Safety, tolerability, pharmacokinetics and pharmacodynamics of HSK31858, a novel oral dipeptidyl peptidase‐1 inhibitor, in healthy volunteers: An integrated phase 1, randomized, double‐blind, placebo‐controlled, single‐ and multiple‐ascending dose study

Abstract

Aim

Dipeptidyl peptidase‐1 (DPP‐1) inhibitors have been studied for the treatment of neutrophil‐mediated inflammatory diseases including bronchiectasis, bronchial asthma and cystic fibrosis. This study evaluated the pharmacokinetics, pharmacodynamics, safety and tolerability of DPP‐1 inhibitor HSK31858 in healthy Chinese volunteers.

Methods

Volunteers in Part A randomly received single doses of HSK31858 (15, 40, 60 and 80 mg) or placebo in fasted states. The 40‐mg cohort also received HSK31858 40 mg or placebo in fed states. In Part B, volunteers randomly received HSK31858 10, 20 and 40 mg or placebo once daily for 28 days in fasted states. The primary endpoints were safety and tolerability of HSK31858.

Results

Among 38 volunteers in Part A and 36 in Part B, HSK31858 was well tolerated; no deaths, serious adverse events, or discontinuations due to adverse events occurred. The median T _max was 0.75 to 1.0 h and the mean terminal t _1/2 was 16.5 to 21.0 h in the fasted state with single doses of HSK31858. Both C _max and AUC_0‐t exhibited a dose‐dependent rise. Food had no effect on AUC. Multiple doses of HSK31858 demonstrated a similar pharmacokinetics profile, with about 2‐fold accumulation in AUC. HSK31858 dose‐dependently inhibited neutrophil count‐normalized neutrophil elastase (NE_norm) activity. The maximal percentage decrease in NE_norm activity relative to baseline during 28 days of HSK31858 treatments was 13.6% and 76.4% with HSK31858 10 and 40 mg once‐daily, respectively.

Conclusion

HSK31858 was safe and well tolerated. The pharmacokinetics and pharmacodynamics profile of HSK31858 supports further clinical development for the treatment of neutrophil‐mediated inflammatory diseases.

Trial Registration

NCT05663593.

What is already known about this subject

• Non‐cystic fibrosis bronchiectasis is an inflammatory chronic respiratory disease with a protracted course punctuated by recurrent episodes of infections, culminating in irreversible dilatation of the bronchi.

• Currently, there is a high unmet need for a novel effective and safe therapeutic agent targeting aberrant inflammation in non‐cystic fibrosis bronchiectasis.

What this study adds

• The current study evaluated the PK/PD and safety of DPP‐1 inhibitor HSK31858 in healthy Chinese volunteers and was successful in establishing the safety profile of HSK31858 and identifying a recommended dose of HSK31858 20 mg or 40 mg once‐daily for subsequent clinical trials.

1. INTRODUCTION

Non‐cystic fibrosis bronchiectasis is an inflammatory chronic respiratory disease with recurrent episodes of infection, culminating in irreversible dilatation of the bronchi. ¹ The current standard of care for bronchiectasis includes pharmacotherapy with macrolides to decrease exacerbations, mucolytics and airway clearance techniques to enhance mucociliary clearance. ² , ³ , ⁴ Neutrophil‐mediated inflammation contributes to airway destruction in bronchiectasis and represents a rational therapeutic target. ⁵ , ⁶ Existing evidence does not support routine long‐term use of inhaled corticosteroids in adults with stable state bronchiectasis. ⁷ Currently, there is a high unmet need for a novel effective and safe therapeutic agent targeting aberrant inflammation in non‐cystic fibrosis bronchiectasis.

Neutrophils remain a key player in the inflammatory process in bronchiectasis. ⁸ However, targeting neutrophil migration and chemotaxis in bronchiectasis so far has not been successful clinically. ⁹ Neutrophil elastase (NE) , which is crucial in the initiation of the neutrophil extracellular trap formation process, ¹⁰ is associated with more frequent exacerbations of bronchiectasis and impaired lung function in bronchiectasis patients, ¹¹ but compounds targeting NE alone have so far proven ineffective for bronchiectasis. ¹² , ¹³ Cathepsin C , also known as dipeptidyl peptidase 1 (DPP‐1), is a cysteinyl proteinase of the lysosomal papain family that is involved in intracellular protein degradation. It activates not only NE but also proteinase 3 and cathepsin G during neutrophil maturation by cleaving the N‐terminal dipeptide of the target protein. Brensocatib is the first‐in‐class selective and reversible inhibitor of DPP‐1. ¹⁴ The topline results of the phase 3 ASPEN study showed that brensocatib significantly reduced the frequency of exacerbations in bronchiectasis patients vs placebo, ¹⁵ , ¹⁶ cementing a role of DPP‐1 inhibitors in the treatment of bronchiectasis. Another DDP‐1 inhibitor, GSK2793660, in once‐daily (QD) doses, demonstrated modest reduction (approximately 20%) in NE activity but was associated with a high rate of epidermal desquamation in healthy volunteers. ¹⁷

