Pharmacokinetics of Fipaxalparant, a Small‐Molecule Selective Negative Allosteric Modulator of Lysophosphatidic Acid Receptor 1, and the Effect of Food in Healthy Volunteers

Dysregulated lysophosphatidic acid receptor 1 (LPAR1) signaling is implicated in fibrotic diseases, including systemic sclerosis (SSc) and idiopathic pulmonary fibrosis (IPF). Fipaxalparant (HZN‐825) is a small molecule acting as a negative allosteric modulator of LPAR1 and is in phase 2 clinical evaluations for treating diffuse cutaneous SSc and IPF. This open‐label, phase 1 study examined the pharmacokinetics (PKs), food effect, and safety of fipaxalparant in healthy volunteers. Dose proportionality was evaluated for fipaxalparant single doses of 150, 300, and 450 mg under fasted conditions. Food effect was tested with a 450‐mg single dose under fasted conditions or with a high‐fat meal. Multiple‐dose PKs for twice‐daily dosing of either 300 or 450 mg with low‐ or high‐fat meals was also assessed. Fipaxalparant was safe and well tolerated in healthy volunteers (n = 36) under all conditions. Fipaxalparant exposure increased in a less than dose‐proportional manner from 150 to 450 mg. At 450 mg, a high‐fat meal increased the maximum observed concentration and area under the curve by approximately 1.9‐ and 2.1‐fold, respectively. These results, combined with prior preclinical and phase 2a data, informed dose selection of fipaxalparant 300 mg once and twice daily with a meal for phase 2b studies.

Systemic sclerosis (SSc) is a rare immune-mediated disease characterized by fibrosis affecting the skin, internal organs, and vascular system. 1 Compared to limited cutaneous SSc, diffuse cutaneous SSc (dcSSc) has a more rapid progression, widespread skin involvement, and higher risk of internal organ involvement, including severe pulmonary fibrosis. 2Approximately 25.9 per 100,000 individuals in the United States are affected by dcSSc, which has one of the highest mortality rates among rheumatic diseases. 1,3reatment for SSc is challenging due to the disease's heterogeneous, multisystem disease manifestations and complex pathology.Pharmacological therapies are often targeted to the afflicted organs for symptom management but are not disease modifying. 46][7] Morbidity and mortality remain high de-spite these interventions, and novel disease-modifying therapies are needed to manage complications across multiple organ systems and improve patient survival. 8isease pathogenesis of SSc begins with vasculopathy, leading to activation of fibroblasts and immune pathways. 9Autoinflammation and fibrosis are propagated by cytokine activity, T-cell and B-cell signaling, and fibroblast differentiation that leads to extracellular matrix production. 9Lysophosphatidic acid (LPA), a bioactive glycophospholipid, is mainly produced via the cleavage of lysophospholipids by autotaxin (ectonucleotide pyrophosphatase/phosphodiesterase family member 2) activity. 10LPA signaling via the G protein-coupled LPA receptors (LPARs) 1-6 is an integral part of several physiologic pathways, and LPAR1 specifically is implicated in SSc pathogenesis via mechanisms related to inflammation and/or cell injury. 10,118][19][20][21] Treatment of IPF with an LPAR1selective antagonist resulted in slower rates of forced vital capacity (FVC) decline and modified biomarkers of fibrosis and inflammation in clinical studies; treatment of PPF with an LPAR1 antagonist also resulted in slower rates of FVC decline. 12,15,16,22Fipaxalparant (formerly HZN-825 and SAR-100842) is a small molecule 23 acting as a negative allosteric modulator of LPAR1 and is under evaluation in phase 2 trials for the treatment of dcSSc and IPF.In a phenotyping in vitro study in human primary hepatocytes, multiple metabolism pathways contributed to the elimination of fipaxalparant, including cytochrome P450 (CYP) metabolism (such as CYP2C9 and CYP2D6), and glucuronidations (data on file).Fipaxalparant is primarily eliminated through fecal elimination, with urine elimination as a minor pathway. 24Fipaxalparant exposure was increased with rifampin (600-mg single dose) based on data from a physiologically based pharmacokinetic (PK) model and a drug-drug interaction (DDI) phase 1 study in healthy volunteers. 25his study also demonstrated no clinically relevant DDI between fipaxalparant and itraconazole/rifampin, and confirmed that fipaxalparant is an organic anion transporting polypeptide substrate. 25Another phase 1 study confirmed that there are no mutual DDIs between fipaxalparant and pirfenidone/nintedanib, which are standard-of-care medicines for IPF treatment. 26A previous phase 2a exploratory study in patients with dcSSc demonstrated early signals of efficacy through numerical improvements in modified Rodnan skin scores, patient-assessed pruritus severity, and Health Assessment Questionnaire Disability Index (HAQ-DI) scores in patients who received fipaxalparant ver-sus placebo; fipaxalparant treatment was also well tolerated. 14his phase 1 study evaluated the PKs and food effect of a tablet formulation of fipaxalparant in healthy volunteers to inform phase 2 doses and dosing conditions.

