Clinical evaluation of PF614, a novel TAAP prodrug of oxycodone, versus OxyContin in a multi‐ascending dose study with a bioequivalence arm in healthy volunteers

Abstract

PF614, a trypsin‐activated abuse protection oxycodone prodrug designed to reduce recreational drug abuse, was compared to OxyContin for safety and pharmacokinetics (PKs) of plasma oxycodone following oral administration. This study was a two‐part design including a multi‐ascending dose (part A) and a bioequivalence (BE) study (part B) in healthy volunteers. In part A, 24 subjects were randomized 3:1 to receive PF614 (50, 100, or 200 mg, n = 6/cohort) or OxyContin (20, 40, or 80 mg; n = 2/cohort) in ascending cohorts, delivered every 12 h for a total of nine doses. In part B, 60 subjects randomized in a four‐way crossover to evaluate BE, received PF614 100 mg and OxyContin 40 mg in fasted and fed (high‐fat diet) states. All subjects were naltrexone blocked prior to first study drug administration to protect against opioid‐related adverse effects; repeat doses were provided on days 1–5. In part A, PF614 was well‐tolerated following twice daily doses of up to 200 mg for 5 days. Plasma oxycodone maximal plasma concentration and area under the concentration time curve increased linearly with increasing doses. Part B showed that plasma oxycodone BE was achieved following 100 mg PF614 or 40 mg OxyContin under both fasted and fed conditions. Additionally, PF614 provided similar oxycodone exposures following both fasted and fed states. This study confirms findings from our single‐ascending dose study, showing that PF614 100 mg releases oxycodone with a PK profile comparable to 40 mg OxyContin under both fasted and fed conditions and with a similar safety profile under naltrexone‐blocked conditions.

Abbreviations

AD

abuse deterrent

AUC

area under the concentration times curve

BE

bioequivalence

b.i.d.

twice daily

C _max

maximum plasma concentration

MAD

multi‐ascending dose

PFR06104

(PF614 intact prodrug)

PFR06082

[PF614 nucleophilic amine intermediate metabolite]

PFR06110

[cyclic urea metabolite]

PFR06112

[L‐arginine‐glycine‐N‐malonate metabolite]

PK

pharmacokinetic

R_ac

drug accumulation ratio

SAD

single ascending dose

TAAP

trypsin activated abuse protection

t _1/2

terminal half‐life

TEAE

treatment‐emergent adverse event

Study Highlights.

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

Prescription opioid abuse is a major burden to society, resulting in significant costs, illnesses, and deaths. It has been suggested that slower onset, extended‐release (ER) pharmacokinetic (PK) profiles may reduce abuse liability profiles for many drugs of abuse. Despite the introduction of ER opioids 40 years ago, there is still a need for better approaches to reduce prescription opioid abuse.

• WHAT QUESTION DID THIS STUDY ADDRESS?

This study evaluated a novel trypsin activated abuse protection (TAAP) oxycodone prodrug, PF614, for PKs and bioequivalence (BE) in comparison to the PK profile of OxyContin, a conventional ER formulated oxycodone product.

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

PF614 demonstrated a slower onset ER profile for oxycodone delivery, even when administered as an oral solution, had a good safety profile, and was found to be BE to the ER formulation, OxyContin under both fasted and fed conditions.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

TAAP chemical modifications, applied to both novel and existing therapeutics, can be designed to control rate of release and provide PK properties that may lead to improved therapeutic outcomes or reduced abuse of prescription drugs.

INTRODUCTION

Prescription opioid abuse and addiction are major burdens to society, resulting in significant costs, illnesses, and deaths. ¹ The intertwined issues of (i) the widespread and increasing abuse of prescription opioids, ² and (ii) reluctance of prescribers to write prescriptions for opioid analgesics have resulted in the undertreatment of patients with moderate‐to‐severe pain. ³ , ⁴ It is imperative that patients have access to potent pain medications with products that reduce the possibility of abuse.

Farré and Camí ⁵ suggested that pharmacokinetic (PK) profiles may be important to explain differences in abuse liability profiles for drugs from within the same pharmacological class; drugs with a slower onset of action and slower elimination rates may have lower abuse liability than drugs that have a fast onset of action and rapid elimination kinetics. The current generation of extended‐release (ER) opioids have provided formulations of morphine, oxycodone, and other familiar opioids with slower onset rates and extended durations of action, allowing twice‐daily or even once‐daily administration of products that may offer improved PK profiles for patients who require around‐the‐clock opioids for intractable chronic pain. ⁶ However, over 40 years of experience with ER opioids since the introduction of MS Contin in the United Kingdom (1981) and the United States (1987), followed by Kadian (ER morphine, US Food and Drug Administration [FDA] approved in 1996) and both the original and revised formulations of OxyContin (ER oxycodone, 1996 and 2010, respectively) have shown that much more needs to be accomplished to reduce the abuse potential of ER opioid products.

Trypsin activated abuse protection (TAAP), a novel oral delivery technology, is designed to deter prescription drug abuse by controlling release and oral uptake through novel chemistry rather than through “abuse deterrent formulation” technology. TAAP prodrugs function as molecular delivery devices that are “activated” to release the active compound only when exposed to pancreatic trypsin in the intestinal tract. To this end, TAAP tamper‐ and abuse‐deterrent (AD) prodrugs have key features that differentiate these from formulated AD products, including robust chemical stability and systemic exposure of the active drug that cannot be augmented by chewing or crushing.

Early proof‐of‐concept efforts with TAAP technology focused on PF329, an AD prodrug of hydromorphone that had an extended‐release profile. ⁷ Our lead TAAP product in clinical development is PF614, a prodrug of oxycodone. ⁸ Following ingestion of PF614, activation of oxycodone release from PF614 proceeds via a two‐step process including (i) trypsin activation via metabolism in the small intestine and (ii) a subsequent intramolecular cyclization‐release reaction (Figure S1). The trypsin activation produces a nucleophilic amine intermediate PFR06082 and L‐arginine‐glycine‐N‐malonate (PFR06112). Oxycodone release occurs when PFR06082 undergoes a spontaneous intramolecular cyclization reaction in a time‐dependent manner that is controlled chemically by the amine intermediate structure. This reaction releases oxycodone with concomitant formation of a cyclic urea metabolite (PFR06110).

