Optimization and Structure-Activity Relationships of Phosphinic Pseudotripeptide Inhibitors of Aminopeptidases That Generate Antigenic Peptides

The oxytocinase subfamily of M1 aminopeptidases, consisting of ER aminopeptidase 1 (ERAP1), ER aminopeptidase 2 (ERAP2), and insulin-regulated aminopeptidase (IRAP), plays critical roles in the generation of antigenic peptides and indirectly regulates human adaptive immune responses. We have previously demonstrated that phosphinic pseudotripeptides can constitute potent inhibitors of this group of enzymes. In this study, we used synthetic methodologies able to furnish a series of stereochemically defined phosphinic pseudotripeptides and demonstrate that side chains at P₁' and P₂' positions are critical determinants in driving potency and selectivity. We identified low nanomolar inhibitors of ERAP2 and IRAP that display selectivity of more than 2 and 3 orders of magnitude, respectively. Cellular analysis demonstrated that one of the compounds that is a selective IRAP inhibitor can reduce IRAP-dependent but not ERAP1-dependent cross-presentation by dendritic cells with nanomolar efficacy. Our results encourage further preclinical development of phosphinic pseudotripeptides as regulators of adaptive immune responses.

Screening Identifies Thimerosal as a Selective Inhibitor of Endoplasmic Reticulum Aminopeptidase 1

We employed virtual screening followed by in vitro evaluation to discover novel inhibitors of ER aminopeptidase 1, an important enzyme for the human adaptive immune response that has emerged as an attractive target for cancer immunotherapy and the control of autoimmunity. Screening hits included three structurally related compounds carrying the (E)-N'-((1H-indol-3-yl)methylene)-1H-pyrazole-5-carbohydrazide scaffold and (2-carboxylatophenyl)sulfanyl-ethylmercury as novel ERAP1 inhibitors. The latter, also known as thimerosal, a common component in vaccines, was found to inhibit ERAP1 in the submicromolar range and to present strong selectivity versus the homologous aminopeptidases ERAP2 and IRAP. Cell-based analysis indicated that thimerosal can effectively reduce ERAP1-dependent cross-presentation by dendritic cells in a dose-dependent manner.

Cholestasis Reveals Severe Cortisol Deficiency in Neonatal Pituitary Stalk Interruption Syndrome

OBJECTIVES

Cholestasis has been reported during the course of congenital hypothalamic-pituitary deficiency, but crucial information is lacking regarding both its origin and prognosis. We aimed to characterize the course of cholestasis and factors contributing to it in patients with deficiency due to pituitary stalk interruption syndrome (PSIS).

METHODS

We conducted a retrospective single-center, case-cohort study including 16 patients with PSIS diagnosed before one year of age. We collected clinical and biological parameters from medical records and compared the characteristics of the endocrine syndrome in PSIS patients with and without cholestasis.

RESULTS

5/16 patients had cholestasis, all with a neonatal onset and multiple hypothalamic-pituitary deficiency. Patients with cholestasis presented with lower Apgar score and higher rate of ophthalmic malformations: 3/5 vs 1/11, p = 0.03 and 5/5 vs 4/11, p = 0.02, respectively. The plasma cortisol level was strongly decreased in patients with cholestasis: 12.4 ng/mL (8-15 ng/mL) vs 79.4 ng/mL (10-210 ng/mL), p = 0.04. Cholestasis resolved within 9 months following hormone supplementation. No development of chronic liver disease was observed during a median follow-up of 9.4 years (range, 1.3-13.3 years).

CONCLUSIONS

Cholestasis is a frequent symptom at presentation of PSIS during the neonatal period that may help earlier diagnosis and that indicates a profound cortisol deficiency.

3,4-diaminobenzoic acid derivatives as inhibitors of the oxytocinase subfamily of M1 aminopeptidases with immune-regulating properties

Members of the oxytocinase subfamily of M1 aminopeptidases (ERAP1, ERAP2, and IRAP) play important roles in both the adaptive and innate human immune responses. Their enzymatic activity can contribute to the pathogenesis of several major human diseases ranging from viral and parasitic infections to autoimmunity and cancer. We have previously demonstrated that diaminobenzoic acid derivatives show promise as selective inhibitors for this group of aminopeptidases. In this study, we have thoroughly explored a series of 3,4-diaminobenzoic acid derivatives as inhibitors of this class of enzymes, achieving submicromolar inhibitors for ERAP2 (IC50 = 237 nM) and IRAP (IC50 = 105 nM). Cell-based analysis indicated that the lead compounds can be effective in downregulating macrophage activation induced by lipopolysaccharide and interferon-γ as well as cross-presentation by bone marrow-derived dendritic cells. Our results indicate that this class of inhibitors may be useful for the targeted downregulation of immune responses.