Novel MOA — WAKIX® Increases Histamine in the Brain

The mechanism of action (MOA) of WAKIX in excessive daytime sleepiness (EDS) in adult patients with narcolepsy is unclear; however, its efficacy could be mediated through its activity as an antagonist/inverse agonist at histamine 3 (H₃) receptors.

  • H₃ receptors are found primarily in the brain1,2
  • Normally, when histamine levels in the brain are high, histamine binds to H₃ receptors to inhibit histamine synthesis and release in the brain3,4

WAKIX Selectively Binds to H₃ Receptors in the Brain to Increase Histamine

  • WAKIX binds to presynaptic H₃ autoreceptors, preventing histamine from binding to these receptors (antagonist effect)5
  • This binding also results in increased histamine synthesis and release (inverse agonist effect)3,5,6

WAKIX increases the levels of histamine in the brain

WAKIX binds to H₃ receptors with a high affinity (Ki = 1 nM)

  • No appreciable binding to other histamine receptors (H₁, H₂, H₄ receptors; Ki ≥ 10 μM)

Ki inhibitory constant.

WAKIX is the first and only FDA-approved non-scheduled treatment for patients with narcolepsy

  • WAKIX is not a controlled substance
    • Drugs are designated as controlled substances at varying levels based on degree of abuse potential and risk for dependence7

WAKIX is NOT a stimulant

  • WAKIX does not directly release or inhibit reuptake or dopamine or norepinephrine8

INDICATIONS AND USAGE & IMPORTANT SAFETY INFORMATION

  • WAKIX® (pitolisant) is indicated for the treatment of excessive daytime sleepiness (EDS) in adult patients with narcolepsy.

IMPORTANT SAFETY INFORMATION

Contraindications

  • WAKIX is contraindicated in patients with severe hepatic impairment.

Warnings and Precautions

  • WAKIX prolongs the QT interval; avoid use of WAKIX in patients with known QT prolongation or in combination with other drugs known to prolong the QT interval. Avoid use in patients with a history of cardiac arrhythmias, as well as other circumstances that may increase the risk of the occurrence of torsade de pointes or sudden death, including symptomatic bradycardia, hypokalemia or hypomagnesemia, and the presence of congenital prolongation of the QT interval.
  • The risk of QT prolongation may be greater in patients with hepatic or renal impairment due to higher concentrations of pitolisant; monitor these patients for increased QTc. Dosage modification is recommended in patients with moderate hepatic impairment and moderate or severe renal impairment (see full prescribing information). WAKIX is not recommended in patients with end-stage renal disease (ESRD).

Adverse Reactions

  • In the placebo-controlled clinical trials conducted in patients with narcolepsy with or without cataplexy, the most common adverse reactions (≥5% and twice placebo) for WAKIX were insomnia (6%), nausea (6%), and anxiety (5%). Other adverse reactions that occurred at ≥2% and more frequently than in patients treated with placebo included headache, upper respiratory infection, musculoskeletal pain, heart rate increased, hallucinations, irritability, abdominal pain, sleep disturbance, decreased appetite, cataplexy, dry mouth, and rash.

Drug Interactions

  • Concomitant administration of WAKIX with strong CYP2D6 inhibitors increases pitolisant exposure by 2.2-fold. Reduce the dose of WAKIX by half.
  • Concomitant use of WAKIX with strong CYP3A4 inducers decreases exposure of pitolisant by 50%. Dosage adjustments may be required (see full prescribing information).
  • H receptor antagonists that cross the blood-brain barrier may reduce the effectiveness of WAKIX. Patients should avoid centrally acting H receptor antagonists.
  • WAKIX is a borderline/weak inducer of CYP3A4. Therefore, reduced effectiveness of sensitive CYP3A4 substrates may occur when used concomitantly with WAKIX. The effectiveness of hormonal contraceptives may be reduced when used with WAKIX and effectiveness may be reduced for 21 days after discontinuation of therapy.

Use in Specific Populations

  • WAKIX may reduce the effectiveness of hormonal contraceptives. Patients using hormonal contraception should be advised to use an alternative non-hormonal contraceptive method during treatment with WAKIX and for at least 21 days after discontinuing treatment.
  • There is a pregnancy exposure registry that monitors pregnancy outcomes in women who are exposed to WAKIX during pregnancy. Patients should be encouraged to enroll in the WAKIX pregnancy registry if they become pregnant. To enroll or obtain information from the registry, patients can call 1-800-833-7460.
  • The safety and effectiveness of WAKIX have not been established in patients less than 18 years of age.
  • WAKIX is extensively metabolized by the liver. WAKIX is contraindicated in patients with severe hepatic impairment. Dosage adjustment is required in patients with moderate hepatic impairment.
  • WAKIX is not recommended in patients with end-stage renal disease. Dosage adjustment of WAKIX is recommended in patients with moderate or severe renal impairment.
  • Dosage reduction is recommended in patients known to be poor CYP2D6 metabolizers; these patients have higher concentrations of WAKIX than normal CYP2D6 metabolizers.

Please see the Full Prescribing Information for WAKIX.

To report suspected adverse reactions, contact Harmony Biosciences, LLC at 1-800-833-7460 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

References:

  1. Panula P, Chazot PL, Cowart M, et al. International union of basic and clinical pharmacology. XCVIII. Histamine receptors. Pharmacol Rev. 2015;67(3):601-655.
  2. Schlicker E, Kathmann M. Role of the histamine H₃ receptor in the central nervous system. Handb Exp Pharmacol. 2017;241:277-299.
  3. Nieto-Alamilla G, Márquez-Gómez R, García-Gálvez AM, Morales-Figueroa GE, Arias-Montaño JA. The histamine H₃ receptor: structure, pharmacology, and function. Mol Pharmacol. 2016;90:649-673.
  4. Scammell TE, Jackson AC, Franks NP, Wisden W, Dauvilliers Y. Histamine: neural circuits and new medications. Sleep. 2019;42(1). doi: 10.1093/sleep/zsy183.
  5. Schwartz JC. The histamine H₃ receptor: from discovery to clinical trials with pitolisant. Br J Pharmacol. 2011;163:713-721.
  6. Stahl SM. Special properties of receptors. In: Essential Psychopharmacology: Neuroscientific Basis and Practical Applications. 2nd ed. New York, NY: Cambridge University Press, 2000:77-98.
  7. US Department of Justice, Drug Enforcement Administration. Drugs of Abuse, A DEA Resource Guide. 2017. http://dea.gov/sites/default/files/drug_of_abuse.pdf. Accessed September 10, 2019.
  8. McMillen BBA. CN stimulants: two distinct mechanisms of action for amphetamine-like drugs. Trends Pharmacol Sci. 1983;4:429-432.