Preemptive Approach to Combatting and Characterizing Emerging Synthetic Opioids

This webinar originally occurred on February 8, 2021
Duration: 1 hour

Overview

This webinar described how preemptive synthesis and characterization of potent psychoactive substances from the literature can aid forensic scientists in the identification of unknowns appearing in samples emerging from illicit markets. Additionally, the presenter provided understanding of how gaps in pharmacological knowledge of old drugs can be exploited to find new emerging synthetic drugs. This webinar covered the following topics in detail:

Combinatorial approaches with commercially available starting materials to create both reported and novel analogs within each of the series.  The focus was on the currently emerging threat AH-7921 related analogs including the geometrical isomer U-47700, and other related analogs.  AH-7921 & related analogs were synthesized using the methods in the Allen & Hanburys patents.  U-47700 & related analogs were synthesized as single pure stereoisomers using the methods in the Upjohn patents.  The AH-series compounds were finished as the hydrochloride salts as in the patents and the U-series compounds were as either the free bases, as in the patents, or as their hydrochloride salts.

The need for pure stereoisomers is important as different stereoisomers exhibit dirrering pharmacology.  There is the potential for confusion in the literature due to incomplete or incorrect identification of the stereochemical nature of the material being tested.  A reader could be confused by this ambiguity, especially when comparing to data from single isomers that would appear significantly different.

Activity and potency of emerging opioid analogs at cloned and expressed hMOR.  Seventeen analogs based on the AH-7921 core structure were assessed for hMOR pharmacological activity. In addition to A01 (aka, AH-7921) two analogs were found to result in significant suppression of FSK-induced cAMP accumulation that was reversed by naloxone coadministration. A02 significantly decreased FSK-induced cAMP levels at (0.1µM) and showed further increasing dose-dependent decrease of cAMP levels.  Expanded dose ranges for these two molecules was tested in multiple experiments (n=3 or more) to determine EC₅₀ values and Thus, of the AH-series analogs we synthesized and tested, A01 (EC₅₀ 26.9nM ± 11.2nM) and A02 (EC₅₀ 59.3nM ± 2.0nM) were classified as highest potency hMOR agonists followed only by A04, which we classified as a low potency agonist.  The remainder of the AH-7921 compound series demonstrated either no activity at the level of detection of this assay or activity that was not reversible by naloxone treatment.

Activity and potency of U-47700 and structural analogs at hMOR. Sixteen different U-47700 related analogs with (R,R) stereochemistry were synthesized and assessed for hMOR activity. Of these U01 and U04 were classified as hMOR selective high potency agonists with EC₅₀ values 8.8nM ± 4.9nM and 26.0nM ± 11.1nM, respectively. Pharmacological profiling also revealed U02, U05 and U08 as low potency agonists.  Analogous to findings with AH-7921 analogs, most of the U-47700 analogs were found to have no activity at hMOR at 1mM or lower concentrations.  U06-07 and U10-17 were inactive based on comparison to FSK only control.  U03 and U09 showed significant decreases in cAMP levels in the range of concentrations tested, but their regulation of cAMP was not naloxone reversible.

Activity and potency of Udes- and US-series of analogs at hMOR. To study the effect of removing N-methyl group on the amide in (R,R)-U-series, Udes-series (compounds Udes01-09) were synthesized and screened for hMOR signaling. Initial screening of Udes01 resulted in a significant decrease of FSK-induced cAMP levels at 10nM, and specific for hMOR was confirmed by naloxone reversibility.  The EC50 value of Udes01 was subsequently determined to be 3.0nM ± 0.3nM characterizing it as the most potent analog of that series that we discovered. The summary of the pharmacological activity of Udes-series of compound analogs at the hMOR are shown in Table 2.3. The remaining Udes-series (Udes 02-09) did not significantly alter FSK-induced cAMP accumulation at any of the tested concentrations.  The US-series was synthesized to assess for pharmacological activity of the S,S enantiomer of the U-47700 analogs. The nine US-series analogs were synthesized and screened for hMOR agonism (Table 2.4). Of these nine, only US01 (3,4-dichlorobenzoyl substituent) demonstrated significant decrease in cAMP levels at the highest screening dose of 1µM but not at the lower (0.1µM or 0.01µM) concentration ranges indicating that the S,S enantiomer of U-47700 was significantly less potent then the R,R enantiomer.

Learning Objectives

1. Describe how preemptive synthesis and characterization of potent psychoactive substances from the literature can aid forensic scientists in the identification of unknowns appearing in samples emerging from illicit markets.
2. Understand how gaps in pharmacological knowledge of old drugs can be exploited to find new emerging synthetic drugs.
3. Describe the strategies used by illicit suppliers to circumvent scheduling laws.

Presenter

• John Krstenansky, Ph.D., MBA, FRSC | Chair and Professor of Biopharmaceutical Sciences at the KGI School of Pharmacy and Health Sciences