PF614 is a novel chemically modified analog of oxycodone that is designed to release oxycodone in a two‐step release process, as described above. The active metabolite (oxycodone) is expected to have the same pharmacodynamic properties as oral oxycodone administered as ER oxycodone hydrochloride. The conversion of PF614 to oxycodone has been demonstrated in multiple animal studies as well as in a single ascending dose (SAD) phase Ia study in healthy subjects. ⁹ To confirm the activation of PF614 to oxycodone was trypsin mediated, several in vivo PK experiments were conducted to examine the effect of PF614 co‐administered with a trypsin inhibitor (nafamostat mesylate) in rats and dogs. In the presence of nafamostat, the metabolism of PF614 to oxycodone was reduced, supporting the role of trypsin in vivo. Additionally, as expected, conversion of PF614 to oxycodone was minimal following i.v. administration of PF614 to rats (2 mg/kg) and dogs (0.45 mg/kg), supporting the importance of pancreatic trypsin for initiating the conversion of PF614 to oxycodone. In common with other opioids, oxycodone hydrochloride released from PF614 is expected to produce potent opioid‐level analgesia and, at higher doses, may cause respiratory depression, inhibition of gastrointestinal function, and opioid‐like effects on the central nervous system, cardiovascular system, endocrine system, and immune system [data on file; Ensysce Biosciences, Inc.].

In the phase Ia SAD study, we evaluated the safety and PKs of oral PF614 in comparison to OxyContin in a phase I randomized single ascending dose study (study PF614‐101). ⁹ PF614 was administered at doses of 15, 25, 50, 100, and 200 mg. The time‐course of oxycodone release from PF614, a function of the kinetics of (i) the trypsin hydrolysis and (ii) the cyclization‐release reaction, mirrored that of OxyContin with a similar time to peak plasma concentrations (C _max) but a longer terminal elimination half‐life (t _1/2). Time to peak plasma oxycodone concentration (T _max) and t _½ following administration of PF614 ranged from ~4 to 7 h and ~10 to 22 h, respectively. A 50 mg PF614 dose yielded exposure comparable to a 20 mg dose of OxyContin, indicating a potency ratio (based on area under the curve from 0 to infinity [AUC_0–inf]) of 0.40. Finally, administration of naltrexone did not significantly affect total exposure to oxycodone (bioequivalent for AUC_0–inf) following administration of PF614 but resulted in slightly lower peak exposure (~12%–25% decrease in C _max).

PF614 is expected to produce analgesia similar to that of oxycodone ER formulations (e.g., OxyContin) with reduced potential for abuse via injection, inhalation, snorting, or plugging, as these routes of administration lack trypsin to initiate the release of oxycodone. Additionally, the delayed release kinetics of PF614 are not altered by chewing, crushing, or dissolving, and therefore should lead to reduced abuse via the oral route.

The objectives of the current clinical study were: (a) to assess the safety, tolerability, and PKs of 5‐days repeat b.i.d. doses of intact prodrug, PF614, and its pharmaceutically active moiety, oxycodone (part A); and (b) to evaluate the bioavailability and bioequivalence (BE) of plasma oxycodone released from single oral doses of PF614 versus oxycodone derived from OxyContin in healthy adult subjects (part B). The effect of a high‐fat meal was also evaluated in comparison to overnight fasting. In part A, twice daily dosing of PF614 at 50, 100, and 200 mg/dose was chosen to match the commonly prescribed OxyContin doses of 20, 40, and 80 mg used in the management of moderate to severe pain. In part B, the oral bioavailability of oxycodone derived from a single 100 mg dose of PF614 in a capsule formulation was compared to that of a 40 mg dose of reference drug, OxyContin, in both the fasted and fed conditions.

MATERIALS AND METHODS

Test articles

PF614 (Lot 4346.D.20.1) was supplied either as dry powder to be prepared into oral solution (doses 50 and 100 mg multiple ascending dose [MAD] part A), or in a 100 mg capsule formulation (Lot PRP0191423; 200 mg MAD part A and 100 mg BE part B). The ER oxycodone hydrochloride (OxyContin; Purdue Pharma) was supplied as 20 and 40 mg tablets that were obtained from commercial sources (Lots WP5J1 and WK8P0A [20 mg] and WM2E1 [40 mg]). Naltrexone HCl tablets (50 mg, Mallinckrodt) were obtained from a commercial source (Lots 1170E10888 and 1170E11632).

All procedures were in accordance with the ethical standards of the Helsinki Declaration of 1975. Institutional review board (IRB) approval No: 20213857 was received from WCG IRB on July 28, 2021.

Experimental

Selection of subjects

A total of 24 healthy subjects were randomized into part A of the study (8 subjects in each of the 3 cohorts; Table S1). A CONSORT diagram showing randomization for part A is shown in Figure S2. A total of 60 subjects were randomized into part B (i.e., 15 subjects in each of the treatment sequences of the Williams design) in order to achieve at least 52 total subjects who completed part B (i.e., at least 13 subjects in each of the 4 treatment sequences) for the evaluation of BE. A CONSORT diagram, Figure S3, shows randomization for part B and the Williams crossover design.

Study design

Part A utilized a randomized, open‐label, MAD design with three separate dose groups of eight subjects per group. Within each dose group, subjects in a fasted state were randomized to receive either PF614 (n = 6) or OxyContin (n = 2). Subjects received repeated b.i.d. doses, administered every 12 h (q12h) over a 5‐day period, for a total of nine doses (morning dose only was administered on day 5). The doses of PF614 and OxyContin selected were previously found to deliver oxycodone with comparable C _max and AUC. ⁹ Primary key end points in part A included evaluation of the safety, tolerability, and PKs of intact prodrug, PF614, as well as the PKs of its pharmaceutically active moiety, oxycodone. The secondary objectives of this study were to evaluate and characterize the PKs of the two metabolic fragments of PF614, PFR06082 and PFR06110, that were found to be quantifiable in the SAD study.

Naltrexone HCl (50 mg tablet) opioid blocking medication was administered orally starting on day −1 at 12 h prior to the first study drug administration, on day 1 at 1 h prior to the first study drug administration, and then every 24 h thereafter through day 7 (total 8 doses).