HSK31858, currently under development for the treatment of non‐cystic fibrosis bronchiectasis, is a potent, selective and reversible small molecule inhibitor of DDP‐1 (Supporting Information Figure S1). Our in‐house in vitro and in vivo studies showed that HSK31858 reversibly inhibited recombinant DPP‐1 activity with an IC₅₀ of 3.7 nM (vs brensocatib 12.5 nM) (Supporting Inforamtion Figure S2) and had no off‐target effects. Another DDP‐1 inhibitor, BI 1291583, was shown to have an IC₅₀ of 0.9 nM for DDP‐1. ¹⁸ In our preclinical studies, HSK31858 exhibited comparable inhibitory potency on NE activities in rat bone marrow cells (ED₅₀ of 1.13 mg/kg vs 1.45 mg/kg for brensocatib, unpublished data). We speculated that HSK31858 could help restore the protease‐antiprotease balance in the inflammatory milieu of neutrophil‐mediated diseases by suppressing DDP‐1 and downstream NE activities with an acceptable safety profile. HSK31858 was investigated in a phase 1 trial (NCT05023525) among healthy volunteers in Australia with the aim of evaluating the safety and pharmacokinetics (PKs) characteristics of single ascending doses of HSK31858 (5, 15, 40 and 60 mg). A phase 2, randomized, double‐blind, placebo‐controlled, multicenter study (NCT05601778) of HSK31858 for patients with non‐cystic fibrosis bronchiectasis was completed and the results are yet to be reported. A phase 3 randomized, double‐blind, placebo‐controlled, multicenter trial is ongoing, with the aim of assessing the efficacy and safety of HSK31858 in patients with non‐cystic fibrosis bronchiectasis (NCT06660992).

In this phase 1 study, we aimed to evaluate the PK and pharmacodynamics (PD) characteristics and the safety and tolerability of single and multiple ascending doses of HSK31858 in healthy Chinese volunteers.

2. METHODS

2.1. Volunteers and trial oversight

This trial enrolled healthy volunteers of either sex who were between the ages of 18 and 45 years. Eligible volunteers were healthy based on their personal and family medical history, physical examination, vital signs, electrocardiograms (ECGs) and clinical laboratory tests performed at screening visits. Key inclusion criteria were a body mass index (BMI) ≥18.0 and ≤28.0 kg/m² and a body weight ≥45 kg during screening, and abstinence from smoking for >1 month prior to the first dose of the investigational drug. We excluded volunteers with a history of drug abuse or alcoholism and volunteers who had taken any prescription or over‐the‐counter drugs within 14 days prior to the first dose or within five half‐lives of the investigational drug, whichever was longer. Pregnant or lactating women were ineligible. The full eligibility criteria are described in the trial protocol.

The HSK31858‐102 study was approved by the ethics committee of Peking University (PKU)Care Luzhong Hospital (NO: BLYYL [2022] No. 09) and undertaken in adherence with the principles of the Declaration of Helsinki and Good Clinical Practice Guidelines ¹⁹ and regulations from the National Medical products Administration of China. The trial, along with its subsequent amendments, is registered with Clinicaltrials. Gov (NCT05663593). Written informed consent was obtained from all study participants.

2.2. Trial design and treatment

This randomized, double‐blind, placebo‐controlled phase I study was conducted between 23 February 2022 and 26 July 2022 and had two parts. In Part A, volunteers were sequentially enrolled into four cohorts, with 14 in the 40‐mg cohort and eight each in the 15‐, 60‐ and 80‐mg cohorts. The first‐in‐human study (NCT05023525) in Australia confirmed the safety profile of HSK31858 in humans in the dosing range between 5 and 60 mg; the starting dose of HSK31858 5 mg corresponds to 0.083 mg/kg for a person with a body weight of 60 kg and therefore corresponds to a safety factor of 115 and 194 based on the no‐observed‐adverse‐effect‐level in rats (60 mg/kg) and dogs (30 mg/kg), respectively. Therefore, this current dose escalation study in China was initiated from the 15‐mg dose. Volunteers in the 15‐, 60‐ and 80‐mg cohorts were randomized 3:1 and volunteers in the 40‐mg cohort were randomized 6:1 to receive a single dose of HSK31858 (Haisco Pharmaceutical Group Co., Ltd) or matching placebo in fasted states (overnight fast of ≥10 h). Part A also included a food effect study in which volunteers in the 40‐mg cohort received an additional single dose of HSK31858 40 mg or matching placebo in fed states after a 7‐day washout period. In Part B, volunteers were sequentially enrolled into three cohorts with 12 volunteers in each cohort and randomized 3:1 to receive HSK31858 10, 20 and 40 mg or matching placebo QD for 28 consecutive days in fasted states. A Safety Review Committee (SRC) reviewed the safety and tolerability data of each dosing cohort period prior to a decision on each dose escalation, and the Principal Investigator analysed the safety and tolerability data of each dosing cohort following the SRC recommendation.

No concomitant medication was allowed throughout the study, except for those used to treat adverse events (AEs).

2.3. Assessment and study endpoints

Physical examinations, including vital signs, gingival and palmoplantar assessment, routine blood chemistries and haematological tests, routine urine and faeces tests, and 12‐lead electrocardiography, were undertaken. Safety was assessed based mainly on the occurrence, and frequency of AEs and serious AEs (SAEs). In addition, AEs of special interest (AESIs) were monitored throughout the study and included hyperkeratosis, periodontitis/gingivitis and infections, including serious infections. The AESIs were identified based on the results reported for brensocatib ¹⁴ and GSK2793660. ¹⁷

The primary endpoints of the study were the safety and tolerability of single and multiple ascending doses of HSK31858 in healthy volunteers. The secondary endpoints included the PK characteristics of single and multiple ascending doses of HSK31858, food effects on the PK characteristics of HSK31858 and the rate of change of neutrophil‐count normalized NE activity (NE_norm) relative to baseline in healthy volunteers receiving multiple ascending doses of HSK31858.