Study Design
This open-label, phase 1 study assessed the PKs, food effect, safety, and tolerability of single-and multipledose oral administration of fipaxalparant tablets at up to 3 dose levels.Eligible healthy volunteers were enrolled and randomly assigned to 1 of 3 cohorts (Figure S1).A 2-way, 2-period crossover design was used for cohorts 1 and 2. In cohort 1, participants received a single dose of fipaxalparant at either 150 or 300 mg after fasting.In cohort 2, fipaxalparant was administered as a single dose of 450 mg in a fasted state or following a high-fat, high-calorie meal.The dose proportionality of fipaxalparant was evaluated from cohorts 1 and 2 under fasting conditions and food effect was evaluated from cohort 2. Cohort 3 was designed to measure multiple-dose PKs and was divided into 2 subgroups (designated 3a and 3b) that received either 300 or 450 mg of fipaxalparant twice daily (BID) for 5 days on a fixed-sequence diet.The 3a subgroup received 300 mg of fipaxalparant BID with a low-fat meal in the first period and a high-fat, reduced-calorie meal in the second.The 3b subgroup received 450 mg of fipaxalparant BID with a low-fat meal in the first period (as in 3a) and a high-fat, high-calorie meal in the second period.All BID fipaxalparant doses were given 12 hours apart in the morning and in the evening.Participants were randomized 1:1 to the sequences of treatment within each cohort.
For the single-dose administration with a meal (cohort 2) and the first BID administration with a meal (cohort 3), participants were required to fast overnight for at least 10 hours until 30 minutes prior to their scheduled morning dose.All other BID doses, with either a high-or low-fat meal, required fasting for at least 2 hours prior to dosing.Meals were to be entirely consumed within 30 minutes and participants returned to fasting for at least 2 hours postdose.
High-fat meals contained either 33-44 g of fat and 600-800 calories (reduced-calorie, high-fat meals) or 55-65 g of fat and 800-1000 calories (high-calorie, high-fat meals), where 50% of the calories were from fat.Low-fat meals contained 11-14 g of fat and 400-500 calories, where 25% of the calories were from fat.All study participants were administered their respective doses of fipaxalparant via 150-mg oral tablets.Oral administration of fipaxalparant was successfully carried out at the designated time points under the supervision of clinic personnel for full compliance.