Full PK sampling was performed on day 1 (over the first 12‐h dosing interval) and on day 5 (up to 120 h post final dose); trough PK samples were collected at 12 h postdose on days 2 to 4. OxyContin, at comparable dose levels (i.e., 20, 40, and 80 mg vs. 50, 100, and 200 mg of PF614), was dosed and sampled for PKs in parallel with PF614 dosing.

Part B utilized an open‐label, single‐dose, randomized, four‐way crossover design with single oral doses of PF614 and OxyContin administered in both the fasted state and following an FDA‐prescribed high‐fat breakfast. End points included the bioavailability/BE of single oral doses of the PF614 prodrug and oxycodone derived from PF614 versus oxycodone derived from OxyContin. Subjects were randomized to receive each of the single oral doses of study drugs in a Williams crossover design with doses separated by a washout interval of 5 days.

Doses were administered in a fasted state after a 10 h overnight fast or about 30 min after a high‐fat, high calorie breakfast (800–1000 calories). Water was allowed ad libitum except 1 h pre‐ or post‐study drug administration.

In parts A and B, safety assessments, including adverse events (AEs), vital signs (pulse rate, blood pressure, respiratory rate, and oxygen saturation [SpO2]), clinical laboratory tests, 12‐lead electrocardiograms (ECGs), and cardiac telemetry were monitored throughout the study. Subjects were also monitored for AEs of special interest that included hypotension, hypopnea, apnea, and oxygen desaturation.

Plasma pharmacokinetic parameter analysis

PK parameters from sampling after study drug administration up to 120 h postdose, were determined using noncompartmental methods with Phoenix WinNonlin (version 8.1 Certara, L.P.) using best fit regression for selection of the lambda z range. The PK parameters were determined from the concentration‐time profiles, and AUCs were calculated using the linear up/log down method.

Bioequivalence and food effect (part B)

The BE and food effect of plasma oxycodone released from PF614 were compared to plasma oxycodone derived from OxyContin using the ratios and 90% confidence intervals (CIs) of the geometric least‐squares (LS) means of the plasma PK parameters: C _max, AUC_0–t , and AUC_0–inf of oxycodone. A linear mixed‐effects model with fixed effects for treatment, period, sequence, and subject nested in sequence as a random effect was performed using the natural log‐transformed parameters. Estimates on the original scale of measurement were obtained by exponentiating point estimates on the natural log scale. Geometric LS means were provided for each treatment. In both comparisons, OxyContin (fed and fasted status) was used as the reference. No adjustments were made for multiplicity. BE and lack of a food effect were concluded when the 90% CIs of the geometric LS mean ratios lay entirely within the reference drug confidence limits of 80%–125%.

Supplementary materials and methods

Supplementary materials available for download include the following:

• Bioanalytical methods: PF614, oxycodone, and PF614 fragments/metabolites

• Pharmacokinetic methods: Noncompartmental analysis.

RESULTS

Demographics and disposition

Part A

A total of 24 subjects participated in part A randomized in a three to one ratio to one of two treatment groups (PF614 n = 6/dose at 50, 100, or 200 mg; OxyContin n = 2/dose at 20, 40 or 80 mg). Across all treatment groups, the majority of subjects were male (14 [58.3%]), White (20 [83.3%]), not Hispanic or Latino (14 [58.3%]), with a mean age (range) of 29.7 (20 to 46) years, and a mean (range) body mass index (BMI) of 25.15 (20.4 to 31.7) kg/m² (Table S1).

One (16.7%) subject in the 200 mg PF614 group discontinued the study drug due to a treatment‐emergent adverse event (TEAE) of emesis and one (50.0%) subject in the 80 mg OxyContin group was lost to follow‐up. Therefore, 22 (91.7%) subjects completed part A. All 24 subjects were included in the randomized set, safety set, and PK set.

Part B

A total of 60 subjects were randomized to one of four treatment sequences to receive a single dose of 100 mg PF614 or 40 mg OxyContin under both fed and fasted conditions according to their assigned treatment sequences, separated by 5‐day washouts. The majority of subjects in part B were men (34 [56.7%]), White (45 [75.0%]), not Hispanic or Latino (41 [68.3%]), with a mean age (range) of 28.4 (19 to 50) years, and a mean BMI of 24.84 (18.4 to 31.8) kg/m² (Table S1).

Three subjects discontinued the study due to TEAEs of vomiting and one subject discontinued due a TEAE of colitis. Therefore, 56 (93.3%) subjects completed part B. All 60 subjects were included in the randomized set and safety set. Of these, 57 subjects were included in the PK set.

Systemic oxycodone pharmacokinetics

PF614 administration

Oxycodone in systemic circulation following PF614 administration on day 1 was first observed (T _lag) at a mean of 0.083 h to 0.67 h across the different dose groups demonstrating efficient conversion from the parent prodrug, reaching a median T _max of 6.00 h at all dose levels. Arithmetic mean C _max and AUC_0–12 of oxycodone increased dose proportionately over the dose range of 50 mg to 200 mg PF614 (Table 1, Figure 1a).

TABLE 1.

Summary of oxycodone plasma PK parameters following PF614 and OxyContin administration (day 1) – part A.