2.4. Pharmacokinetics

Venous blood was collected via the cubital vein. Intensive sampling was done predose and for the first 12 h postdose, and sparse sampling was carried out up to 72 h postdose in part A, including the 40‐mg cohort in fed states. In part B, intensive sampling was done predose and for the first 12 h after the first and final dose, and sparse sampling was done predose on days 2, 3, 4, 19, 22 and 25 and up to 96 h post the last dose.

Plasma HSK31858 concentrations were measured by a validated liquid chromatography‐tandem mass spectrometry assay. The lower limit of quantification was defined as 0.500 ng/mL (details of the assay methods are in the Supporting Information). The PK parameters after a single dose of HSK31858 included the area under the concentration‐time curve from time zero to the last observation (AUC_0‐t ), the AUC from time zero to the extrapolated time infinity (AUC_0‐∞) and the maximum concentration (C _max) and time to reach C _max (T _max) and terminal elimination half‐life (t _1/2). The PK parameters after multiple doses of HSK31858 also included in the accumulation ratio calculated according to C _max [Rac_(Cmax)] and AUC [Rac_(AUC)].

2.5. Pharmacodynamics

In part B, venous samples were obtained predose on day 1 and every 3 days thereafter and 72 h post the last dose in each cohort for analysis of NE activity using a fluorometric method. Details of the assay methods are described in the Supporting Information. The final NE activity was reported as NE_norm, where NE activity was normalized by the absolute neutrophil count for each sample to derive a measure of NE activity per concentration of neutrophils. ¹⁴

2.6. Statistical analyses

No statistical power was defined for sample size calculation in either part A or part B. PK and PD variables were analysed using descriptive statistics. The PK parameters were calculated by the non‐compartmental analysis model using WinNonlin® version 8.3 (Certara USA Inc.). A power model was used to evaluate the linear relationship between the main PK parameters (AUC_0‐t , AUC_0‐∞ and C _max) and dose. The main PK parameters of HSK31858 were log‐transformed and analysis of variance was performed to calculate the geometric mean ratio of AUC_0‐t , AUC_0‐∞ and C _max and the 90% confidence interval (90% CI) under fasting and fed states.

Statistical analysis was done using SAS® (9.4, SAS Institute, Inc.).

2.7. Nomenclature of Targets and Ligands

Key protein targets and ligands in this article are hyperlinked to corresponding entries in http://www.guidetopharmacology.org, the common portal for data from the IUPHAR/BPS Guide to PHARMACOLOGY, and are permanently archived in the Concise Guide to PHARMACOLOGY 2019/20. ²⁰

3. RESULTS

3.1. Subject disposition and characteristics

Part A enrolled 38 volunteers, including 26 men (68.4%). Their mean age was 28.4 ± 6.4 years, with a mean BMI of 22.6 ± 2.7 kg/m². Part B enrolled 36 volunteers, including 29 men (80.6%). Their mean age was 28.5 ± 6.7 years, with a mean BMI of 23.2 ± 2.6 kg/m². One volunteer in the 40 mg cohort of part B withdrew on day 21 from the study due to family illness and all volunteers in part A completed the scheduled treatments (Figure 1). The groups in each part were comparable in demographic and anthropometric characteristics (Table 1).

FIGURE 1.

Dosing schemes and volunteer disposition. HSK31858 or matching placebo was given once daily (QD) for 28 consecutive days in fasted states in the MAD study. SAD, single ascending dose; MAD, multiple ascending dose.

TABLE 1.

Subject characteristics.

Variables	HSK31858, single ascending dose cohorts
	15 mg	40 mg	60 mg	80 mg	All	Placebo	All
	N = 6	N = 12	N = 6	N = 6	N = 30	N = 8	N = 38
Male sex, n (%)	6 (100)	6 (50.0)	5 (83.3)	4 (66.7)	21 (70.0)	5 (62.5)	26 (68.4)
Age, mean (SD), years	24.2 (3.4)	30.8 (6.6)	28.0 (6.9)	27.7 (5.2)	28.3 (6.1)	29.1 (7.9)	28.4 (6.4)
Ethnicities, n (%)
Han Chinese	6 (100)	12 (100)	6 (100)	6 (100)	30 (100)	8 (100)	38 (100)
Others	0	0	0	0	0	0	0
Body mass index, mean (SD), kg/m2	22.0 (2.4)	23.8 (2.8)	20.7 (2.2)	22.7 (2.0)	22.6 (2.6)	22.6 (3.1)	22.6 (2.7)

Variables	HSK31858, Multiple ascending dose cohorts
		10 mg, QD	20 mg, QD	40 mg, QD	All	Placebo	All
		N = 9	N = 9	N = 9	N = 27	N = 9	N = 36
Male sex, n (%)	‐	9 (100)	8 (88.9)	4 (44.4)	21 (77.8)	8 (88.9)	29 (80.6)
Age, mean (SD), years	‐	32.1 (5.8)	26.6 (6.1)	30.1 (8.5)	29.6 (7.1)	25.3 (4.3)	28.5 (6.7)
Ethnicities, n (%)‐
Han Chinese	‐	9 (100)	9 (100)	9 (100)	27 (100)	9 (100)	36 (100)
Others	‐	0	0	0	0	0	0
Body mass index, mean (SD), kg/m2	‐	23.7 (3.0)	23.4 (2.7)	23.0 (3.0)	23.3 (2.8)	22.9 (1.8)	23.2 (2.6)

