Side Compared to the Opposite Side?” in an Assessment of Hyperalgesia   [ Time Frame: Baseline Phase (Day -7 to Randomization Day 0) ]

17.  Secondary:

Number of Participants With the Indicated Responses at the End of the MP to the Question: “How Painful Was the Affected Side Compared to the Opposite Side?” in an Assessment of Tactile Allodynia   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

18.  Secondary:

Number of Participants With the Indicated Responses at the End of the MP to the Questions of “Is it Cool?” and “Is it Painful?” in an Assessment of Cold Threshold and Allodynia   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

19.  Secondary:

Number of Participants With Indicated Responses at the End of the MP to the Questions: “How Sharp Was the Affected Side Compared to the Opposite Side?” and “How Painful Was the Affected Side Compared to the Opposite Side?” in an Assessment of Hyperalgesia   [ Time Frame: End of Maintenance Phase (MP) (Week 4) ]

20.  Secondary:

Change From Baseline in the Average Diary Pain Score to the Last 7 Days of the Maintenance Phase by Post Herpetic Neuralgia (PHN) Subtype "Irritable Nociceptors"   [ Time Frame: Baseline and Week 4 Maintenance Phase (MP) ]

21.  Secondary:

Change From Baseline in the Average Diary Pain Score to the Last 7 Days of the Maintenance Phase by Post Herpetic Neuralgia (PHN) Subtype"Deafferentation Type 1 (D Type 1)"   [ Time Frame: Baseline and Week 4 Maintenance Phase (MP) ]

22.  Secondary:

Change From Baseline in the Average Diary Pain Score to the Last 7 Days of the Maintenance Phase by Post Herpetic Neuralgia (PHN) Subtype "Deafferentation Type 2 (D Type 2)"   [ Time Frame: Baseline and Week 4 Maintenance phase (MP) ]

23.  Secondary:

Change From Baseline in the Average Diary Pain Score to the Last 7 Days of the Maintenance Phase by Post Herpetic Neuralgia (PHN) Subtype "Unclassifiable"   [ Time Frame: Baseline and Week 4 Maintenance Phase (MP) ]