A Phase 1 Study To Evaluate Safety and Pharmacokinetics following Administration of Single and Multiple Doses of the Antistaphylococcal Lysin LSVT-1701 in Healthy Adult Subjects

ABSTRACT

Thirty-two healthy male subjects (8 per cohort) were randomized 6:2 to active:placebo. LSVT-1701, an antistaphylococcal lysin, was administered intravenously as a 6-mg/kg single dose and as 1.5, 3, and 4.5 mg/kg twice daily for 4 days. LSVT-1701 exposure increased in a greater than dose proportional manner and did not accumulate. Treatment-emergent adverse events (TEAEs) were predominantly of mild intensity. The most common TEAEs were chills, pyrexia, headache, infusion site events, cough, rhinorrhea, and increases in C-reactive protein. (This study has been registered at ClinicalTrials.gov under identifier NCT03446053.)

TEXT

LSVT-1701 (previously known as SAL200) is a recombinantly produced, bacteriophage-encoded lysin that specifically targets staphylococci via cell wall hydrolysis (1, 2). LSVT-1701 exhibited bactericidal activity against biofilm-forming and planktonic Staphylococcus aureus cells (1, 2). LSVT-1701 demonstrated potent in vitro activity against contemporary global clinical isolates of S. aureus and coagulase-negative staphylococci regardless of resistance phenotypes (3). In vivo, LSVT-1701 in combination with standard-of-care antibiotics significantly reduced bacterial bioburden in blood and tissues in methicillin-resistant S. aureus mouse bacteremia and rabbit left-sided infective endocarditis models (4, 5). In addition, LSVT-1701 was safe and well tolerated following administration of single ascending doses in a first human study (6).

This phase 1, randomized, double-blind, placebo-controlled study (ClinicalTrials.gov identifier NCT03446053) was conducted at a single center (Seoul National University Hospital) from February 2018 to February 2019. The study was conducted in accordance with the Declaration of Helsinki. The schedule of assessments is provided in Table 1. The Republic of Korea Ministry of Food and Drug Safety and the Institutional Review Board of Seoul National University Hospital approved the protocol. LSVT-1701 (18 mg/mL) was prepared as previously described (7). Healthy adult males were recruited. All volunteers provided written informed consent to participate before enrollment. LSVT-1701 concentrations and anti-LSVT-1701 antibodies were measured as described previously (6). The accuracy (% bias) and precision (interbatch coefficient of variation [CV] %) of the pharmacokinetic assay were −9.1 to −2.5% and ≤7.5%, respectively. Pharmacokinetic parameters were calculated via noncompartmental methods, with the log-linear method for area under the concentration-time curve (AUC) estimation, using Phoenix WinNonlin (version 7.0; Certara, Inc., Princeton, NJ). Dose proportionality was assessed by a power model (lnY = a + b ln[Dose], where Y is the pharmacokinetic parameter [C_max, AUC]), to estimate the slope and associated 95% confidence interval. All statistical analyses were performed using SAS software (version 9.4; SAS Institute, Cary, NC).

TABLE 1.

Schedule of assessments^a

Assessment	Screening (days −28 to −2)	Day
		−1	1	2	3	4	5	8	15	22	29	50
Informed consent	•
Entry criteria	•
Admission		•
a.m. dosing (1-h i.v. infusion)			•	▲	▲	▲
p.m. dosing (1-h i.v. infusion)				▲	▲
Discharge				*			▲
Pharmacokinetic samplingb			•	•	▲	▲	▲
Antidrug antibody			•	*			▲	•	•	•	•	•
Vital signsc	•	•	•	•	▲	▲	▲	•	•	•	•	•
12-lead ECG	•		•	•	▲	▲	▲		•			•
Clinical chemistry (fasted), hematology, urinalysis	•		•	•	▲	▲	▲	•	•			•
Anaphylatoxin labsd			▲			▲
Physical exam	•	•	•	•	▲	▲	▲	•	•	•	•	•
Adverse events		•	•	•	▲	▲	▲	•	•	•	•	•
Concomitant medications	•	•	•	•	▲	▲	▲	•	•	•	•	•

^a•, all cohorts; *, single dose cohort; ▲, twice daily cohorts; ECG, electrocardiography; i.v., intravenous.

