Updated
February 19th, 2018

Opioid Antagonist Candidate Completes Phase 1 Study

OPNT003 intranasal nalmefene is a long-lasting opioid antagonist for the treatment of opioid overdose

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A long-lasting opioid antagonist candidate successfully completed a phase 1 clinical trial.

The drug company that invented the Narcan-branded naloxone nasal spray for opioid overdose victims announced it is currently at work on a long-lasting antagonist that would trigger a person's body to generate antibodies that would bind heroin in their bloodstream.

This process would prevent the opioid from entering the brain.

This Phase I clinical study of candidate OPNT003 (intranasal nalmefene), was an inpatient, double-blind, randomized, crossover study involving 14 healthy volunteers.

Data generated in the Phase I study completed under a clinical trial agreement with the National Institute on Drug Abuse (NIDA) demonstrate that an intranasal nalmefene formulation containing a proprietary absorption enhancer (Intravail®, from Aegis Therapeutics) resulted in rapid increases in plasma levels with an onset faster than an intramuscular injection.

OPNT003, as a long-lasting opioid antagonist for the treatment of opioid overdose, demonstrated a half-life (6.7-7.8 hours).

Naloxone, the only FDA medication currently approved to treat an opioid overdose, has a half-life of approximately 2 hours.

Roger Crystal, M.D., Chief Executive Officer of Opiant Pharmaceuticals, Inc said: "We now have a well-defined development and regulatory pathway to pursue approval of OPNT003 in the U.S. for the treatment of opioid overdose.”

Dr. Crystal said, "Based on the NIH calling for longer-acting overdose-reversal drugs, we are optimistic that this grant will be funded."

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Synthetic opioids, such as fentanyl, are now responsible for more overdose deaths than either heroin or prescription opioids.

Preliminary estimates of U.S. drug overdose deaths exceeded 60,000 in 2016 and were partially driven by a five-fold increase in overdose deaths involving synthetic opioids (excluding methadone), from 3,105 in 2013 to approximately 20,000 in 2016.

Fentanyl and derivatives, such as carfentanil, are especially dangerous because of a long half-life of seven to ten hours that may require repeated dosing of naloxone to overdose victims to prevent a relapse. A long-lasting overdose-reversal drug may reduce this burden.

Fentanyl was detected in 56.3% of 5,152 opioid overdose deaths in the 10 states during July–December 2016, reports the Centers for Disease Control and Prevention (CDC).

An easy-to-use nasal formulation of nalmefene would be a ready-to-use tool for non-medically trained persons to administer, reported Dr. Crystal.

If approved by the FDA, OPNT003 may be especially useful in rural areas, where a rapidly growing number of overdoses are occurring, and where access to emergency medical response may be delayed by hours.

Opiant Pharmaceuticals, Inc. is a specialty pharmaceutical company developing pharmacological treatments for addictions. For more information please visit: www.opiant.com.