3.2. Safety

There were no clinically meaningful findings or trends in the vital signs or physical examination findings, ECG and clinical laboratory studies in any volunteers in parts A and B. The most frequent TEAEs were increased blood triglycerides (23.3% [7/30] vs placebo 50.0% [4/8]), increased alanine aminotransferase (6.7% [2/30] vs placebo 0% [0/8]) and glucose urine present (6.7% [2/30] vs placebo 0% [0/8]) in healthy volunteers receiving single ascending doses of HSK31858. The most frequent TEAEs were increased blood triglycerides (37.0% [10/27] vs placebo 11.1% [1/9]), increased alanine aminotransferase (11.1% [3/27] vs placebo 1.1% [1/9]) and decreased white blood cell count (7.4% [2/27] vs placebo 0% [0/9]) and positive bacterial test (7.4% [2/27] vs placebo 0% [0/9]) in healthy volunteers receiving multiple ascending doses of HSK31858. In addition, mouth ulceration and lymphadenopathy each occurred in two volunteers (7.4%) receiving multiple ascending doses of HSK31858 vs one (11.1%) and none of the volunteers receiving placebo, respectively.

Skin‐related events were the only AESIs reported. Macule occurred in 3.3% (1/30) of the volunteers receiving single ascending doses of HSK31858 (placebo 0% [0/9]) and in no volunteers receiving multiple ascending doses of HSK31858 (0% [0/27] vs placebo 0% [0/9]). In addition, skin exfoliation occurred in 3.3% (1/30) of the volunteers receiving single ascending doses of HSK31858 (placebo 0% [0/9]) and 3.7% (1/27) of the volunteers receiving multiple ascending doses of HSK31858 (placebo 11.1% [1/9]) (Tables 2 and 3 ). No dental events including gingival disorder and infections occurred in the overall population.

TABLE 2.

Treatment‐emergent and treatment‐related adverse events of part A, all grades.

Events	HSK31858, single ascending doses, fasted states						Food effects, fed states
	Total	15 mg	40 mg	60 mg	80 mg	Placebo	HSK31858 40 mg	Placebo
	N = 30	N = 6	N = 12	N = 6	N = 6	N = 8	N = 12	N = 2
Treatment‐emergent adverse event
Blood triglycerides increased	7 (23.3)	2 (33.3)	3 (25.0)	2 (33.3)	0	4 (50.0)	0	1 (50.0)
Alanine aminotransferase increased	2 (6.7)	0	2 (16.7)	0	0	0	0	0
Glucose urine present	2 (6.7)	0	2 (16.7)	0	0	0	0	0
Monocyte count increased	1 (3.3)	0	0	0	1 (16.7)	0	0	0
Urinary occult blood positive	1 (3.3)	0	0	1 (16.7)	0	0	0	0
White blood cells urine positive	1 (3.3)	1 (16.7)	0	0	0	0	0	0
Protein total decreased	1 (3.3)	0	1 (8.3)	0	0	0	0	0
Blood bilirubin increased	1 (3.3)	0	1 (8.3)	0	0	0	1 (8.3)	0
Macule	1 (3.3)	0	0	0	1 (16.7)	0	0	0
Skin exfoliation	1 (3.3)	0	0	1 (16.7)	0	0	0	0
Anaemia	1 (3.3)	0	1 (8.3)	0	0	0	0	0
Treatment‐related adverse events
Blood triglycerides increased	4 (13.3)	0	3 (25.0)	1 (16.7)	0	3 (37.5)	0	0
Alanine aminotransferase increased	2 (6.7)	0	2 (16.7)	0	0	0	0	0
Blood bilirubin increased	1 (3.3)	0	1 (8.3)	0	0	0	0	0
Macule	1 (3.3)	0	0	0	1 (16.7)	0	0	0
Skin exfoliation	1 (3.3)	0	0	1 (16.7)	0	0	0	0

Note: Data are expressed as number, n (%).

TABLE 3.

Treatment‐emergent and treatment‐related adverse events of part B, all grades.