	Statistic	Treatment
		50 mg PF614 (N = 6)	20 mg OxyContin (N = 2)	100 mg PF614 (N = 6)	40 mg OxyContin (N = 2)	200 mg PF614 (N = 6)	80 mg OxyContin (N = 2)
Day 1 parameter
C max (ng/mL)	n	6	2	6	2	6	2
	Mean	24.7	21.7	42.2	38.7	107	90.3
	SD	6.34	2.33	9.22	4.31	32.1	67.5
	% CV	25.7	10.8	21.8	11.2	30.0	74.7
	Median	24.1	21.7	44.7	38.7	98.4	90.3
	Min, Max	17.6, 33.1	20, 23.3	30.8, 52.2	35.6, 41.7	73.4, 158	42.6, 138
	Geo Mean	24.1	21.6	41.3	38.5	103	76.7
T max (h)	n	6	2	6	2	6	2
	Median	6.00	5.00	6.00	2.50	6.00	6.00
	SD	4.00, 6.00	4.00, 6.00	4.00, 6.00	2.00, 3.00	4.00, 8.03	6.00, 6.00
AUC0–t (h*ng/mL)	n	6	2	6	2	6	2
	Mean	168	186	305	243	668	720
	SD	41.6	16.8	73.3	8.21	235	456
	% CV	24.8	9.0	24.0	3.4	34.2	63.3
	Median	158	186	340	243	638	720
	Min, Max	124, 227	174, 198	210, 367	237, 248	468, 1036	398, 1043
	Geo Mean	164	185	297	243	656	644
T lag (h)	n	6	2	6	2	6	2
	Mean	0.25	0	0.083	0	0.67	0
	SD	0.27	0	0.20	0	0.26	0
	% CV	110	–	245	–	38.7	–
	Median	0.25	0	0	0	0.50	0
	Min, Max	0, 0.50	0, 0	0, 0.50	0, 0	0.50, 1.0	0, 0
	Geo Mean	0.50	–	0.50	–	0.63	–
Day 5 parameter
C max,ss (ng/mL)	n	6	2	6	2	5	2
	Mean	33.4	30.0	62.2	46.6	134	111
	SD	9.14	9.12	14.6	6.72	37.0	49.6
	% CV	27.4	30.5	23.5	14.4	27.6	44.7
	Median	32.1	30.0	68.2	46.6	136	111
	Min, Max	24.7, 50	23.5, 36.4	42.1, 78.9	41.8, 51.3	86.6, 180	75.9, 146
	Geo Mean	32.5	29.2	60.6	46.3	130	105
T max (h)	n	6	2	6	2	5	2
	Median	4.05	4.00	6.00	1.5	6.00	4.00
	SD	4.00, 6.00	4.00, 4.00	4.00, 6.00	1.00, 2.00	4.00, 6.07	4.00, 4.00
AUC0–inf,ss (h*ng/mL)	n	6	2	6	2	5	2
	Mean	432	334	978	415	1972	1370
	SD	115	41.0	301	33.4	690	746
	% CV	26.7	12.3	30.8	8.0	35.0	54.5
	Median	421	334	1079	415	2024	1370
	Min, Max	318, 631	305, 363	544, 1272	392, 439	1291, 3054	842, 1897
	Geo Mean	420	333	934	414	1882	1264
AUCtau (h*ng/mL)	n	6	2	6	2	5	2
	Mean	263	245	532	338	1062	958
	SD	61.0	29.7	124	40.4	321	493
	% CV	23.2	12.1	23.3	12.0	30.2	51.4
	Median	243	245	592	338	1122	958
	Min, Max	205, 377	224, 266	349, 629	309, 366	701, 1478	609, 1306
	Geo Mean	258	244	518	336	1022	892
AUC0–t,ss (h*ng/mL)	n	6	2	6	2	5	2
	Mean	421	328	969	413	1948	1364
	SD	108	36.3	298	33.9	687	742
	% CV	25.6	11.1	30.8	8.2	35.3	54.4
	Median	412	328	1066	413	1987	1364
	Min, Max	312, 604	303, 354	541, 1266	389, 437	1262, 3030	839, 1889
	Geo Mean	410	327	925	412	1859	1259
t 1/2 (h)	n	4	1	4	2	2	0
	Mean	13.4	4.87	19.7	4.56	23.7	–
	SD	4.58	–	7.24	0.365	2.95	–
	% CV	34.3	–	36.9	8.0	12.4	–
	Median	14.1	4.87	19.2	4.56	23.7	–
	Min, Max	7.67, 17.7	4.87, 4.87	11.7, 28.5	4.30, 4.82	21.6, 25.8	–
	Geo Mean	12.7	4.87	18.6	4.55	23.6	–
CL/Fss (L/h)	n	6	2	6	2	5	2
	Mean	198	82.3	199	119	203	96.3
	SD	38.4	9.99	54.8	14.3	63.9	49.5
	% CV	19.4	12.1	27.6	12.0	31.4	51.4
	Median	206	82.3	169	119	178	96.3
	Min, Max	133, 244	75.3, 89.4	159, 287	109, 129	135, 285	61.3, 131
	Geo Mean	194	82.0	193	119	196	89.7
Vz/F (L)	n	6	2	6	2	5	2
	Mean	3717	1755	5210	789	8364	1161
	SD	1156	1594	1785	157	4652	69.8
	% CV	31.1	90.9	34.3	19.9	55.6	6.0
	Median	3721	1755	4595	789	5559	1161
	Min, Max	2366, 5541	628, 2882	3415, 7476	678, 900	5031, 15,511	1111, 1210
	Geo Mean	3570	1345	4968	781	7474	1159

Note: (a) OxyContin PK data in Table 1 should be interpreted with caution because they are based on concentration‐time data from a maximum of two subjects. (b) Incomplete results for AUC_0–12 are reported for day 1 because this parameter could be reported for only one out of six subjects due to inestimable Lz. Table 3 provides more robust comparisons of PK values for single doses of PF614 and OxyContin. BQL values (<0.200 ng/mL) were set to zero for the computations of summary statistics.

Abbreviations: AUC_0–t is effectively equivalent to AUC_0–12 in Table 1, part A (day 1) AUC_0‐inf,ss, area under the concentration‐time curve (AUC) from the time of dosing extrapolated to time infinity (day 5 only); AUC_0‐t , area under the concentration‐time curve from the time of dosing to the last measurable concentration; BQL, below quantifiable limit; CL/F, apparent clearance; C _max, maximum plasma concentration; C _max,ss, maximum plasma concentration at steady state (day 5 only); CV, coefficient of variation; Geo, geometric; Max, maximum; Min, minimum; SD, standard deviation; PK, pharmacokinetic; t _1/2, terminal elimination phase half‐life; T _lag, time prior to the time corresponding to the first measurable (nonzero) concentration (day 1 only); T _max, time to maximum plasma concentration; Vz/F, apparent volume of distribution.

FIGURE 1.