Eligibility Criteria
Participants were recruited if they were 18-60 years of age, a nonsmoker, a female within 45.0-85.0kg or a male within 50.0-95.0kg, body mass index of 18.0-32.0kg/m 2 , and medically healthy with no clinically significant medical history.Individuals who were mentally or legally incapacitated, or had abnormal coagulation tests or abnormal orthostatic vital signs (defined as a reduction of systolic blood pressure [BP] by >20 mmHg or a reduction of diastolic BP by >10 mmHg) at screening were excluded.
Plasma concentrations of fipaxalparant were determined using a validated high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS) assay (Labcorp Bioanalytical Services, Indianapolis, IN, USA).Fipaxalparant was extracted from plasma using protein precipitation, and fipaxalparant indanyl-d4 was used as the internal standard.Liquid chromatography was performed using a Nexera 30 Series system (Shimadzu Corporation, Kyoto, Japan) equipped with a Gemini C18 column (50 × 2 mm, 5.0 μm; Phenomenex Inc., Torrance, California).Mobile phase A consisted of 20-mM ammonium formate:formic acid (100:0.1)and mobile phase B consisted of acetonitrile:formic acid (100:0.1);both were delivered at a flow rate of 0.500 mL/min with a column temperature of 35°C.Fipaxalparant and fipaxalparant indanyl-d4 were detected using an API 5500/5000 mass spectrometer (AB Sciex LLC, Framingham, MS, USA) equipped with an electrospray ionization source in the positive ionization mode.The mass spectrometry transitions observed were 446.3-269.2for fipaxalparant and 450.3-269.2for fipaxalparant indanyl-d4.The high and low calibration curve ranges were 250-50,000 and 25-25,000 ng/mL, respectively.
In the open-label phase 1 study, interassay precision (coefficient of variation [CV%]) for the calibration standards ranged from 2.8% to 5.4% (high range) and 4.1% to 5.9% (low range).Interassay precision for quality control samples ranged from 3.7% to 7.2% (high range) and 4.3% to 6.5% (low range).Interassay accuracy (percentage difference) ranged from −1.3% to 2.4% (high range) and −3.0% to 2.4% (low range).In the validations, the within-day variability (CV%) for the quality control samples at 5 concentrations did not exceed 4.5% for the high range and 5.6% for the low range.For the calculation of descriptive statistics, plasma concentrations below the limit of quantification were set to 0.

Study Endpoints
Study endpoints included PK parameters and measurements of the food effect on single-dose and twice-daily oral administration of fipaxalparant in healthy adults.The following parameters were calculated for cohorts 1 and 2 from the day 1 fipaxalparant plasma concentrations: area under the plasma concentration time curve (AUC) from 0 to the 12-hour time point (AUC 0-12 ), AUC from 0 to the last measured non-0 concentration (AUC 0-last ), AUC from 0 extrapolated to infinity (AUC 0-inf ), percentage of AUC 0-inf extrapolated (AUC %extrap ), maximum observed concentration (C max ), time to C max (T max ), mean terminal half-life (t 1 2 ), apparent total plasma clearance after a single oral dose (CL/F), dose-normalized (DN) AUC 0-last , DN AUC 0-inf , and DN C max .For cohort 3, day 1, only AUC 0-12 , C max , and T max were calculated.Multipledose steady-state (ss) PK parameters were determined for day 5 of treatment for cohort 3: AUC 0-12 on day 5 (AUC tau ), C max,ss , predose trough concentration (C trough ), T max,ss , CL ss /F, accumulation ratio based on AUC after the first and last dose (AR.AUC), and accumulation ratio based on C max (AR.C max ).
Other endpoints included the safety and tolerability of single-dose and twice-daily fipaxalparant in healthy adults.Safety assessments included monitoring for adverse events (AEs), physical examination, clinical laboratory tests, 12-lead electrocardiograms (ECGs), and vital sign measurements (BP, heart rate [HR], orthostatic measurements, respiratory rate, and temperature).All AEs were coded according to the Medical Dictionary for Regulatory Activities (Med-DRA) Version 23.1.

Statistical Analysis
Descriptive summary statistics were calculated for the fipaxalparant plasma concentrations and PK parameters.Concentrations and parameter statistics were generated from analysis in Phoenix WinNonlin Version 8.2.0.4383 and SAS Version 9.4 or higher.Dose proportionality of PK parameters was determined through an analysis of variance (ANOVA) where the AUC 0-last , AUC 0-inf , and C max were normalized to the 150-mg dose and natural log-transformed.The geometric least square means (LSMs) were exponentiated and compared between treatment groups via 90% confidence intervals (CIs) calculated for the resulting geometric mean ratios (GMRs).A 90% CI between 0.7 and 1.43 was considered indicative of dose proportionality, which was transformed from a 30% exposure difference based on the log scale. 27,28This is appropriate as the CV% of fipaxalparant is between 30% and 50%, and demonstrated tolerability in a previous phase 2 study. 14ood effect was evaluated by ANOVA on the natural log-transformed PK parameters.The ANOVA model included sequence, treatment, and period as fixed effects and participant nested within sequence as a random effect.Geometric LSMs, GMRs for high-fat meals versus fasted dosing, and 90% CIs for the PK parameters AUC and C max were calculated from the ANOVA model.Only summary statistics were presented for cohort 3 due to the exploratory nature and small sample size.
Safety measurements were assessed by summary statistics.Tabulated treatment-emergent adverse events (TEAEs) and treatment-related AEs were expressed as a percentage of participants for each cohort.