^bPharmacokinetic samples were collected before dosing and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, and 24 h after the start of the i.v. infusion on days 1 and 4, and before dosing and 1 and 12 h after the start of the i.v. infusion on days 2 and 3.

^cBody temperature, heart rate, systolic blood pressure, and diastolic pressure were collected before dosing and at 1, 4, 8, 12, 13, and 24 h after the start of the i.v. infusion on days 1 and 4 and at 1 and 12 h after the start of each i.v. infusion on days 2 and 3.

^dComplement C3a, C4a, tryptase, interleukin (IL)-1β, IL-2, IL-6, and tumor necrosis factor alpha (TNF-α) samples were collected before dosing and 1 h after the start of each i.v. infusion on days 1 and 4.

Thirty-two healthy male subjects (8 per cohort) were randomized 6:2 to active:placebo. LSVT-1701 was administered by a 1-h intravenous (i.v.) infusion as a 6-mg/kg single dose and as 1.5, 3, and 4.5 mg/kg twice daily for 4 days. Subjects were male with mean ± standard deviation age of 30.2 ± 5.6 years and body mass index of 23.7 ± 2.1 kg/m². In total, 30 of 32 (94%) subjects completed the study. One subject in the 6-mg/kg single dose group discontinued on day 22, and one subject in the 4.5 mg/kg twice daily group discontinued after dosing on day 1; both discontinuations were due to subject withdrawal of consent.

LSVT-1701 exposure increased in a greater than dose proportional manner (Table 2; Fig. 1). Across single doses (day 1) and multiple (twice daily) doses (day 4), the slope estimates for the relationships between C_max, AUC_last (day 1), and AUC_tau (day 4) versus dose ranged from 1.95 to 2.17. LSVT-1701 concentrations did not accumulate following twice daily dosing, in accordance with the observed t_1/2 of <4 h.

TABLE 2.

Summary of LSVT-1701 pharmacokinetic parameters in healthy subjects^a

LSVT-1701 dose (mg/kg)	N	Mean (SD)
		AUC (μg·h/mL)b	Cmax (μg/mL)	t1/2 (h)	R(AUC)c
Day 1
1.5	6	1.14 (0.519)	1.24 (0.509)	0.39 (0.08)
3	6	5.70 (1.35)	4.93 (1.08)	0.73 (0.21)
4.5	6d	11.8 (1.15)	10.8 (1.53)	1.16 (0.29)
6	6	24.8 (7.05)	21.4 (3.91)	3.38 (3.40)
Day 4
1.5 twice daily	6e	1.23 (0.657)	1.30 (0.696)	0.45 (0.16)	1.06 (0.179)
3 twice daily	6	5.70 (1.34)	5.01 (1.21)	2.02 (0.78)	1.00 (0.072)
4.5 twice daily	5	10.3 (1.56)	10.2 (1.43)	3.72 (2.85)	0.909 (0.066)

^aAUC_inf, area under the curve from time zero and extrapolated to infinity; AUC_tau, area under the curve over a dosing interval; C_max = maximum concentration; t_1/2 = half-life; R(AUC), AUC_tau accumulation ratio.

^bAUC = AUC_inf for a single dose (day 1) and AUC_tau for multiple doses (day 4).

^cR(AUC) = AUC_{tau day 4}/AUC_{tau day 1}.

^d4.5 mg/kg day 1: N = 4 for AUC_inf and t_1/2.

^e1.5 mg/kg day 4: N = 5 for AUC_tau and t_1/2.

FIG 1.

Mean (± SD) LSVT-1701 concentrations over time by dose group. LLOQ, lower limit of quantification.

LSVT-1701 was safe and well tolerated. Treatment-emergent adverse events (TEAEs) were predominantly (97%) of mild intensity. There were no severe adverse events (AEs), no serious AEs, and no deaths, and no subjects withdrew due to AEs. Overall, 15 of 32 (47%) subjects reported 59 TEAEs (Table 3). Respiratory TEAEs occurred with similar frequency between LSVT-1701 and placebo groups, whereas other TEAEs occurred more frequently in the LSVT-1701 dose groups. Chills, pyrexia, and headache began within 24 h after dosing and resolved within one to a few days. Infusion site events occurred with the last (sixth) dose and were not dose related.