Part A: Semi‐log plot of mean (SD) oxycodone plasma concentrations versus time. Part A: day 1 0–12 h; Part B: day 5 0–120 h. Mean plasma concentrations of plasma oxycodone on day 1 (a) versus day 5 (b) are shown following single oral dose administrations of 50 mg, 100 mg, or 200 mg PF614, or 20 mg, 40 mg, or 100 mg OxyContin. PK concentrations were collected for 18 subjects in the PF614 group (6 subjects in each dose cohort) or six subjects in the OxyContin group (2 subjects in each dose cohort). Oxycodone mean plasma concentrations were above the LLOQ (0.200 ng/mL) within 0.50 h to 1.00 h postdose. LLOQ, lower limit of quantification; PK, pharmacokinetic.

Oxycodone plasma exposure (C _max,ss and AUC_0–inf,ss) following administration of multiple oral b.i.d. doses (day 5) of 50 mg, 100 mg, and 200 mg PF614 increased in a dose‐proportional manner. Arithmetic mean t _1/2 increased with increased dose, going from 13.4 h (50 mg) to 23.7 h (200 mg) PF614. A similar pattern of increasing mean volume of distribution based on the terminal phase with increasing dose was observed while mean total apparent clearance at steady‐state remained similar at all PF614 doses (Table 1, day 5, Figure 1b).

PF614‐derived oxycodone drug accumulation (R _ac), represented by the day 5 versus day 1 ratios of AUC_tau/AUC_0–t was considered minimal at all three PF614 dose levels (R _ac = 1.6×, 1.7×, and 1.5× following b.i.d. doses of 50 mg, 100 mg, and 200 mg, respectively).

OxyContin administration

After a single oral OxyContin dose on day 1, systemic oxycodone levels were evaluated in two subjects and found to peak at median T _max ranging from 2.5 to 6.0 h, similar to that seen with PF614 administration. Arithmetic mean C _max and AUC_0–12 of oxycodone increased with increasing dose over the dose range (Table 1, day 1, Figure 1a).

Oxycodone plasma exposure from OxyContin following multiple b.i.d. doses (day 5) (C _max,ss and AUC_0–inf,ss) increased with increasing dose. Median T _max ranged from 1.5 to 4.0 h. The mean t _1/2 ranged from 4.6 to 4.9 h, which was less than that observed with oxycodone delivered from PF614 (Table 1, day 5, Figure 1b).

Trough concentrations of oxycodone (Table 2) were generally similar at corresponding dose levels from day 2 through day 4, suggesting that subjects achieved steady state by day 2 after oral b.i.d. dosing of both PF614 and OxyContin.

TABLE 2.

Summary of oxycodone plasma trough concentrations – part A.

Visit	Statistic	Treatment
		50 mg PF614 (N = 6)	20 mg OxyContin (N = 2)	100 mg PF614 (N = 6)	40 mg OxyContin (N = 2)	200 mg PF614 (N = 6)	80 mg OxyContin (N = 2)
Day 2	n	6	2	6	2	6	2
	Mean	12.9	13.3	31.7	12.1	81.1	65.3
	SD	2.38	1.77	9.86	2.55	39.6	43.1
Day 3	n	6	2	6	2	6	2
	Mean	13.4	13.9	33.9	12.7	82.8	55.8
	SD	5.14	2.47	9.67	2.69	33.2	29.8
Day 4	n	6	2	6	2	5	2
	Mean	15.8	11.1	34.3	13.1	80.6	58.8
	SD	5.56	1.20	7.27	3.32	31.0	23.6

Systemic PF614 (Prodrug) pharmacokinetics

After a single PF614 oral dose on day 1, a small portion of PF614 parent prodrug was absorbed rapidly with median T _max ranging from 0.75 to 1.50 h (Table S2). Arithmetic mean C _max and AUC_0–12 of PF614 increased with increasing dose over the range of 50–200 mg PF614. Elimination of PF614 was rapid with a mean t _1/2 (range 0.81–0.58 h) across doses tested. Metabolite PFR06082 and PFR06110 plasma levels were also evaluated and are reported in Table S3.

Bioequivalence pharmacokinetic data (part B)

Systemic oxycodone pharmacokinetics

Following administration of 100 mg of PF614 or 40 mg of OxyContin, oxycodone was observed in the systemic circulation (above lower limit of quantification of 0.200 ng/mL) within 0.50 h postdose and quantifiable until 120 h postdose (PF614) or until 72 h postdose (OxyContin) under both fed and fasted dosing conditions (Figure S4). It was determined the mean peak oxycodone concentration from OxyContin was significantly higher in the fed condition. The terminal elimination phase was comparable between fasted and fed subjects for each drug individually, however a between‐drug comparison shows that the half‐life for oxycodone from PF614 was 2.4 times longer, on the average, than that measured from OxyContin (Table 3). The number of subjects per dose level as shown in Table 3 (N = 55–57 in both fed and fasted conditions) should be considered adequate to make comparisons about the relative PK profiles of bioequivalent doses of PF614 and OxyContin.

TABLE 3.

Summary of oxycodone plasma pharmacokinetic parameters: part B.

