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ABOUT LEMS

Lambert-Eaton myasthenic syndrome (LEMS) is a disorder of the neuromuscular junction7

Neuromuscular junction (NMJ) disorders may be the result of exposure to certain toxins, immune-mediated diseases, or genetic disorders.7

Chart showing neuromuscular junction disorders Chart showing neuromuscular junction disorders
While all neuromuscular junction disorders are uncommon, the immune-mediated diseases—LEMS and myasthenia gravis (MG)—are the ones most often encountered in the EMG lab7

KEY FACTS ABOUT LEMS

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    SYMPTOMS

    LEMS is a rare autoimmune neuromuscular disorder characterized by debilitating and progressive muscle weakness and fatigue.4,5 See more on the LEMS Symptoms Map.

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    BURDEN

    LEMS results in diminished physical functioning, impairments in activities of daily living (ADL), and patients’ quality of life.7-10

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    PREVALENCE

    LEMS affects up to 3,000 people in the US8—up to 50% of whom are currently undiagnosed or misdiagnosed.8,11

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    COMORBIDITY

    LEMS is associated with an underlying cancer, usually small cell lung cancer, in up to 60% of cases.12,13 This paraneoplastic form of LEMS typically has a faster progression of symptoms than non-tumor LEMS.14 Because LEMS symptoms often precede tumor detection by months or years, LEMS patients’ lives may be saved by an earlier diagnosis and treatment of the cancer.

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    PATHOPHYSIOLOGY

    LEMS is caused by autoantibodies to presynaptic P/Q-type voltage-gated calcium channels (VGCCs) that reduce the release of acetylcholine into the NMJ, inhibiting neuromuscular transmission.4,8,11

LEMS mechanism of disease

DISEASE BURDEN

Progression of LEMS symptoms worsens disease burden9,15

IN A 2012 SURVEY OF PATIENTS LIVING WITH LEMS:

75% reported partial or total restriction in activities of daily living, such as rising from a chair or climbing stairs9

58% were hospitalized prior to diagnosis, while >90% were hospitalized after diagnosis9

More than 50% reported severe leg weakness, dry mouth, and difficulty focusing their sight9

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Based on EQ-5D scores, the health-related quality of life for LEMS patients is comparable to the most severe forms of multiple sclerosis9

In a 2001 study, 25% of LEMS patients required a wheelchair all the time or for mobilization outside of the home15

JOURNEY TO DIAGNOSIS

Many LEMS patients endure a long journey to diagnosis9

Mean time to LEMS diagnosis is 4.4 years Mean time to LEMS diagnosis is 4.4 years

REASONS FOR DELAY

  • Nonspecific and fluctuating symptoms11
  • Slow progression of disease11
  • Misdiagnosis due to similar clinical presentation as other conditions10,11

MISDIAGNOSIS IS COMMON

58% of patients were misdiagnosed at least once in a cohort of 241 adult patients with LEMS.11

Despite the significant burden it places on patients and their families, LEMS is often underrecognized9

Clinical presentation of LEMS resembles other more common diagnoses

The symptoms of LEMS are often mistaken for more common diseases and disorders, such as myasthenia gravis (MG), multiple sclerosis (MS), myopathies, fibromyalgia, amyotrophic lateral sclerosis (ALS), and depression.10,11

COMMON LEMS MISDIAGNOSES11

  • MG
  • Intracranial/spinal cord abnormalities
  • Myopathies
  • Depression
  • Peripheral nerve abnormalities
  • Other

Prevalence of misdiagnoses among patients with LEMS11

Pie chart showing common misdiagnoses of LEMS
  • MG
  • Myopathies
  • Peripheral nerve abnormalities
  • Intracranial/spinal cord abnormalities
  • Depression
  • Other
More than 1/3 of misdiagnosed LEMS patients were initially diagnosed as having MG11
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Indication and Important Safety Information

indications and usage:

FIRDAPSE is a potassium channel blocker indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults.