Ethics
All study documents were reviewed and approved by the Advarra Institutional Review Board prior to study initiation.The clinical portion of the study was conducted by Celerion (Tempe, Arizona) and was performed in compliance with Celerion standard operating procedures, which are based on the requirements for Good Clinical Practice and in accordance with the principles of the Declaration of Helsinki.Participants received a copy of the informed consent form (ICF) prior to their initiation in the study; the form was explained to them by the Principal Investigator or an appropriate representative, and participant questions were answered.All participants provided informed consent by signing and dating the ICF.

Baseline Participant Characteristics
A total of 36 healthy adults who satisfied all eligibility criteria were enrolled in the study, with 12 participants per cohort (Table S1).In cohorts 1 and 2, participants were randomized 1:1 between 2 treatment sequences (n = 6 per sequence).In cohort 3, participants were randomized 1:1 between 2 subgroups (n = 6 per group).The median participant age across the cohorts was between 38 and 46 years, and each cohort had an even ratio of females to males.Most participants were Hispanic or Latino (cohort 1, 83%; cohort 2, 67%; cohort 3, 58%).All participants completed the study and were included in the safety analysis.

Single-Dose PKs of Fipaxalparant
Plasma concentrations of fipaxalparant over time under fasted conditions increased across 150-to 450-mg doses but were less than dose proportional, which was reflected in the PK parameters (Figure 1 and Table 1).Peak plasma concentrations were reached in a median of 3-4 hours (T max ) for each single dose of fipaxalparant.The median t 1 2 of fipaxalparant was approximately 22, 22, and 18 hours following administration of the 150-, 300-, and 450-mg doses, respectively.The GMRs of DN AUC 0-last , DN AUC 0-inf , and DN C max were similar for the 300-mg:150-mg (range 68%-73%) and 450-mg:300-mg comparisons (range 68%-69%), further suggesting that increasing fipaxalparant doses resulted in a less than dose-proportional increase in exposure (Table 2).

Food Effect on the PKs for Single-Dose Fipaxalparant Treatment
A high-fat, high-calorie meal increased the exposure of fipaxalparant compared with a fasted state after a single 450-mg dose (Figure 2 and Table 3).At 450 mg, the GMRs of fipaxalparant AUC 0-last , AUC 0-inf , and C max were approximately 212%, 212%, and 191%,  respectively, for dosing with high-fat meals versus under fasted conditions (Table 4).Median peak plasma concentration occurred at 4 hours postdose in participants receiving the 450-mg dose with a high-fat meal versus 3 hours postdose under a fasted state.

Multiple-Dose PKs of Fipaxalparant
Multiple-dose PK parameters were similar between 300 and 450 mg of fipaxalparant (Table 5).Following multiple BID doses of fipaxalparant, geometric mean AUC tau and C max,ss values increased less than proportionally between the 300-and 450-mg doses.Geometric mean AUC tau , C max,ss , and C trough values were higher following a high-fat versus low-fat meal within each dose level.Visual inspection of mean fipaxalparant C trough plots suggested steady state was achieved after 2 days of BID dosing.Little to no accumulation was observed with repeated BID dosing, with an accumulation ratio of 1.0-1.3 for AUC and 0.8-1.0 for C max .Each combination of dose and meal sequence resulted in consistent C trough values across the 5-day periods starting from 24 hours postdose on day 2.