Parameter	Statistic	Treatment
		100 mg PF614, fasted (N = 57)	100 mg PF614, fed (N = 57)	40 mg OxyContin, fasted (N = 57)	40 mg OxyContin, fed (N = 55)
C max (ng/mL)	n	57	57	57	55
	Mean	51.4	61.2	49.1	69.1
	SD	14.2	13.8	10.7	14.1
	% CV	27.6	22.6	21.8	20.3
	Median	50.5	57.5	48.5	66.8
	Min, Max	28.1, 87	30.7, 85.7	30.4, 74.3	46, 98.4
	Geo Mean	49.5	59.6	48.0	67.8
T max (h)	n	57	57	57	55
	Median	6.00	6.00	4.00	6.00
	Min, Max	4.00, 8.00	3.00, 12.00	2.00, 6.28	2.00, 8.05
AUC0–inf (h*ng/mL)	n	57	57	57	54
	Mean	589	667	527	606
	SD	163	153	141	149
	% CV	27.7	23.0	26.8	24.6
	Median	554	664	516	606
	Min, Max	338, 1232	405, 1149	299, 1113	390, 1135
	Geo Mean	569	650	510	589
AUC0–t (h*ng/mL)	n	57	57	57	55
	Mean	580	660	523	604
	SD	163	152	141	148
	% CV	28.1	23.1	26.9	24.5
	Median	544	651	511	604
	Min, Max	327, 1226	403, 1139	295, 1099	384, 1124
	Geo Mean	560	643	506	587
pAUC (h*ng/mL)	n	57	57	57	55
	Mean	332	411	393	447
	SD	87.0	87.0	87.5	90.0
	% CV	26.2	21.2	22.3	20.1
	Median	317	390	378	447
	Min, Max	170, 603	214, 586	242, 652	254, 722
	Geo Mean	322	402	384	439
t 1/2 (h)	n	38	33	31	20
	Mean	11.412	9.778	4.389	4.300
	SD	4.6511	2.9776	0.6317	0.7682
	% CV	40.8	30.5	14.4	17.9
	Median	10.6	9.29	4.19	4.14
	Min, Max	5.13, 27.15	5.11, 17.37	3.33, 6.06	3.34, 7.05
	Geo Mean	10.6	9.35	4.35	4.25
CL/F (L/h)	n	57	57	57	54
	Mean	181	158	80.8	69.8
	SD	45.4	35.4	20.0	16.1
	% CV	25.0	22.5	24.8	23.1
	Median	181	151	77.5	66.0
	Min, Max	81.1, 296	87.0, 247	35.9, 134	35.3, 103
	Geo Mean	176	154	78.4	67.9
Vz/F (L)	n	57	57	57	54
	Mean	2963	2056	557	449
	SD	1950	944	280	184
	% CV	65.8	45.9	50.3	41.0
	Median	2472	1751	487	407
	Min, Max	1209, 11,398	925, 6694	304, 2430	270, 1609
	Geo Mean	2595	1901	524	428
T lag (h)	n	57	57	57	55
	Mean	0.53	0.86	0.0088	0.25
	SD	0.26	0.38	0.066	0.37
	% CV	48.9	43.6	755	146
	Median	0.50	1	0	0
	Min, Max	0, 1.0	0, 2	0, 0.50	0, 1
	Geo Mean	0.57	0.88	0.50	0.66

Note: Parameters were excluded from analysis based on diagnostic criteria defined in the statistical analysis plan.

Abbreviations: AUC, area under the concentration time curve; CL/F, total apparent clearance; C _max, maximal plasma concentration; CV, coefficient of variation; Geo, geometric; Max, maximum; Min, minimum; SD, standard deviation; t _1/2, terminal half‐life; T _lag, time prior to the time corresponding to the first measurable (nonzero) concentration; Vz/F, volume of distribution based on the terminal phase.

Bioequivalence for oxycodone delivered by PF614 versus OxyContin

The BE of oxycodone released by 100 mg PF614 compared to 40 mg OxyContin under fed and fasted condition was evaluated using a linear mixed‐effects analysis of variance (ANOVA) model. The results are presented in Table 4. A scatter plot of individual C _max and AUC_0–inf values are shown in Figure 2 and a scatter plot of individual T _max values is shown in Figure S5. The geometric LS mean ratios and 90% CI for C _max, AUC_0–t and AUC_0–inf of oxycodone were contained within the standard bioequivalence criteria of 80%–125% under both conditions. PF614 100 mg was determined to be bioequivalent to 40 mg OxyContin under both fed and fasted conditions.

TABLE 4.

Statistical analysis of bioequivalence on oxycodone for PF614 versus OxyContin: part B.

Status	Parameter	Geometric LS mean
		100 mg PF614 (test)		40 mg OxyContin (reference)		Geometric LS mean ratio (test/reference)
		n	LS Mean	n	LS Mean	Estimate	90% CI
Fasted	C max (ng/mL)	57	49.56	57	47.90	0.97	(0.92, 1.02)
	AUC0–t (h*ng/mL)	57	561.8	57	506.2	0.90	(0.87, 0.93)
	AUC0–inf (h*ng/mL)	57	570.8	57	510.0	0.89	(0.87, 0.92)
Fed	C max (ng/mL)	57	59.72	55	67.55	1.13	(1.07, 1.19)
	AUC0–t (h*ng/mL)	57	645.1	55	580.2	0.90	(0.87, 0.93)
	AUC0–inf (h*ng/mL)	57	652.3	54	584.2	0.90	(0.87, 0.92)

Note: The C _max and AUC analyses were performed on ln‐transformed parameters using a linear mixed‐effects model with treatment, period, and sequence as fixed effects and subject nested in sequence as a random effect. Parameters were excluded from analyses based on diagnostic criteria defined in the statistical analysis plan.

Abbreviations: AUC_0‐inf, area under the concentration‐time curve (AUC) from the time of dosing extrapolated to time infinity (day 5 only); AUC_0‐t , area under the concentration‐time curve from the time of dosing to the last measurable concentration; CI, confidence interval; C _max, maximal plasma concentration; LS, least squares.

FIGURE 2.

Part B: scatter plot of individual oxycodone. Part A: C _max and B: AUC_0–inf values. Individual subject (n = 57) C _max (a) or AUC_0–inf (b) values are plotted for 100 mg PF614 or 40 mg OxyContin dose groups administered in the fed and fasted state. Mean (filled bar) and median (open bar) values are shown for each group. BE between groups is demonstrated by the BE brackets. AUC_0–inf, area under the curve from 0 to infinity; BE, bioequivalence; C _max, maximal plasma concentration.

Food effect

Statistical analysis of the effect of food on oxycodone plasma PK parameters (C _max, AUC_0–t , and AUC_0–inf) after a single oral dose of PF614 (100 mg) or OxyContin (40 mg) under fed (high‐fat meal) versus fasted conditions was evaluated using a linear mixed‐effect model; the results are presented in Table 5.

TABLE 5.

Statistical analysis of food effects on oxycodone bioavailability following oral PF614 or OxyContin: part B.