	HSK31858, multiple ascending doses
	Total	10 mg, QD	20 mg, QD	40 mg, QD	Placebo
	N = 27	N = 9	N = 9	N = 9	N = 9
Treatment‐emergent adverse events
Blood triglycerides increased	10 (37.0)	6 (66.7)	1 (11.1)	3 (33.3)	1 (11.1)
Alanine aminotransferase increased	3 (11.1)	1 (11.1)	1 (11.1)	1 (11.1)	1 (11.1)
White blood cell count decreased	2 (7.4)	0	1 (11.1)	1 (11.1)	0
Bacterial test positive	2 (7.4)	0	0	2 (22.2)	0
Monocyte count increased	1 (3.7)	1 (11.1)	0	0	0
Aspartate aminotransferase increased	1 (3.7)	0	0	1 (11.1)	0
White blood cells urine positive	1 (3.7)	0	0	1 (11.1)	0
Red blood cells urine positive	1 (3.7)	0	1 (11.1)	0	0
Blood fibrinogen decreased	1 (3.7)	0	0	1 (11.1)	0
Blood creatine phosphokinase increased	1 (3.7)	0	0	1 (11.1)	0
Blood bilirubin increased	1 (3.7)	0	0	1 (11.1)	0
Acne	1 (3.7)	0	1 (11.1)	0	0
Skin exfoliation	1 (3.7)	0	1 (11.1)	0	1 (11.1)
Sebaceous adenitis	1 (3.7)	1 (11.1)	0	0	0
Mouth ulceration	2 (7.4)	1 (11.1)	1 (11.1)	0	1 (11.1)
Abdominal pain	1 (3.7)	1 (11.1)	0	0	0
Lymphadenopathy	2 (7.4)	0	2 (22.2)	0	0
Chest pain	1 (3.7)	1 (11.1)	0	0	0
Treatment‐related adverse events
Blood triglycerides increased	7 (25.9)	3 (33.3)	1 (11.1)	3 (33.3)	0
Alanine aminotransferase increased	1 (3.7)	1 (11.1)	0	0	1 (11.1)
Blood bilirubin increased	1 (3.7)	0	0	1 (11.1)	0
Acne	1 (3.7)	0	1 (11.1)	0	0
Skin exfoliation	1 (3.7)	0	1 (11.1)	0	1 (11.1)
Mouth ulceration	1 (3.7)	0	1 (11.1)	0	1 (11.1)
Lymphadenopathy	1 (3.7)	0	1 (11.1)	0	0

Note: Data are expressed as number, n (%).

Treatment‐related AEs (TRAEs) of any grade were less frequent than TEAEs in single and multiple ascending doses of HSK31858 and placebo.

In both parts A and B, no SAEs occurred in any of the cohorts. All the TEAEs or TRAEs resolved or had abated by the end of the study and required no treatment. No volunteers discontinued the study due to TEAEs or TRAEs. No death occurred during the study.

3.3. PK characteristics and food effects

The arithmetic mean concentration‐time curves of single and multiple oral doses of HSK31858 are illustrated in Figure 2. The plasma concentration of HSK31858 rapidly climbed after a single dose in the fasted state and reached its C _max with a median T _max between 0.75 and 1.0 h. Both C _max and AUC_0‐t exhibited a dose‐dependent rise from 53.7 ng/mL and 796 ng*h/mL with HSK31858 15 mg to 823 ng/mg and 8270 ng*h/mL with HSK31858 80 mg, respectively. Dose proportionality showed minor signs of supra‐proportionality (C _max: β point estimate 1.59, 90% CI 1.44‐1.75; AUC_0‐t : β point estimate 1.39, 90% CI 1.26‐1.52). The mean terminal t _1/2 after a single dose was between 16.5 ± 1.6 h with HSK31858 15 mg and 21.0 ± 3.3 h with HSK31858 40 mg. Interindividual variability in systemic exposure to HSK31858 was minor to moderate across doses with a geometric coefficient of variation (CV) for C _max and AUC_0‐t between 19.8% and 35.4%, and between 7.9% and 34.4%, respectively (Table 4).

FIGURE 2.

Pharmacokinetics of HSK31858. (A) Arithmetic mean concentration‐time plots of single ascending doses of HSK31858. (B) Arithmetic mean concentration‐time plots of multiple ascending doses of HSK31858. (C) Food effects on the pharmacokinetics of HSK31858. Arithmetic concentration‐time plots of a single oral dose of HSK31858 40 mg in the fasted and fed states. Semi logarithmic coordinates. Error bars represent standard deviations (SDs).

TABLE 4.

Summary of plasma pharmacokinetics parameters of HSK31858 after oral administrations in healthy volunteers in the single and multiple ascending dose trials.

	Single ascending dose				Multiple ascending doses, day 28
	15 mg	40 mg	60 mg	80 mg	10 mg	20 mg	40 mg
	N = 6	N = 12	N = 6	N = 6	N = 9 a	N = 9	N = 8
t 1/2 (h)	16.5(1.6)	21.0(3.3)	18.3(1.3)	18.1(2.8)	25.7 (2.9)	26.8(3.1)	26.5(2.3)
T max (h) b	1.0(0.5, 1.5)	1.0(0.5, 2.0)	0.75(0.5, 1.5)	0.75(0.25, 1.5)	1.5(0.5, 3.5)	1.5(1.0, 2.5)	1.5(1.0, 2.5)
C max (ng/mL) c	53.7(29.9%)	247(35.4%)	435(22.6%)	823(19.8%)	58.6(23.8%)	161(20.2%)	380(24.8%)
AUC0‐∞ (ng*h/mL) c	835(35.3%)	3590(29.9%)	5680(8.5%)	8740(20.7%)	1600(30.4%)	3770(37.3%)	8810(26.2%)
AUC0‐t (ng*h/mL) c	796(34.4%)	3290(28.0%)	5370(7.9%)	8270(19.8%)	1450(30.8%)	3500(35.4%)	8160(26.6%)
Rac(AUC)	/	/	/	/	2.2 (0.3)	2.1 (0.4)	2.1 (0.3)
Rac(Cmax)	/	/	/	/	1.4 (0.3)	1.6 (0.5)	1.6(0.5)

Note: Data are expressed as mean (SD) unless otherwise noted. Slash indicates it is not applicable as it falls under single‐dose studies.

