Manufacturing-dependent change in biological activity of the TLR4 agonist GSK1795091 and implications for lipid A analog development

Abstract

A phase I trial (NCT03447314; 204686) evaluated the safety and efficacy of GSK1795091, a Toll-like receptor 4 (TLR4) agonist, in combination with immunotherapy (GSK3174998 [anti-OX40 monoclonal antibody], GSK3359609 [anti-ICOS monoclonal antibody], or pembrolizumab) in patients with solid tumors. The primary endpoint was safety; other endpoints included efficacy, pharmacokinetics, and pharmacodynamics (PD). Manufacturing of GSK1795091 formulation was modified during the trial to streamline production and administration, resulting in reduced PD (cytokine) activity. Fifty-four patients received GSK1795091 with a combination partner; 32 received only the modified GSK1795091 formulation, 15 received only the original formulation, and seven switched mid-study from the original to the modified formulation. Despite the modified formulation demonstrating higher systemic GSK1795091 exposure compared with the original formulation, the transient, dose-dependent elevations in cytokine and chemokine concentrations were no longer observed (e.g., IP-10, IL10, IL1-RA). Most patients (51/54; 94%) experienced ≥1 treatment-emergent adverse event (TEAE) during the study. Safety profiles were similar between formulations, but a higher incidence of TEAEs associated with immune responses (chills, fatigue, pyrexia, nausea, and vomiting) were observed with the original formulation. No conclusions can be made regarding GSK1795091 anti-tumor activity due to the limited data collected. Manufacturing changes were hypothesized to have caused the change in biological activity in this study. Structural characterization revealed GSK1795091 aggregate size in the modified formulation to be twice that in the original formulation, suggesting a negative correlation between GSK1795091 aggregate size and PD activity. This may have important clinical implications for future development of structurally similar compounds.

FIGURE 1

Structural characterization of the original and modified GSK1795091 formulations. Evaluation of the original and modified formulations using (a) dynamic light scattering, revealing that the diameter of GSK1795091 particles in the modified formulation was twice the diameter of the original formulation, and (b) cryo‐transmission electron microscopy (TEM) images, showing formation of large aggregates of globular‐like structures in the modified formulation while the original formulation has mostly sheet‐like morphologies with no globular structures. The globular‐like structures appeared to be sensitive to beam electron due to the presence of ethanol which evaporates under the effect of heat resulting in the dark shades in the image. Globular structures are small, round bodies or spherical objects formed by attractive forces between molecules or group of molecules. Complex structures are multidimensional arrangements of molecules or group of molecules.

FIGURE 2

CONSORT flow diagram of study disposition. *Patients switched from original to modified GSK1795091 formulation during the study. ^†Patients continued combination partner monotherapy following GSK1795091 discontinuation. LTFU, long‐term follow‐up.

FIGURE 3

Median GSK1795091 pharmacokinetic concentration–time plots with (a) original formulation and (b) modified formulation (combination partners pooled)*. Horizontal dashed line represents the default lower limit of quantification for the assay (2.0 pg/ml). *Data for combination partners were pooled for both formulations due to limited sample sizes and to specifically evaluate the effect of the two formulations on the pharmacokinetic profile of GSK1795091. Combination partners included GSK3174998 (anti‐OX40 monoclonal antibody), GSK3359609 (anti‐ICOS monoclonal antibody), or pembrolizumab (anti–PD‐1 monoclonal antibody). ICOS, inducible T‐cell costimulatory; PD‐1, programmed cell death protein 1.

FIGURE 4

Maximum change from baseline in pharmacodynamic (PD) biomarkers versus GSK1795091 C_max for original and modified formulations (combination partners pooled)*. *Data for combination partners were pooled for both formulations due to limited sample sizes and to specifically evaluate the effect of the two formulations on the PD profile of GSK1795091. Combination partners included GSK3174998 (anti‐OX40 monoclonal antibody), GSK3359609 (anti‐ICOS monoclonal antibody), or pembrolizumab (anti–PD‐1 monoclonal antibody). C_max, concentration maximum; ICOS, inducible T‐cell costimulatory; IP‐10, interferon gamma‐induced protein 10; PD‐1, programmed cell death protein 1.