CONTRAINDICATIONS

FIRDAPSE is contraindicated in patients with:

  • A history of seizures
  • Hypersensitivity to amifampridine phosphate or another aminopyridine

WARNINGS AND PRECAUTIONS

Seizures: FIRDAPSE can cause seizures. Consider discontinuation or dose-reduction of FIRDAPSE in patients who have a seizure while on treatment. FIRDAPSE is contraindicated in patients with a history of seizures.

Hypersensitivity: If a hypersensitivity reaction such as anaphylaxis occurs, FIRDAPSE should be discontinued and appropriate therapy initiated.

ADVERSE REACTIONS

The most common (> 10%) adverse reactions are: paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms.

To report SUSPECTED ADVERSE REACTIONS, contact Catalyst Pharmaceuticals at 1-844-347-3277 (1-844-FIRDAPSE) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

References:
  1. Yoon CH, Owusu-Guha J, Smith A, Buschur P. Amifampridine for the management of Lambert-Eaton myasthenic syndrome: a new take on an old drug. Ann Pharmacother. 2020;54(1):56-63.
  2. Full Prescribing Information for FIRDAPSE (amifampridine). Catalyst Pharma; 2018.
  3. Orange Book: Approved drug products with therapeutic equivalence evaluations. US Food and Drug Administration website. https://www.accessdata.fda.gov/scripts/cder/ob/search_product.cfm. Accessed June 10, 2020.
  4. Lennon VA, Kryzer TJ, Griesmann GE, et al. Calcium-channel antibodies in the Lambert-Eaton syndrome and other paraneoplastic syndromes. N Engl J Med. 1995;332(22):1467-1474.
  5. Skeie GO, Apostolski S, Evoli A, et al. Guidelines for treatment of autoimmune neuromuscular transmission disorders. Eur J Neurol. 2010;17(7):893-902.
  6. Data on file, Catalyst Pharmaceuticals.
  7. Muppidi S, Wolfe GI, Barohn RJ. Diseases of the neuromuscular junction. In: Swaiman K, Ashwal S, Ferriero D, Schor N, eds. Pediatric Neurology: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier; 2011:1549-1569.
  8. Sanders DB. Lambert-Eaton myasthenic syndrome: diagnosis and treatment. Ann NY Acad Sci. 2003;998:500-508.
  9. Harms L, Sieb JP, Williams AE, et al. Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: results of a patient interview survey in Germany. J Med Econ. 2012;15(3):521-530.
  10. Merino-Ramírez MÁ, Bolton CF. Review of the diagnostic challenges of Lambert-Eaton syndrome revealed through three case reports. Can J Neurol Sci. 2016;43(5):635-647.
  11. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10(12):1098-1107.
  12. Titulaer MJ, Wirtz PW, Willems LNA, et al. Screening for small-cell lung cancer: a follow-up study of patients with Lambert-Eaton myasthenic syndrome. J Clin Oncol. 2008;26(26):4276-4281.
  13. Wirtz PW, Smallegange TM, Wintzen AR, Verschuuren JJ. Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases. Clin Neurol Neurosurg. 2002;104(4):359-363.
  14. Wirtz PW, Wintzen AR, Verschuuren JJ. Lambert-Eaton myasthenic syndrome has a more progressive course in patients with lung cancer. Muscle Nerve. 2005;32(2):226-229.
  15. Maddison P, Lang B, Mill K, Newsom-Davis J. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001;70(2):212-217.
  16. Zalewski NL, Lennon VA, Lachance DH, et al. P/Q- and N-type calcium-channel antibodies: oncological, neurological, and serological accompaniments. Muscle Nerve. 2016;54(2):220-227.
  17. Lennon VA. Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology. 1997;48(suppl 5):S23-S27.
  18. Gilhus NE. Lambert-Eaton myasthenic syndrome; pathogenesis, diagnosis, and therapy. Autoimmune Dis. 2011;2011:973808.
  19. Quartel A, Turbeville S, Lounsbury D. Current therapy for Lambert-Eaton myasthenic syndrome: development of 3,4-diaminopyridine phosphate salt as first-line symptomatic treatment. Curr Med Res Opin. 2010;26(6):1363-1375.
  20. Bain PG, Motomura M, Newsom-Davis J, et al. Effects of intravenous immunoglobulin on muscle weakness and calcium-channel autoantibodies in the Lambert-Eaton myasthenic syndrome. Neurology. 1996;47(3):678-683.
  21. Ivanovski T, Miralles F. Lambert-Eaton myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis. 2019;9:27-37.
  22. Wirtz PW, Verschuuren JJ, van Dijk JG, et al. Efficacy of 3,4-diaminopyridine and pyridostigmine in the treatment of Lambert-Eaton myasthenic syndrome: a randomized, double-blind, placebo-controlled, crossover study. Clin Pharmacol Ther. 2009;86(1):44-48.
  23. Oh SJ, Sieb JP. Update on amifampridine as a drug of choice in Lambert-Eaton myasthenic syndrome. US J Neurol. 2014;10(2):83-89.
  24. Strupp M, Teufel J, Zwergal A, et al. Aminopyridines for the treatment of neurologic disorders. Neurol Clin Pract. 2017;7(1):65-76.
  25. Lindquist S, Stangel M. Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine. Neuropsychiatr Dis Treat. 2011;7:341-349.
  26. Shieh P, Sharma K, Korhman B, Oh SJ. Amifampridine phosphate (FIRDAPSE) is effective in a confirmatory phase 3 clinical trial in LEMS. J Clin Neuromuscul Dis. 2019;20(3):111-119.
  27. Jacob S, Muppidi S, Guidon A, et al; International MG/COVID-19 Working Group. Guidance for the management of myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) during the COVID-19 pandemic. J Neurol Sci. 2020;412:116803.