Abbreviations: N, number of volunteers included in statistical analysis; t _1/2, elimination of half‐life at terminal phase; T _max, time to maximum blood concentration; C _max, maximum blood concentration; AUC_0‐∞, area under the plasma concentration‐time curve from time zero to time infinity; AUC_0‐t , area under the plasma concentration‐time curve from time zero till the last quantifiable point; Rac_(Cmax), accumulation ratio calculated from C _max; Rac_(AUC), accumulation ratio calculated from AUC.

^a One volunteer with AUC__%Extrap > 20%, so N = 8 for t _1/2, and AUC_0‐∞ in the 10 mg cohort on day 28.

^b Median (range).

^c Geometric mean (geometric coefficient of variation).

After multiple dosing, HSK31858 demonstrated a PK profile comparable to that of single‐dose administrations. The levels of systemic exposure to HSK31858 (C _max and AUC) at the steady state (D28) tended to increase as the dose level increased from HSK31858 10 mg QD to HSK31858 40 mg QD, with C _max of 58.6 and 380 ng/mL, respectively, and AUC_0‐t of 1450 and 8160 ng*h/mL, respectively (Table 4). Under steady states, the geometric mean trough concentrations (C _min) also rose dose‐dependently from 18.7 ng/mL with HSK31858 10 mg QD to 102 ng/mL with HSK31858 40 mg QD (Figure 2B). HSK31858 reached the peak plasma concentration in 1.5 h and with a terminal t _1/2 between 25.7 ± 2.9 h with HSK31858 10 mg QD and 26.8 ± 3.1 h with HSK31858 20 mg QD, which tended to be longer than for single‐dose HSK31858 (range 16.5 ± 1.6 to 21.0 ± 3.3 h).

Accumulation with regards to C _max and AUC was comparable across the dosing cohorts, ranging from 1.4 to 1.6 for Rac_(Cmax) and from 2.1 to 2.2 for Rac_(AUC), indicating obvious drug accumulation in AUC after multiple oral doses of HSK31858.

After a single oral dose of HSK31858 40 mg, the median T _max was 1 h in the fasted state and 4 h in the fed state, but food had no effect on the lag time (Table 5). The geometric mean C _max was 247 ng/mL in the fasted state and 162 ng/mL in the fed state, with a geometric mean ratio of 65.6% (90% CI 56.3%‐76.4%), indicating that the high‐fat meal had a minor effect on C _max (Figure 2C). Meanwhile, the geometric mean ratios of AUC_0‐t and AUC_0‐∞ were 101.5% (90% CI 97.9%‐105.3%) and 103.2% (90% CI 99.5%‐107.0%), respectively, indicating that the high‐fat meal had no effect on AUC.

TABLE 5.

Pharmacokinetics parameters of HSK31858 under fasted and fed states in healthy volunteers in the 40 mg cohort of Part a.

Pharmacokinetics parameters	Fasted Geometric mean	Fed Geometric mean	Geometric mean ratio (fed/fasted)	Geometric mean ratio 90% confidence interval (%)
C max (ng/mL) a	247	162	65.6	56.3, 76.4
AUC0‐t (ng*h/mL) a	3290	3340	101.5	97.9, 105.3
AUC0‐∞ (ng*h/mL) a	3590	3700	103.2	99.5, 107.0
T max (h) b	1.0(0.5, 2.0)	4.0(1.5, 8.0)*	/	/
t lag (h) b	0.00	0.00	/	/

Note: Slash indicates it is not applicable as it falls under single‐dose studies.

Abbreviations: C _max, maximum plasma concentration; AUC_0‐t , area under the plasma concentration‐time curve, from time zero till the last quantifiable point; AUC_0‐∞, area under the plasma concentration‐time curve from time zero to time infinity; T _max, time to maximum plasma concentration; t _lag, lag time.

^a Log‐transformed values were subjected to analysis of variance (ANOVA) to calculate the geometric mean ratio and the 90% confidence interval (90% CI) under fasting and fed states.

^b Median (range).

^* P < 0.001.

3.4. PD characteristics

HSK31858 dose‐dependently inhibited NE_norm at doses between 10 and 40 mg (Figure 3). Inhibition of NE_norm was not apparent over 28 days of treatment with HSK31858 10 mg, with only a maximum inhibition of 13.6% accompanied by a large variability, but a reduction of 43.2% in NE_norm was observed on day 31 after the discontinuation of treatment. NE_norm showed a maximal 44.1% reduction from day 16 to day 28 with HSK31858 20 mg QD, with a further decrease after discontinuation of treatment (64.9%, day 31). Meanwhile, HSK31858 40 mg QD led to a significant reduction in NE_norm on day 19 (61.6%), with a maximal reduction of 76.4% in NE_norm on day 28. Notable inhibition of NE_norm (65.4%, day 31) was observed after the discontinuation of treatment. By day 56, NE_norm had almost returned to baseline levels in all dosing cohorts.

FIGURE 3.

Changes in neutrophil count normalized neutrophil elastase activity (%) over time (mean + SD). For each volunteer, baseline neutrophil elastase NE activity was defined as the mean of all observations on day 1, 4 and 7. Placebo data were pooled from all three cohorts.