Safety of Fipaxalparant Treatment in Healthy Adults
The 150-, 300-, and 450-mg doses of fipaxalparant administered in this study were well tolerated by healthy volunteers.There were no deaths, serious AEs (SAEs), AEs of special interest (AESIs), or treatment discontinuations due to AEs.AUC, area under the curve; AUC 0-inf , AUC from time 0 extrapolated to infinity; AUC 0-last , AUC from time 0 to the time of the last observed non-0 concentration; CL/F, apparent total plasma clearance after a single oral dose; C max , maximum observed concentration; CV, coefficient of variation; PK, pharmacokinetic; SD, standard deviation; t 1 2 , terminal halflife; T max , time to peak exposure.a AUC and C max are presented as mean (CV%).b T max and t 1 2 are presented as median (minimum-maximum) unless otherwise stated.Other parameters are presented as arithmetic mean ± SD.
Five TEAEs were reported by 3 (25.0%)participants in cohort 1.A total of 16 TEAEs were documented by 4 (33.3%)participants in cohort 2 (Table S2).All TEAEs were considered mild in severity.In cohort 3, 12 TEAEs were reported by 4 (33.3%)participants (Table S2).Increased HR was reported 3 times by 2 participants.One of these participants experienced elevated HR of 116 and 109 bpm on 2 nonconsecutive days approximately 12 hours after receiving 450 mg BID fipaxalparant; the events resolved within 4.5 and 1.7 hours, respectively.Another participant experienced an increased HR of 102 bpm 12 hours following the first dose of 300 mg BID fipaxalparant; this event also resolved within 2.8 hours.In the latter case, the participant also experienced throat tightness and vomiting just prior to the increased HR.All cases of increased HR were considered related to treatment.All TEAEs were considered mild in severity and 7 were reported to be related to treatment.
All laboratory values were considered within reference parameters at all postdose time points for each cohort.There were no clinically notable trends in vital signs for any participants, including no AESIs related to orthostatic hypotension.There were no ECG-related AEs or clinically significant individual results.

Discussion
Dysregulation of LPA signaling may contribute to fibrotic disease by promoting inflammation and fibroblast recruitment. 11,20Preclinical and clinical studies of LPAR1 deletion and antagonism have demonstrated attenuated dermal fibrosis in mice and reduced fibroblast responses in bronchoalveolar lavage samples from patients with IPF. 20,29Given that LPAR signaling is involved in a wide range of biologic functions and cellular processes, with LPAR1 specifically implicated in fibrotic disease, targeted inhibition of LPAR1 may offer a better tolerability profile with fewer off-target effects over strategies that broadly inhibit LPA production or LPAR signaling.
The PK parameters determined in this study from the 3 single doses of fipaxalparant under fasted conditions reflected a less than dose-proportional increase in plasma concentrations, with a minimal increase from the 300-to 450-mg dose.This pattern was further supported by the similar GMRs of DN AUC 0-last , DN AUC 0-inf , and DN C max between each pairwise comparison of doses and the lower bounds of the 90% CIs below the reference interval (0.7-1.43).
Food affected fipaxalparant PK parameters in a dose-dependent manner in this study; a high-fat, highcalorie meal increased the C max and AUC of fipaxalparant 450 mg by approximately 1.9-and 2.1-fold, respectively.A prior phase 1 study of fipaxalparant 100 mg showed no evidence of a food effect after coadministration with a high-fat breakfast (GMRs of C max , AUC last , and AUC inf were 1.15, 1.07, and 1.05, respectively [estimate 1.07; 90% CI, 0.80-1.45])compared to fasting conditions (study report FED11254, Sanofi, July 2011, unpublished data on file).The findings in the present study indicate a potential dose-dependent food effect for fipaxalparant., and T max,ss , which are presented as median (minimum-maximum) unless otherwise stated.AUC, area under the curve; AR.AUC, accumulation ratio based on AUC after the first and last dose; AR.C max , accumulation ratio based on C max ; AUC 0-12 , AUC from time 0 to the 12-hour time point; AUC tau , AUC 0-12 on day 5; BID, twice daily; CL/F, apparent total plasma clearance after a single oral dose; CLss/F, apparent total plasma clearance at steady state after a single oral dose; C max , maximum observed concentration; C max,ss , maximum observed concentration during at steady state; C trough , predose trough concentration; CV, coefficient of variation; FDA, US Food and Drug Administration; NA, not applicable; PK, pharmacokinetic; SD, standard deviation; t 1 2 , terminal half-life; T max , time to peak exposure; T max,ss , time to peak exposure at steady state.a Low-fat meals as in FDA guidance, containing 11-14 g of fat, 400-500 total calories, 25% of calories from fat. b High-fat, reduced-calorie meals, containing 600-800 total calories, 50% of calories from fat. c High-fat, high-calorie meal as in FDA guidance, containing 800-1000 total calories, 50% of calories from fat.
The goal of this study was to identify a dose regimen of fipaxalparant for phase 2 trials involving patients with SSc or IPF that would achieve a similar C trough as observed in a prior phase 2a study (Allanore et al 14 ; unpublished PK data from trial NCT01651143).The phase 2a study was double blind, randomized, and placebo controlled, with participants completing 8 weeks of treatment with fipaxalparant 300 mg ad-ministered orally BID.As expected, the fipaxalparant exposure following administration of fipaxalparant 300 mg BID with food in the current study was similar to what was observed in the phase 2a study (Allanore et al 14 ; unpublished PK data from trial NCT01651143: median [25%-75% quartile] C trough , 6500 [5215-8198] ng/mL; C max,ss , 16,600 [13,000-20,600] ng/mL).Therefore, 300 mg BID of fipaxalparant administered with