	Parameter	Geometric LS mean				Geometric LS mean ratio (test/reference)
		Fed (test)		Fasted (reference)
		N	LS Mean	n	LS Mean	Estimate	90% CI
PF614, fasted versus PF614, fed	C max (ng/mL)	57	59.72	57	49.56	1.20	(1.14, 1.27)
	AUC0–t (h*ng/mL)	57	645.1	57	561.8	1.15	(1.11, 1.18)
	AUC0–inf (h*ng/mL)	57	652.3	57	570.8	1.14	(1.11, 1.18)
OxyContin, fasted versus OxyContin, fed	C max (ng/mL)	55	67.55	57	47.90	1.41	(1.34, 1.49)
	AUC0–t (h*ng/mL)	55	580.2	57	506.2	1.15	(1.11, 1.18)
	AUC0–inf (h*ng/mL)	54	584.2	57	510.0	1.15	(1.11, 1.18)

Note: The C _max and AUC analyses were performed on ln‐transformed parameters using a linear mixed‐effects model with treatment, period, and sequence as fixed effects and subject nested in sequence as a random effect.

Abbreviations: AUC_0‐inf, area under the concentration‐time curve (AUC) from the time of dosing extrapolated to time infinity (day 5 only); AUC_0‐t , area under the concentration‐time curve from the time of dosing to the last measurable concentration; CI, confidence interval; C _max, maximal plasma concentration; LS, least squares.

In comparing oxycodone PK post 100 mg PF614 oral dose given with and without food, the geometric LS mean ratio for AUC_0–t of oxycodone administered under fed versus fasted conditions was 1.15 with a 90% CI of 1.11 to 1.18. Similarly, the geometric LS mean ratio for AUC_inf was 1.14 with a 90% CI of 1.11 to 1.18. The ratio of geometric LS means and the corresponding 90% CI for AUC_0–t and AUC_0–inf were contained within the equivalence limits of 80% to 125%, indicating no effect of a high fat meal on the total exposure (AUC) of oxycodone post 100 mg PF614 administration. The results indicate a decrease in the geometric LS mean C _max of oxycodone by 17% in fasted subjects compared to fed state. The geometric LS mean ratio for C _max of oxycodone administered in the fed versus fasted state was 1.20 with a 90% CI (1.14 to 1.27) marginally outside the standard equivalence limits of 80%–125%. Therefore, the statistical analysis could not support a conclusion that there is no effect of a high‐fat meal on the C _max of oxycodone following 100 mg PF614 administration.

With or without food, the geometric LS mean ratio and 90% CI for AUC_0–t and AUC_0–inf of oxycodone were completely contained within the equivalence limits of 80%–125% following administration of both PF614 and OxyContin. This indicates no effect of a high‐fat meal on the total exposure of oxycodone following either agent. The geometric LS mean ratio and 90% CI for C _max of oxycodone was marginally (PF614) or completely (OxyContin) outside the standard equivalence limits of 80% to 125%, with the C _max of oxycodone increased by 20% (PF614) and 41% (OxyContin) in the fed state.

Systemic exposure of the parent prodrug PF614 was higher in the fasted compared to the fed state (high‐fat meal), and reached C _max faster (median T _max of 1.0 h in fasted and 2.0 h in fed state). The arithmetic mean C _max (4.43 ng/mL vs. 1.69 ng/mL), AUC_0–t (11.7 h*ng/mL vs. 3.98 h*ng/mL), and AUC_0–inf (14.5 h*ng/mL vs. 7.63 h*ng/mL) were two‐ to three‐fold higher in fasted versus fed subjects, respectively. The arithmetic mean t _1/2 was 1.2 h both in fed and fasted subjects.

Oral solution versus capsule formulation of 100 mg PF614

PF614 (100 mg) was administered as an oral solution to subjects in part A and as capsules for subjects in part B, allowing for an exploratory comparison of oxycodone delivery from the two formulations. The oxycodone PK had similar T _max (6 h) and C _max values (oral solution: 42.2 ± 9.22 ng/mL [n = 6] vs. capsule: 51.4 ± 14.2 [n = 57], respectively; Tables 1 and 3, Figure S6). Due to the limited number of subjects in the oral solution group, statistical analyses were not performed. These results demonstrate, however, that PF614 delivers oxycodone similarly whether provided as an intact capsule or by opening the capsule and dissolving the contents into water. Because PF614 maintains its AD properties even when dissolved in water, it offers flexible dosing options for patients with dysphagia.

Safety

Part A safety

PF614 was generally well‐tolerated following twice daily doses of 50 mg, 100 mg, or 200 mg for 5 days under naltrexone blockade. One subject in the 200 mg PF614 group discontinued study drug due to TEAEs of nausea and vomiting. Reported TEAEs were most frequently classified as gastrointestinal disorders, nervous system disorders, and skin and subcutaneous disorders (Table S4).

Dizziness was the most frequently reported TEAE (4 [16.7%] subjects). Except for TEAEs of headache reported by two (33.3%) subjects with 200 mg PF614, all TEAEs were reported by not more than one subject in a given treatment group, with no clear pattern among treatment groups.

There was no dose‐related trend in the frequency of treatment‐related TEAEs across PF614 treatment groups. No TEAEs were reported for vital sign values and no dose‐related trends in mean vital signs values were observed for pulse rate, blood pressure, body temperature, or oxygen saturation across PF614 treatments or differences in mean values between PF614 and OxyContin treatment groups.

No TEAEs were reported for 12‐lead ECG results and no dose‐related trends in mean values for 12‐lead ECGs (PR‐interval, QRS‐duration, QT‐interval, QTcB‐interval, QTcF interval, or RR‐interval) across PF614 treatments or clinically meaningful differences in mean values between PF614 and OxyContin treatment groups were observed.

Part B safety

A summary of the TEAEs occurring in part B of the study is shown in Table S5. Four subjects discontinued study drug due to AEs: three (5.1%) subjects with 40 mg OxyContin, fasted (colitis in 1 subject and vomiting in 2 subjects), and one (1.7%) subject with 40 mg OxyContin, fed (vomiting). Reported TEAEs were most frequently classified as gastrointestinal disorders, nervous system disorders, general disorders and administrative site conditions, and musculoskeletal and connective tissue disorders.

The frequency (percentage) of subjects reporting TEAEs was similar across treatments: 100 mg PF614, fasted (14 [24.1%] subjects); 100 mg PF614 fed (12 [20.7%] subjects); 40 mg OxyContin, fasted (12 [20.3%] subjects); and 40 mg OxyContin, fed (9 [15.5%] subjects). The most frequently reported TEAEs (≥3 subjects overall) were nausea (13 [21.7%] subjects), headache (8 [13.3%] subjects), somnolence (8 [13.3%] subjects), vomiting (6 [10.0%] subjects), constipation (4 [6.7%] subjects), fatigue (3 [5.0%] subjects), and pain in the extremities (3 [5.0%] subjects); most of these were reported with similar frequency across treatments.

