Single-dose of LC51-0255, a selective S1P1 receptor modulator, showed dose-dependent and reversible reduction of absolute lymphocyte count in humans.

Reducing the peripheral absolute lymphocyte count (ALC) is a promising therapeutic approach in treating autoimmune diseases. LC51-0255 is a sphingosine-1-phosphate 1 receptor modulator, which is known to decrease the peripheral ALC. We aimed to assess the pharmacokinetics (PKs), pharmacodynamics (PDs), safety, and tolerability profiles of LC51-0255 after a single oral administration in healthy subjects. A randomized, double-blind, placebo-controlled, dose-escalation study was conducted in 50 healthy subjects. Each subject orally received LC51-0255 (0.25, 0.5, 1, 2, or 4 mg) or its matching placebo in an 8:2 ratio. Blood and urine samples were collected to assess the PKs, and PDs was evaluated using peripheral ALC and 24-h hourly heart rate data. Safety and tolerability were assessed by monitoring treatment emergent adverse events (TEAEs), vital signs, 12-lead electrocardiogram (ECG), continuous 24-h ECG (via Holter monitoring), clinical laboratory tests, ophthalmologic tests, pulmonary function tests, and physical examinations. A single dose of LC51-0255 reduced ALC and heart rate in a reversible and dose-dependent manner. Systemic exposure of LC51-0255 increased dose-dependently and its half-life ranged from 72.2 to 134.0 h. ALC and the systemic exposure of LC51-0255 seemed to be negatively correlated. LC51-0255 was well-tolerated up to 2 mg, and the most common TEAE was bradycardia. The results of this study suggest that LC51-0255 can be developed into a beneficial treatment option for autoimmune disease.