Abstract Prescription opioid abuse, addiction and overdose are major burdens to patients and society, resulting in significant costs, illnesses, and deaths. The intertwined issues of i) the ongoing abuse of prescription opioids, and ii) reluctance of prescribers to write prescriptions for opioid analgesics, have resulted in the under-treatment of patients with moderate-to-severe pain. Several abuse-deterrent opioid products (primarily formulations) are currently marketed, but they fall short of being resistant to abuse. Notably, currently marketed abuse deterrent technologies do not effectively deter one of the most common forms of opioid abuse – swallowing an increased number of tablets or capsules than are prescribed. In order to address this crisis Ensysce Biosciences has created two complementary, novel technologies that control the release of known opioids. The abuse resistant and overdose protection features of Ensysce Biosciences’ TAAP™ (Trypsin Activated Abuse Protection) with MPAR® (multi-pill-abuse-resistant) prodrugs are built into the chemical modification of the opioid and are not just formulation-based changes. PF614-MPAR is the first opioid being developed with overdose protection. PF614-MPAR is a combination product of the TAAP-oxycodone prodrug, PF614, and the trypsin inhibitor nafamostat. Because exposure to trypsin is required to activate PF614 for the release of oxycodone, it provides a number of features that deter abuse while addition of nafamostat adds the overdose protection. As a combination product, we have filed two INDs to evaluate both PF614 and the trypsin inhibitor separately for safety and PK, and have filed a third IND to evaluate the combination. The data from the Phase 1 study that evaluated the combination of PF614 and nafamostat, have provided the first proof of concept that we can deliver pain relieving levels of oxycodone from PF614-MPAR administration and still achieve overdose protection. The overdose protection of PF614-MPAR only is activated when more than a prescribed dose is taken at one time. The amount of nafamostat in a dose unit of PF614-MPAR is designed to be ineffective when taken at the prescribed dose. However, small increments over the prescribed dose or if taken in large excess, the increased amount of nafamostat will inhibit the trypsin conversion of PF614 to oxycodone reducing the opioid release. It is designed to put the brakes on the activation of PF614 if too much is taken at one time, averting an overdose. We have now examined the PF614-MPAR 25 mg dosage strength in a two-part Phase 1 study and found that the combination showed an equivalent safety profile to PF614 alone. A 25 mg PF614-MPAR dose unit was defined in Part 1 of the study and proof-of-concept was demonstrated successfully when overdose protection was provided when excess PF614-MPAR 25 mg was taken simultaneously in Part 2. PF614-MPAR was designed to allow an anticipated prescribed dose of 1 to 2 dose units twice daily to pr...