The most frequently reported TEAEs considered possibly related to study drug were nausea and headache (3 [5.0%] subjects each). The most frequently reported TEAEs considered likely related to the study drug were nausea (5 [8.3%] subjects), constipation (3 [5.0%] subjects), and somnolence (4 [6.7%] subjects). One (1.7%) subject reported a TEAE of nausea considered by the investigator as definitely related to the study drug.

Most TEAEs were mild in severity. Moderate severity TEAEs were reported by one subject each with 100 mg PF614, fed (neutropenia and constipation), with 40 mg OxyContin, fasted (nausea, vomiting, constipation, colitis, arthralgia, and headache), and with 40 mg OxyContin, fed (headache).

The frequency of reported abuse potential TEAEs was similar with 100 mg PF614, fasted and fed. Somnolence was reported across all treatments.

No TEAEs were reported for 12‐lead ECG results and no clear trends or differences between PF614, fasted and fed treatments, or between PF614 fasted and fed treatments and OxyContin, fasted and fed treatments, were observed in 12‐lead ECG mean values for PR interval, QRS‐duration, QT‐interval, QTcB‐interval, QTcF‐interval, or RR‐interval.

DISCUSSION

This study was performed in two parts. Part A evaluated the PKs of oxycodone following administration of multiple (b.i.d.) ascending oral doses of PF614 and OxyContin and compared the steady‐state PKs of plasma oxycodone released from each agent. Additionally, part A evaluated the PK of the parent prodrug, PF614, and its metabolites. Part B of this study evaluated the BE of PF614 100 mg and OxyContin 40 mg by measuring plasma oxycodone derived from single oral doses of a capsule formulation of PF614 versus from the reference drug, OxyContin, under both fasted and fed conditions. This allowed a pivotal food effect assessment to be conducted to assess the impact of a high‐fat meal on the oral bioavailability of oxycodone following a single oral dose of PF614 as compared to OxyContin.

Part A showed that SADs of PF614 from 50 mg to 200 mg produced a linear increase in C _max and AUC_0–12 of oxycodone on day 1. Following b.i.d. dosing, oxycodone from PF614 appeared to reach steady‐state rapidly and exhibited an approximately dose proportional increase in C _max and AUC_0–inf,ss of oxycodone on day 5. Similar trends were observed for oxycodone derived from OxyContin from 20 mg to 80 mg. A limitation of the data from part A, which was designed to be exploratory, is that the PK data shown in Table 1 represents five to six per dose for the PF614 subjects and two per dose for the OxyContin subjects. A more representative comparison of the PK profiles for PF614 and OxyContin is presented in part B where there are 55–57 for both PF614 and OxyContin in the fed/fasted cross‐over design, as shown in Table 3. The PF614 dose capsules used in part B are designed to represent the final commercial formulation of PF614.

Part B successfully demonstrated BE between PF614 100 mg and OxyContin 40 mg under both fasted and fed conditions. The plasma oxycodone from 100 mg PF614 compared to plasma oxycodone from 40 mg OxyContin under fasted and fed conditions was assessed using a linear mixed‐effects ANOVA model. The geometric LS mean ratios and 90% CI for C _max, AUC_0–t , and AUC_0–inf of oxycodone were contained within the standard BE criteria of 80%–125% under both fasted and fed states. Therefore, it was concluded that 100 mg PF614 was bioequivalent to 40 mg OxyContin under both fasted and fed conditions.

Despite observing BE, the half‐life of plasma oxycodone from PF614 had a significantly longer half‐life (11.4 h fasted; 9.8 h fed) than that observed from OxyContin (4.4 h fasted; 4.3 h fed). These data suggest that PF614 will provide a true twice‐a‐day option for treating moderate to severe pain.

There was no effect of a high‐fat meal on the total exposure (AUC) of oxycodone post 100 mg PF614 and 40 mg OxyContin administration. However, in fed subjects, there was a modest increase in the geometric LS mean C _max of oxycodone from 20% (PF614) and 41% (OxyContin), respectively, as compared to the fasted state.

Due to the administration of PF614 100 mg as an oral solution, part A, and in capsule form, part B, we were able to evaluate the effect of dosage form on oxycodone PK. The plasma oxycodone T _max, C _max, and AUC values were found to be comparable, demonstrating that PF614 maintains its sustained‐release PK properties even in solution. This provides potential dosing options for patients with dysphagia or where a liquid formulation may be preferred. It also validates that the PK properties of PF614 are intrinsic to its prodrug chemistry and in vivo bioconversion, as opposed to a formulation controlling the dissolution of the active pharmaceutical ingredient, as with Oxycontin.

Both PF614 and OxyContin were well‐tolerated following b.i.d. oral administration for 5 days under naltrexone blockade, part A, and as single doses in fasted and fed states, part B. Overall, the data from this study suggest that PF614 is a good alternative for OxyContin based on PKs, its safety profile, and its longer half‐life.

AUTHOR CONTRIBUTIONS

D.L.K., L.A.P., and W.K.S. wrote the manuscript. D.L.K., W.K.S., C.E., L.A.P., J.M., and E.M. designed the research and analyzed the data. M.J. performed the research. All authors reviewed and approved the final draft of the manuscript.

FUNDING INFORMATION

Funding provided by Ensysce Biosciences Inc.

CONFLICT OF INTEREST STATEMENT

D.L.K., C.E., L.A.P., J.M., and W.K.S. are employees of Ensysce Biosciences Inc., and own stock or hold stock options in Ensysce Biosciences. M.J. and E.M. are employees of ICON Clinical Research.

Supporting information

Table S1.

Kirkpatrick DL, Evans C, Pestano LA, et al. Clinical evaluation of PF614, a novel TAAP prodrug of oxycodone, versus OxyContin in a multi‐ascending dose study with a bioequivalence arm in healthy volunteers. Clin Transl Sci. 2024;17:e13765. doi: 10.1111/cts.13765