Moxidectin, First New Treatment for River Blindness in 30 Years, Approved by FDA

The US FDA has approved the antihelminthic drug moxidectin (developed by Medicines Development for Global Health) for the treatment of onchocerciasis.¹

Merck’s ivermectin, developed in the late 1970s, is the only other pharmaceutical agent approved for treating onchocerciasis.  Moxidectin has outperformed ivermectin in clinical trials, demonstrating superior efficacy and comparable safety.

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Moxidectin Overview

Indication

Moxidectin is approved for the treatment of onchocerciasis due to Onchocerca volvulus in patients aged 12+.

Mechanism

Moxidectin is thought to increase the activity of glutamate-gated chloride channels (GluCl), gamma-aminobutyricacid (GABA) receptors and ATP-binding cassette (ABC) transporters.  Increased GABA receptor and GluCl activity leads to increased intracellular chloride concentration, increased neuronal and neuromuscular hyperpolarization, and parasite paralysis.  All stages of the parasite experience decreased motility following moxidectin treatment, although the medication appears to be toxic primarily against the microfilarial stage.

Administration and Dosing

8 mg ( 4 x 2 mg tablets) taken orally a single time, +/- food.

Safety

  • Mazzotti Reaction (label warning, 99% of patients)
  • Orthostatic Hypotension (label warning)
  • Encephalopathy in Loa loa coinfection (label warning)
  • Edema and Worsening of Onchodermatitis (label warning)
  • Eosinophilia (>50% in clinical trials)
  • Pruritis (>50% in clinical trials)
  • MSK Pain (>50% in clinical trials)
  • Lymphocytopenia/Neutropenia/Leukocytosis (>25% in clinical trials)
  • Hypotension/Tachcardia (>25% in clinical trials)

Contraindications

  • Avoid use or use caution when treating patients co-infected with Loa loa
  • Use caution when treating patients with sowda, a variant of onchodermatitis

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Evidence-Basis

  • Two randomized active(ivermectin)-controlled clinical trials:
    • Trial 1 (efficacy): 1472 patients; after 12 months nearly half of participants in moxidectin arm had undetectable cutaneous microfilariae, compared to 5% in ivermectin group
    • Trial 2 (dose-ranging): 172 participants; those receiving 8 mg moxidectin experienced more side effects than those receiving ivermectin, but experienced increased resolution of microfilarial skin infection

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What is River Blindness?

Onchocerciasis, also known as river blindness, is caused by the nematode Onchocerca volvulus.  It is transmitted by Simulium blackflies, and is endemic in rural areas of sub-Saharan Africa.  It is associated with cutaneous manifestations (pruritis, atrophy), visual changes and blindness.  The WHO estimates that 18 million people worldwide are currently infected with Onchocerca volvulus.²  Most infected individuals (99%) live in sub-Saharan Africa and 1-2% are blind due to the disease.

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References

  1. FDA Access Data: Moxidectin. (2018). Drugs@FDA: FDA Approved Drug Products. [online] Available at: https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=210867 [Accessed 20 Jun. 2018].
  2. Who.int. (2018). WHO | Onchocerciasis – river blindness. [online] Available at: http://www.who.int/mediacentre/factsheets/fs095/en/ [Accessed 20 Jun. 2018].
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