Phase 3 Study to Evaluate Efficacy of Amifampridine Phosphate in Lambert-Eaton Myasthenic Syndrome (LEMS)

This was a randomized (1:1), double-blind, placebo-controlled, parallel-group, withdrawal
study designed to evaluate the efficacy and safety of amifampridine phosphate in patients
diagnosed with LEMS. The study was planned to include approximately 28 male and female
patients.

Prior to the study, patients were receiving unblinded treatment in the expanded access
program (EAP-001). Patients had to be on a stable dose and frequency of amifampridine
phosphate for at least 1 week prior to randomization into LMS-003. Screening and
randomization (Day 0) may have been into a single visit.

Patients who met eligibility criteria were randomized 1:1 to amifampridine phosphate (at the
patient's optimal dose) or placebo on Day 0.

Baseline assessments were obtained on Study Day 0, while the patient has been on open-label
amifampridine phosphate and in relationship to the usual dosing schedule. Patients took
blinded study medication on Day 1 through Day 3. On Day 4, a dose of blinded study medication
was administered by the site study personnel. This was the same medication that the patient
took on Day 1 through Day 3. The assessments listed below were performed following either the
second, third, or fourth dose of medication taken on Day 4, and this should be the same dose
after which Day 0 assessments were performed. For example, if the patient took their second
dose of amifampridine in the clinic on Day 0 and had assessments started 40 minutes later,
then on Day 4, that patient should be assessed after taking their second dose of
investigational product (IP).

Beginning with the next dose after all Day 0 baseline assessments were completed, the patient
received IP through Day 4, with a clinic visit on the last day (Day 4) for assessments.

The planned duration of participation for each patient was up to 12 days, including screening
(up to 7 days), Day 0 assessments and randomization, and IP administration (Day 1 through Day
4).

Inclusion Criteria:

1. Male or female ≥18 years of age and currently receiving amifampridine phosphate for
LEMS.

2. Diagnosis of LEMS by antibody testing or electromyography (EMG).

3. Completion of anti-cancer treatment at least 3 months (90 days) prior to Screening.

4. If receiving peripherally acting cholinesterase inhibitors (e.g. pyridostigmine), a
stable dose of cholinesterase inhibitors is required for at least 7 days prior to
randomization and throughout the study.

5. If receiving permitted oral immunosuppressants (prednisone or other corticosteroid), a
stable dose is required for at least 30 days prior to randomization and throughout the
study.

6. Female patients of childbearing potential must practice an effective, reliable
contraceptive regimen during the study.

7. Able to perform all study procedures and assessments.

8. Willing and able to travel to study site and attend all clinic study visits.

9. Willing and able to provide written informed consent.

Exclusion Criteria:

1. Clinically significant long corrected QT (QTc) interval on ECG in previous 12 months.

2. Seizure disorder.

3. Active brain metastases.

4. Unable to ambulate.

5. Pregnant or lactating females.

6. Any other condition which, in the opinion of the Investigator, might interfere with
the patient's participation in the study or confound the assessment of the patient.