Indication and Important Safety Information

indications and usage:

FIRDAPSE is a potassium channel blocker indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults.

CONTRAINDICATIONS

FIRDAPSE is contraindicated in patients with:

  • A history of seizures
  • Hypersensitivity to amifampridine phosphate or another aminopyridine

WARNINGS AND PRECAUTIONS

Seizures: FIRDAPSE can cause seizures. Consider discontinuation or dose-reduction of FIRDAPSE in patients who have a seizure while on treatment. FIRDAPSE is contraindicated in patients with a history of seizures.

Hypersensitivity: If a hypersensitivity reaction such as anaphylaxis occurs, FIRDAPSE should be discontinued and appropriate therapy initiated.

ADVERSE REACTIONS

The most common (> 10%) adverse reactions are: paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms.

To report SUSPECTED ADVERSE REACTIONS, contact Catalyst Pharmaceuticals at 1-844-347-3277 (1-844-FIRDAPSE) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

References:
  1. Yoon CH, Owusu-Guha J, Smith A, Buschur P. Amifampridine for the management of Lambert-Eaton myasthenic syndrome: a new take on an old drug. Ann Pharmacother. 2020;54(1):56-63.
  2. Full Prescribing Information for FIRDAPSE (amifampridine). Catalyst Pharma; 2018.
  3. Orange Book: Approved drug products with therapeutic equivalence evaluations. US Food and Drug Administration website. https://www.accessdata.fda.gov/scripts/cder/ob/search_product.cfm. Accessed June 10, 2020.
  4. Lennon VA, Kryzer TJ, Griesmann GE, et al. Calcium-channel antibodies in the Lambert-Eaton syndrome and other paraneoplastic syndromes. N Engl J Med. 1995;332(22):1467-1474.
  5. Skeie GO, Apostolski S, Evoli A, et al. Guidelines for treatment of autoimmune neuromuscular transmission disorders. Eur J Neurol. 2010;17(7):893-902.
  6. Data on file, Catalyst Pharmaceuticals.
  7. Muppidi S, Wolfe GI, Barohn RJ. Diseases of the neuromuscular junction. In: Swaiman K, Ashwal S, Ferriero D, Schor N, eds. Pediatric Neurology: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier; 2011:1549-1569.
  8. Sanders DB. Lambert-Eaton myasthenic syndrome: diagnosis and treatment. Ann NY Acad Sci. 2003;998:500-508.
  9. Harms L, Sieb JP, Williams AE, et al. Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: results of a patient interview survey in Germany. J Med Econ. 2012;15(3):521-530.
  10. Merino-Ramírez MÁ, Bolton CF. Review of the diagnostic challenges of Lambert-Eaton syndrome revealed through three case reports. Can J Neurol Sci. 2016;43(5):635-647.
  11. Titulaer MJ, Lang B, Verschuuren JJ. Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies. Lancet Neurol. 2011;10(12):1098-1107.
