Complex sentence: JDTic is a long-acting ("irreversible") antagonist of the KOR, and is highly selective for the KOR over the μ-opioid receptor (MOR), δ-opioid receptor (DOR), and nociceptin receptor (NOP).
Split into simpler sentences: JDTic is a long-acting (irreversible) antagonist of the κ-opioid receptor (KOR). It is selective for the KOR over the μ-opioid receptor (MOR), δ-opioid receptor (DOR), and nociceptin receptor (NOP).