4. DISCUSSION

DPP‐1 plays an important role in the activation of granule serine proteases including NE, proteinase 3, neutrophil serine protease 4 and cathepsin G, and is also involved in the activation of chymase and tryptase in mast cells and lymphocyte granzymes. To date, several DPP1 inhibitors have progressed to clinical trials but none has been approved by regulatory authorities globally. A phase 2 trial of HSK31858 has been completed (NCT05601778) and a phase 3 trial is ongoing (NCT06660992). Our in vitro study showed HSK31858 had greater inhibitory effects on recombinant DPP‐1 activity than brensocatib (IC₅₀ 3.7 nM vs 12.5 nM; Supporting Information Figure S3 and Table S1) and had no off‐target effects. The results of the phase 2 trial of HSK31858 (NCT05601778) are yet to be released, but the data in this study suggested that HSK31858 20 mg or 40 mg QD led to greater inhibition of NE activities than brensocatib. GSK2793660 is an irreversible DPP‐1 inhibitor; a phase 1 trial in healthy volunteers was prematurely terminated due to the rapid onset of serious skin toxicities. ¹⁷ The current study evaluated the PK/PD and safety of DPP‐1 inhibitor HSK31858 in healthy Chinese volunteers and was successful in establishing the safety profile of HSK31858 and identifying a recommended dose of HSK31858 20 mg or 40 mg QD for subsequent clinical trials (NCT05601778 and NCT06660992) based on the safety and ≥50% inhibition of NE_norm activities and in reference to the trial results of brensocatib. ²¹ Given that neutrophilic inflammation is a cardinal feature of bronchiectasis, bronchial asthma and cystic fibrosis, our findings suggest that HSK31858 could be an effective treatment for these neutrophil‐mediated diseases and other diseases in which neutrophils play a prominent role, including autoimmune disease and chronic inflammatory disease. ²²

PK assessments in this study showed that HSK31858 was rapidly absorbed through the intestine and reached the peak concentration in approximately 0.75‐1.5 h postdose. HSK31858 was eliminated with a half‐life of 16.5‐21.0 h after a single dose and approximately 26 h after multiple doses, supporting the once‐daily dosing regimen. At the steady state, HSK31858 showed approximately 2‐fold accumulation, which is similar to brensocatib in healthy Japanese and Caucasian healthy volunteers. ²³ Our current data indicated that the exposure of HSK31858 increased more than proportional to the dose, showing minor signs of supra‐proportionality in the dose range between 15 and 80 mg, which may be due to the saturation of P‐glycoprotein (P‐gp) transporters in the intestine at high drug concentrations as HSK31858 is a P‐gp substrate. In addition, like brensocatib and BI 1291583, ²⁴ food had small effects on the PK properties of HSK31858.

HSK31858 is a reversible inhibitor on DPP‐1, rendering it difficult to quantify the direct inhibition on DPP1 due to possible detachment during sample processing, therefore the downstream NE activity has been selected as a surrogate marker. Neutrophil serine proteases are activated during neutrophil maturation in the bone marrow by DPP‐1 and subsequently released from neutrophils into the circulation and cause damages to the airway. ¹⁴ A notable treatment response in terms of NE activity started at around 16 days after treatment initiation with HSK31858 and was maintained until the end of the 28‐day administration. This delay in response is consistent with the maturation time of neutrophils and was also observed with other DPP‐1 inhibitors. ¹⁴ Regarding inhibitory effect on NE activity, preclinical studies showed that HSK31858 exhibited comparable inhibitory potency on NE activities in rat bone marrow cells with an ED₅₀ of 1.13 mg/kg for HSK31858 vs 1.45 mg/kg for brensocatib (unpublished data). Consistently, in this study, HSK31858 exhibited a dose‐dependent inhibition of NE activity, with a maximal 44.1% and 76.4% reduction during treatment for the 20‐mg QD and 40‐mg QD cohorts, respectively, which is better than the inhibitory effect of brensocatib at 10 mg (30%) and 25 mg (49%), both of which doses have been proved successful in the phase III topline results. In addition, the maximal percentage decrease (I _max) in NE_norm activity relative to baseline during 28 days of HSK31858 treatments increased overall with increasing systemic exposure of HSK31858 (C _{max, ss}, C _{trough, ss} or AUC_0‐τ,ss) between 10 and 40 mg and had a saturation trend (Supporting Information Figure S4). Based on the inhibition level of NE activity in healthy volunteers, HSK31858 20 mg and 40 mg have been recommended as phase II doses in subsequent clinical studies of HSK31858.