  12. Titulaer MJ, Wirtz PW, Willems LNA, et al. Screening for small-cell lung cancer: a follow-up study of patients with Lambert-Eaton myasthenic syndrome. J Clin Oncol. 2008;26(26):4276-4281.
  13. Wirtz PW, Smallegange TM, Wintzen AR, Verschuuren JJ. Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases. Clin Neurol Neurosurg. 2002;104(4):359-363.
  14. Wirtz PW, Wintzen AR, Verschuuren JJ. Lambert-Eaton myasthenic syndrome has a more progressive course in patients with lung cancer. Muscle Nerve. 2005;32(2):226-229.
  15. Maddison P, Lang B, Mill K, Newsom-Davis J. Long term outcome in Lambert-Eaton myasthenic syndrome without lung cancer. J Neurol Neurosurg Psychiatry. 2001;70(2):212-217.
  16. Zalewski NL, Lennon VA, Lachance DH, et al. P/Q- and N-type calcium-channel antibodies: oncological, neurological, and serological accompaniments. Muscle Nerve. 2016;54(2):220-227.
  17. Lennon VA. Serologic profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology. 1997;48(suppl 5):S23-S27.
  18. Gilhus NE. Lambert-Eaton myasthenic syndrome; pathogenesis, diagnosis, and therapy. Autoimmune Dis. 2011;2011:973808.
  19. Quartel A, Turbeville S, Lounsbury D. Current therapy for Lambert-Eaton myasthenic syndrome: development of 3,4-diaminopyridine phosphate salt as first-line symptomatic treatment. Curr Med Res Opin. 2010;26(6):1363-1375.
  20. Bain PG, Motomura M, Newsom-Davis J, et al. Effects of intravenous immunoglobulin on muscle weakness and calcium-channel autoantibodies in the Lambert-Eaton myasthenic syndrome. Neurology. 1996;47(3):678-683.
  21. Ivanovski T, Miralles F. Lambert-Eaton myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis. 2019;9:27-37.
  22. Wirtz PW, Verschuuren JJ, van Dijk JG, et al. Efficacy of 3,4-diaminopyridine and pyridostigmine in the treatment of Lambert-Eaton myasthenic syndrome: a randomized, double-blind, placebo-controlled, crossover study. Clin Pharmacol Ther. 2009;86(1):44-48.
  23. Oh SJ, Sieb JP. Update on amifampridine as a drug of choice in Lambert-Eaton myasthenic syndrome. US J Neurol. 2014;10(2):83-89.
  24. Strupp M, Teufel J, Zwergal A, et al. Aminopyridines for the treatment of neurologic disorders. Neurol Clin Pract. 2017;7(1):65-76.
  25. Lindquist S, Stangel M. Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine. Neuropsychiatr Dis Treat. 2011;7:341-349.
  26. Shieh P, Sharma K, Korhman B, Oh SJ. Amifampridine phosphate (FIRDAPSE) is effective in a confirmatory phase 3 clinical trial in LEMS. J Clin Neuromuscul Dis. 2019;20(3):111-119.
  27. Jacob S, Muppidi S, Guidon A, et al; International MG/COVID-19 Working Group. Guidance for the management of myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) during the COVID-19 pandemic. J Neurol Sci. 2020;412:116803.
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