The VIPR2-selective antagonist KS-133 changes macrophage polarization and exerts potent anti-tumor effects as a single agent and in combination with an anti-PD-1 antibody.

We have previously demonstrated that KS-133 is a specific and potent antagonist of vasoactive intestinal peptide receptor 2 (VIPR2). We have also shown that vasoactive intestinal peptide-VIPR2 signaling affects the polarity and activation of tumor-associated macrophages, which is another strategy for cancer immunotherapy apart from the activation of effector T cells. In this study, we aimed to examine whether the selective blockade of VIPR2 by KS-133 changes the polarization of macrophages and induces anti-tumor effects. In the presence of KS-133, genetic markers indicative of tumor-aggressive M1-type macrophages were upregulated, and conversely, those of tumor-supportive M2-type macrophages were downregulated. Daily subcutaneous administration of KS-133 tended to suppress the growth of CT26 tumors (murine colorectal cancer-derived cells) implanted subcutaneously in Balb/c mice. To improve the pharmacological efficacy and reduce the number of doses, we examined a nanoformulation of KS-133 using the US Food and Drug Administration-approved pharmaceutical additive surfactant Cremophor® EL. KS-133 nanoparticles (NPs) were approximately 15 nm in size and stable at 4°C after preparation. Meanwhile, KS-133 was gradually released from the NPs as the temperature was increased. Subcutaneous administration of KS-133 NPs once every 3 days had stronger anti-tumor effects than daily subcutaneous administration of KS-133. Furthermore, KS-133 NPs significantly enhanced the pharmacological efficacy of an immune checkpoint-inhibiting anti-PD-1 antibody. A pharmacokinetic study suggested that the enhancement of anti-tumor activity was associated with improvement of the pharmacokinetic profile of KS-133 upon nanoformulation. Our data have revealed that specific blockade of VIPR2 by KS-133 has therapeutic potential for cancer both alone and in combination with immune checkpoint inhibitors.

Identification of cytochrome P450 enzymes involved in the metabolism of FK228, a potent histone deacetylase inhibitor, in human liver microsomes.

FK228 (FR901228, depsipeptide) is a potent histone deacetylase inhibitor currently in phase II clinical trials for cancer treatment. In the present study, the cytochrome P450 (P450) enzymes responsible for FK228 metabolism in human liver microsomes were investigated. Incubation with human liver microsomes in the presence of an NADPH-generating system revealed that FK228 is metabolized to at least 10 different metabolites. Km and Vmax values for FK228 disappearance were 20.3 microM and 561.9 pmol/min/mg protein, respectively. Further studies were performed at a substrate concentration of 10 microM (half the Km value for FK228 disappearance). FK228 disappearance activities in human liver microsomes from 12 individuals strongly correlated (r2=0.957) with testosterone 6beta-hydroxylase activities, a marker enzyme activity of CYP3A4/5, but not with other P450 enzyme-specific activities (CYP1A2, 2A6, 2C8, 2C9, 2C19, 2D6, and 4A). Among 14 recombinant heterologously expressed human P450s examined, CYP3A4 exhibited the highest activity of FK228 disappearance. CYP3A5, 1A1, 2B6, and 2C19 showed 16.8%, 5.2%, 1.6%, and 1.3% of the activity of CYP3A4, respectively. Other P450s showed no significant metabolic activity toward FK228. In addition, FK228 disappearance in human liver microsomes was markedly inhibited by ketoconazole, a potent CYP3A4 inhibitor, and an anti-CYP3A4 antibody. These results indicate that the metabolism of FK228 in human liver microsomes is catalyzed mainly by CYP3A enzymes, particularly CYP3A4.