HSK31858 was overall well tolerated and exhibited an acceptable toxicity profile. Food had no impact on the safety profile of HSK31858. No grade 3 or higher TRAE occurred and no volunteers in the safety analysis population had an SAE or discontinued the study due to TEAEs or TRAEs. Neutrophils are essential for innate immune defence against infection. No notable reduction in neutrophil count was observed and no TEAE of infection occurred, suggesting that HSK31858 had no effect on the number of neutrophils, which are important for innate immune defence. No measures were taken for all AEs, all of which were resolved or had abated by the end of the study. Blood triglycerides increase was the most frequent TEAE in volunteers receiving HSK31858 in both parts A and B. There were no TEAEs of headache, dyspnea or periodontal toxicity. In comparison, headache, skin exfoliation and nasopharyngitis were the most common TEAEs in healthy volunteers receiving brensocatib. ²³ Regarding the AESIs, skin exfoliation occurred in <5% of the study volunteers receiving HSK31858 compared to 10% in healthy Japanese and Caucasian volunteers receiving brensocatib. ²³ The first‐in‐human study of brensocatib reported five skin‐related AEs in the MAD study, among which four were seen in the highest dosing group. Symptoms include mild exfoliation in the palms, heel bone area and big toes. In this study, treatment‐related skin and subcutaneous disorders only occurred in two volunteers each in of parts A and B, which were all grade 1 and resolved without treatment. Additionally, no gingival disorder was reported, suggesting HSK31858 shows a more acceptable safety profile with regard to the AESIs. Skin‐related AEs are likely due to inhibition of cathepsin C, which plays an important role in maintaining the structural integrity of plantar and palmar epidermal surfaces via regulated proteolysis in epithelia as demonstrated by the identification of cathepsin C mutations in Papillon‐Lefevre syndrome. ²⁵ , ²⁶ In a phase 1 trial, GSK2793660, an irreversible cathepsin C inhibitor, was associated with a rapid onset of marked skin desquamation within 7‐10 days of dosing in healthy volunteers ¹⁷ ; the rapid onset of skin toxicities was associated with cathepsin C inhibition and did not correlate with NE activities and led to the terminal of the trial. Dose‐dependent skin events were also observed in a phase 1 trial of brensocatib in healthy volunteers. ¹⁴

The study has several limitations. The effects of HSK31858 on targets downstream of DPP‐1, including proteinase 3 and cathepsin G, were not investigated. In addition, the highest dose of HSK31858 was 40 mg QD during MAD and no higher dose was examined for exploring the inhibition of NE_norm activities by HSK31858. However, as discussed above, the maximal percentage decrease (I _max) in NE_norm activities showed a saturation trend up to 40 mg. Escalating the dose of HSK31858 beyond 40 mg might not lead to further significant inhibition of NE_norm activities. Finally, due to the limited sample size, the variability of NE_norm activities was large, especially in the 10‐mg dose group (Figure 3).

In conclusion, HSK31858 is safe and well tolerated in healthy volunteers, which supports subsequent clinical development. Based on the toxicity and PK/PD profile, HSK31858 displayed an acceptable toxicity profile and concentration‐dependent inhibition of NE activity, with HSK31858 20 mg and 40 mg QD achieving therapeutically relevant reduction (about 50% or more). Our results support that oral HSK31858 is safe and effective in NE activity reduction in Chinese healthy volunteers and is a promising candidate for the treatment of neutrophil‐mediated inflammatory diseases, including bronchiectasis, and could be an important addition to the current standard‐of‐care treatments for bronchiectasis.

AUTHOR CONTRIBUTIONS

Yuhao Wang, Mengyue Hu, Nan Wu and Jie Hou contributed to the study conception and design. Lu Wang, Yuhao Wang and Hanmo Liu collected the data and performed the data analysis. All authors contributed to the interpretation of the data and the completion of figures and tables. All authors contributed to the drafting of the article and final approval of the submitted version.

ETHICAL APPROVAL AND CONSENT TO PARTICIPATE

This study was approved by the ethics committee of PKUCare Luzhong Hospital (BLYYL [2022] No. 09) and undertaken in adherence with the principles of the Declaration of Helsinki and Good Clinical Practice Guidelines and regulations by the National Medical products Administration of China. The trial, along with its subsequent amendments, is registered with Clinicaltrials.gov (NCT05663593). Written informed consent was obtained from all study participants.

CONFLICT OF INTEREST STATEMENT

All authors declare that they have no conflicts of interest.

CONSENT FOR PUBLICATION

Not applicable.

Supporting information

SUPPORTING INFORMATION FIGURE S1 Molecular structure of HSK31858.

SUPPORTING INFORMATION FIGURE S2 Dose‐dependent inhibition of DPP1 by INS1007 and HSK31858. (A, B) Plots of fluorescence intensity vs logarithm concentrations of INS1007 (A) and HSK31858 (B), respectively. Dose‐response curves were plotted and IC₅₀ values were generated from curve fitting with GraphPad Prism 8.0 software. Points are triplicates and fit to a hyperbola on logarithmic scale.

SUPPORTING INFORMATION FIGURE S3 Plots of initiate reaction rates vs DPP1 concentration. (A) The curve of the reaction rate vs DPP1 concentration when DPP1 was incubated with different concentrations of INS1007 (80, 20, 5 and 0 nM). (B) The curve of the reaction rate vs enzyme concentration when DPP1 was incubated with different concentrations of HSK31858 (16, 4, 1 and 0 nM). The compound concentration at 0 nM indicated the vehicle control containing 0.1% DMSO. All straight lines were obtained from curve fitting with GraphPad Prism 8.0 software.

SUPPORTING INFORMATION TABLE S1 Inhibitory type of compounds on DPP1.

SUPPORTING INFORMATION FIGURE S4 Scatter plots and E _max model (E = E _max × C/[EC₅₀ + C]) of C _max,ss, C _trough,ss and AUC_0‐τ,ss with I _max in NE_norm activity relative to baseline during 28 days of HSK31858 treatments.

Wang Y, Yu C, Hu M, et al. Safety, tolerability, pharmacokinetics and pharmacodynamics of HSK31858, a novel oral dipeptidyl peptidase‐1 inhibitor, in healthy volunteers: An integrated phase 1, randomized, double‐blind, placebo‐controlled, single‐ and multiple‐ascending dose study. Br J Clin Pharmacol. 2025;91(8):2262‐2272. doi: 10.1002/bcp.70027

DATA AVAILABILITY STATEMENT

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.