Effectiveness of 3,4-Diaminopyridine in Lambert-Eaton Myasthenic Syndrome

The objectives of the study were to confirm the safety and to test the efficacy of 3,4-DAP in the treatment of LEMS-related weakness.

This was a phase 2 randomized double-blind placebo-controlled withdrawal study in subjects with known clinically active LEMS who had been on a chronic stable dose of compassionate distribution Jacobus 3,4-DAP provided through FDA-approved individual investigator-held INDs.

• Continuous 3,4-DAP (Drug), also known as 3,4-Diaminopyridine, 3,4-Pyridinediamine, Diamino-3,4-pyridine: Subjects were maintained on their usual personal dose and schedule of 3,4-DAP base
• Taper 3,4-DAP to Placebo (Drug), also known as 3,4-Diaminopyridine, 3,4-Pyridinediamine, Diamino-3,4-pyridine, Placebo: Subjects were tapered over 3 days from their usual regimen of 3,4-DAP base to placebo with up to an additional 16 hours of placebo before resuming their usual pre-study regimen of 3,4-DAP base

Primary outcomes

• Number of Participants With 30% or More Deterioration in Triple Timed Up & Go (3TUG) Test, Compared to Time-matched Baseline [Baseline period (days 0, 1, 2); Randomized treatment period (starting with last dose of day 2, and days 3, 4, 5, and ending with first dose on day 6 when pre-randomization regimen was resumed, or rescue, if indicated sooner)]: The 3TUG time obtained 2 hours after the last dose of the withdrawal period (i.e., at time of theoretical "peak drug effect") was compared to the average time-matched 3TUG tests performed during 2 days of baseline observation prior to randomization. The study endpoint was a change of more than 30% in the final post-dose 3TUG during the withdrawal period and was based on blinded readings of video recordings of 3TUG tests.

Secondary outcomes

• Self-assessment of LEMS-related Weakness, W-SAS [Participants were followed for up to 7 days]: The last post-dose self-assessment of LEMS-related weakness from the withdrawal period with categories of much much weaker (-3), much weaker (-2), somewhat weaker (-1), about the same (0), somewhat stronger (1), much stronger (2), and much much stronger (3).

Sex: All, ages: 18 Years to any

Inclusion Criteria:

1. Age 18 or over
2. Ambulatory while taking 3,4-DAP, i.e. the patient was able to perform the timed up and go (TUG), either with or without an assistive device
3. Established diagnosis of LEMS, with documentation provided
4. Continuous use of Jacobus 3,4-DAP for at least 3 months
5. Minimum of 3 doses per day with no single dose less than 10 mg of 3,4-DAP
6. The patient needed to wait about 15 to 30 minutes to experience an unequivocal improvement in a LEMS-induced dysfunction after they take their first dose of 3,4-DAP in the morning \[a patient who remains in bed past this point by choice may still be eligible\]
7. Stable regimen of all LEMS-related treatments for at least 3 months
8. Stable daily regimen of other medications (prescription and over-the-counter) for a minimum of 1 month
9. Willing to chance being tapered off of 3,4-DAP
10. Fluency in English
11. If applicable, agreed to use birth control during heterosexual intercourse until at least 2 weeks after completion of study
12. A signed informed consent by the study subject

Exclusion Criteria:

1. Last monoclonal antibody treatment (e.g. rituximab) was less than 6 months ago (i.e., recent treatment is an exclusion)
2. Clinically significant or poorly controlled condition that in the opinion of the study personnel might pose an unacceptable risk to the patient if entered into the study
3. Respiratory failure requiring intubation while on 3,4-DAP with no precipitating event or medication
4. Use of any investigational drug other than 3,4-DAP within the last 30 days
5. Pregnant or lactating
6. Current use of other aminopyridines (e.g.4-AP) or guanidine
7. Did not display a sufficiently large response to 3,4-DAP during the baseline observation period in the CRU to detect a decline during withdrawal of 3,4-DAP

Participant flow

Outcome results

• Number of Participants With 30% or More Deterioration in Triple Timed Up & Go (3TUG) Test, Compared to Time-matched Baseline (Primary), Count of participants, Participants: Continuous 3,4-Diaminopyridine (3,4-DAP) 0; 3,4-DAP Taper to Placebo 13 (p <0.0001)
• Self-assessment of LEMS-related Weakness, W-SAS (Secondary), Mean, units on a scale: 3,4-DAP -0.2 +/- 1.24; 3,4-DAP Taper to Placebo -2.4 +/- 0.85 (p 0.0001)

Adverse events

Time frame: Adverse events were collected during the inpatient stay of up to 7 days on the clinical research unit and then weekly with standard telephone follow-up and diary entries for one month following discharge from the clinical research unit.

Serious adverse events by term

Other adverse events by term

• Kathy L Aleš, MD, Study director, Jacobus Pharmaceutical