Figure 1 .
Figure1.Arithmetic mean (SEM) plasma fipaxalparant concentration versus time profiles following the administration of a single oral dose of fipaxalparant 150, 300, or 450 mg under fasted conditions.Error bars represent SEM; values below the limit of quantitation were treated as 0 and were included in the calculation of the mean and error bars at each point.SEM, standard error of the mean.

Figure 2 .
Figure2.Arithmetic mean (SEM) plasma fipaxalparant concentration versus time profiles following the administration of a single oral dose of fipaxalparant 450 mg under fasted and fed (highfat, high-calorie meal) conditions.Error bars represent SEM; values below the limit of quantitation were treated as 0 and were included in the calculation of the mean and error bars at each point.SEM, standard error of the mean.

Table 1 .
Pharmacokinetic Parameters Following a 150-, 300-, and 450-mg Dose Administered Under Fasted Conditions AUC, C max , DN AUC, and DN C max are presented as mean (CV%).b T max and t 1 2 are presented as median (minimum-maximum) unless otherwise stated.Other parameters are presented as arithmetic mean ± SD. a

Table 2 .
Statistical Comparisons of Plasma Fipaxalparant Pharmacokinetic Parameters Following 150-, 300-, or 450-mg Dosing Under Fasted Conditions ANOVA, analysis of variance; AUC, area under the curve; AUC 0-inf , AUC from time 0 extrapolated to infinity; AUC 0-last , AUC from time 0 to the time of the last observed non-0 concentration; CI, confidence interval; C max , maximum observed concentration; DN, dose-normalized; GMR, geometric mean ratio; LSM, least squares mean.a Geometric LSMs are calculated by exponentiating the LSMs from the ANOVA.b GMR = 100*(test/reference).

Table 3 .
Plasma Fipaxalparant Pharmacokinetic Parameters Following 450-mg Dosing Under Fed and Fasted Conditions

Table 4 .
Statistical Comparisons of Plasma Fipaxalparant Pharmacokinetic Parameters Following 450-mg Dosing Under Fed and Fasted Conditions ANOVA, analysis of variance; AUC, area under the curve; AUC 0-inf , AUC from time 0 extrapolated to infinity; AUC 0-last , AUC from time 0 to the time of the last observed non-0 concentration; CI, confidence interval; C max , maximum observed concentration; CV, coefficient of variation; FDA, US Food and Drug Administration; GMR, geometric mean ratio; LSM, least squares mean; PK, pharmacokinetic.a Geometric LSMs are calculated by exponentiating the LSMs from the ANOVA.b High-fat, high-calorie meal as in FDA guidance, containing 800-1000 total calories, 50% of calories from fat.

Table 5 .
Summary of Plasma Fipaxalparant Pharmacokinetic Parameters Following Administration of BID Oral Doses of Fipaxalparant Under Fed Conditions (Days 1 and 5)