TABLE 3.

Number of subjects reporting TEAEs (for TEAEs reported in at least two subjects receiving LSVT-1701)^a

TEAE	Twice daily			Single dose of 6 mg/kg (N = 6)	Overall LSVT-1701 (N = 24)	Placebo (N = 8)
	1.5 mg/kg (N = 6)	3 mg/kg (N = 6)	4.5 mg/kg (N = 6)
Any TEAE	3 (50)	1 (17)	3 (50)	6 (100)	15 (47)	2 (25)
No. of events	11	1	14	26	52	7
General disorders and administration site conditions
Chills	1 (17)	0	1 (17)	4 (67)	6 (25)	0
Pyrexia, hyperthermia, fever	1 (17)	0	1 (17)	4 (67)	6 (25)	0
Infusion site erythema	2 (33)	0	1 (17)	0	3 (13)	0
Infusion site pain	2 (33)	0	1 (17)	0	3 (13)	0
Infusion site induration	2 (33)	1 (17)	0	0	3 (13)	0
Nervous system disorders
Headache	1 (17)	0	0	3 (50)	4 (17)	0
Respiratory, thoracic, and mediastinal disorders
Cough	1 (17)	0	1 (17)	1 (17)	3 (13)	2 (25)
Productive cough	1 (17)	0	1 (17)	0	2 (8)	1 (13)
Rhinorrhea	0	0	0	2 (33)	2 (8)	2 (25)
Investigations
C-reactive protein increased	0	0	2 (33)	5 (83)	7 (29)	0

^aThe values are given as the number of patients (%), unless noted otherwise. TEAE, treatment-emergent adverse event.

There were no trends in blood pressure or electrocardiographs (ECGs). In the 6-mg/kg single dose group, elevated body temperature (37.8 to 38.8°C) was accompanied by elevated heart rate. No clinically remarkable changes in clinical safety labs or anaphylatoxin test results were observed, except for transient increases in C-reactive protein. Subjects who received LSVT-1701 were negative for antidrug antibodies from baseline through day 14; 8 of 24 (33%) subjects were positive at day 50. There was no apparent impact of antidrug antibodies on LSVT-1701 pharmacokinetics. Subjects who received placebo were negative for antidrug antibodies throughout the study.

Pharmacokinetic and safety data from this study suggest that the incidence of TEAEs is driven by C_max. A higher incidence of TEAEs was reported in the 6-mg/kg single dose group compared with the 4.5 mg/kg twice daily group (Table 3). The mean LSVT-1701 AUC_inf achieved with a single dose of 6 mg/kg (24.8 μg·h/mL) was comparable to the daily AUC achieved with 4.5 mg/kg twice daily (23.6 μg·h/mL [day 1 mean, 11.8 μg·h/mL × 2]), whereas the mean C_max for the 6-mg/kg single dose group was approximately twice that of the 4.5 mg/kg twice daily group (Table 2).

Based on a rabbit model of left-sided infective endocarditis, the estimated target exposure index (AUC/minimal inhibitory concentration [MIC]) for LSVT-1701 is 24, and the optimal duration of treatment is 4 days (Ref. 5; unpublished data). Based on 415 clinical isolates, the estimated MIC₅₀ and MIC₉₀ for LSVT-1701 are 1 and 2 μg/mL, respectively (3). The mean daily AUCs for LSVT-1701 doses of 4.5 mg/kg twice daily and 6 mg/kg once daily match the target exposure index for the MIC₅₀. In a prior study, a single 10-mg/kg dose of LSVT-1701 achieved a mean AUC_inf of 60 μg·h/mL (6), which exceeds the target exposure index for both the MIC₅₀ and MIC₉₀.

The human safety and pharmacokinetic data in combination with nonclinical efficacy and in vitro susceptibility data suggest that safe and efficacious LSVT-1701 exposures (AUCs) can be achieved in the target populations of patients with S. aureus bacteremia and infective endocarditis. Longer infusion durations may be a useful strategy to minimize the incidence of TEAEs (C_max-driven).